Description Small nudibranch up to 14mm in length. Quite variable in color, the typical pattern is the translucent body with white patching on the head and behind the rhinophores that may form a broad continuous median dorsal band from the front of the head to the tip of the tail. There can also be an opaque white irregular band along each side of the body, below the cerata. It has orange markings on the head, often consisting of an orange line from the base of the oral tentacles to the base of the rhinophores. There can also be an orange patch on each side of the head (cheek patch) that could be replaced by an orange line from the base of the rhinophores to the foot, or from below the rhinophores forward to the front of the head below the oral tentacles. The rhinophores are often described as annulate, perfoliate or lamellate, but they consistently have an irregular arrangement of 6-10 rings or annulations, some of which are irregular or incomplete (Edmunds, 1964). The oral tentacles are smooth. The cerata stand in about 8 groups laid in arches, the hindmost of which are indistinctly separated; they are translucent with a few scattered white patches (covering most of the cerata in certain specimens), a subterminal white band (there could be an orange band in certain specimens) and a white cnidosac on the tip. The digestive gland can be seen, by transparency, inside the cerata and it could be colored from light brown to dark brown or even black. The eyes are black. The foot is narrower than the body, specially in the anterior side, it has a bilabiate anterior border with tappered propodial tentacles normally facing backwards as the animal moves. The tail is short.
Biology The animals appear to move little. Sometimes it forms clusters on the hydroids they feed on (Halocordyle disticha in the Canary Islands). It has the ability to retain undischarged nematocysts from their preys and store them in the cnidosacs at the tips of cerata. The spawn is a convoluted spiral of white eggs laid on the hydroids they feed on.
Learchis, of uncertain meaning, seems related to the Greek mythology, where there’s a story about Ino (a mortal queen of Thebes) and Athamas (a Boeotian king, son of Aeolus and Enarete) who hunted his own son Learchos as a stag and slew him. Classical authors like Bergh rarely explained the origins of the names they proposed, but they used to inspire in the Greek and Roman mythology.
Poica. No information available about the origin of the specific name.
Distribution The present species is the first Atlantic member of the genus, and it has been found in Aruba, Bahamas, Barbados, Cayman Islands, Costa Rica, Curaçao, Grenada, Jamaica, Martinique, Mexico, Puerto Rico, St. Lucia, St. Vincent & the Grenadines, Virgin Islands, USA and Venezuela. Also in Ghana, West Africa (Edmunds, 1968), Madeira (Cervera & Malaquias, unpubl. data), Azores (Moro, pers.comm.) and the Canary Islands (Moro, Bacallado y Ortea, 2010).
Known georeferenced records of the species: Learchis poica
Caballer, M., J. Ortea, N. Rivero, G. Carias-Tucker, M. A. E. Malaquías, and S. Narciso. 2015. The opisthobranch gastropods (Mollusca: Heterobranchia) from Venezuela: an annotated and illustrated inventory of species. Zootaxa 4034 (2): 201–256.
Cervera, J. L., G. Calado, C. Gavaia, M. A. E. Malaquías, J. Templado, M. Ballesteros, J. C. García-Gómez, and C. Megina. 2004. An annotated and updated checklist of the opisthobranchs (Mollusca: Gastropoda) from Spain and Portugal (including islands and archipelagos). Boletín Instituto Español de Oceanografía, 20 (1-4): 1-111. L.
Edmunds, M.1968. Eolid Mollusca from Ghana, with further details of west Atlantic species. Bulletin of Marine Science 18(1):203-219.
Edmunds, M.1970. Opisthobranchiate Mollusca from Tanzania. II. Eolidacea (Cuthonidae, Piseinotecidae and Facelinidae). Proceedings of the Malacological Society of London 39(1):15-57; tbls. 1-3; figs. 1-24.
Edmunds, M.2015. Opisthobranchiate Mollusca from Ghana, Aeolidiidae, with consideration of several caribbean species. Journal of Conchology Vol. 42(2): 125-161.
Edmunds, M.1966. Protective mechanisms in the Eolidacea (Mollusca, Nudibranchia). Journal of the Linnean Society (Zoology) 46(308):27-71, pls. 1-4.
Edmunds, M.1977. Larval development, oceanic currents, and origins of the Opisthobranch fauna of Ghana. Journal of Molluscan studies 43:301-308.
Edmunds, M.1964. Eolid Mollusca from Jamaica, with the description of two new genera and three new species. Bulletin of Marine Science of the Gulf and Caribbean 14 (1): 1-32.
Edmunds, M., and H. Just. 1983. Eolid nudibranchiate mollusca from Barbados. Journal of Molluscan Studies 49 (3): 185-203.
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Moro, L., J. J. Bacallado, and J. A. Ortea. 2010. Babosas marinas de las islas Canarias. Actas VI Semana Científica Telesforo Bravo, Instituto de Estudios Hispánicos de Canarias.
Moro, L., J. Ortea, and J. J. Bacallado. 2016. Nuevas citas y nuevos datos anatómicos de las babosas marinas (Mollusca: Heterobranchia) de las islas Canarias y su entorno. Revista de la Academia Canaria de las Ciencias., 48: 9-52.
Ortea, J., and L. Moro. 2018. Nuevas citas y nuevos datos sobre las lesmas do mar (Mollusca: Gastropoda) de las islas de Cabo Verde (II). Avicennia. 22: 49–58.
Ortea, J., M. Caballer, and L. Moro. 2004. Dos aeolidaceos con ceratas rojos de la region macaronesica y el mar Caribe (Mollusca: Nudibranchia). Vieraea 32: 83-96.
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Rosenberg, G.2009. Malacolog 4.1.1. A Database of Western Atlantic Marine Mollusca. The Academy of Natural Sciences, Philadelphia, PA.
Rosenberg, G., F. Moretzsohn, and E. F. García. 2009. Gastropoda (Mollusca) of the Gulf of Mexico, Pp. 579–699 in Felder, D.L. and D.K. Camp (eds.), Gulf of Mexico–Origins, Waters, and Biota. Biodiversity. Texas A&M Press, College Station, Texas.
Shoemaker, A. H., H. J. Porter, B. Boothe, R. E. Petit, and L. S. Eyster. 1978. Marine mollusks; pp. 123-135, In: An annotated checklist of the biota of the coastal zone of South Carolina, 364 pp. University of South Carolina Press.
Templado, J., A. A. Luque, and J. A. Ortea. 1991. A commented check-list of the amphiatlantic Ascoglossa and Nudibranchia (Mollusca: Opisthobranchia). Lavori della Societa Italiana di Malacologia 23:295-326.
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Thompson, T. E.1977. Jamaican Opisthobranch Molluscs I. Journal of Molluscan Studies 43: 93-140.
Turgeon, D., J. F. Quinn, A. E. Bogan, E. V. Coan, F. G. Hochberg, W. G. Lyons, P. M. Mikkelsen, R. J. Neves, C. F. E. Roper, G. Rosenberg, B. Roth, A. Scheltema, F. G. Thompson, M. Vecchione, and J. D. Williams. 1998. Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. 2nd ed. American Fisheries Society Special Publication, 26.
Valdés, A., J. Hamann, D. W. Behrens, and A. DuPont. 2006. Caribbean sea slugs: a field guide to the opisthobranch mollusks from the tropical northwestern Atlantic. Washington: Sea Challengers Natural History Books. 289 pp.
Walls, J. G.1982. Encyclopedia of marine invertebrates, 736 pp T.F.H. Publications.
Pontes, Miquel, Manuel Ballesteros, Enric Madrenas (2022) "Learchis poica" in OPK-Opistobranquis. Published: 27/10/2016. Accessed: 22/05/2022. Available at (https://opistobranquis.info/en/SQh2I)
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Many thanks to Sandra Edwards, Judy Townsend, Lureen Ferretti and specially to Anne DuPont by putting us in contact with her diving buddies who provided us the Florida pictures of Learchis poica illustrating the record of this species. Thank you very much as well to Susan and Rick Coleman by the Bonaire pictures of Learchis poica, that show a chromatic variation not present in Florida.
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