A cryptic radiation of Caribbean sea slugs revealed by integrative analysis: Cyerce ‘ antillensis’ (Sacoglossa: Caliphyllidae) is six distinct species Author Moreno, Karina Department of Biological Sciences, California State Polytechnic University Pomona, Pomona, CA 91768, USA Author Rico, Diane M. Department of Biological Sciences, California State University, Los Angeles, CA 90032 - 8201, USA Author Middlebrooks, Michael Department of Biology, University of Tampa, Tampa, FL 33609, USA Author Medrano, Sabrina Department of Biological Sciences, California State Polytechnic University Pomona, Pomona, CA 91768, USA Author Valdés, Ángel A. Department of Biological Sciences, California State Polytechnic University Pomona, Pomona, CA 91768, USA Author Krug, Patrick J. Department of Biological Sciences, California State University, Los Angeles, CA 90032 - 8201, USA pkrug@calstatela.edu text Zoological Journal of the Linnean Society 2024 2023-10-12 200 4 940 979 http://dx.doi.org/10.1093/zoolinnean/zlad111 journal article 10.1093/zoolinnean/zlad111 0024-4082 PMC10983082 38566915 11240925 E8CC81A3-E625-4C48-B783-29AA9BFC83C3C Cyerce ellingsonorum sp.nov. ( Figs 1–3 , 5 , 8C , 16 ) ZooBank registration: lsid:zoobank.org:act: 960213E3-2A4A-4173-9413-55EE6D137788 Cyerce antillensis — Thompson 1977: 135–137 , figs 22g , 30. Type material Holotype : Discovery Bay , Jamaica , March 2006 , 3 mm preserved length ( LACM 3841 ; isolate 06Jam09). Additional material examined Jamaica , March 2006 , one specimen preserved, isolate 06Jam05b . Range Jamaica (present study). Description External morphology: From Thompson (1977) : brown in overall colour with scattered red specks. Rhinophores dark brown. Anal papilla prominent. Cerata paddle shaped, pale brown, with darker brown markings and white margins. Internal morphology: Buccal mass < 1 mm ; buccal bulb larger than pharyngeal pouch. Radula of holotype specimen 2.4 mm long ( LACM 3841 ), with six teeth on ascending limb and 10 teeth on descending limb ( Fig. 16A ). Teeth shallow, bent at an angle of 20°, tapering to pointed tip; 125 µm in length ( Fig. 16A, B ). Thompson (1977) reported a leading tooth 290 μm long for a 55-mm-long specimen from the type locality. A row of ~10 low, rectangular denticles along each cutting edge; denticles widest where tooth bends (≤ 6 μm wide), narrowing towards tip ( Fig. 16B ). Ascus with dense mass of ≥ 10 pre-radular teeth ( Fig. 16C ). Penis with straight, cylindrical stylet with wide base, 65 µm long; triangular opening at pointed tip ( Fig. 8C ). Ecology Collected from the green alga Pe. dumetosus at the type locality; approximately five specimens per 400 g wet weight of algae were collected on two separate days. No other Cyerce specimens were obtained from collections of Udotea spp. , Halimeda spp. or any other green alga made in Jamaica at the time the specimens of C. ellingsonorum were collected. Etymology Named in joint honour of Gary Ellingson and his son, Dr Ryan A. Ellingson, who co-collected the specimens analysed in the present study and helped P.J.K. to establish a molecular systematics research programme. Remarks Cyerce ellingsonorum was not recognized as a distinct species at the time of collection, and no photographs of live animals were taken, nor were photographs of living Cyerce specimens from Jamaica available to us. The best available description of the live animal is likely to be that of Cyerce specimens collected at the type locality of C. ellingsonorum by Thompson (1977) . The specimens described by Thompson (1977) do not match C. antillensis well in external morphology, and the size and shape of the radular tooth are very different from C. antillensis but compatible with C. ellingsonorum . No specimens of C. antillensis were obtained from collections of H. opuntia made in Discovery Bay, Jamaica , when the specimens of C. ellingsonorum were collected. Based on molecular data, C. ellingsonorum was supported as distinct in all species delimitation analyses and might be endemic to Jamaica . In phylogenetic analyses, C. ellingsonorum was sister to three other C. antillensis complex members in a supported clade of four species. Notably, three of those four species are potential endemic taxa: C. ellingsonorum from Jamaica ; C. willetteorum from Great Stirrup Cay, Bahamas ; and C. browneveorum from the Florida Keys, USA . Only C. nicholasi had a widespread range among members of this clade. At least two of the four species are lecithotrophic ( Table 5 ). If all four species inherited lecithotrophy from a common ancestor, limited dispersal potential might have promoted species formation in this lineage by reducing the scale of gene flow and favouring local adaptation. The radular teeth of C. ellingsonorum were more angled than those of any Caribbean species except C. antillensis and bore the widest rectangular denticles of any complex member; the denticles were up to twice as wide on the teeth of C. ellingsonorum as on the teeth of C. nicholasi , which had the most similar radular morphology. A straight penial stylet bearing a triangular pointed tip differentiated C. ellingsonorum from most C. antillensis complex members, which had stylets that either curved or had oval openings ( Table 5 ).