Macandrewella serratipes, Ohtsuka & Nishida & Nakaguchi, 2002

Ohtsuka, Susumu, Nishida, Shuhei & Nakaguchi, Kazumitsu, 2002, Three new species of the genus Macandrewella (Copepoda: Calanoida: Scolecitrichidae) from the Paci ® c Ocean, with notes on distribution and feeding habits, Journal of Natural History 36 (5), pp. 531-564 : 554-559

Macandrewella serratipes new species

(®gures 19, 20)

Synonym. Macandrewella chelipes sensu Wilson, 1950 .

Material examined. Fiji Is. (16 ss 32 ¾ S, 119 ss 59 ¾ W), 40 fathoms, 21 January 1905 (Wilson leg.): 7 and 6. Note: the ledger book for the USNM numbers says only Fiji, and the latitude/longitude of the locality described in the vial plots out to the South Paci ®c near Tuamotu Is. but not in Fiji. Hence the type locality is in question (Walter, personal communication) .

Types. HOLOTYPE: 1, appendages dissected and mounted on glass slides, body in vial, USNM 67242 . PARATYPES: 1 and 3, appendages dissected and mounted on glass slides, body in vial; 5 and 3, whole specimens, USNM 232823 .

Body length.: 2.91±3.23 mm (3.04 Ô 0.11 mm, n 57).: 3.16±3.74 mm (3.45 Ô 0.23, n 56).

Description. The new species was brie¯y described as Macandrewella chelipes by Wilson (1950), but several characters were overlooked or misunderstood. These are newly or precisely described in the present study.

Female: Prosome (®gure 19A) with fourth and ®fth pedigers almost completely coalescent; prosomal ends (®gure 19A±D) slightly asymmetrical, with dorsolateral processes reaching posterior end of genital double-somite. Urosome (®gure 19A, D) less than one-third length of prosome; genital double-somite asymmetrical, with two anterior round knobs and posterior swollen corner on right side; genital operculum (®gure 19E) wider than long; seminal receptacles extending laterally (®gure 19A); second and third urosomites with striated frill along posterior margin; anal somite small, almost telescoped into preceding somite; anal operculum rounded posteriorly; caudal rami symmetrical in original description, but not con®rmed in present description, as in all specimens examined caudal seta V was missing.

Antennule exceeding beyond prosomal ends by last two segments (®gure 19A); armature and fusion pattern of segments as in M. stygiana . Antenna, mandible (®gure 19F), maxillule and maxilla similar to those of M. stygiana . Maxilliped (®gure 19G) with proximal patch of long setules on syncoxa.

Legs 1±4 (®gure 19H±J) basically resembling those of M. stygiana (see ®gure 6), but diOEering in number of minute prominences. Leg 4 (®gure 19J) lacking large prominences on both surfaces of rami. Leg 5 absent.

Male: Habitus similar to two new species described above; rostrum (®gure 20A) with pair of sharply pointed prominences beneath bases of ®laments; prosomal ends (®gure 20B±D) slightly asymmetrical, with right dorsolateral prominence larger than left. Urosome (®gure 20B) with ®rst two somites asymmetrical; genital somite with small round dorsal knob on both sides; second urosomite swollen on left side.

Antennules (®gure 20K±M) reaching posterior margin of third urosomite; armature and fusion pattern of segments of both antennules similar to two new species described above. Antenna with proximal-most seta on endopod longer than in female, as in M. stygiana . Mandible with two basal setae shorter than in female (®gure 19K, arrowed); second seta on ®rst endopodal segment diOEering from female in being plumose, instead of spinulose. Maxillule and maxilla similar to female. Maxilliped (®gure 19L) bearing proximal tuft of short setules on syncoxa.

Legs 1±4 similar to female. Number of large processes on posterior surface of endopods of legs 2 and 3 (®gure 19M, N) as in female. Leg 4 (®gure 19O) furnished only with minute prominences on both surfaces, as in M. omorii .

Leg 5 (®gure 20E±J) similar to that of M. omorii , except for: right leg (®gure 20E±G) with relatively long protopod; endopod abruptly curved outward at distal quarter; ®rst exopodal segment bearing minute outer prominence midway, without inner irregular knobs except proximal swelling; second exopodal segment with two inner proximal processes, ®rst process longer and thicker, second process with truncate tip; third exopodal segment evenly curved inward, with outer middle process. Left leg (®gure 20H±J) with endopod bearing serration along posterior half of inner margin; ®rst exopodal segment with two low round protuberances at midlength; second exopodal segment slightly produced into round projection at outer distal corner; distal processes as in ®gure 20J.

Variation. The number and position of minute prominences on the anterior and posterior surfaces of rami of legs 2±4 vary among individuals, and even between the right and left legs of the same individual. The outer middle process on the third exopodal segment of the male right leg 5 is round at the tip in one paratype but curved distally in another paratype.

Remarks. Giesbrecht (1896) described Scolecithrix chelipes from the Red Sea, on the basis of a single male. Later, Scott (1909) transferred this species to the genus Macandrewella when he established it with the description of a new species, M. joanae . The male of M. chelipes was subsequently recorded from the Nicobar Islands in the Indian Ocean ( Sewell, 1929). The female was ®rst described from the southern Paci®c by Wilson (1950); however the corresponding male is rather diOEerent from those previously recorded from the Indian Ocean. Recently, both sexes of the species have been redescribed from the Gulf of Elat, Red Sea, by Campaner (1989). Unfortunately Campaner (1989) described only the lens, rostrum, parts of the mouthparts, and legs 1±3 of the female of M. chelipes , but not the habitus, which makes detailed comparison between the females of M. chelipes and M. serratipes di cult. Although other congeners have a restricted distribution (see ®gure 21), M. chelipes apparently had a broad distribution in the Red Sea, the Indian Ocean, and the southern Paci®c. Hence we suspected that Wilson’s (1950) specimens of the southern Paci®c M. chelipes might correspond to a new species.

The male of the new species is similar to those of M. sewelli Farran, 1936 , M. joanae , M. omorii n. sp. and, possibly, M. asymmetrica , all of which share a serration along the distal half of the inner margin of the left endopod of leg 5. However, the new species is distinguishable from the latter three species by the following characters: (1) the second exopodal segment of left leg 5 without a large triangular process at the outer distal corner; (2) the second exopodal segment of right leg 5 has a proximal inner process much shorter than the segment proper. Although M. sewelli bears also a relatively short inner proximal process on the second exopodal segment of the right leg, it has a large outer digitiform process at the outer distal corner of the ®rst exopodal segment of the right leg, and a truncate tip on the left endopod.

Wilson (1950) erroneously assigned the male of the new species to M. chelipes Giesbrecht, 1896 , but the latter is distinctly diOEerent as follows: (1) the second exopodal segment of right leg 5 has a single proximal inner process, which is directed proximally and tapers distally (two processes, the tips of which are truncate, are displayed in M. serratipes ); (2) the third exopodal segment of right leg 5 with an outer process half as long as the segment (one-tenth as long as the segment in M. serratipes ).

The new species exhibits sexual dimorphism in the antenna and mandible like M. stygiana . In addition, the maxillipedal syncoxa bears proximally a patch of long setules in the female, but of short setules in the male.

Distribution. According to Wilson (1950, note in vials), the new species was collected at a depth of 40 fathoms oOE Fiji (see ®gure 21).

Etymology. The speci®c name,`serratipes ’ is derived from the inner serration along the distal half of the left endopod of male leg 5 (Latin serratus, serrated, and pes, leg).