SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships
The retractable proboscis of acanthocephalans is equipped with hooks for attachment to the intestine of the definitive host. Throughout their evolutionary history, acanthocephalans have developed a variety of ways to maximize their anchoring to host gut and to avoid dislodgement. Hooks vary in their...
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Zoodiversity| _version_ | 1874092710800916480 |
|---|---|
| author | Amin, O. M. Heckmann, R. A. |
| author_facet | Amin, O. M. Heckmann, R. A. |
| author_institution_txt_mv | [
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"author": "O. M. Amin",
"institution": "Institute of Parasitic Diseases, Arizona, USA",
"orcid": ""
},
{
"author": "R. A. Heckmann",
"institution": null,
"orcid": ""
}
] |
| author_sort | Amin, O. M. |
| baseUrl_str | https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/oai |
| collection | OJS |
| container_end_page | |
| container_issue | 4 |
| container_start_page | |
| container_title | Zoodiversity (Vestnik Zoologii) |
| container_volume | 56 |
| datestamp_date | 2026-08-20T12:37:15Z |
| description | The retractable proboscis of acanthocephalans is equipped with hooks for attachment to the intestine of the definitive host. Throughout their evolutionary history, acanthocephalans have developed a variety of ways to maximize their anchoring to host gut and to avoid dislodgement. Hooks vary in their size and shape along the longitudinal axis of the proboscis, texture,  structure, and hardness as well as in their contribution to the absorption of nutrients. Hooks also vary in their chemical composition, especially calcium, phosphorus, and sulfur, contributing to their hardness. Hook roots are paramount in anchoring them to the cuticular and subcuticular layers of the proboscis. Roots vary in size and shape and are often simple and directed posteriorly but often have anterior manubrial or may be vestigial or absent especially posteriorly. The core layer of roots is usually continuous with that of the hook. Hooks often, but not always, maintain a similar pattern in families. Because of the inconsistencies and inadequacies in the description of hooks, especially in line drawings, in various groups of acanthocephalans, we have decided to provide the largest assortment of morphological and anatomical variabilities among the many species that we have studied over the years. We are, thus, reporting the SEM of hooks of 30 selected species of acanthocephalans in 13 families in an attempt to elucidate patterns and trends characteristic of acanthocephalan families. |
| doi_str_mv | 10.15407/zoo2022.04.265 |
| first_indexed | 2025-07-17T12:36:14Z |
| format | Article |
| fulltext |
UDC 595.133
SEM STUDY OF HOOKS IN THE ACANTHOCEPHALA WITH
EMPHASIS ON STRUCTURAL-FUNCTIONAL RELATIONSHIPS
O. M. Amin1*, R. A. Heckmann2
1Institute of Parasitic Diseases, 11445 E. Via Linda 2-419, Scottsdale, Arizona 85259, USA
2Department of Biology, Brigham Young University, 1114 MLBM, Provo, Utah 84602, USA. Deceased.
Corresponding author
E-mail: omaramin@aol.com
O. M. Amin (https://orcid.org/0000-0003-2088-8628)
SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships.
Amin, O. M., Heckmann, R. A. — The retractable proboscis of acanthocephalans is equipped with hooks
for attachment to the intestine of the definitive host. Throughout their evolutionary history, acanthoceph-
alans have developed a variety of ways to maximize their anchoring to host gut and to avoid dislodgement.
Hooks vary in their size and shape along the longitudinal axis of the proboscis, texture, structure, and
hardness as well as in their contribution to the absorption of nutrients. Hooks also vary in their chemical
composition, especially calcium, phosphorus, and sulfur, contributing to their hardness. Hook roots are
paramount in anchoring them to the cuticular and subcuticular layers of the proboscis. Roots vary in size
and shape and are often simple and directed posteriorly but often have anterior manubria or may be ves-
tigial or absent especially posteriorly. The core layer of roots is usually continuous with that of the hook.
Hooks often, but not always, maintain a similar pattern in families. Because of the inconsistencies and
inadequacies in the description of hooks, especially in line drawings, in various groups of acanthocepha-
lans, we have decided to provide the largest assortment of morphological and anatomical variabilities
among the many species that we have studied over the years. We are, thus, reporting the SEM of hooks
of 30 selected species of acanthocephalans in 13 families in an attempt to elucidate patterns and trends
characteristic of acanthocephalan families.
Key words : Acanthocephala, hook morphology and anatomy, scanning electron microscopy, func-
tional relationships.
Introduction
Acanthocephalans are called “spiny-headed worms” for a reason. Actually, they have no heads. They have
a proboscis which is studded with hooks, not spines. Over 1,400 species of acanthocephalans are known to
science (Amin, 2013 and new species described since) each of which has developed anchoring hooks on the
proboscis for attachment to the gut of the definitive hosts. Cystacanths have also developed proboscis hooks
similar to those of adults of the same species. Hooks are usually arranged in longitudinal rows that sometimes
assume a spiral arrangement. They are normally smallest apically and posteriorly but occasionally are largest
basally. There can be as few as 6 in each of 3 circles on the proboscis as in Neoechinorhynchidae to many as
in Rhadinorhynchidae. The chemical composition of hooks, using Energy Dispersive x-ray analysis (EDXA),
varies for each species including many measurable elements that contribute to their degree of hardness. This
presentation provides a wide coverage of the structural-functional relationships of hooks of many species of
acanthocephalans that we have studied over the years, among others.
Zoodiversity, 56(4):265–284, 2022
DOI 10.15407/zoo2022.04.265
Fauna and Systematics
266 O. M. Amin, R. A. Heckmann
Material and methods
C o l l e c t i o n s
All specimens imaged using scanning electron microscopy (SEM) were collected from localities referenced
in table 1 where complete names of species of acanthocephalans and hosts, collecting sites, and figure numbers
are listed.
Acanthocephalans are listed by families in alphabetical order.
S c a n n i n g e l e c t r o n m i c r o s c o p y ( S E M )
Specimens that have been fixed and stored in 70 % ethanol were processed for SEM following standard
methods (SM) (Lee, 1992). These included critical point drying (CPD) and mounting on aluminum SEM
sample mounts (stubs) using conductive double-sided carbon tape. The sample was sputter coated with an
80–20 % gold-palladium target for 3 minutes using a sputter coater Q150T ES (Quorum, www.quorumtech.
com) equipped with a planetary stage, depositing an approximate thickness of 20 nm. Sample was placed and
observed in an FEI Helios Dual Beam Nanolab 600 Scanning Electron Microscope (FEI, Hillsboro, Oregon).
Samples were imaged using an accelerating voltage of 5 kV, and a probe current of 86 pA, at high vacuum using
a SE detector.
Used SEM images were sourced from our large stockpile of saved SEM material including those listed in
table 1. Published material listed are copyrighted to OMA or modified from original publication. A few other
images used were not previously published.
M i c r o s c o p e i m a g e s
Microscope images were created using 10x or 40x objective lenses of a BH2 light Olympus microscope
(Olympus Optical Co., Osachi-shibamiya, Okaya, Nagano, Japan) attached to an Am Scope 1000 video camera
(United Scope LLC, dba AmScope, Irvine, California), linked to an ASUS labtop equipped with HDMI high-
definition multimedia interface system (Taiwan-USA, Fremont, California). Images from the microscope are
transferred from the labtop to a USB and stored for subsequent processing on a computer.
F o c u s e d I o n B e a m ( F I B ) s e c t i o n i n g o f h o o k s
A dual-beam SEM with gallium (Ga) ion source (GIS) is used for the Liquid Ion Metal Source (LIMS)
part of the process. Hooks were sectioned at two positions (tip and middle) using the FEI Helios Dual Beam
Nano lab mentioned above. The dual-beam FIB/SEM is equipped with a gallium (Ga) Liquid Ion Metal Source
(LIMS). The hooks of the acanthocephalans were centered on the SEM stage and cross-sectioned using an ion
accelerating voltage of 30 kV and a probe current of 2.7 nA following the initial cut. The time of cutting is
based on the nature and sensitivity of the tissue. The sample also went through a cleaning cross-section milling
process to obtain a smoother surface. The cut was analyzed with an X-ray normally at the tip, middle, and base
of hooks for chemical ions with an electron beam (Tungsten) to obtain an X-ray spectrum. The intensity of the
GIS was variable according to the nature of the material being cut.
Results were stored with the attached imaging software then transferred to a USB for future use.
T a b l e 1 . A listing of acanthocephalan species studied for proboscis hook patterns and their hosts and
distribution
Family & species Type and
other hosts Distribution Published
sources
Fig.
nos.
Arhythmacanthidae
Heterosentisholos pinus Amin,
Heckmannm & Ha, 2011
Plotosus lineatus (Thunberg);
striped eel catfish
Vietnam;
Halong Bay
Amin et al.,
2011a & Amin
et al., 2019 d
1–3
Cavisomidae
Cavisoma magnum (Southwell,
1927) Van Cleave, 1931
Mugil cephalus Linn.; flathead
grey mullet
Arabian Gulf;
Iraq
Amin et al.,
2018 a
4–6
Pararhadinorhynchus magnus Ha,
Amin, Ngo & Heckmann, 2018
Scatophagus argus (Linn.);
spotted scat
Vietnam; Hai
Phong
Ha et al., 2018 7–9
Centrorhynchidae
Centrorhynchus globirostris
Amin, Heckmann, Wilson,
Keele & Khan, 2015
Centropus sinensis (Stephens);
pheasant crow
Pakistan; Sind Amin et al.,
2015 b
10–12
Centrorhynchus globocaudatus
(Zeder, 1800) Lühe, 1911
Falco tinnunculus Linn.; falcon
Buteo buteo Linn.; buzzard
Italy; Ferrara Amin et al.,
2020 a
13–18
Echinorhynchidae
Acanthocephalus parallelcement-
glandatus Amin,
Heckmann & Ha, 2018
Clarias batrachus (Linn.); walking
catfish. Odorrana sp. & Hylarana
sp. frogs. Tylosurus sp.; needle fish
Vietnam; cen-
tral & Ma River
Amin et al.,
2018 b
19–22
267SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Echinorhynchus cinctulus (Porta,
1905) Amin, 2013
Lota lota (Linn.); burbot Russia; Lake
Baikal
Amin et al.,
2015 a
25–28
Echinorhynchus gadi Zoega in
Müller, 1776
Hippoglossus stenolepis
Schmidt; Pacific halibut
USA, Alaska Amin et al.,
2021 a
29–30
Echinorhynchus salmonis Müller,
1784
Coregonus lavaretus (Linn.);
whitefish
Russia; Lake
Baikal
Amin et al.,
2015 a
23
Pseudoacanthocephalus lutzi
(Hamann, 1891)
Chaunus limensis Werner;
Peru coast toad
Peru; Lima Amin & Heck-
mann, 2014
24
Gigantorhynchidae
Intraproboscis sanghae Amin,
Heckmann, Sist & Basso, 2021
Phataginus tetradactyla Linn.;
black-bellied pangolin
Central African
Republic
Amin et al.,
2021 b
31–34
Mediorhynchus africanus Amin, Ev-
ans, Heckmann & El-Naggar, 2013
Numida meliagris Linn.; helmeted
Guinea fowl & other fowl spp.
South Africa;
Limpopo
Amin et al.,
2013 a
35–37
Mediorhynchus gallinarum
(Bhalerao, 1937)
Gallus gallus Linn.; chicken
(Isa brown egg-laying hen)
Indonesia;
Yogykarta
Amin et al.,
2013 b
38
Heteracanthocephalidae
Aspersentis megarhynchus (von
Linstow, 1892) Golvan, 1960
Notothenia coriiceps Richard-
son; rock cod
W. Antarctica;
Galindez Island
Amin et al.,
2021 c
39–42
Moniliformidae
Moniliformis cryptosaudi Amin,
Heckmann, Sharifdini &
Albayati, 2019
Hemiechinus auratus (Gme-
lin); long-eared hedgehog
Iraq; Baquba,
Diyala Gov.
Amin et al.,
2019 b
43–48
Moniliformis saudi Amin, Heck-
mann, Mohammed & Evans, 2016
Paraechinus aethiopicus
(Ehenberg); desert hedgehog
Saudi Arabia;
Unaizah
Amin et al.,
2016
49–50
Moniliformis kalahariensis
Meyer, 1931
Atelerix frontalis Smith; South
African hedgehog
South Africa;
Limpopo
Amin et al.,
2014 b
51–54
Neoechinorhynchidae
Neoechinorhynchus dimorphos-
pinus Amin & Sey, 1966
Chelon macrolepis (Smith),
Lizaklunzigeri (Day) & 4 ma-
rine spp. in 4 fish families
Arabian Gulf;
Kuwait
Amin et al.,
1984 & Amin et
al., 2015 c
61–63
Neoechinorhynchus johnii Yama-
guti, 1939
Eleuthero nemate tradactylus
(Shaw), Johnius carouna (Cu-
vier), Johnius sp., Otolithes
ruber (Bloch & Schneider)
Vietnam; along
north & south
coasts
Amin et al.,
2019 a
65–68
Neoechinorhynchus manubria-
nus Amin, Ha & Ha, 2011
Johnius carouna (Cuvier); Ca-
roun croaker, Nibea albiflora;
yellowdrum, (Richardson),
Pennahia argentata (Hout-
tuyen); silver croaker
Vietnam; Ha-
long Bay
Amin et al.,
2011 b & Amin,
Heckmann,
2012
64
Neoechinorhynchus personatus
Tkach, Sarabeev& Shvetsova, 2014
Neoechinorhynchus ponticus
Amin, Sharifdini, Heckmann,
Rubtsova& Chine, 2020
Mugil cephalus Linn.; flathead
grey mullet
Chelon auratus Risso; golden
grey mullet
Mediterranean
off Tunisia &
Black Sea
Amin et al.,
2020 b
55–60
Oligacanthorhynchidae
Macracanthorhynchus hirudina-
ceus (Pallas, 1781) Travassos, 1917
Sus scrofa Linn.; wild boar Ukraine; Zhyro-
myr Region,
Amin et al.,
2021 d
69–72
Nephridiacanthus major (Brem-
ser, 1811 in Westrumb, 1821)
Golvan, 1962
Hemiechinus auratus (Gme-
lin); Middle Eastern long-
eared hedgehog & Erinaceus
concolor Martin; Eastern
European hedgehog
Iran; Mashhad,
Khorasan
Heckmann
et al., 2013 &
Amin et al.,
2020 c
73–78
Pachysentis canicola Meyer, 1931 Chrysocyon brachyurus (Il-
liger, 1815); maned wolf
USA, Texas Amin et al.,
2021 e
79–82
Polymorphidae
Corynosoma strumosum (Rudol-
phi, 1802) Lühe, 1904
Pusa caspica (Gmelin); Cas-
pian seal
Caspian Sea; Ma-
zandaran, Iran
Amin et al.,
2011 c
83–84
Neoandracantha peruensis Amin
& Heckmann, 2017
Ocypodegaudi chaudii Milne-
Edwards & Lucas; ghost crab
Peru; Pacific
coast at Callao
Amin & Heck-
mann, 2017 a
85–88
Profilicollis altmani (Perry, 1942)
Van Cleave, 1947
Emerita analoga (Simpson);
mole crab & Larus belcheri
(Vigors); Belcher’s gull
Peru; Lurin&
Chorrillos,
Lima, Punta,
Miraflora, Lima
Amin et al.,
2022 a
89–90
268 O. M. Amin, R. A. Heckmann
Southwellina hispida (Van
Cleave, 1925) Witenberg, 1932
Gillichthys mirabilis Cooper;
longjaw mudsucker
USA; California Amin et al.;
2022 b
91–96
Quadrigyridae
Acanthogyrus (Acanthosentis)
kashmirensis Amin, Heckmann
& Zargar, 2017
Schizothorax plagiostomus
Heckel; snow trout; S. labiatus
(McClelland), S. curvifrons
Heckel, S. esocinus Heckel
Kashmir; Jhe-
lum & Sandran
rivers
Amin et al.,
2017 b
97–99
Acanthogyrus (Acanthosentis)
fusiformis Amin, Chaudhary,
Heckmann, Ha & Singh, 2019
Arius sp.; catfish Vietnam; Gulf
of Thailand
Amin et al.,
2019 b
100
Pallisentis (Brevitritospinus)
indica Mital & Lal, 1976
Channa gachua Hamilton;
dwarf snakehead & Channa
punctatus Block & Schneider;
spotted snakehead
India; Kali Nadi
River, Aligarh
Amin et al.,
2017 c
101–102
Pallisentis (Pallisentis) nandai
Sarkar, 1953
Nandus nandus (Hamilton);
Gangetic leaffish
India;
Ganga River,
Calcutta & Bijnor
Amin et al.,
2021 f
103–107
Pallisentis (Pallisentis) paranandai
Amin, Chaudhary, Heckmann,
Rubtsova& Singh, 2021
Channam arulius (Hamilton);
great snakehead
India; Ganga
River at Bijnor,
Uttar Pradesh
Amin et al.,
2021 g
108
Rhadinorhynchidae
Leptorhynchoides polycristatus
Amin, Heckmann, Halajian, El-
Naggar & Tavakol, 2013
Acipenser stellatus Pallas;
starry sturgeon & A. nudiven-
tris Lovetzsky; fringebarbel
sturgeon
Iran; Caspian
Sea Chaparsara-
rea
Amin et al.,
2013c
109
Rhadinorhynchus hiansi Soota &
Bhattacharya, 1981
Ablennes hians Valenciennes;
needlefish & Sarda orientalis
Temminck Schlegel; striped
bonito
Vietnam; Nha-
Trang & India;
Kerala
Amin et al.,
2020 d
113–116
Rhadinorhynchus laterospinosus
Amin, Heckmann & Ha, 2019
Balistes sp., Alectis ciliaris
(Bloch), Auxis rochi (Lacé-
pède), A. thazard (Lacépède)
& 5 other spp.
Vietnam;
Halong Bay and
other Pacific
localities
Amin et al.,
2011d, Amin et
al., 2019 c
117–120
Rhadinorhynchus oligospinosus
Amin & Heckmann, 2017
Scomber japonicus Houttuyn;
chub mackerel & Trachurus
murphyi Nichols; Chilean
Jack mackerel
Peru; Port of
Chicama, La
Libertad
Amin & Heck-
mann,
2017 b
110–112
Transvenidae
Paratrajectura longcementglan-
datus Amin, Heckmann & Ali,
2018
Nemipterus japonicus Bloch;
Japanese threadfin bream &
Otolithes ruber Bloch &
Schneider; tigertooth croaker
Arabian Gulf;
Iran & Iraq at
Basrah
Amin et al.,
2018 c
121–126
Results
The SEM of 30 species of acanthocephalans in 13 families representing the widest
morphological and anatomical spectra that we have come across, among the many species
that we have studied, are selected for this presentation. The quality and extent of diversity
covered is limited to the species that we have sampled for which we have selected SEM
images as reported herein. From our experience, this presentation covers most, if not all,
morphological and structural diversity of proboscides and hooks in the 13 selected families.
The coverage is presented alphabetically by family following the arrangement in table 1,
and not by any specific taxonomic order. SEM figures emphasize hook arrangement on
the proboscis, hook shape, size, external topography, and internal anatomy. Some of the
images are published herein for the first time. The text gives an overview by family.
269SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Arhythmacanthidae
This family is represented by one species only, H. holospinus, which characteristically
has a small anteriorly globular proboscis with long smooth anterior hooks having a heavy
core and thin cortical layer continuing into the roots (figs 1–3). See Legends.
Cavisomidae
Both cavisomid species presented, C. magnum and P. magnus (figs 4–9) have relatively
long proboscides with many uniform hooks in longitudinal rows; smallest hooks apical and
posterior. Hooks are without prominent grooves or serrations. Serrations are shallow in
C. magnum (fig. 5) or nearly absent in P. magnus (fig. 8). Structurally, cross sections show
a prominent core and narrow to moderate cortical layer (figs 6, 9).
Centrorhynchidae
The two representative species in this family (figs 10–18) have either globular proboscis
or cylindrical with two types of hooks (see figs 10 & 13) separated at the insertion point
of the anterior end of the receptacle to the inner proboscis wall. Hooks are usually in
longitudinal rows elevated or recessed (fig. 15) with either external serrations (fig. 11) or
latero-ventral pebble-like surface (fig. 16). Hook core is usually extensive and solid and the
cortical layer thin (figs 17, 18).
Echinorhynchidae
Five species in three genera are represented in this family (figs 19–30). In
A. parallelcemenglandatus, a few similar hooks in longitudinal rows (fig. 19) have extensive
micropores for nutritional uptake (fig. 20). They also have an extensive solid core and
moderate cortical layer (figs 21, 22). Pseudoacanthocephalus lutzi also has hooks with
micropores (fig. 24), and some specimens of E. salmonis from Lake Baikal have additional
apical mini-hooks (fig. 23). Anterior hooks of E. cinctulus, also from Lake Baikal, have
unique dorsal mini-hooks (spurs) branching off the dorsal side of the original hooks (figs
25–27). Hooks of E. cinctulus also have well developed core and slim cortical layer (fig. 28).
Most species of Echinorhynchus have many similar hooks in longitudinal rows. In E. gadi,
anterior hooks are usually raised (fig. 29) and posterior hooks are recessed deeper in the
proboscis cuticle (fig. 30).
Gigantorhynchidae
Three species in two genera are presented (figs 31–38). Intraproboscis sanghae has a
large apically flat proboscis (figs 31–33) enclosing the receptacle (fig. 32). Its hooks have
serrations on the latero-ventral side (fig. 34). Two species of Mediorhynchus from birds
have 2-part proboscides with 2 types of smooth hooks each (fig. 35) embedded in elevated
cuticular lobes (fig. 36) each with lateral grooves (figs 37, 38).
Heteracanthocephalidae
Aspersentis megarhynchus exhibits the characteristic feature of heteracanthocephalid
acanthocephalans of dorso-ventral differentiation of hooks (fig. 39). The sharp posterior
angulation of smooth hooks (figs 40, 41) and the relatively thick cortical hook layer (fig. 42)
are also characteristic.
Moniliformidae
All species of Moniliformis presented were recovered from mammals (hedgehogs).
The hooks of M. cryptosaudi, a cryptic species (figs 43–48), are distinguished from
those of M. saudi, its mirror image (figs 49, 50), by having a collagenous spongy texture
(figs 43–48) and the virtual absence of calcium and phosphorous in its composition.
The normal looking hooks of M. saudi (figs 49, 50) have the usual levels of calcium
270 O. M. Amin, R. A. Heckmann
and phosphorous. The hooks of both species are smooth and have no evident special
serrations, micropores, or projections. The hooks of adult M. kalahariensis (figs 53,
54) however, were similar to those of 2 species of Mediorhynchus from birds (figs 37,
38) in having distinct lateral grooves. These lateral grooves appear to manifest
developmentally as underdeveloped immature worms in the intermediate cockroach
host do not have them (fig. 52) and juveniles show stages in their development
(fig. 53).
Neoechinorhynchidae
Five species of Neoechinorhynchus were recovered from marine fish in various waters
(figs 55–68). Hooks of most species, i.e., N. dimorphospinus, N. personatus, and N. ponticus
had solid well-developed core and thin corrugated coat with deep external lamellae
(figs 56–60, 62, 63). The hooks of N. johnii and N. manubrianus also had solid to variably
vacuolated core (figs 64, 66–68) and thin cortical layer that did not show evident lamellae,
micropores, or branching.
Oligacanthorhynchidae
Macracanthorhynchus hirudinaceus (figs 69–72), N. major (figs 73–78), and P. canicola
(figs 79–82) are parasites of mammals that have developed very similar morphological and
structural features. The shape of the proboscis, the rounded heavy hooks deeply set within
cuticular elevations, the proximal base of hooks with ventral expansion, and their solid core
almost without cortical layer are all features in common. The proboscis armature is clearly
designed for strength.
Polymorphidae
The four presented species in four genera (figs 83–96) have been recovered
from mammals, birds, and fish as well as from crabs (intermediate hosts) and hooks’
morphology offered a corresponding variety of shapes and morphology. The proboscis
of all species, except P. altmani, enlarges posteriorly (figs 83, 85, 91) and hooks in all
proboscides are similar, except in C. strumosum where they enlarge considerably at
bulge (fig. 83). In addition, anterior hooks of S. hispida are more slender (fig. 92) than
shorter middle hooks (fig. 93). All hooks are smooth without lamellae but only those of
C. strumosum that have many micropores (fig. 84). Hook sections of the polymorphid
worms that we examined had virtually no cortical layer and either totally solid (fig. 88)
or partially vacuolated core (figs 94, 96). Intraspecific variability in degree of vacuolation
is noted.
Quadrigyridae
Five species in two genera, all from freshwater fish in India and Vietnam, are presented
(figs 97–108). No micropores or longitudinal grooves on the epicuticle of hooks were found
in this family. The organization of hooks (figs 97, 100, 101, 103) was comparable except
for the additional presence of inter-hook bumps in P. indica (fig. 101). The proboscis of
A. fusiformis is unusual in being narrow anteriorly and with the basal hooks being the
largest (fig. 100). Gallium-cut sections show that hooks had a moderate cortical layer
and either near solid core as in P. nandai (figs 106, 107) or totally vacuolated core as in
A. kashmirensis (fig. 99) making hooks appearing collapsed (fig. 98). Hooks in this family
were smooth except for the presence of noticeable serrations on the basal latero-ventral
aspects of hooks as in P. nandai and P. paranandai (figs 104, 105, 108).
Rhadinorhynchidae
Four species in two genera (figs 109–120) from marine fish in Iran, Vietnam, and Peru
are presented. The Proboscis is long with many hooks in longitudinal rows (figs 110, 113,
271SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
117). Hooks in all species have epicuticular serrations that vary from prominent (figs 109,
114, 115, 118, 119) to barely noticeable as in R. oligospinosus (fig. 111). Hook cortical layer is
of moderate thickness and the core varied between solid as in R. hiansi and R. laterospinosus
(figs 116, 120) to partially vacuolated as in R. oligospinosus (fig. 112) reflecting on the hooks
looking emaciated (fig. 111).
Transvenidae
Only one species of Paratrajectura, P. longcementglandatus, is known in this
family. It has 2 types of hooks, larger elevated anterior hooks (fig. 121) and smaller
recessed hooks posteriorly (fig. 122), in longitudinal rows. Longitudinal Gallium-
cut sections show hooks of both types to have solid core and thin cortical layer but
variations in cross sections show partial vacuolations (fig. 125). Most unusually, some
hooks branch (fig. 126).
Discussion
The evolutionary significance and value of the various adaptations in hook morphology,
surface texture, anatomy, structural strength, and hardness vs. flexibility directly contribute
to acanthocephalans’ attachment and survival in host gut and avoiding loss once
established. Examples include the epicuticular hook lamellae in Neoechinorhynchidae and
Rhadinorhynchidae, the deep lateral grooves in hooks of species of Mediorhynchus and
Moniliformis, the solid hook core in Oligacanthorhynchidae and species of Centrorhynchus,
Neoandracantha, and Rhadinorhynchus. spurs on the anterior hooks of E. cinctulus and
double branching hooks in P. longcementglandatus also contribute to more efficient
attachment. In addition to the solid hook core of acanthocephalans of land mammals such
as Oligacanthorhynchidae, hooks are rendered even stronger by having a ventral expansion
near their base interfacing with proboscis cuticle and sub-cuticle for additional strength
and support. Related metabolic function includes the contribution of hooks of some species
to nutrition uptake through a multitude of micropores in the hooks as is commonly the
case in the trunk. In our study, we found micropores in hooks of acanthocephalans in
2 families, A. parallelcemenglandatus, and P. lutzi (Echinorhynchidae), C. strumosum
(Polymorphidae). In general, we found a relationship between host groups (classes) and
proboscis hooks’ morphology and anatomy. The energy dispersive X-ray analysis has been
used to describe the level of metals that contribute to the hardness and flexibility of hooks
in many reported species.
This project was supported in part by the Department of Biology, Brigham Young University (BYU),
Provo, Utah, and by the Parasitology Center, Inc. (PCI), Scottsdale, Arizona. We thank Elisabeth Trimble, Bean
Museum (BYU) for expert help in the preparation and organization of plates and figures and to Dr. Nataliya
Rubtsova (PCI) for additional help. We extend our special appreciation to Michael Standing, Electron Optics
Laboratory (BYU), for his technical help and expertise in the creation of the SEM images.
Declarations
Compliance with ethical standards
Conflict of interest. The authors declare no conflicts of interest or competing interests.
Ethical approval. The authors declare that they have observed all applicable ethical standards.
Availability of data. All presented and related data are available by contacting the senior author especially for
previously unpublished images.
272 O. M. Amin, R. A. Heckmann
Figs 1—6. SEM of proboscides and hooks
of Heterosentis holospinus (Arythmacan-
thidae) (figs 1—3) and Cavisoma mag-
num (Cavisomidae) (figs 4–6): 1 — pro-
boscis of H. holospinus with very long
anterior hooks and spiny anterior trunk
with spine-free anterior cone; 2 — high
magnification of posterior spines; 3 — a
Gallium-cut longitudinal section of an
anterior hook showing thin cortical layer
and thick solid core with high levels of
calcium and phosphorous; 4 — a partially
retracted proboscis of C. magnum show-
ing the gradual reduction in hook size
posteriorly; 5 — a high magnification of a
middle hook showing its shallow serrated
surface; 6 — a Gallium-cut cross section
of a middle hook showing its moderately
thick cortical layer and core with high sul-
fur content.
Figs 7–12. SEM of proboscides and hooks
of Parhadinorhynchus magnus (Cavi-
somidae) (figs 7–9) and Centrorhynchus
globirostris (Centrorhynchidae) (figs 10–
12): 7 — long cylindrical proboscis with
gradually decreasing hook size posterior-
ly; 8 — a ventral hook; note its curvature
and robust base; 9 — a Gallium-cut cross
section of a middle hook showing in thick
core with high phosphorous and calcium
content, and thin cortical layer; 10 — the
globular proboscis of C. globirostris show-
ing the separation line between the larger
anterior hooks and the smaller posterior
spine-like hooks where the anterior end
of the receptacle inserts; 11 — an anterior
hook showing the ribbed surface found
on all hooks; 12 — a Gallium-cut longitu-
dinal section of a hook showing its thick
core and marginal cortical layer.
273SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Figs 13–18. SEM of proboscis and hooks
of Centrorhynchus globocaudatus (Cen-
trorhynchidae): 13 — the proboscis of a
female specimen showing the spiral ar-
rangement of longitudinal hook rows;
14 — the prominent bare-apical surface
of a proboscis; 15 — near apical and an-
terior hooks in indentations on proboscis
surface; 16 — basal part of hook showing
latero-ventral pebble-like protrusions;
17, 18 — a longitudinal and cross Galli-
um-cut hook sections showing its promi-
nent core and very thin cortical layer with
high levels of calcium and phosphorous.
Figs 19–24. SEM of proboscis and hooks of
Acanthocephalaus parallelcemenglanda-
tus (figs 19–22), Echinorhynchus salmonis
(fig. 23), and Pseudoacanthocephalus lutzi
(fig. 24) (Echinorhynchidae): 19 — a typi-
cal proboscis A. parallelcementglandatus
with parallel sides and a sensory pore on
the neck; 20 — a high magnification of
a hook showing numerous micropores;
21, 22 — a Gallium-cut lateral and cross
sections of hooks with solid core extend-
ing into the root and a relatively thick cor-
tical layer and with high levels of calcium
and moderate levels of phosphorous. Sul-
fur levels were negligible; 23 — an apical
view of a proboscis of E. salmonis showing
2 odd mini-hooks; 24 — a high magnifica-
tion of a hook of P. lutzi showing many
micropores.
274 O. M. Amin, R. A. Heckmann
Figs 25–30. SEM of proboscis and hooks
of Echinorhynchus cinctulus (figs 25–28)
and Echinorhynchus gadi (figs 29–30)
(Echinorhynchidae): 25–27 — anterior
hooks in some specimens of E. cinctulus
with a variety of spines or thorns mostly
on the dorsal side of hooks; 28 — the well-
developed core and thinner cortical layer
of a Gallium-cut longitudinal section of
a middle hook; 29 — a proboscis of an
E. gadi specimen with 15 hooks per row
and elevated anterior hooks; 30 — a high
magnification of depressed posterior
hooks on the same proboscis in fig. 29.
Figs 31–36. SEM and microscope im-
age of proboscis and hooks of Intrapro-
boscis sanghae (figs 31–34) and SEM of
Mediorhynchus africanus (figs 35, 36)
(Gigantorhynchidae): 31 — anterior and
posterior proboscis of I. sanghae; 32 —
a microscope black and while image of
proboscides showing the dark receptacle
within the posterior proboscis; 33 — the
flat apical end of the anterior proboscis
with hooks; 34 — a higher magnification
of an anterior hook showing the lamellar
texture of the lateral and ventral surface;
35 — proboscis of M. africanus showing
the divide between anterior hooks and
posterior spine-like hooks; 36 — face view
of anterior hooks of M. africanus showing
proboscis swelling at insertion.
275SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Figs 37–42. SEM of proboscis and hooks
of Mediorhynchus africanus (fig. 37),
Mediorhynchus gallinarum (fig. 38) (Gi-
gantorhynchidae), and Aspersentis mega-
rhynchus (figs 39–42) (Heteracanthoce-
phalidae): 37 — lateral view of anterior
hooks of M. africanus showing the lat-
eral grooves; 38 — lateral view of anterior
hooks of M. gallinarum showing the same
type of lateral grooves; 39 — proboscis
of A. megarhynchus showing the spiral
arrangement of hook rows, the gradual
decline in hook size posteriorly, and the
larger ventral hooks; 40 — anterior hook
showing its extreme angular curvature;
41 — high magnification of a hook with
very small micropores on its surface;
42 — a Gallium-cut cross section of a
large hook exhibiting a large solid core
with very high level of Calcium and a
relatively thick cortical layer with highest
level of sulfur.
Figs 43–48. SEM of proboscis and hooks
of Moniliformis cryptosaudi (Monilifor-
midae): 43 — the proboscis of a male spec-
imen showing the smaller posterior hooks
and the dome-shaped proboscis surface at
hook insertion site; 44 — the apical end of
a proboscis showing 2 sensory pores; 45 —
a posterior hook in a dome-like proboscis
base at insertion point; 46 — a Gallium-
cut hook base showing its collagenous,
porous, and spongy composition; 47 — a
middle hook showing the porous texture
of its collagenous forming elements; 48 —
a Gallium-cut section of a posterior hook
and root showing the continuity of their
collagenous and porous nature. The levels
of calcium, sulfur and phosphorous in all
hooks were very scarce.
276 O. M. Amin, R. A. Heckmann
Figs 49–54. SEM of proboscis and hooks
of Moniliformis Saudi (figs 49–50) and
Moniliformis kalahariensis (figs 51–54)
(Moniliformidae): 49 — apical end of
a proboscis of M. Saudi also had 2 sen-
sory pores like M. cryptosaudi; 50 — a
middle hook with high levels of calcium
and phosphorous; 51 — the proboscis of
M. kalahariensis; hooks gradually de-
crease in size posteriorly; 52 — undevel-
oped hooks from cockroach; 53 — devel-
oping hooks in a juvenile beginning to
develop lateral grooves; 54 — fully devel-
oped hooks in an adults with completely
formed lateral grooves. Hooks of M. kala-
hariensis, also had high levels of calcium
and phosphorous like hooks of M. saudi.
Figs 55–60. SEM of proboscis and hooks
of Neoechinorhynchus ponticus (figs 55,
56) and Neoechinorhynchus personatus
(figs 57–60) (Neoechinorhynchidae):
55 — proboscis of N. ponticus with a
sensory pore at level of posterior hooks;
56 — anterior hook showing angle of pro-
jection and external serrations; 57 — pos-
terior hook of N. personatus showing serra-
tions; 58 — a high magnification showing
pattern of serrations on an anterior hook;
59 — outermost layer of a hook showing
detail of longitudinal serrations in cross
section; 60 — a part of a Gallium-cut sec-
tion of an anterior hook showing its thin
cortical layer and dense core, and its ar-
ticulation vs. the root of the same core
density.
277SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Figs 61–66. SEM of proboscis and hooks
of Neoechinorhynchus dimorphospinus
(figs 61–64) and Neoechinorhynchus joh-
nii (figs 65–66) (Neoechinorhynchidae):
61 — the proboscis of a specimen of
N. dimorphospinus showing the longer
lateral hooks (top & bottom); 62 — a
longer anterio-lateral hook showing lon-
gitudinal serrations; 63 — a Gallium-cut
cross section of an anterior hook showing
its extensive core and thin serrated corti-
cal layer; 64 — a longitudinal section of an
anterior longer hook showing the conti-
nuity of its solid core with that of the root;
65 — the globular proboscis and narrow
neck of a N. johnii male specimen; 66 —
a Gallium cut longitudinal section of an
anterior hook showing its thick and solid
core continuous with that of the root and
its thin cortical layer.
Figs 67–72. SEM of proboscis and hooks
of N. johnii (Neoechinorhynchidae) (figs
67–68) and Macracanthorhynchus hirudi-
naceus (Oligacanthorhynchidae) (figs 69–
72): 67–68 — variations in the degree of
vacuolations of partially hollowed hooks
of N. johnii specimens in Gallium-cut sec-
tions; 69 — the girthy proboscis showing
the organization of hooks of various sizes
antero-posteriorly and the robust neck;
70 — the external shape and curvature of
a large hook with smooth surface embed-
ded in a cuticular proboscis distention;
71, 72 — a Gallium-cut cross sections of
a small hook near its base showing ventral
distention (fig. 71), and of a larger round
hook near its terminal end (fig. 72).
278 O. M. Amin, R. A. Heckmann
Figs 73–78. SEM of proboscis and hooks
of Nephridiacanthus major (Oligacan-
thorhynchidae): 73 — hook arrangement
and prominent neck of N. major; 74 — a
dorso-lateral view of proboscis showing
slightly elevated surface of apical organ;
75 — dorsal view of a short posterior
hook; 76 — a Gallium-cut section of a
hook near its base with prominent ventral
expansion similar to that in M. hirudina-
ceus with almost no cortical layer seen;
77 — a perfectly spherical Gallium cut
cross section of another hook near its
terminal end; 78 — a lateral Gallium-cut
section of another hook showing the same
core-cortical relationships as in figs 76 &
77. Note the continuity with the elaborate
root.
Figs 79–84. SEM of proboscis and hooks
of Pachysentis canicola (Oligacantho-
rhynchidae) (figs 79–82) and Corynosoma
strumosum (Polymorphidae) (figs 83, 84):
79 — the proboscis of a female P. canicola
showing hook arrangement and sensory
pores at posterior proboscis and neck;
80 — an anterior hook deeply recessed in
thick cuticular fold; 81 — a posterior hook
also deeply recessed in a boat-like cuticu-
lar fold; 82 — a Gallium-cut cross section
of a hook near its base showing the ventral
protrusion as seen in other oligacantho-
rhynchid genera: Macracanthorhynchus
and Nephridiacanthus; 83 — the probos-
cis of a specimen of C. strumosum show-
ing its bare apical end and larger hooks at
the bulge; 84 — a high magnification of a
hook showing micropores.
279SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Figs 85–90. Proboscis and hooks of Neo-
andracantha peruensis (figs 85–88) and
Profilicollis altmani (figs 89–90) (Poly-
morphidae): 85 — the proboscis of a
cystacanth of N. peruensis showing the
arrangement of hooks on all parts of the
proboscis; 86 — a higher magnification of
hooks deeply embedded in cuticular folds
of proboscis showing their shape and ori-
entation; 87–88 — a Gallium-cut longitu-
dinal and cross sections of hooks showing
their solid core and thin cortical layer ex-
hibiting high levels of calcium and phos-
phorous and miniscule levels of sulfur;
89 — mid-proboscis section in a speci-
men of P. altmani showing deeply em-
bedded hooks in cuticular furrows of the
proboscis; 90 — an enlarged hooks from
fig. 89 showing its girth being almost as
wide at base as it is long. These hooks had
high levels of sulfur and low levels of cal-
cium and phosphorous.
Figs 91–96. Proboscis and hooks of South-
wellina hispida (Polymorphidae): 91 — a
proboscis of a juvenile S. hispida showing
the long anterior hooks, the shorter and
thicker middle hooks at swelling, and the
smaller posterior hooks; 92 — a few ante-
rior hooks; 93 — shorter and more robust
middle hooks at swelling; 94–95 — varia-
tions on the degree of vacuolation of the
core of hooks with relatively thick corti-
cal layer; 96 — a Gallium-cut section of a
middle hook showing a thin cortical layer
and solid core.
280 O. M. Amin, R. A. Heckmann
Figs 97–102. Proboscis and hooks of
Acanthogyrus (Acanthosentis) kashmiren
sis (figs 97–99), Acanthogyrus (Acant
hosentis) fusiformis (fig. 100), and Palli
sentis (Brevitritospinus) indica (figs
101–102) (Quadrigyridae): 97 — proboscis of
A. kashmirensis showing hook arran
gement and sensory pore at its base;
98 — profile of anterior and middle hooks
showing their emaciated appearance;
99 — the appearance of the hooks in fig.
98 is explained by their hollow core; see
this figure of a Gallium-cut cross section of
an anterior hook; 100 — the unusual shape
of the proboscis of A. fusiformis with the
smaller hooks on the anterior constricted
part of the proboscis; 101 — the probos-
cis of P. indica showing proboscis bumps
and sensory pore at its posterior end;
102 — a middle hook showing its angle
and relative dimensions.
Figs 103–108. Proboscis and hooks of Pal-
lisentis (Pallisentis) nandai (figs 103–107)
and Pallisentis (Pallisentis) paranandai
(fig. 108) (Quadrigyridae): 103 — an api-
cal view of the proboscis of P. nandai
showing the hook arrangement and the
proboscis bumps; 104 — an anterior hook
with latero-ventral serrations; 105 — a
higher magnification of the base of an an-
terior hook at indented insertion in ele-
vated proboscis ring; note the latero-ven-
tral serrations; 106–107 — a Gallium-cut
longitudinal and cross sections of anterior
hooks showing the proportion of cortical
and core layers and continuity with root
elements. These hooks had very high lev-
els of calcium and sulfur but negligible
levels of phosphorous; 108 — anterior
and middle hooks of P. paranandai also
showing elevated serrations at their base.
281SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Figs 109–114. Proboscis and hooks of
Leptorhynchoides polycristatus (fig. 109),
Rhadinorhynchus oligospinosus (figs
110–112), Rhadinorhynchus hiansi (figs
113–114) (Rhadinorhynchidae): 109 —
the particular pattern of serrations on
a middle hook of L. polycristatus can be
seen; all hooks are similarly serrated; 110–
111 — the proboscis and anterior hook of
R. oligospinosus; note the hook curvature
and thickness at base; 112 — a Gallium
cut hook showing its thick cortical layer
and partially vacuolated core; 113 — a
very long proboscis with many hooks of
R. hiansi; 114 — deeply set almost strait
middle hooks barely showing their tex-
ture.
Figs 115–120. Proboscis and hooks of
Rhadinorhynchus hiansi (cont.) (figs
115–116), Rhadinorhynchus laterospino-
sus (figs 117–120) (Rhadinorhynchidae):
115 — a high magnification of a R. hiansi
hook showing detail of its external stria-
tions; 116 — a longitudinal Gallium-cut
section of a hook showing a thin cortical
layer and a dense core. Whole anterior
hooks have high levels of calcium, mod-
erate levels of phosphorous and sulfur;
117 — the proboscis of R. laterospinosus
with many hooks in longitudinal rows;
118–119 — the angle of a middle hook
and the serrated pattern on its surface;
120 — a Gallium cut cross section of an-
other hook showing its dense core and
thin cortical layer. These hooks have high
levels of sulfur and low levels of calcium
and phosphorous.
282 O. M. Amin, R. A. Heckmann
Figs 121–126. Proboscis and hooks of Para-
trajectura longcementglandatus (Trans
venidae): 121 — proboscis of P. longce-
mentglandatus with longer anterior
hooks; 122 — shorter and more deeply
embedded posterior hooks. Note sensory
pore just posterior to basal hooks; 123,
124 — a Gallium-cut longitudinal sec-
tions of a middle and a more posterior
hook, respectively, showing consistent
solid core and thin cortical layers contin-
uous with roots; 125 — a partially vacu-
olated core of another hook in a Gallium
cut cross section; 126 — an unusually
branched hook in middle of proboscis.
References
Amin, O. M. 2013. Classification of the Acanthocephala. Folia Parasitologica, 60 (4), 273–305.
Amin, O. M., Chaudhary, A., Heckmann, R., Ha, N. V., Singh, H. S. 2019 a. Redescription and molecular
analysis of Neoechinorhynchus (Neoechinorhynchus) johnii Yamaguti, 1939 (Acanthocephala,
Neoechinorhynchidae) from the Pacific Ocean off Vietnam. Parasite, 26, 43.
Amin, O. M., Chaudhary, A., Heckmann, R., Ha, N. V., Singh, H. S. 2019 b. The morphological and molecular
description of Acanthogyrus (Acanthosentis) fusiformis n. sp. (Acanthocephala: Quadrigyridae) from
the catfish Arius sp. (Ariidae) in the Pacific Ocean off Vietnam, with notes on zoogeography. Acta
Parasitologica, 64 (4), 779–796. https://doi.org/10.2478/s11686-019-00102-3
Amin, O. M., Chaudhary, A., Heckmann, R .A., Swenson, J., Singh, H. S. 2021 e. Redescription and Molecular
Characterization of Pachysentis canicola Meyer, 1931 (Acanthocephala: Oligacanthorhynchidae) from the
Maned Wolf, Chrysocyon brachyurus (Illiger, 1815) in Texas. Acta Parasitologica. https://doi.org/10.1007/
s11686-021-00458-5
Amin, O. M., Chaudhary, A., Heckmann, R. A., Rubtsova, N. Y., Singh, H. S. 2021 g. Description of Pallisentis
(Pallisentis) Paranandai n. sp. (Acanthocephala: Quadrigyridae) from the Intestine of the Great snake-
head Channa marulius (Hamilton) (Channidae) in the Ganga River, India. International Journal of Zool-
ogy and Animal Biology, 4 (4), 000321. Medwin Publishers ISSN: 2639-216X
Amin, O. M. Chaudhary, A. Singh, H. S. 2022 b. Morphological and molecular description of immature South-
wellina hispida (Van Cleave, 1925) Witenberg, 1932 (Acanthocephala: Polymorphidae) from the body
cavity of the paratenic host Gillichthys mirabilis Cooper (Gobiidae) in California, with analyses of the
chemical composition of hooks and spines. Acta Parasitol. https://doi.org/10.1007/s11686-022-00552-2.
April, 2022.
Amin, O. M., Evans, P., Heckmann, R. A., El-Naggar, A. M. 2013 a. The description of Mediorhynchus africanus
n. sp. (Acanthocephala: Gigantorhynchidae) from galliform birds in Africa. Parasitology Research, 112
(8), 2897–2906.
Amin, O. M., Ha, N. V., Ha, D. N. 2011 b. First report of Neoechinorhynchus (Acanthocephala: Neoechino-
rhynchidae) from marine fish of the eastern seaboard of Vietnam, with the description of six new species.
Parasite, 18 (1), 21–34.
Amin, O. M., Heckmann, R. A. 2014. First description of Pseudoacanthocephalus lutzi from Peru using SEM.
Scientia. Parasitologica, 15 (1), 19–26.
283SEM Study of Hooks in the Acanthocephala with Emphasis on Structural-Functional Relationships
Amin, O. M., Heckmann, R. A. 2017 a. Neoandracantha peruensis n. gen., n. sp. (Acanthocephala: Polymor-
phidae) described from cystacanths infecting the ghost crab Ocypode guadichaudi in the Peruvian coast.
Parasite, 24, 40.
Amin, O. M., Heckmann, R. A. 2017 b. Rhadinorhynchus oligospinosus n. sp. (Acanthocephala, Rhadinorhyn-
chidae) from mackerels in the Pacific Ocean off Peru and related rhadinorhynchids in the Pacific, with
notes on metal analysis. Parasite, 24, 19.
Amin, O. M., Heckmann, R. A., Ha, N. V. 2011 a. Description of Heterosentis holospinus n. sp. (Acanthoceph-
ala: Arhythmacanthidae) from the Striped Eel Catfish, Plotosus lineatus, in Halong Bay, Vietnam, with a
Key to Species of Heterosentis and reconsideration of the Subfamilies of Arhythmacanthidae. Compara-
tive Parasitology, 78 (1), 29–38
Amin, O. M., Heckmann, R. A., Halajian, A., El-Naggar, A. M. 2011 c. The morphology of a unique popula-
tion of Corynosoma strumosum (Acanthocephala: Polymorphidae) from the Caspian Seal, Pusa caspica,
in the land-locked Caspian Sea using SEM, with special notes on histopathology. Acta Parasitologica, 56
(4), 438–445.
Amin, O. M., Heckmann, R. A., Ha, N. V. 2011 d. Description of two new species of Rhadinorhynchus (Acan-
thocephala: Rhadinorhynchidae) from marine fish in Halong Bay, Vietnam, with a key to species. Acta
Parasitologica, 56 (1), 67–77.
Amin, O. M., Heckmann, R. A. 2012. Expanded description of Neoechinorhynchus (Hebesoma) manubrianus
from marine fish in Halong Bay, Vietnam. Parasite, 19, 267–270
Amin, O. M., Heckmann, R. A., Sahara, A., Yudhanto, S. 2013 b. The finding of Mediorhynchus gallinarum
(Acanthocephala: Gigantorhynchidae) in chickens from Indonesia, with expanded description using
SEM. Comparative Parasitology, 80 (1), 39–46
Amin, O. M., Heckmann, R. A., Halajian, A., El-Naggar, A. M, Tavakol, S. 2013 c. The description and histo-
pathology of Leptorhynchoides polycristatus n. sp. (Acanthocephala: Rhadinorhynchidae) from sturgeons,
Acipenser spp. (Actinopterogii: Acipenseridae) in the Caspian Sea, Iran, with emendation of the genus.
Parasitology Research, 112 (11), 3873–3882.
Amin, O. M., Heckmann, R. A., Halajian, A., El-Naggar, A., Tavakol, S. 2014 b. Description of Moniliformis ka-
lahariensis (Acanthocephala: Moniliformidae) from the South African hedgehog, Atelerix frontalis (Eri-
naceidae) in South Africa. Comparative Parasitology, 81 (1), 33–43.
Amin, O. M., Heckmann, R. A., Baldanova, D. R. 2015 a. Revisiting echinorhynchid acanthocephalans in Lake
Baikal with the use of scanning electron microscopy, with some taxonomic reconsiderations. Comparative
Parasitology, 82 (1), 29–39.
Amin, O. M., Heckmann, R. A., Wilson, E., Keele, B., Khan, A. 2015 b. The description of Centrorhynchus globi-
rostris n. sp. (Acanthocephala: Centrorhynchidae) from the pheasant crow, Centropus sinensis (Stephens)
in Pakistan, with gene sequence analysis and emendation of the family diagnosis. Parasitology Research,
114 (6), 2291–2299.
Amin O. M., Heckmann, R. A., Ali, A.H., El-Naggar, A. M., Khamees N. R. 2015 c. New Features of Neoechinorhyn-
chus (Neoechinorhynchus) dimorphospinus (Acanthocephala: Neoechinorhynchidae) from recent collections in
the Arabian Gulf using SEM, with notes on histopathology. Comparative Parasitology, 82 (1), 60–67.
Amin, O. M., Heckmann, R. A., Mohammed, O., Evans, R. P. 2016. Morphological and molecular descriptions
of Moniliformis saudi sp. n. (Acanthocephala: Moniliformidae) from the desert hedgehog, Paraechinus
aethiopicus (Ehrenberg) in Saudi Arabia, with a key to species and notes on histopathology. Folia Para-
sitologica, 63, 014.
Amin, O. M., Heckmann, R. A., Zargar, O. R. 2017 b. Description of a new quadrigyrid acanthocephalan from
Kashmir, with notes on metal analysis and histopathology, and a key to species the subgenus Acanthosen-
tis from the Indian subcontinent. Journal of Parasitology, 103 (5), 458–470.
Amin, O. M., Heckmann, R. A., Shareef, A. 2017 c. Redescription of Pallisentis (brevitritospinus) indica
(Acanthocephala: Quadrigyridae) from Channa punctatus Bloch & Schneider (channidae) in Aligarh,
India with new understandings of old structures. Journal of Parasitology, 103 (3), 251–256.
Amin, O. M., Heckmann, R. A., Bannai, M .A. 2018 a. Cavisoma magnum (Cavisomidae), a unique Pacific
acanthocephalan redescribed from an unusual host, Mugil cephalus (Mugilidae), in the Arabian Gulf, with
notes on histopathology and metal analysis. Parasite, 25, 5.
Amin, O. M., Heckmann, R. A., Ha, N. V. 2018 b. Descriptions of Acanthocephalus parallel cementglandatus
(Echinorhynchidae) and Neoechinorhynchus (N.) pennahia (Neoechinorhynchidae) (Acanthocephala)
from amphibians and fish in Central and Pacific coast of Vietnam, with notes on N. (N.) longnucleatus.
Acta Parasitologica, 63 (3), 572–585.
Amin, O. M., Heckmann, R. A., Ali, A. H. 2018 c. The finding of pacific transvenid acanthocephalan in the
Arabian Gulf, with the description of Paratrajectura longcementglandatus n. gen., n. sp. from perciform
fishes and emendation of Transvenidae. Journal of Parasitology, 104 (1), 39–51.
Amin, O. M., Heckmann, R. A., Sharifdini, M., Albayati, N. Y. 2019 b. Moniliformis cryptosaudi n. sp.
(Acanthocephala: Moniliformidae) from the Long-eared Hedgehog Hemiechinus auritus (Gmelin)
(Erinaceidae) in Iraq; A Case of Incipient Cryptic Speciation Related to M. saudi in Saudi Arabia. Acta
Parasitologica, 64 (1), 195–204.
284 O. M. Amin, R. A. Heckmann
Amin, O. M., Heckmann, R. A., Dallares, S., Constenla, M., Ha, N. V. 2019 c. Morphological and molecular
description of Rhadinorhynchus laterospinosus Amin, Heckmann & Ha, 2011 (Acanthocephala:
Rhadinorhynchidae) from marine fish off the Pacific coast of Vietnam. Parasite, 26, 14.
Amin, O. M., Heckmann, R. A., Dallarés, S., Constenla, M., Rubini, S. 2020 a. Description and molecular analysis
of an Italian population of Centrorhynchus globocaudatus (Zeder, 1800) Lühe, 1911 (Acanthocephala:
Centrorhynchidae) from Falco tinnunculus (Falconidae) and Buteo buteo (Accipitridae). Journal of
Helminthology, 94, e207, 1–21. https://doi.org/10.1017/ S0022149X20000887
Amin, O. M., Heckmann, R. A., Dallares, S., Constenla, M., Ha, N. V. 2020 d. Morphological and
molecular description of Rhadinorhynchus hiansi Soota and Bhattacharya, 1981 (Acanthocephala:
Rhadinorhynchidae) from marine fish off the Pacific coast of Vietnam. Journal of Parasitology, 106 (1),
56–70.
Amin, O. M., Sharifdini, M., Heckmann, R. A., Rubtsova, N., Chine, H. J. 2020 b. On the Neoechinorhynchus agilis
(Heckmann Acanthocephala: Neoechinorhynchidae) complex, with a description of Neoechinorhynchus
ponticus n. sp. from Chelon auratus in the Black Sea. Parasite, 27, 48.
Amin, O. M., Sharifdini, M., Heckmann, R. A., Zarean, M. 2020 c. New perspectives on Nephridiacanthus major
(Acanthocephala: Oligacanthorhynchidae) collected from hedgehogs in Iran. Journal of Helminthology,
94, 1–11.
Amin, O. M., Heckmann, R. A., Dallarés, S., Constenla, M., Kuzmina, T. 2021 a. Morphological and molecular
description of a distinct population of Echinorhynchus gadi Zoega in Müller, 1776 (Paleacanthocephala:
Echinorhynchidae) from the pacific halibut Hippoglossus stenolepis Schmidt in Alaska. Acta Parasitologica,
66 (3), 881–898.
Amin, O. M., Heckmann, R. A., Sist, B., Basso, W. U. 2021 b. A review of the parasite fauna of the black-
bellied pangolin, Phataginus tetradactyla lin. (Manidae), from Central Africa with the description of
Intraproboscis sanghae n. gen., n. sp. (Acanthocephala: Gigantorhynchidae). Journal of Parasitology, 107
(2), 222–238.
Amin, O. M., Heckmann, R. A., Dallarés, S., Constenla, M., Rubtsova, N. Yu., Kuzmina, T. 2021 c. New
perspectives on Aspersentis Megarhynchus (Acanthocephala: Heteracanthocephalidae) from Notothenia
coriiceps Richardson (Nototheniidae) in the West Antarctic, with emended generic diagnosis. Journal of
Helminthology 95, 1–14.
Amin, O. M., Heckmann, R. A., Dallarés, S., Constenla, M., Kuzmina, T. 2021 d. New morphological and molecular
perspectives about Macracanthorhynchus hirudinaceus (Acanthocephala: Oligacanthorhynchidae) from
wild boar, Sus scrofa Linn., in Ukraine. Journal of Helminthology, 95, 1–11.
Amin, O. M., Heckmann, R. A., Chaudhary, A., Rubtsova, N. Y., Singh, H. S. 2021 f. Redescription and
molecular analysis of Pallisentis (Pallisentis) nandai Sarkar, 1953 (Acanthocephala: Quadrigyridae) in
India. Journal of Helminthology, 95, 1–20.
Amin, O. M., Nahhas, F. M., Al-Yamani, F., Abu-Hakima, R. 1984. On three acanthocephalan species from
some Arabian Gulf fishes off the coast of Kuwait. Journal of Parasitology, 70 (1), 168–170.
Amin, O. M., Rodríguez, S. M., Heckmann, R. A. 2019 d. Morphological updates and molecular description
of Heterosentis holospinus Amin, Heckmann, & Ha, 2011 (Acanthocephala, Arhythmacanthidae) in the
Pacific Ocean off Vietnam. Parasite, 26, 73.
Amin, O. M., Rodríguez, S. M., Rubtsova, N., Heckmann, R. A., Peña, C., Castro, T., Rivera, F., D’Elía, G. 2022
a. A comparative assessment of the morphology of Profilicollis altmani (Acanthocephala, Polymorphidae)
from crustaceans and shore birds in Peru, with special notes on hook elemental analysis (EDXA), SEM
imaging, histopathology, and molecular profile. Parasite, 29, 9.
Amin, O. M., Sharifdini, M., Heckmann, R. A., Zarean, M. 2020. New perspectives on Nephridiacanthus major
(Acanthocephala: Oligacanthorhynchidae) collected from hedgehogs in Iran. Journal of Helminthology,
94, 1–11.
Ha, N. V., Amin, O. M., Ngo, H. D., Heckmann, R. A. 2018. Descriptions of acanthocephalans, Cathayacanthus
spinitruncatus (Rhadinorhynchidae) male and Pararhadinorhynchus magnus n. sp. (Diplosentidae), from
marine fish of Vietnam, with notes on Heterosentis holospinus (Arhythmacanthidae). Parasite, 25, 35.
Heckmann, R. A., Amin, O. M., Halajian, A., El-Naggar, A. M. 2013. The morphology and histo-pathology of
Nephridiacanthus major (Acanthocephala: Oligacanthorhynchidae) from hedgehogs in Iran. Parasitology
Research, 112 (2), 543–548.
Lee, R. 1992. Scanning electron microscopy and X-ray microanalysis. Prentice Hall, Englewood Cliffs, New
Jersey, 1–464.
Received 4 May 2022
Accepted 3 August 2022
|
| id | oai:ojs.akademperiodyka.org.ua:article-362 |
| institution | Zoodiversity |
| issn | 2707-7268 |
| keywords_txt_mv | |
| language | English |
| last_indexed | 2026-08-21T01:01:24Z |
| publishDate | 2022 |
| publisher | Publishing House "Akademperiodyka" of the National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | ojsakademperiodykaorgua/98/315456fa2a7c78360538b1735becfd98.pdf |
| spelling | oai:ojs.akademperiodyka.org.ua:article-3622026-08-20T12:37:15Z SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships Amin, O. M. Heckmann, R. A. Acanthocephala hook morphology and anatomy scanning electron microscopy functional relationships The retractable proboscis of acanthocephalans is equipped with hooks for attachment to the intestine of the definitive host. Throughout their evolutionary history, acanthocephalans have developed a variety of ways to maximize their anchoring to host gut and to avoid dislodgement. Hooks vary in their size and shape along the longitudinal axis of the proboscis, texture,  structure, and hardness as well as in their contribution to the absorption of nutrients. Hooks also vary in their chemical composition, especially calcium, phosphorus, and sulfur, contributing to their hardness. Hook roots are paramount in anchoring them to the cuticular and subcuticular layers of the proboscis. Roots vary in size and shape and are often simple and directed posteriorly but often have anterior manubrial or may be vestigial or absent especially posteriorly. The core layer of roots is usually continuous with that of the hook. Hooks often, but not always, maintain a similar pattern in families. Because of the inconsistencies and inadequacies in the description of hooks, especially in line drawings, in various groups of acanthocephalans, we have decided to provide the largest assortment of morphological and anatomical variabilities among the many species that we have studied over the years. We are, thus, reporting the SEM of hooks of 30 selected species of acanthocephalans in 13 families in an attempt to elucidate patterns and trends characteristic of acanthocephalan families. Publishing House "Akademperiodyka" of the National Academy of Sciences of Ukraine 2022-08-16 Article Article application/pdf https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/article/view/362 10.15407/zoo2022.04.265 Zoodiversity; Vol. 56 No. 4 (2022): Zoodiversity Zoodiversity (Vestnik Zoologii); Том 56 № 4 (2022): Zoodiversity 2707-7268 2707-725X 10.15407/zoo2022.04 en https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/article/view/362/173 Copyright (c) 2022 O. M. Amin, R. A. Heckmann |
| spellingShingle | Amin, O. M. Heckmann, R. A. SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships |
| title | SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships |
| title_full | SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships |
| title_fullStr | SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships |
| title_full_unstemmed | SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships |
| title_short | SEM study of hooks in the Acanthocephala with emphasis on structural-functional relationships |
| title_sort | sem study of hooks in the acanthocephala with emphasis on structural-functional relationships |
| topic_facet | Acanthocephala hook morphology and anatomy scanning electron microscopy functional relationships |
| url | https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/article/view/362 |
| work_keys_str_mv | AT aminom semstudyofhooksintheacanthocephalawithemphasisonstructuralfunctionalrelationships AT heckmannra semstudyofhooksintheacanthocephalawithemphasisonstructuralfunctionalrelationships |