Synaptiphilus longicaudus, Kim, 2000

Kim, Il-Hoi, 2000, Poecilostomatoid Copepods from an Intertidal Mud Flat in the Yellow Sea, Journal of Natural History 34 (3), pp. 367-432 : 384-389

Synaptiphilus longicaudus n. sp.

( Figures 10 ±12)

Material examined. One hundred and thirty-®ve mm and 47 ll from the external body surface of about 40 individuals of the holothurian, Protankyra bidentata (Woodward and Barrett) , collected in the intertidal mud ¯at at Jakyak-do Island o Inchon, on 1 September 1996. Holotype (m), allotype (l) and 52 paratypes (40 mm and 12 ll) have been deposited in the US National Museum of Natural History , Smithsonian Institution. Remaining specimens (94 mm and 34 ll) are kept in the collection of the author.

Female. Body (®gure 10A) dorsoventrall y ¯attened, and 853 mm long. Greatest width 438 mm. Prosome broad, composed of cephalothorax and three pedigerous somites. Somites with well developed epimera. Tergites of cephalothorax and two following somites with acutely pointed posterolateral processes. Cephalothorax much wider than long. Fourth pedigerous somite distinctly narrower than those of anterior somites, its mid-posterior margin curved, W-shaped, with round lateral margins. Urosome (®gure 10B) ®ve-segmented, narrow, tapering, and originating from ventral side of fourth pedigerous somite. Ventral surface of ®rst three urosomites with minute spinules. Fifth pedigerous somite much broader than genital double-somite. Genital double-somite obscurely delimited dorsally from ®fth pedigerous somite but distinctly delimited ventrally, 53Ö 88 mm (measured ventrally). Genital areas located dorsolaterally in anterior part. Posteroventral border of genital double- and ®rst two abdominal somites fringed with row of spinules. Three abdominal somites 32 Ö65, 23 Ö60, and 23Ö 50 mm, respectively (measured ventrally). Anal somite narrowed distally and incised posteromedially. Caudal ramus very long and slender, 113Ö 13 mm (8.7:1), terminated in pointed process (®gure 10C). All six caudal setae smooth, aggregated in terminal portion of caudal ramus. Inner one of two median terminal setae distinctly larger than others.

Spermatophore (®gure 10F) elongate, 192Ö 42 mm. Egg sac 290Ö 155 mm, extending beyond tip of caudal rami.

Rostrum nearly circular, with point at posterior tip (®gure 11A). Antennule (®gure 10D) six-segmented, with armature formula 4 (or 5), 14, 9, 4 +1 aesthetasc, 2 +1 aesthetasc, and 7 +1 aesthetasc. First segment with three or four proximal claws in addition to setae. Third segment with hairs on posterior margin. Antenna (®gure 10E) four-segmented. First segment with one inner distal seta and long setules on outer margin. Second segment with one subterminal seta and long spinules near outer distal corner. Third segment very short, with one strong claw and one seta. Terminal segment with setules on outer side, and terminally three setae and four spatulate claws.

Labrum tapering posteriorly and not covering mouth parts (®gure 11A). Mandible (®gure 11B) armed with one strong, posteriorly pectinated, terminal element and one subterminal process-like element. The latter distally bi®d, with setules on posterior margin. Paragnath not seen. Maxillule (®gure 11C) a lobe armed distally with three setae. Maxilla (®gure 11D) two-segmented. First segment with long setules basally, ventral row of spinules, and one large spine distally. Second segment small, terminally with one strong spine and two dorsal setae (one of them plumose), and one smaller ventral seta; the latter directed laterally, recurved around segment. Maxilliped (®gure 11E) two-segmented. Basal segment very broad, armed distally with one large spine extending beyond end of distal segment. Distal segment elongateoval, tapering but roundly ended, with many spinules basally, and distally one seta and several setules.

Legs 1±4 with three-segmented exopod and two-segmented endopod. Intercoxal plate of leg 1 with long setules on posterior margin (®gure 11F), but those of legs 2 (®gure 11G) and 3 (®gure 12A) with spinules on this margin. All legs 1±4 without inner seta on coxa. Middle portion of posterior margin of legs 1±4 pectinated. Distal endopodal segment of leg 1 curved outward and bearing terminal process. Outer distal corner of ®rst endopodal segment of legs 1±4 with acutely pointed process. Armature formula of legs 1± 4 as follows:

Leg 5 (®gure 12C) two-segmented. Basal segment as long as wide, well delimited from ®fth pedigerous somite, with one distal seta and spinules near base of seta. Free segment 77Ö 40 mm (1.93:1), tapering in distal half, with four setae and densely arranged spinules on both margins.

Leg 6 represented by two spiniform elements in genital area (®gure 12D).

Male. Body (®gure 12E) similar to that of female. Length 842 mm. Greatest width 400 mm. Posterior margin of fourth pedigerous somite incised medially, its curvature di erent from that of female. Urosome (®gure 12F) six-segmented. Genital somite slightly narrower than ®fth pedigerous somite, much wider than long, 42Ö 123 mm. Four abdominal somites gradually shorter and narrower, 42 Ö88, 37 Ö68, 25 Ö57, and 22Ö 48 mm, respectively. Caudal ramus 98Ö 13 mm (7.54:1).

Antennule di erent from that of female in bearing ten setae on third segment, instead of nine. Antenna as in female.

Maxilliped (®gure 12G) consisting of three segments and terminal claw. First segment unarmed, distally broadened. Second segment greatly expanded inwards, nearly quadrangular, as long as wide, more broadened distally, armed on distal margin with one seta, about two rows of spinules and a membranous fringe on inner part of distal margin and spinules on lateral surfaces. Third segment short and unarmed. Claw thick, long, weakly curved terminally, with two small proximal setae. Other mouth organs as in female.

Legs 1±4 not di erent from those of female. Basal segment of leg 5 well delimited from ®fth pedigerous somite as in female. Distal segment 58 Ö 26 mm (2.23:1), without spinules on inner margin. Leg 6 represented by one thin seta on genital ¯ap (®gure 12F).

Etymology. The speci®c name longicaudus alludes to the very long caudal rami of the new species.

Remarks. The genus Synaptiphilus is known by three species associated with Atlantic holothurians: S. luteus Canu and Cuenot, 1892 , S. tridens T. and A. Scott, 1894, and S. cantacuzenei Bocquet and Stock, 1957 . The latter is a polytypic species, with a subspecies S. cantacuzenei mixtus Guille and Laubier, 1965 .

Identi®cation of S. longicaudus n. sp. is very easy due to its extremely long caudal rami, a characteristic observable without dissection. The ratio of length to width of its caudal rami is 8.7:1, whereas in all other known species it does not exceed 3:1. Other salient morphological features of the new species are: (1) ®rst endopodal segment of leg 1 unarmed (one medial seta on this segment in other species) and (2) second endopodal segment of leg 1 with two spines and one seta (I, I, 1) compared with one spine and two setae (I, 2) in other species.

Figures

FIG. 10. Synaptiphilus longicaudus n. sp., female: (A) habitus, dorsal; (B) urosome, dorsal; (C) same, ventral; (D) antennule; (E) antenna; (F) spermatophore. Scales: A = 0.1 mm; B±D, F= 0.05 mm; E=0.02 mm.