Revision of the genus Tapholeon Wells, 1967 (Copepoda, Harpacticoida, Laophontidae) Author Gheerardyn, Hendrik Author Fiers, Frank Author Vincx, Magda Author Troch, Marleen De text Journal of Natural History 2007 2010-12-02 41 37 - 40 2479 2510 http://dx.doi.org/10.1080/00222930701695629 journal article 10.1080/00222930701695629 1464-5262 5233167 Tapholeon arenicolus ( Chappuis, 1954 ) comb. nov. ( Figures 5 , 6 ) Synonym. Asellopsis arenicola Chappuis, 1954 . Type locality Comoro Islands , Grande Comore (beach of Mitsamiouli), very fine coral sand, and gravel with coral rubble and shell debris ( Chappuis 1954 ) . Type material Unknown. Additional material Comoros , southeastern coast of Grande Comore , Ouroveni (11 ° 549S, 43 ° 299E), small protected creek with mangrove, sample of fine sand, two dissected females ( COP 1984 , COP 1985 ), one dissected male ( COP 1986 ), and more than 50 specimens preserved in alcohol ( COP 1987 ); collected 3 August 1984 by Groupe Plongée de l’Expedition Karthala . Redescription of female Total body length 354–398 Mm ( n 510; average5373 Mm; measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalothorax: 97 Mm. Measurements by Chappuis (1954) : 0.4 mm without caudal setae. Rostrum triangular and prominent; fused to cephalothorax. Habitus ( Figure 5A ): body elongate and slender; urosome weakly tapering towards anal somite. Genital double-somite and following urosomite slightly extended laterally. Integument of cephalothorax and pleurotergites with irregular pattern of small denticles. Posterodorsal margin of cephalothorax smooth, of free prosomites smooth along median part but serrate laterally, of all urosomites serrate. Posterodorsal margins of all free somites (except second urosomite) clothed with slender hairs. Anal operculum convex with slightly serrate margin, not protruding. Ventral surface of genital double-somite and following urosomites smooth. Posteroventral margins of genital double-somite and of next two urosomites with long, slender hairs. Figure 5. (A–F) Tapholeon arenicolus ( Chappuis, 1954 ) comb. nov. : (A) female habitus, dorsal; (B) female caudal rami, dorsal; (C) female caudal rami, lateral; (D) male antennule (armature omitted), ventral; (E) female antennule (armature omitted), ventral; (F) female antennary exopod. (G) Tapholeon ornatus Wells, 1967 : female anal somite and caudal rami, dorsal. Scale bars in Mm. Figure 6. Tapholeon arenicolus ( Chappuis, 1954 ) comb. nov. (A) Female P1, posterior; (B) female P2, anterior; (C) female P3, anterior; (D) female P5, anterior; (E) female P4, posterior; (F) male P6, anterior; (G) male P5, anterior. Scale bar in Mm. Caudal rami ( Figure 5B, C ) flattened; as long as wide, with subquadrate appearance in dorsal view; tapering strongly towards apical margin in lateral view. Surface strongly concave beyond implantation of dorsal seta. Distal inner corner rounded, strongly serrate. Lateral margin spinulose. Seta IV short; seta V about two times length of caudal ramus and pinnate; all other setae naked. Seta VII inserted near middle of ramus. Antennule ( Figure 5E ) six-segmented. First, second, and third segment each with row of spinules. Second segment with strong, armed spine along outer margin. Ultimate segment with rounded tip. Armature formula as in type species. Antenna ( Figure 5F ) and mouthparts as in type species. P1 ( Figure 6A ) with pattern of spinules as figured. Exopod two-segmented; exp-2 bearing four setae. Enp-1 four times as long as exp. P2–P4 ( Figure 6B–D ) with three-segmented exopods and two-segmented endopods, with pattern of spinules as figured. Setal formula in Table I. P5 ( Figure 6D ) with separate exopod and baseoendopod. Margins of rami furnished with spinules, surface smooth. Baseoendopod reaching beyond middle of exopod; bearing one apical and three lateral setae. Exopod ovate; two times as long as wide; bearing five setae. P6 vestige bearing one seta. Redescription of male Total body length 346–384 Mm ( n 510; average5362 Mm; measured from anterior margin of rostrum to posterior margin of caudal rami). Largest width measured at posterior margin of cephalothorax: 88 Mm. Habitus as in female; except for fully separated second and third urosomites and lack of lateral extensions in second to fourth urosomites. Ventral surface of third urosomite with transversal row of large spinules. Antennule ( Figure 5D ) sub-chirocer. Shape of first and second segment as in female. Armature formula as in type species. Antenna, mouthparts, and P1–P4 as in female. P5 ( Figure 6G ): endopodal lobe obsolete; without seta. Exopod small; bearing three strongly armed setae. P6 vestiges ( Figure 6F ) asymmetrical; each bearing a plumose inner and a naked outer seta. Remarks Chappuis (1954) assigned this species to the genus Asellopsis Brady and Robertson, 1873 because of the remarkably flattened (asellopsiform) caudal rami. Also, at the time of description the genus Tapholeon had not been established. However, Chappuis (1954) made no reference to a three-segmented endopod P 3 in the male, but only mentioned a slightly shorter inner seta on the second endopodal segment of this leg. In the present material, neither a three-segmented male endopod nor a differentiated seta was found. Therefore, A. arenicola should be excluded from the genus Asellopsis , which typically displays pronounced sexual dimorphism in the third leg. Fortunately, Chappuis (1954) illustrates the peculiar seta on the second antennular segment. The thickened antennular seta, the lack of sexually dimorphic structures in the legs, and the strongly reduced shape of the P 5 in the male clearly indicate that A. arenicola must be transferred to the genus Tapholeon . Other differences with the original decription are: P1 exopod with four setae on the second segment, instead of three as shown by Chappuis (1954) ; the much longer setae (reaching far beyond the exopod) of the endopods of P2–P4; the presence of an inner seta on exp-2 of P3, and the plumose setae on the rami of the P5. Differential diagnosis The present species bears three outer spines on the ultimate segments of the exopods of P2–P4, lacks an inner seta on exp-2 of P4, and bears two, three and three setae on the second endopodal segments of P2–P4, respectively. Distribution Grande Comore , Comoros ( Chappuis 1954 ; present report).