Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni
Amblypygi have a tropical and sub-tropical distribution and their first of the four pairs of legs, is modified as feelers. Their activity period and dark habitats render visual cues ineffective and they rely on non-visual sensory perception. There is agreement among researchers that the whip spiders...
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| Date: | 2023 |
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| author | Borkar, M. R. Quadros D'Sa , V. Sail , P. Lizanne, M. A. C. |
| author_facet | Borkar, M. R. Quadros D'Sa , V. Sail , P. Lizanne, M. A. C. |
| author_institution_txt_mv | [
{
"author": "M. R. Borkar",
"institution": "Department of Zoology, Carmel College for Women, Goa University, Goa, India",
"orcid": ""
},
{
"author": "V. Quadros D'Sa ",
"institution": "Department of Zoology, Carmel College for Women, Goa University, Goa, India",
"orcid": ""
},
{
"author": "P. Sail ",
"institution": "Department of Zoology, Carmel College for Women, Goa University, Goa, India",
"orcid": ""
},
{
"author": "M. A. C. Lizanne",
"institution": "Department of Zoology, Carmel College for Women, Goa University, Goa, India",
"orcid": ""
}
] |
| author_sort | Borkar, M. R. |
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| container_title | Zoodiversity (Vestnik Zoologii) |
| container_volume | 57 |
| datestamp_date | 2026-08-20T12:36:50Z |
| description | Amblypygi have a tropical and sub-tropical distribution and their first of the four pairs of legs, is modified as feelers. Their activity period and dark habitats render visual cues ineffective and they rely on non-visual sensory perception. There is agreement among researchers that the whip spiders invest in olfactory and tactile senses imparted by sensory structures concentrated on the tarsal segment of the first pair of long, well-articulated non-ambulatory legs that are constantly moved in all directions to sample the environment for detecting location of prey, as also for navigating. This is the first attempt to elucidate the sensory structures present on the antenniform legs of the whip spider, Phrynichus phipsoni (Pocock, 1894), collected from the state of Goa, India; using scanning electron micro[1]scope, and paves way for further research on sensory biology of this cryptic arachnid order. The examined specimen generally conforms to the diversity and morphology of sensory assemblage on the antenniform legs reported in other amblypygi species. Sensory structures elucidated include terminal trident tarsal claws, tarsal organ, bristles, porous sensilla, club sensilla, rod sensilla, slit sensilla, trichobothria, plate organ, pit organ and foliate leaf like hairs. |
| doi_str_mv | 10.15407/zoo2023.05.451 |
| first_indexed | 2025-07-17T12:36:44Z |
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© Publisher Publishing House "Akademperiodyka" of the NAS of Ukraine, 2023. The article is published under
an open access license CC BY-NC-ND (https://creativecommons.org/licenses/by-nc-nd/4.0/)
UDC 595.45(540.55)
SENSORY STRUCTURES ON THE ANTENNIFORM LEGS
OF WHIP SPIDER PHRYNICHUS PHIPSONI (ARACHNIDA,
AMBLYPYGI) FROM THE INDIAN STATE OF GOA: SCANNING
ELECTRON MICROSCOPIC ELUCIDATION
M. R. Borkar1*, V. Q. D'Sa2, P. Sail3 & M. A. C. Lizanne4
Biodiversity Research Cell, Department of Zoology, Carmel College of Arts, Science & Commerce for Women,
Goa University, Goa, India
E-mail: 1borkar.manoj@rediffmail.com, 2vinitadsa@gmail.com, 3pratikshasail2210@gmail.com,
4maria.lizanne@gmail.com
*Corresponding author
M. R. Borkar (https://orcid.org/0000-0003-0582-1978)
V. Q. D'Sa (https://orcid.org/0009-0002-2460-2770)
P. Sail (https://orcid.org/0000-0002-6772-835X)
M. Lizanne A. C. (https://orcid.org/0000-0003-3575-8367)
urn:lsid:zoobank.org:pub:300574AF-B455-40C9-ACF7-0545E174FFBF
Sensory Structures on the Antenniform Legs of Whip Spider Phrynichus phipsoni (Arachnida,
Amblypygi) from the Indian State of Goa: Scanning Electron Microscopic Elucidation. Borkar, M. R.,
D'Sa, V. Q., Sail, P. & Lizanne, M. — Amblypygi have a tropical and sub-tropical distribution and their
first of the four pairs of legs, is modified as feelers. Their activity period and dark habitats render visual
cues ineffective and they rely on non-visual sensory perception. There is agreement among researchers
that the whip spiders invest in olfactory and tactile senses imparted by sensory structures concentrated
on the tarsal segment of the first pair of long, well-articulated non-ambulatory legs that are constantly
moved in all directions to sample the environment for detecting location of prey, as also for navigating.
This is the first attempt to elucidate the sensory structures present on the antenniform legs of the whip
spider, Phrynichus phipsoni (Pocock, 1894), collected from the state of Goa, India; using scanning electron
microscope, and paves way for further research on sensory biology of this cryptic arachnid order. The
examined specimen generally conforms to the diversity and morphology of sensory assemblage on the
antenniform legs reported in other amblypygi species. Sensory structures elucidated include terminal
trident tarsal claws, tarsal organ, bristles, porous sensilla, club sensilla, rod sensilla, slit sensilla,
trichobothria, plate organ, pit organ and foliate leaf like hairs.
Key words : sensory structures, antenniform legs, whip spider, electron microscope.
Zoodiversity, 57(5):451–460, 2023
DOI 10.15407/zoo2023.05.451
Morphology
452 M. R. Borkar, V. Q. D’Sa, P. Sail & M. A. C. Lizanne
Introduction
Whip spiders belong to Amblypygi, an order of cryptic arachnids distributed in tropics and subtropics
occupying diverse microhabitats such as tree hollows, cave crevices and leaf litter; seeking refuge from harsh
environment and potential predators. (Weygoldt, 2000).
Generally nocturnal, these flat-bodied predators are distinguished by their robust raptorial pedipalps and
long whip like antenniform first pair of walking legs that have lost the ambulatory function. While their com-
plex habitat and nocturnal habit offers little visual cue for navigation, homing, mate recognition and prey find-
ing; the sensory assemblage on the tarsal segment of their whip like first pair of modified legs is replete with
sensilla and structures that aid in chemo-sensory, mechano-sensory and hygro-sensory perception (Foelix,
1975; Beck et al., 1977; Santer & Hebets, 2011).
As of 2020, there are five extant families, 17 genera and over 210 species of Amblypygi that have been de-
scribed globally (American Arachnology Society, 2023). India has eight Amblypygi species, of which five belong
to family Charinidae and three belong to family Phrynichidae. Of these, four species belong to the genus Sarax
and one species to genus Charinus under family Charinidae; whereas family Phrynichidae has a single genus
Phrynichus with three species.
Since the current investigation involves whip spider genus Phrynichus, it is only pertinent to understand the
current distribution of its species globally and in India. Thus far 17 valid species of Phrynichus (Karsch, 1879) have
been reported across Asia, Arabian Peninsula and Africa, Seychelles Islands, Mauritius Island, Madagascar; higher
species diversity being reported from the countries along African east coast like Somalia, Kenya and Tanzania (Mi-
randa et al., 2018; Weygoldt, 1998). Yemen has the highest number of species reported in the Arabian Peninsula.
India has three phrynichid species namely Phrynichus phipsoni (Pocock, 1894), P. nigrimanus (C. L. Koch,
1847) and P. andhraensis (Bastawade, Rao, Maqsood Javed and Krishna, 2005).Thus far only a single species
P. phipsoni has been reported from the Indian state of Goa (Borkar et al., 2006). The relatively low count of
Amblypygi species in India despite its large spatial extent only reflects insufficient exploratory surveys, a view cor-
roborated by Weygoldt (1998, 1999).
Of the many interesting research questions in amblypygid biology, their behavior concerning habitat
selection, navigation and prey-finding is intriguing; but apart from some gross ethological observations, not
much species-specific information is available on structural correlates of their sensory ability. While Gebhardt
(1983) has contributed to our understanding of physiology of rudimentary vision in Amblypygi, sensory depri-
vation by ablating tarsal portion of antenniform legs have clearly implicated the whips in chemo-mechanical
perception critical to navigation as well prey detection (Hebets, 2014 a, b).
In all probability, navigation, homing and prey finding behavior of amblypygi is aided by neural integra-
tion of multimodal sensory cues, a view also corroborated by Weigmann et al. (2016). However, investigations
on neuroanatomy and sensory integration pathways of amblypygids are lacking.
Unlike true spiders, the first pair of legs in whip spiders is covered with thousands of mechanosensory,
olfactory, and gustatory sensilla; conveying critical sensations through unique sensory pathways (Sinakevitch
et al., 2021). Charting these sensory structures on the antenniform legs is a prerequisite to understanding neu-
roethology of amblypygi, and the present study elucidates these sensory structures in Phrynichus phipsoni from
the state of Goa, using scanning electron microscopy. This is the first ever attempt at charting sensory assem-
blage of the whip of any Indian species of amblypygi.
Material and Methods
Individuals of Phrynichus phipsoni (Pocock, 1894) were collected from the Dharbandora taluka of the In-
dian state of Goa (15°23'6.34" N, 74° 7'8.53" E), and brought to the Biodiversity Research Cell of Carmel College
for Women, Nuvem Goa. The collection was individually housed in ventilated plastic containers, measuring
10 cm × 15 cm, with dry leaf litter bedding and a wooden climb. The terrarium interiors were mist sprayed to
maintain requisite hygro-thermal profile. The set-up was subject to natural photoperiod. Individuals were given
a weekly feed of freshly collected live grasshoppers.
Procurement of sample for SEM
Adult live specimen was restrained and placed in the refrigerator at 2 °C for approximately thirty sec-
onds to be mildly anesthetized. Surgical ablation of antenniform legs was performed when the specimen was
significantly less responsive to touch. The cold anesthetized specimen was positioned on dissection board for
ablation of the antenniform leg at the patella-tibia and tibia-tarsus joints. The surgically manipulated specimen
was given adequate hydration and observed for recovery. The ablated tibia and tarsal segments were further cut
into relatively shorter pieces, leaving the distal tip of the tarsal segment intact. All regions of the antenniform
453Sensory Structures on the Antenniform Legs of Whip Spider Phrynichus phipsoni from the Indian State of Goa…
tibia and tarsus were processed following standard protocol, before being examined under scanning electron
microscope (Models JEOL 5800LV and JSM-6360LV).
Results
In situ observations on morphology, morphometry, and movement of an-
tenniform legs of Phrynichus phipsoni (Pocock, 1894)
Observations in field and captivity reveal that the whip spider activity in general is
clearly guided by a diurnal rhythm. During the day, the individuals retreat to dark micro-
habitats and lay still without any movement, while the ambulatory appendages as well as
the antenniform first pair is folded and held close to the body. The pedipalps are folded and
held parallel to the ground with femur-patella-tibia (f-t) joint of each pedipalp projecting
laterally. The horizontal distance between the two f-t joints measure the maximum width
of any part of the body in resting position. The folding pattern of the antenniform legs in
resting individual is archetypical (see fig. 1) across the order that gives it the name ‘whip
spiders’. Antenniform legs of Phrynichus phipsoni in this investigation were the longest of
the prosomal appendages; each individual whip of the investigated specimen measured a
total length of 17 cm. These non-ambulatory appendages were motile and rotated in differ-
ent planes being constantly moved in front, back and sides as the individual resumed activ-
ity in its dark habitat. This extraordinary manoeuvrability is imparted by joints between
femur-patella-tibia, tibia-tarsus and the inter-tarsal joints. The number of articles on the
tibio-tarsal segments is species-specific and in the investigated specimen of P. phipsoni the
count was found to be 31 tibial and 68 tarsal articles.
The entire sequence of prey detection, approach and capture occurred in a ritualized behav-
ioural sequence that can be broadly divided into 1. Steering antenniform legs in the direction of
prey without movement of body. 2. Orientation of the body in the direction of the prey and slow
cautious inching towards the prey 3. Forward lunge and capture of prey with raptorial pedipalps.
During captive feeding it was observed that after introducing a live prey in the enclo-
sure, the antenniform legs were raised and slowly moved in all directions and also over
the substrate. The animal then oriented itself in the direction where the prey had settled
Fig. 1. Resting captive specimen of whip spider Phrynichus phipsoni (Pocock, 1894).
Note the whip like configuration, position, and length of the antenniform first pair of non-ambulatory leg. The
various segments have been marked for reference: 1 — vertically raised femur; 2 — femur-patella-tibia joint;
3 — tibia; 4 — tibio-tarsal articulation; 5 — tarsus; 6 — distal tarsal tip.
454 M. R. Borkar, V. Q. D’Sa, P. Sail & M. A. C. Lizanne
and slowly crept towards it. If the prey moved in the meantime to another spot, the whip
spider would reorient only after completing the first trail and repeating the movement of
antenniform legs for fresh detection. Every time, there was a lag of a few minutes between
the movement of the prey and the predator. The movement all along was slow with simul-
taneous manoeuvring of the whips. It seemed necessary that the whips touch the prey or
the substrate where the prey had settled, after which the whip spider approached it within
striking distance and then rushed forward to clasp the prey with its raptorial pedipalps,
simultaneously retracting the antenniform legs away from the prey.
Sensory s tructures on the antenniform legs of P. phipsoni (Pocock, 1894)
with specia l emphasis on tarsa l port ion
As stated in the previous section, the observations on P. phipsoni activity clearly indi-
cate the significant role of antenniform legs in sensory perception of the environment. Fur-
ther, that most of the activity happens in dark, the eyes may only be appreciative of sensing
changes in light intensity but not image formation (Weygoldt, 2000).
Micro-morphological character of the antenniform legs of P. phipsoni revealed an as-
sortment of sensory structures particularly located in the apical tarsal segments. Particu-
Fig. 2. Sensory assembly on the whip (Antenniform leg) of Phrynichus phipsoni from Goa, India: 1 — terminal
tarsal claw; 2 — bristles; 3 — leaf like sensilla; 4 — pore sensilla; 5 — club sensilla; 6 — tarsal organ; 7 — pit organ.
455Sensory Structures on the Antenniform Legs of Whip Spider Phrynichus phipsoni from the Indian State of Goa…
larly, the whip tarsus was seen to be covered with a whorl of several longitudinal rows of
bristles right up to the terminal tip, interspersed between which were shorter hair and club
like structures, besides other sensory micro-sculpture.
The following distinctive structures were observed.
1. Terminal tarsal claws (fig. 2, A). This presented as a stunted apical protrusion of 3
claw like projections with a common base; middle being straight and shorter, and the
two-lateral showing a curvature. Their maximum length from base to tip varied in the
range of 70–75µm. The terminal location appeared strategic in sensory perception.
2. Brist les (fig. 2, B). These were among the most conspicuous, longest, thickest and
abundant of the tibio-tarsal projections comprising of a proximal socket arising from
which is a moveable serrated shaft. The bristles arise from the cuticle with which it is
articulated in a girdled socket. Their distribution was not close set, and within each
tarsal annulus the longer bristles were distally placed, their length varying in the range
of 74–88 µm.
3. Leaf-l ike sensi l la (fig. 2, C). These were relatively sparse and irregularly spaced with-
in the bristle rows. Much smaller (ranging between 30–35 µm length) than a regular
bristle sensilla, in construct they were similar to bristles in having an articulated base
lodged in the cuticle, but differed with respect to the foliate shape of their shaft which
is flattened like a blade whose tip tapered into an angular point. The flattened, blade
like shaft was seen to be stiffly articulated into the cuticular socket.
4. Pore sensi l la (fig. 2, B). These were found between rows of bristles at the distal po
domeres of the antenniform tarsus and differed from the bristles in two respects i. e.
their size is smaller, and variable length from 55 to 78 µm and filiform shape. Unlike
the bristles, the pore sensilla were not socketed in the cuticle.
5. Club sensi l la (fig. 2, A, B, D). Unmistakable by their characteristic appearance that
gives them the name, these socketed sensilla have a short shaft that terminates into a
swollen tip. Their lengths ranged between 15 to 23 µm. They were frequently encoun-
tered on the distal podomeres of the tarsus.
6. Tarsal organ (fig. 2, E). A discrete knob like structure with apical region showing
presence of papillae, this structure was positioned beneath the terminal tarsal claw.
7. Pit organ (fig. 2, F). In the examined specimen, this sensory structure resembled a
small eye shaped pit (30 µm long and 12 µm wide) with thickened cuticular ridges and
was located on the S1 tarsal annulus. A few protuberances could be seen inside the pit,
presumably with the raised pore openings.
8. Rod sensi l la . These were closely set clusters of long (70–100 µm) and short sensilla
(21–25 µm) that sat in a narrow longitudinal groove measuring 340 x 88 µm (L x W)
on the dorsal surface of the apical tarsal segment in the examined specimen (fig. 3, G).
Additionally small clusters of a few short rod sensilla were also seen on the dorsal edge
of the lower tarsal podomeres (fig. 3, H).
9. Plate organ (fig. 3, I, J). This structure occurred as a distinct oval depression measuring
about 80 µm long on the proximal end of the S8 tarsal article of the antenniform leg. Ly-
ing centrally in the depression along its floor was seen a single elongate projection.
10. Sl i t sensi l la (fig. 3, K). A single slit with raised borders, measuring 57 µm was present
parallel to the length of the antenniform leg on the lower tarsal podomere. Its location
close to the inter-annular junction. Also, the annulus bearing this slit sensillum did not
show any other sensory structures except for a few bristles.
11. Trichobothria (fig. 3, L). These filiform fine hair sensilla measuring about 280–
320 µm were among the longest sensory structures and occurred on the tibial segments
456 M. R. Borkar, V. Q. D’Sa, P. Sail & M. A. C. Lizanne
of the antenniform legs; but conspicuously absent on the tarsal segment. They abound-
ed on the ambulatory appendages, but the one on the antenniform legs were seen to be
shorter. The base of the shaft was lodged in a deep cup shaped socket surrounded by
a rosette of cuticular scales that were arranged in concentric whorls and differed from
the archetypical triangular scales on the general surface. Inter-trichobothrial distance
in a row varied from 75 to 100 µm.
Discussion
Much of the work on this enigmatic arachnid order of Amblypygi is hitherto focused
on their species diversity, and a few classical works have addressed their behavior in situ
and captivity. Of the most intriguing among the many behavioural attributes of this cryptic
arachnid; is their ability to assess the habitat, navigate and detect conspecifics and prey,
in spite of being visually compromised (Beck & Gorke, 1974; Peretti, 2002; Hebets et al.,
2014 a; Bingman et al, 2017; Wiegmann et al., 2019). Recent field experiments implicate
sensory inputs from the antenniform legs in amblypygid navigation, and confirm that vi-
Fig. 3. Sensory assembly on the whip (Antenniform leg) of Phrynichus phipsoni from Goa, India: 8 — rod sen
silla within groove, 9 — plate organ, 10 — slit sensilla, 11 — trichobothria, 12 — sockets of trichobothria
457Sensory Structures on the Antenniform Legs of Whip Spider Phrynichus phipsoni from the Indian State of Goa…
sual cues alone are insufficient for navigation and homing of whip spiders (Wiegmann et
al., 2016). The quintessential whip like non-ambulatory first pair of antenniform legs is
the functional analogue of ‘blind man's stick’ in whip spiders across the species diversity.
Yet, a few species of amblypygi have been investigated for the sensory investments of these
antenniform appendages.
In the present investigation, prey detection behaviour in captivity has been observed
with special reference to use and orientation of antenniform legs in Phrynichus phipsoni,
to ascertain importance of these appendages in prey detection and capture. From the re-
corded observations of several trials following introduction of prey in the captive arena, it is
clear that the whip spider that initially has its whips folded, raises and opens them wide. It
remains stationary though the movement of whips gets progressively rotatory and intense,
both in air as also touching the substratum as if to sample olfactory cues. The ritualized se-
quence of antenniform leg activity documented in P. phipsoni is similar to that documented
in other species of amblypygi (Santer & Hebets, 2009; Seiter et al., 2019). The flexibility of
the tarsal portion of the whip despite absence of musculature is attributed to changes in
hemolymph pressure there within (Foelix et al., 1975).
The morphology and morphometry of the antenniform leg is valuable information in
species typing, for instance the respective tibial and tarsal article numbers of 31 and 68 in
the investigated specimen tallies with the count prescribed for the Phrynichus phipsoni spe-
cies (Weygoldt, 2000). The impressive extension and rotator ability of the whips does not
require of the individual to move the whole body.
The eyes of amblypygi may sense light intensity flux but unlikely to form image (Wey-
goldt, 2000; Lehmann et al., 2018), as such they rely on non-visual perception of the en-
vironmental variables including substratum characteristic, mates and prey by investing in
chemo-mechanoreceptors and olfactory sensilla concentrated on the distal articles of the
antenniform legs, that continually ‘palpate’ the surroundings. The role of olfactory cues in
navigation (Bingman et al., 2017) and the significance of visual inputs for shelter recogni-
tion have been recently recognized (Flanigan et al., 2021).
Sensory structures on the antenniform leg of Phrynichus phipsoni (Pocock, 1894) have
been studied using scanning electron microscopy. In all, 11 discrete sensory structures were
elucidated, measured and described. Their basic structure corroborates well with previous
reports in other species. Thus, the variety is constant across the species but positions and
fine morphology is variable and species-specific.
Sinakevitch et al. (2021) have thrown light on the neural circuitry of these sensory
structures on the antenniform legs of whip spiders, though not many amblypygi species
have been investigated from this perspective. The dorso-ventrally compact body and lat-
erigrade legs of whip spider allows it to creep into crevices and fissures, as also seek shelter
under tree bark (Weygoldt, 2000). Their nocturnal foraging habits and site fidelity has been
well documented (Weygoldt, 2000; Hebets et al., 2014 a, Bingman et al., 2017).
All the sensory structures listed for amblypygids by Weygoldt (2000) have been iden-
tified and described in our present study. However, in absence of transmission electron
microscopy (TEM) studies, their neural investments could not be ascertained, as such
the functions assigned are based on established structural corroborations. Barring the
trichobothria which were located on the tibia of the antenniform legs, rest of the sensilla
were present on the distal tarsal podomeres. The terminal tarsal podomere particularly has
as many as 7 sensory structures, such concentration being strategic as arthropods generally
have the tips of their legs bearing structures for interaction with substratum (Wolff et al.,
2013).
458 M. R. Borkar, V. Q. D’Sa, P. Sail & M. A. C. Lizanne
The distally located tarsal claw is a strategic contact chemoreceptor (Foelix et al., 1975;
Foelix & Hebets, 2001) and is reasoned to be a vestigial apotele of the tarsus. Similar triad
of claws have been reported from the pre-tarsus of spiders (Wolff et al., 2013). Bristles
abound all over the cuticle of the terminal segments of the antenniform legs, particularly
the tarsal article; and are arranged in several rows forming a whorl around the antenniform
leg when seen in axial view. Their arrangement and morphology in P. phipsoni matched
with the description given by Weygoldt (2000). The micro-morphology is commensurate
with previous descriptions in other species (Beck et al., 1977; Igelmund, 1987). The leaf-like
sensilla or the ‘foliate bristles’ were sparse and distinguished by their flat blade-like shaft
(Igelmund, 1987). Such a design is somewhat nonconforming for a typical air flow sensors
that the bristles are, and their strategic location at the tibia-tarsal joint has led to the specu-
lation that these structures could be aiding in generation of action potential for kinaesthetic
responses from the lyriform organ (Igelmund, 1987). The pore sensilla could be easily dif-
ferentiated from the bristles from the differences in length and lack of cuticular sockets.
There is evidence that these could be olfactory in function and operate similar to the ones
on antennae of insects (Hebets & Chapman, 2000). The quintessential club sensilla are the
smallest of the sensory projections distributed on the tarsal annuli, and have been impli-
cated in dual sensory perception. Likelihood of their sensitivity to humidity was suggested
by Altner & Loftus (1985) and later their olfactory role was proposed by Weygoldt (2000).
The rod sensilla have a close-set arrangement unlike any other and are either located in a
groove or on the proximal edge of lower tarsal segments. Similar arrangement has been
reported from P. marginemaculatus (Spence & Hebets, 2006). This is one structure whose
exact function has not been clear, but in the classical SEM-TEM correlative investigation
of antenniform legs of Admetus pumilio (Foelix et al., 1975) the innervations did not com-
mensurate with olfactory purpose. There have been no fresh attempts to address this gap,
and the question is yet unanswered.
In our investigation of sensory structures on antenniform legs, we have come across
a tarsal organ whose construct matches with that described in Charinus asturius (Segovia
et al., 2020). Its functional significance in amblypygi remains unknown, though the fine
morphology is suggestive of its receptivity to humidity, temperature and odours (Anton &
Tichy, 1994; Talarico et al., 2005; Gainett et al., 2017). The pit and the plate organs on the
whips of P. phipsoni are in structural conformity with those reported in a few other species.
While the pit organ is implicated in hygro-thermal sensitivity as well as chemoreception
(Ehn & Tichy, 1994), the strategic occurrence of the plate organ near the inter-segmental
joint hints at its proprioceptive ability (Seyfarth, 1985; Barth, 2002). By virtue of its location
at the inter-annular junction, the conspicuous slit organ is also assumed to be sensitive to
bending of the tarsal segment and thereby could be a potential proprioceptor (Igelmund &
Wendler, 1991). This further finds support in the observation that the slit sensilla respond
to minute strains in the cuticular exoskeleton (Barth, 2012; Blickhan et al., 2021). Mechani-
cal significance of different slit sensilla arrays in arachnids has been researched by Hößl et
al. (2007).
The long filiform trichobothria are the longest elucidated sensory structures in this
exercise, their fragile construct indicating a likely role in perception of air turbulence. Whip
spider trichobothria by their ability to detect air movements may affect, critical behaviour
such as locating a mobile prey, and triggering startle response following a sudden change in
micro air currents around it (Beck & Gorke, 1974; Igelmund & Wendler, 1991). The anten-
niform leg of the P. phipsoni clearly is a sensory appendage of immense value with as many
as 11 different sensory structures concentrated on it. Recently, Moore (2019) has upheld
459Sensory Structures on the Antenniform Legs of Whip Spider Phrynichus phipsoni from the Indian State of Goa…
the view that integration of inputs from such multisensorial structures helps in refining
behavioural responses as compared to a single sensory structure.
The diversity of these structures matches with that reported from other investigated
amblypygi species as inferred from literature, however it would be interesting to delve into
their neural investments using TEM approach to verify species specific neural nuances if
any.
Conclusion
From observations on feeding trials in captivity and the SEM elucidation of the sen-
sory structures on the antenniform leg of Phrynichus phipsoni, it is clear that this species
like other amblypygi has an assortment of sensilla on its non-ambulatory whips, and fur-
ther that the whips are indispensable for prey detection, as well as navigatory orientation.
This is the first attempt to elucidate the micromorphology of sensory whip in any Indian
species of Amblypygi.
Acknowledgments
MRB and VQD gratefully acknowledge SEM facilities extended by CSIR, National Institute of Oceanog-
raphy (NIO), and National Centre for Polar and Ocean Research (NCPOR), Ministry of Earth Sciences, Govt.
of India. Dr Guilherme Gainett of Department of Integrative Biology, University of Wisconsin-Madison, USA
kindly provided his latest research paper, besides other pertinent technical literature.
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Received 20 July 2023
Accepted 5 September 2023
|
| id | oai:ojs.akademperiodyka.org.ua:article-521 |
| institution | Zoodiversity |
| issn | 2707-7268 |
| keywords_txt_mv | |
| language | English |
| last_indexed | 2026-08-21T01:01:36Z |
| publishDate | 2023 |
| publisher | Publishing House "Akademperiodyka" of the National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | ojsakademperiodykaorgua/90/1f9a50ad0ecd51de296ed566dd2baa90.pdf |
| spelling | oai:ojs.akademperiodyka.org.ua:article-5212026-08-20T12:36:50Z Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni Borkar, M. R. Quadros D'Sa , V. Sail , P. Lizanne, M. A. C. sensory structures antenniform legs whip spider electron microscope Amblypygi have a tropical and sub-tropical distribution and their first of the four pairs of legs, is modified as feelers. Their activity period and dark habitats render visual cues ineffective and they rely on non-visual sensory perception. There is agreement among researchers that the whip spiders invest in olfactory and tactile senses imparted by sensory structures concentrated on the tarsal segment of the first pair of long, well-articulated non-ambulatory legs that are constantly moved in all directions to sample the environment for detecting location of prey, as also for navigating. This is the first attempt to elucidate the sensory structures present on the antenniform legs of the whip spider, Phrynichus phipsoni (Pocock, 1894), collected from the state of Goa, India; using scanning electron micro[1]scope, and paves way for further research on sensory biology of this cryptic arachnid order. The examined specimen generally conforms to the diversity and morphology of sensory assemblage on the antenniform legs reported in other amblypygi species. Sensory structures elucidated include terminal trident tarsal claws, tarsal organ, bristles, porous sensilla, club sensilla, rod sensilla, slit sensilla, trichobothria, plate organ, pit organ and foliate leaf like hairs. Publishing House "Akademperiodyka" of the National Academy of Sciences of Ukraine 2023-08-23 Article Article application/pdf https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/article/view/521 10.15407/zoo2023.05.451 Zoodiversity; Vol. 57 No. 5 (2023): Zoodiversity Zoodiversity (Vestnik Zoologii); Том 57 № 5 (2023): Zoodiversity 2707-7268 2707-725X 10.15407/zoo2023.05 en https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/article/view/521/234 Copyright (c) 2023 Manoj Borkar, Vinita Quadros D'Sa , Pratiksha Sail , Maria Lizanne AC |
| spellingShingle | Borkar, M. R. Quadros D'Sa , V. Sail , P. Lizanne, M. A. C. Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni |
| title | Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni |
| title_full | Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni |
| title_fullStr | Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni |
| title_full_unstemmed | Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni |
| title_short | Sensory Structures on the Antenniform Legs of Whip Spider, Phrynichus phipsoni (Arachnida, Amblypygi), from the Indian State of Goa: Scanning Electron Microscopic Elucidation: Sensory assembly on the whip of Phrynichus phipsoni |
| title_sort | sensory structures on the antenniform legs of whip spider, phrynichus phipsoni (arachnida, amblypygi), from the indian state of goa: scanning electron microscopic elucidation: sensory assembly on the whip of phrynichus phipsoni |
| topic_facet | sensory structures antenniform legs whip spider electron microscope |
| url | https://ojs.akademperiodyka.org.ua/index.php/Zoodiversity/article/view/521 |
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