Presynaptiphilus minutus, 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 : 380-384

Presynaptiphilus minutus n. sp.

( Figures 7 ±9)

Material examined. Nineteen mm and 13 ll from the external surface of the ophiuroid Amphiura sinicola (Matsumoto) , collected from the intertidal mud ¯at at Jakyak-do Island , on 29 September 1996. Holotype (m), allotype (l), and 26 paratypes (16 mm, 10 ll) have been deposited in the US National Museum of Natural History, Smithsonian Institution. Two mm and two ll(dissected) are kept in the collection of the author.

Female. Body (®gure 7A) very small, elongate, 0.59 mm long. Greatest width 235 mm. Prosome comprising cephalothorax, second and third pedigerous somites. Cephalothorax roughly pentagonal, becoming wider posteriorly. Posterior corners of cephalothorax and succeeding two prosomites rounded. Posteromedian part of tergites of latter two somites fringed with membrane. Third pedigerous somite (second metasome) narrower but distinctly longer than second pedigerous somite.

Urosome (®gure 7B) six-segmented, almost cylindrical, comprising fourth and ®fth pedigerous somites, genital double-somite and three-segmented abdomen. Fourth pedigerous somite very narrow, without epimerae, only slightly wider than ®fth pedigerous somite. The latter 82 mm wide. Genital double-somite quadrangular (®gure 7B), 49Ö 75 mm. Genital area small, located dorsolaterally at about anterior third. Genital double-somite and abdominal somites armed with spinules at posterior corners. Three abdominal somites 35 Ö51, 53 Ö43, and 15Ö 39 mm, respectively. Second abdominal somite very long, and third abdominal somite characteristically short. The latter becoming narrower posteriorly. Caudal rami in contact with each other, small, 19Ö 15 mm (1.27:1). Outer one of two mid-terminal setae shortest among six setae, spiniform, whereas inner one longest, more than four times as long as next longest, outermost terminal seta. All six setae naked.

Rostrum quadrate, with truncate posterior margin. Antennule (®gure 7C) sixsegmented, 125 mm long, tapering, with armature formula 4, 14, 9, 4, 2 +1 aesthetasc, and 7 +1 aesthetasc. Antenna (®gure 7D) four-segmented, with armature formula 1, 1, 3 +1 claw, and 7. Third segment very short; claw strong; innermost one of three setae very tiny. Fourth segment distinctly shorter than wide; three inner ones of seven setae claw-like.

Labrum relatively narrow, only covering part of mandible, and unarmed (®gure 7E). Mandible (®gure 7F) armed with one terminal, distally bifurcate, spiniform element and one subterminal seta. Maxillule (®gure 7G) bilobed, armed with three plumose setae on larger lobe and one smaller glabrous seta on smaller lobe. Maxilla (®gure 7H) two-segmented; ®rst segment with one dorso-distal, proximally thick, spiniform seta; distal segment slender, terminated in spiniform element, with one minute seta on ventral margin and two distal setae. Maxilliped (®gure 8A) twosegmented. First segment prolonged, articulated in the middle, and distally with spinules along posterior margin. Second segment originated from basal part of ®rst segment, pouch-like, 34Ö 25 mm, weakly bilobed terminally, with a pair of small setae on each lobe, and setules on dorsal surface.

Leg 1 (®gure 8B), leg 2 (®gure 8C) and leg 3 with three-segmented rami, but leg 4 (®gure 8D) with two-segmented rami. Posterior margin of intercoxal plates of legs 1±3 armed with acute spinules. These spinules also occurring on posterior margin of basis of legs 1±3 and outer margins of nearly all exopodal and endopodal segments of legs 1±4. Terminal endopodal segment of leg 1 with tapering outer

terminal process; outer spine of this segment located proximally, near border of second segment.

Leg 5 two-segmented (®gure 7B). Basal segment well marked from ®fth pedigerous somite, with one long seta and spinules on outer side. Distal segment 29 Ö 19 mm (1.53:1), with inner margin about twice longer than outer margin; distal margin bevelled, with one seta and three setiform spines. Leg 6 represented by two minute spinules in genital area.

Male. Body (®gure 8E) resembling that of female, gradually narrowed posteriorly. Length 573 mm. Maximum width 218 mm. Prosome three-segmented, and urosome (®gure 9A) seven-segmented. Genital somite 31 Ö 78 mm, more than twice as wide as long. Four abdominal somites 27 Ö60, 34 Ö46, 42 Ö38, and 14Ö 32 mm, respectively. Caudal ramus 17Ö 14 mm (1.21:1).

Antennule with two additional setae: one added on second segment (therefore 15), and another on third (ten). Antenna as in female.

Mouth parts as in female, except for maxilliped. Maxilliped (®gure 9B) consisting of three segments and terminal claw. First segment unarmed. Second segment greatly expanded proximally and strongly tapering; inner proximal region with two setae and a folded area where tip of terminal claw inserts; inner margin with one row of spinules, one of proximal spinules distinctly enlarged. Third segment small and unarmed. Claw long and slender, curved terminally, and proximally with two small setae.

Leg 1 (®gure 9C) with three-segmented exopod and two-segmented endopod. Armature formula of endopod 0-1; I, 3. Inner seta on coxa spiniform, shorter but thicker than that of female. Outer terminal process of distal endopodal segment curved and more prominent than that of female. Outer and inner terminal setae of this segment smaller. Legs 2±4 as in female. Basal segment of leg 5 well marked from ®fth pedigerous somite as in female; distal segment of leg 5 26Ö 16 mm (1.63:1). Leg 6 not seen.

Etymology. The speci®c name minutus refers to the small body size of the new species.

Remarks. The genus Presynaptiphilus includes two known species, P. acrocnidae Bocquet and Stock, 1960 and P. amphiopli Humes and Hendler, 1972 , both from the Atlantic. The new species di ers from these in the following features: (1) the pre-anal somite is longer than wide in both sexes; (2) the terminal endopodal segment of leg 1 with one spine and three setae (I, 3), instead of one spine and ®ve setae (I, 5) as in the other two species; and (3) a short caudal ramus with a length to width ratio of 1.27:1, compared with 2: 1 in P. amphiopli or 3: 1 in P. acrocnidae . Other important di erences are found in leg 1: the ®rst endopodal segment bears one seta (none in P. acrocnidae ), the endopod of this leg in male is two-segmented (three-segmented in P. acrocnidae ); and, the inner element on the the basis is a spine (rather than a seta in P. amphiopli ).

Figures

FIG. 7. Presynaptiphilus minutus n. sp., female. (A) habitus, dorsal; (B) urosome, dorsal; (C) antennule; (D) antenna; (E) mouthparts; (F) mandible; (G) maxillule; (H) maxilla. Scales: A = 0.1 mm; B= 0.05 mm; C±H= 0.02 mm.