Amer et al. Marine Biodiversity Records(2019) 12:18
https://doi.org/10.1186/s41200-019-0177-2

MARINE RECORDOpen AccessFirst record of Polyonyx loimicola Sankolli,
1965 (Crustacea, Decapoda, Anomura,
Porcellanidae) from the Red Sea, Egypt
Mohamed A. Amer1*, Tohru Naruse2 and Masayuki Osawa3

Abstract
The first record of the porcellanid crab, Polyonyx loimicola Sankolli, 1965, from Ain-Sokhna, Suez Gulf, Egypt, the Red
Sea, is provided far away from its known localities in India and Pakistan. The present specimens were found inassociation with one tube-dwelling polychaete species, Chaetopterus variopedatus (Renier, 1804), in soft sandy
habitat. They agree well with the original description of P. loimicola in most of its diagnostic characters. Intraspecificvariation is recognized in the number of ventral spines of the ambulatory propodi.
Keywords: Association habit, Indo-West Pacific, Porcellanidae, Red Sea, Tube-dwelling polychaete

Introduction
The porcellanid genus Polyonyx Stimpson, 1858 includes
32 species globally (Osawa and McLaughlin 2010; Osawa
2015, 2018; Osawa and Ng 2016; Osawa et al. 2018;
Werding and Hiller 2019). Polyonyx species usually livein association with sponges and tube-dwelling polychaetes (Osawa and Chan 2010). Johnson (1958) divided
the Indo-West Pacific species of the genus to three informal groups: P. biunguiculatus, P. denticulatus, and P.
sinensis groups. Among the three groups, the P. denticulatus group was regarded as a different genus Aliaporcellana Nakasone and Miyake 1969. Moreover, Osawa(2015) suggested that the P. biunguiculatus group is very
close to Aliaporcellana. The P. sinensis group now contains 18 species from the Indo-West Pacific (Osawa
2018; Werding and Hiller 2019) and is primary characterized by the carapace without spines on the lateral
margins, the chela with various degrees of setation on
the dorso-anterior surface and the dactyli of the ambulatory legs each with the dorsal claw much smaller thanthe ventral.
The Egyptian coasts represent the northern limits of
the Red Sea, including the complete coasts of the Suez
Gulf and the western coasts of the Aqaba Gulf, and have
* Correspondence: naseramer@azhar.edu.eg
1
Zoology Department (Marine Biology Section), Faculty of Science, Al-Azhar
University, Cairo 11884, Egypt
Full list of author information is available at the end of the article

a total length of about 1300 km (Head 1987). The Suez
Gulf significantly differs from other areas of Egypt (western coasts of Aqaba Gulf and southern Egyptian coasts
in the Red Sea) in geographical position, general environmental conditions and bathymetry. The Suez Gulf isconsidered to be the boundary between Africa and Asia,
which extends from its south running from Ras
Mohamed (Sinai Peninsula) and Westward at Gemsa
Bay to the entrance of the Suez Canal (the northern
limit), the coasts are represented by several habitats including sandy, rocky shores and coral reefs.
Despite the variety of the coasts and habitats, only
three Polyonyx species have been reported from the Red
Sea: P. biunguiculatus (Dana, 1852), P. pedalis Nobili,
1905, and P. triunguiculatus Zehntner, 1894 (Ramadan
1936; Barnard 1950; Lewinsohn 1969; Vine 1986; Osawa
and Ng 2016). Vine (1986) listed four nomina of the “P.
denticulatus group” from the Red Sea. However, as mentioned above, they are now placed in the genus Aliaporcellana: P. denticulatus Paul’son, 1875 and P. suluensis(Dana, 1852) are now considered conspecific and thecurrent valid name is A. suluensis; P. pygmaeus (DeMan, 1902) and P. pugilator Nobili, 1905 (incorrectly
spelled as P. pugilatus by Vine 1986: 108) are also synonymous and the current valid name is A. pygmaea(Osawa and McLaughlin 2010). Werding and Hiller(2007) examined porcellanid collections from the Red© The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0
International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to
the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Amer et al. Marine Biodiversity Records(2019) 12:18

Sea in some museums and listed 18 species including
only one species of Polyonyx, P. triunguiculatus.
Porcellanid crabs from the Egyptian coasts have beenreported only by a few studies (e.g., Nobili 1906; Lewinsohn 1969). Ramadan (1936) listed the decapod and stomatopod crustaceans from the Egyptian coasts, Red Sea,
including seven porcellaniids: Pachycheles sculptus (H.
Milne Edwards, 1834); Petrolisthes boscii (Audouin,
1826); P. leptocheles (Heller, 1861); P. ornatus (Paulson,
1875); P. rufescens (Heller, 1861); P. virgatus Paulson,
1875; and Porcellana inaequalis (Heller, 1861) now
placed in the genus Pisidia Leach, 1820. Moreover,Werding and Hiller (2007) added six species to the
Egyptian porcellanid fauna: Aliaporcellana suluensis(Dana, 1852); Pachycheles natalensis (Krauss, 1843); Petrolithes aegyptiacus Werding and Hiller, 2007; P.
lamarckii (Leach, 1820); P. moluccensis (De Man, 1888)
and Porcellanella haigae Sankarankutty, 1963 (based ona photograph taken by Lieske and Myers 2004, in a
guide of Coral reefs of the Red Sea, Gulf of Aqaba), in
addition to an unconfirmed species recorded as Petrolisthes cf. donanensis Osawa, 1997. Thus, at present 13
species in five genera of the Porcellanidae are recorded
from the Egyptian Red Sea.
The present study reports Polyonyx loimicola Sankolli,
1965, as an addition to the porcellanid fauna of the Red
Sea and Egypt. This species was originally describedfrom the western India and later recorded only from
Pakistan (Siddiqui and Kazmi 2003).

Materials and methods
The specimens examined were collected from the northern part of the Suez Gulf (Ain-Sokhna), Red Sea, Egypt.
They were obtained from tubes of chaetopterid worms
found on soft sandy substratum in shallow intertidal region. The host species was identified in reference to Sun
and Qiu (2014). The specimens are deposited in the Reference Collection and Museum of Zoology, Faculty of
Science, Al-Azhar University, Egypt (RCAZUE.Crus.).
The morphological terminology follows those of
Osawa and Chan (2010) and Osawa (2015). Measurements of the carapace and pereopods were made in accordance with Osawa et al. (2018). Abbreviations are as
follows: CL, carapace length, and CW, carapace width.

Results and discussion
Porcellanidae Haworth, 1825
Polyonyx Stimpson, 1858
Polyonyx loimicola Sankolli, 1965
Polyonyx loimicola Sankolli, 1965: 285, pls. 1, 2.–Sankolli and Shenoy 1965: 316, unnumbered pl. figs. c, d.–Tirmizi et al. 1989: 24.–Siddiqui and Kazmi 2003: 88 (list).

Page 2 of 5

Material examined

RCAZUE.Crus. 36,401, 1 female (CL 4.7 mm, CW 6.1mm), Ain-Sokhna, Suez Gulf, Red Sea, Egypt, 29°50′
43.8˝N, 32°30′0.5˝E, coll. M. A. Amer, Feb. 2018. RCAZUE.Crus. 36,402, 1 male (CL 4.9 mm, CW 5.7 mm),same locality with RCAZUE.Crus. 36,401, using yabby
pump, coll. M. A. Amer, Sep. 2018.
Description

Carapace (Figs. 1a, b, 2a) 1.2–1.3 times as wide as
long, rectangular in general outline; branchial margins
subparallel, slightly convergent posteriorly. Dorsal surface convex longitudinally, almost smooth, with few
disconnected, fine transverse ridges on protogastricregion; pair of mats of minute setae between rostrum
and protogastric ridges; cervical grooves faint; metabranchial and adjacent regions with distinct long transverse ridges; two rounded, shallow depressions
laterally in cardiac region. Branchial margins setose,denser in posterior region but sparser anteriorly.
Rostrum directed somewhat downward, weakly trilobate; median lobe broadly triangular with rounded
apex, barely visible in dorsal view; anterior margin
with row of short setae.
Third thoracic sternite (Fig. 2b) trilobate; anterior
margin with row of setae; median lobe broadly triangular, wider than lateral lobes. Fourth thoracic sternitesmooth on surface, sloping anteriorly; anterior marginmoderately concave medially.
Third maxilliped (Fig. 2c) ischium smooth, length
about as long as maximum width; merus with well demarcated rounded lobe on ventrolateral (flexor) margin;

Fig. 1 Polyonyx loimicola Sankolli, 1965 from Suez Gulf, Red Sea,
Egypt. a, b entire animal, dorsal view (a live coloration; b preservedcoloration); c propodus and dactylus of third pereopod (second
ambulatory leg), lateral view. a RCAZUE.Crus. 36,402, male, Cl 4.9mm; b, c RCAZUE.Crus. 36,401, female, CL 4.7 mm

Amer et al. Marine Biodiversity Records(2019) 12:18

Fig. 2 Polyonyx loimicola Sankolli, 1965, from Suez Gulf, Red Sea,
Egypt; RCAZUE.Crus. 36,401, female, CL 4.7 mm. a carapace, dorsal
view; b third and fourth thoracic sternites, ventral view; c left third
maxilliped, lateral view; d telson, external view. Scales, a–c = 1 mm,
d = 0.5 mm. Setae not partially (a) or fully (b, c) drawn

propodus relatively short; carpus, propodus and dactylus
with long setae on ventral (flexor) margins.
Chelipeds (Fig. 3a–d) unequal in size, larger in malethan female. Larger cheliped with short to long setae on
anterior, posterior and dorso-anterior margins in male,Fig. 3 Polyonyx loimicola Sankolli, 1965, from Suez Gulf, Red Sea,
Egypt; RCAZUE.Crus. 36,401, female, CL 4.7 mm. a larger cheliped,
dorsal view; b same, ventral view; c smaller cheliped, dorsal view; dsame, ventral view; e right second pereopod, lateral view; f same,
propodus and dactylus, lateral view. Scales = 1 mm. Setae not drawn

Page 3 of 5

but with only few short setae on those margins in female. Merus with demarcated transverse striae on dorsal
surface, but with faint striae on ventral surface; relatively
narrow, rounded lobe present on dorso-anterior margin
distally. Carpus 1.7–1.8 times as long as maximum
width, with demarcated transverse striae dorsally in
male, but with only faint striae in female, those striae
more distinct in dorso-anterior and dorso-posterior margins; dorso-anterior margin convex, with most swelling
point posteriorly to half length, proximally with relatively short and shallow concavity. Palm with dense longsetae on anterior margin but with fewer and shorter
setae on posterior margin; dorsal surface strongly convex, with faint, longitudinal median ridge. Fingers distinctly crossing to each other, leaving subdistal gap
when closed (that gap larger in male than female); fixed
finger pointed distally, distally curved upward in malebut nearly straight in female; cutting edges of both fingers denticulated, each with proximal distinct tooth (larger in male than female), nearly smooth on remaining
margin. Dactylus curved to extensor side; cutting edge
concave proximally, with short scattered setae in malebut no setae in female.
Smaller cheliped with setation similar to that of larger
cheliped. Carpus proportionally broader than that of larger cheliped, length 1.4–1.6 times as long as maximum
width. Palm less convex on dorsal and ventral surfaces
than that of larger cheliped, dorsal surface with distinct,
longitudinal median ridge. Fingers pointed distally; cutting edges without distinct gap when closed, denticulated, bearing short setae.
Ambulatory legs (Fig. 3e, f) decreasing in size posteriorly (second pereopod largest), with plumose setae on
anterior margins. Meri and carpi unarmed on entire
margins, meri compressed laterally. Propodi length/
height ratios: 2.8, 2.7 (second), 2.7, 2.6 (third) for eachsex and 2.8 (fourth) for both male and female; ventral
surface with small corneous spines as follows: second
pereopod with two proximal and three distal (one subdistal, two distoventral) spines, third with three proximal
and three distal spines, fourth with two (male) or three(female) proximal and three distal spines. Dactyli eachwith two corneous spines on ventral margin, distal spine
much larger than proximal; terminal claws bifurcated,ventral claw distinctly larger than dorsal.
Telson (Fig. 2d) composed of seven plates; proximolateral plates much smaller than others; small plate-likemembrane between median and distal plates.
Coloration in life

Dorsal surfaces of carapace and chelipeds beige(Fig. 1a), with mottled brown marks as seen in tubes
of host polychaete (Fig. 4c). Ambulatory legs paler
beige on lateral surfaces.

Amer et al. Marine Biodiversity Records(2019) 12:18

Page 4 of 5Distribution

So far recorded only from the eastern coast of the Arabian Sea: Mumbai (= Bombay), India, and Gwadar West
Bay, Pakistan (Sankolli 1965; Tirmizi et al. 1989). Now
from the Suez Gulf in Egypt, north part of the Red Sea.
Remarks

Fig. 4 Chaetopterus variopedatus (Renier, 1804), host of Polyonyx
loimicola Sankolli, 1965, from Suez Gulf, Red Sea, Egypt. a openingsof tube of an uncollected specimen; b worm; c tube

Ecological notes

The present specimens were collected from the tubesof Chaetopterus variopedatus (Renier, 1804) (Fig. 4b,c) in soft sandy substratum of shallow intertidal region (Fig. 4a). The intertidal region of the collection
site in Ain-Sokhna, Egypt, exhibits a wide variation ofsubstrates; it comprises three major habitats: rocky,
sandy-rock (mixed) and sandy shores, in addition topatches of coral reef at the lower border of intertidal
zone. The upper intertidal region is protected byrocks or mixed sand-rock at the shore line and isdominated by porcelain crab Petrolithes rufescens;
followed by sandy bottom habitat inhabited by burrowing invertebrates including tube dwelling polychaetes. The tubes of Chaetopterus variopedatus canbe easily seen in the field because they are partiallyprojected above the ground in sandy substratum submerged in shallow intertidal region (1–2 m). Eachtube is covered with sand particles; only two worms
each associated with a single specimen of Polyonyx
loimicola were obtained.

The present specimens from Egypt belong to the Polyonyx sinensis group defined by Johnson (1958) based on
the following characters: the carapace lacks spines on
the lateral margins, the chela with various degrees ofsetation on the dorso-anterior surface, and the ambulatory dactylus has the dorsal claw being much smaller
than the ventral claw (see Osawa et al. 2018). The group
now includes 18 Indo-West Pacific species, and among
them, the present material is closely assigned to P. loimicola based on the characters used in the key to speciesof the P. sinensis group by Osawa et al. (2018). Nevertheless, the present specimens are different from the original description of P. loimicola by Sankolli (1965) innumber of ventral spines of the ambulatory propodi, fiveor six spines (including two spines on the distoventral
margin) in the Egyptian specimens versus three spines in
the original description. At present, we prefer to identify
the Egyptian specimens as P. loimicola previously known
from the eastern coast of the Arabian Sea, as there is no
sufficient information on the intraspecific variations.
General morphology, including the similar number ofventral spines of the ambulatory propodi, may also linkto the present specimens to P. tulearis Werding, 2001
known only from Madagascar. However, P. tulearis isdifferent from the Egyptian material and the original description of P. loimicola in: carapace branchial margins
distinctly convergent posteriorly; median lobe of third
thoracic sternite absent; and dorso-anterior margin of
carpus of larger cheliped more gently and constantly
convex on entire length.
Sankolli and Shenoy (1965) reported the association
behaviour of P. loimicola in Bombay, India, and the porcellanid was always found in a heterosexual pair inside
tubes of a terebellid polychaete, Loimia medusa, in sandor in a mixture of sand and mud. Such an association
with terebellid is unusual for the Polyonyx sinensis group
because many species of the group have been recorded
from polychaetes of the family Chaetopteridae (cf.
Osawa et al. 2018). The present Egyptian specimens
were found in tubes of Chaetopterus variopedatus insandy substratum.

Conclusion
Polyonyx loimicola was originally described from
Bombay, India and then recorded from Pakistan.
Now its distribution is expanded and recorded forthe first time from the northern part of the Red Sea,

Amer et al. Marine Biodiversity Records(2019) 12:18

Egyptian coast (north Suez Gulf). Moreover, intraspecific variations in the number of ambulatory propodi
spines and host polychaete were observed; theserequir further studies on this species from different
localities including India, the Arabian Gulf and the
Red Sea.
Acknowledgements
The first author (M. A. Amer) is very grateful to the management staff ofIriomote Station, Tropical Biosphere Research Center and James Davis
Reimer, Faculty of Science, University of the Ryukyus, Okinawa, Japan, forhosting and providing laboratory facilities during the present study fromFebruary to August 2018.
Authors’ contributions
MA was involved in the field work, found the recorded species. MA and TN
contributed in the morphological identification and drawings Figs. 2, 3. TN
made the final arrangement of Figs. 2, 3. MO contributed in the final
identification of the recorded specimens. All authors involved in the setup of
the manuscript. All authors read and approved the final manuscript.
Funding
Financial support for the first author (M. A. Amer) was provided by the
Egyptian government, Ministry of Higher Education (Cultural Affairs andMissions Sector, mission call 2015/2016) (grant number 331946).
Availability of data and materials
All data generated or analysed during this study are included in thispublished article. All voucher specimens (RCAZUE.Crus. 36401 and 36402) aredeposited in the Reference Collection and Museum of Zoology, Faculty of
Science, Al-Azhar University, Egypt (RCAZUE.Crus.).
Ethics approval and consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Author details
1
Zoology Department (Marine Biology Section), Faculty of Science, Al-Azhar
University, Cairo 11884, Egypt. 2Iriomote Station, Tropical Biosphere ResearchCenter, University of the Ryukyus, 870 Uehara, Taketomi, Okinawa 907-1541,
Japan. 3Estuary Research Center, Shimane University, 1060 Nishikawatsu-cho,
Matsue, Shimane 690-8504, Japan.
Received: 26 April 2019 Accepted: 12 August 2019

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