The Harlequin crab, Lissocarcinus orbicularis Dana, 1852, (Decapoda: Portunidae) is one of the most common echinoderm symbionts in the Indo-West Pacific (IWP). It is typically found as a single individual or heterosexual pair on sea cucumbers of the genera Stichopus, Thelenota, Actinopyga, Bohadschia, and Holothuria, where it feeds on host integument and detritus (Ng & Jeng 1999; Caulier et al. 2012, 2014). These crabs have a striking color pattern of white spots on a dark red-brown background, or dark spots on white, that often complements their hosts (Caulier et al. 2012).
Lissocarcinus orbicularis has been reported across the IWP from Africa to Hawaii and French Polynesia (Vannini & Innocenti 2000). It has been listed from the Red Sea but without reference to specific specimens or localities (Laurie, 1915; Shankarankutty & Thomas, 1963). The first record, and likely the second, can be attributed to Nobili (1906), which documented a specimen collected at the Banc de La Clocheterie reef, Obock, Djibouti (outside of the Red Sea). All other authors have excluded the Red Sea from the distribution of L. orbicularis (e.g., Guinot 1967, Vannini & Innocenti 2000, DiBattista et al. 2016). Here we provide the first records of L. orbicularis from the Red Sea.
Lissocarcinus currently includes nine species, all putatively symbiotic, primarily on echinoderms, cerianthids, sea anemones, and possibly salps and some corals (Caulier et al. 2012; Evans 2016, 2018; Stephenson, 1972). Lissocarcinus orbicularis, L. holothuricola (Streets, 1876), and L. ornatus Chopra, 1931 are all symbionts of sea cucumbers and exhibit similar colorations (Fig. 1), but they are easily distinguished by differences in their frontal margin, epibranchial ridge, and fifth pereopod (Stephenson, 1972).
During an expedition to Saudi Arabia, an ovigerous female (UGI 3135) was collected from Majjde Reef, Red Sea, near the mouth of the Gulf of Aqaba. Together with three specimens at the Florida Museum (UF) from the Gulf of Aqaba (UF 47297) and Wasaliyat Islands (UF 48601, UF 48625), we report this species across much of the extent of the Red Sea. Recent expeditions to Oman and Djibouti resulted in additional specimens from the region (see http://specifyportal.flmnh.ufl.edu/iz/).
This research was supported by NEOM (grant 5209 - Biodiversity Baseline Assessment and Monitoring), the National Science Foundation (GECCO 1457769, DEB 1856245), and a Japan Society for the Promotion of Science (JSPS) post-doctoral fellowship (P22078).
Caulier, G., Lepoint, G., Van Nedervelde, F., & Eeckhaut, I. (2014). The diet of the Harlequin crab Lissocarcinus orbicularis, an obligate symbiont of sea cucumbers (holothuroids) belonging to the genera Thelenota, Bohadschia and Holothuria. Symbiosis, 62: 91-99. https://doi.org/10.1007/s13199-014-0274-2
Chopra, B. (1931). Further notes on Crustacea Decapoda in the Indian Museum. II. On some decapod Crustacea found in the cloaca of holothurians. Records of the Indian Museum, 33(3): 303-324. https://doi.org/10.26515/rzsi/v33/i3/1931/162506
Evans, N. (2018). Molecular phylogenetics of swimming crabs (Portunoidea Rafinesque, 1815) supports a revised family-level classification and suggests a single derived origin of symbiotic taxa. PeerJ, 6: e4260. https://doi.org/10.7717/peerj.4260
DiBattista, J. D., Roberts, M. B., Bouwmeester, J., Bowen, B. W., Coker, D. J., Lozano‐Cortés, D. F., ... & Berumen, M. L. (2016). A review of contemporary patterns of endemism for shallow water reef fauna in the Red Sea. Journal of Biogeography, 43(3): 423-439. https://doi.org/10.1111/jbi.12649
Guinot, D. (1967). La faune carcinologique (Crustacea Brachyura) de l'Océan Indien occidental et de la Mer Rouge. Catalogue, remarques biogéographiques et bibliographie. In CSA Specialist Meeting on Crustaceans. Zanzibar, 19-26 IV 1964.
Laurie, R.D. (1915). Reports on the marine biology of the Sudanese Red Sea.-XXI. On the Brachyura. Journal of the Linnean Society of London, Zoology 31(209): 407–475. https://doi.org/10.1111/j.1096-3642.1915.tb00463.x
Sankarankutty, C., & Thomas, P. T. (1963). Some abnormalities in Lissocarcinus orbicularis Dana (Crustacea-Portunidae) from Minicoy. Journal of the Marine Biological Association of India, 5(1): 144-145.
Stephenson, W. (1972). An annotated check list and key to the Indo-West-Pacific swimming crabs (Crustacea: Decapoda: Portunidae). Bulletin of the Royal Society of New Zealand, 10: 1-64.
Streets, T.H. (1876). Another case of animal commensalism. American Naturalist, 10(7): 429-430. https://doi.org/10.1086/271701
Vannini, M., & Innocenti, G. (2000). Research on the coast of Somalia. Portunidae (Crustacea Brachyura). Tropical Zoology, 13(2): 251-298. https://doi.org/10.1080/03946975.2000.10531136
Figure. Lissocarcinus orbicularis, ovigerous female (UGI 3135), Majjde Reef, Gulf of Aqaba, Red Sea. Left: dorsal view; Right: map of new Red Sea records.
