Conchyliurus dispar, Moon, Seong Yong & Kim, Il-Hoi, 2014

Moon, Seong Yong & Kim, Il-Hoi, 2014, Description of Conchyliurus dispar n. sp. (Copepoda, Cyclopoida, Clausidiidae) associated with the bivalve Barnea manilensis (Philippi) from the Yellow Sea with a discussion of the male morphotypes in the genus, Zootaxa 3760 (3), pp. 471-478 : 472-476

publication ID	https://doi.org/ 10.11646/zootaxa.3760.3.14
publication LSID	lsid:zoobank.org:pub:25B7F2BD-709C-4CE8-8B31-58ADA7A2EC97
DOI	https://doi.org/10.5281/zenodo.6144732
persistent identifier	https://treatment.plazi.org/id/03C06B01-FFA4-FFC4-E4F3-FCD5FE85FEFB
treatment provided by	Plazi
scientific name	Conchyliurus dispar
status	sp. nov.

Treatment

Conchyliurus dispar n. sp.

( Figs 1–4 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 )

Material examined. 271 ♀ and 73 ♂ (7 large ♂ and 66 small ♂) collected from the bivalve Barnea manilensis (Philippi) (32 individuals) living in the intertidal zone at Muchangpo (36o23'06"N, 126o32'00"E), in the Yellow Sea of Korea, collected by I. H. Kim, 0 6 May 2000. Holotype ♀, NIBRIV0000282414), allotype ♂, NIBRIV0000282415), and 80 paratypes (50 ♀, 3 large ♂, and 27 small ♂, NIBRIV282416) deposited in National Institute of Biological Resources, Inchon. Other specimens are retained in the collection of the junior author.

Other material examined. 306 ♀, 307 ♂ (13 large ♂ and 294 small ♂), and 212 copepodids collected from B. manilensis (about 50 individuals) at the type locality, collected by I. H. Kim, 28 February 2006.

Female. Body ( Fig. 1 View FIGURE 1 A) narrow and flexed dorsally between prosome and urosome. Body length of largest dissected specimen 1.63 mm. Mean body length 1.56 mm (1.52–1.63 mm), based on 10 specimens. Prosome elliptical, 817 Μm long. Greatest width of prosome 517 Μm. Cephalothorax 461 Μm long. Urosome ( Fig. 1 View FIGURE 1 B) 5- segmented. Fifth pedigerous somite 242 Μm wide. Genital double-somite 361 × 300 Μm, 1.20 times as long as wide, without dorsomedian lobe, covered posterodorsally by brownish or blackish cement, with obliquely transverse dorsolateral ridge on both sides and 2 pairs of firmly attached spermatophores. First free abdominal somite about 97 × 144 Μm. Second somite 67 × 122 Μm. Anal somite ( Fig. 4 View FIGURE 4 A) longer than wide, 125 × 115 Μm, ornamented ventrally with 4 short rows of spinules anteriorly and row of spinules at insertion point of caudal ramus. Caudal rami widely separated by more than half width of ramus; each ramus 120 × 41 Μm (ratio 2.93:1), ornamented with fine spinules on posteroventral margin and bearing 6 setae; mid-lateral seta smooth; medio-distal seta pinnate along medial margin only; inner terminal seta with minute spinules along distal half of margins; outer terminal seta with similar spinules along outer margin; outer distal and dorsal setae smooth.

Rostrum prominent, extending anteriorly ( Fig. 1 View FIGURE 1 A). Antennule ( Fig. 1 View FIGURE 1 C) 6-segmented, short, 256 Μm long, tapering, with armature formula: 4, 15, 11, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; first segment with spinules on anterior margin; 1 pinnate seta present on second segment, 2 on fourth, 1 on fifth, and 4 on last. Antenna ( Fig. 1 View FIGURE 1 D) 4-segmented, with armature formula of 1, 1, 1+1 claw, and 7; all segments ornamented excessively with spinules or denticles; seta on second segment not exceeding distal margin of segment; third segment with small, spinulated medio-distal process near base of claw; fourth segment 30 × 24 Μm, with 4 elements distinctly thicker and more sclerotized than other 3.

Labrum ( Fig. 1 View FIGURE 1 E) with shallow median incision, paired spinular rosettes and tapering processes near midline; posterior margin with minute spinules. Mandible ( Fig. 1 View FIGURE 1 F) with spinulate lash and 2 basally articulated, spinulate elements. Paragnath ( Fig. 1 View FIGURE 1 G) bilobate distally, densely spinulate. Maxillule ( Fig. 1 View FIGURE 1 H) armed with 8 stiff setae, one located laterally, others distally. Maxilla ( Fig. 2 View FIGURE 2 A) 2-segmented; first segment longer than wide, unarmed but ornamented with longitudinal rows of fine spinules; second segment forming strong terminal claw, with 2 simple spines (1 medial and 1 outer) and 1 simple, broad anterior seta. Maxilliped ( Fig. 2 View FIGURE 2 B) 2-segmented; first segment expanded proximally, with 1 medial seta and patches of spinules in distal half; second segment claw-like, curved, with 0–2 small denticles on each side.

Legs 1–4 with 3-segmented rami and long setules on each side of intercoxal sclerite, medial margin of basis and outer margin of endopods. Anterior surface of basis of leg 1 with 2 patches of spinules ( Fig. 2 View FIGURE 2 C). Posterior margin of basis (between bases of rami), outer distal margin of endopodal segments and outer margin of first exopodal segment of legs 1–4 ornamented with row of spinules ( Fig. 2 View FIGURE 2 C–D, F). Medio-distal corner of legs 1 and 2 nearly angular. Distal seta on third endopodal segment of leg 2 whip-like and distinctly broader than other setae on same leg. Armature formula of legs 1–4 ( Fig. 2 View FIGURE 2 C–F) as follows:

Leg 5 ( Fig. 1 View FIGURE 1 B) consisting of free exopod and 1 seta near base of exopod. Exopod ( Fig. 2 View FIGURE 2 G) slightly broadened distally, 116 × 41 Μm (ratio 2.83:1), armed with 1 outer mid-lateral spine (40 Μm long), 2 distal spines (70 and 57 Μm long) and 1 distally pinnate seta; medio-distal process small and acutely pointed; posterior margin of exopod with rows of minute spinules near base of distal spines. Leg 6 ( Fig. 1 View FIGURE 1 B) represented by digitiform process tipped with small seta on disto-median surface of genital double-somite.

Large male. Body ( Fig. 3 View FIGURE 3 A) similar to that of female, but cephalothorax slightly more expanded. Body length of largest dissected specimen 1.58 mm. Mean body length 1.51 mm (1.47–1.58 mm), based on 7 specimens. Prosome 769 × 529 Μm. Cephalothorax 465 Μm long; mid-lateral margins with cuticular thickening. Urosome ( Fig. 3 View FIGURE 3 C) 6-segmented. Fifth pedigerous somite 267 Μm wide. Genital somite slightly wider than long, 203 × 238 Μm. Four free abdominal somites 107 × 154, 107 × 143, 73 × 130, and 140 × 113 Μm. Caudal ramus 120 × 45 Μm (ratio 2.67:1). Spermatophore ( Fig. 3 View FIGURE 3 D) elongate, sac-like, 227 × 83 Μm.

Maxilliped ( Fig. 3 View FIGURE 3 E) massive and consisting of 3 segments and terminal claw; first segment much wider than long, with small depression on medial margin to accommodate tip of terminal claw and papilliform denticles at medio-distal prominence; second segment approximately 167 × 100 Μm, with 1 subdistal circle of small spinules on medial side, several spinules on medial margin, 2 weak proximal corrugations, and 1 large distal seta; third segment small and unarmed; terminal claw about 150 Μm long, armed with 2 unequal setae and small process proximally on medial margin, and distally with subsidiary claw.

Leg 5 exopod 107 × 42 Μm (ratio 2.55:1). Leg 6 ( Fig. 3 View FIGURE 3 C) represented by 1 weak plumose seta on posterior part of genital operculum.

Small male. Body ( Fig. 3 View FIGURE 3 B) distinctly smaller than large male. Body length 1.24 mm (1.10–1.35 mm), based on 20 specimens. Prosome 585 Μm long. Cephalothorax 350 Μm long, not expanded as in large male, and 381 Μm wide.

Fifth pedigerous somite 203 Μm wide. Genital somite 162 × 98 Μm. Four abdominal somites 100 × 130, 88 × 120, 63 × 110, and 110 × 95 Μm, respectively. Caudal ramus 100 × 37 Μm (ratio 2.70:1). Spermatophore 190 × 63 Μm.

Maxilliped ( Fig. 3 View FIGURE 3 F) much more slender than that of large male; second segment about 124 × 54 Μm, more than twice as long as wide, without proximal corrugation. Terminal claw 141 Μm long, distinctly more slender than in large male.

Leg 5 exopod 84 × 32 Μm (ratio 2.63:1).

Etymology. The specific name dispar is a Latin word meaning “unequal” and alludes to the new species being different from the morphologically similar C. quintus .

Remarks. Initially, the examined specimens were thought to belong to C. quintus , a very common copepod associate of bivalves in Korea. But, the absence of posterolateral processes on the male genital somite revealed that the specimens are not C. quintus (see Fig. 3 View FIGURE 3 C and G) but represent a new species. In addition, the left and right caudal rami of the new species are widely separated from each other ( Fig. 4 View FIGURE 4 A), unlike in C. quintus where the rami are in contact with each other proximally ( Fig. 4 View FIGURE 4 B). Other differences between the two species are the followings: (1) the female of C. dispar n. sp. is larger than that of C. quintus , i.e., 1.52–1.63 mm in C. dispar , compared to 1.38 to 1.44 mm ( Tanaka 1961) in C. quintus ; (2) the caudal ramus of C. dispar (120 × 41 Μm, ratio 2.93:1) is longer than that of C. quintus (100 × 42 Μm, ratio 2.38:1, based on the newly examined specimen); and (3) the spines on the distal segment of the maxilla of C. dispar are simple ( Figs. 2 View FIGURE 2 A, 4C), unlike those of C. quintus which usually bear accessory spine(s) ( Fig. 4 View FIGURE 4 D–E).

There are two other congeners lacking posterolateral processes on the male genital somite: C. cardii Gooding, 1957 known from Europe and C. lobatus Humes & Cressey, 1958 known from West Africa. Although C. dispar is very similar to these species, it may be distinguished from them by the larger body [1.83 mm long, according to Gooding (1957)] of the female C. cardii and a prominent spinulated process on the medio-distal corner of the third segment of the antenna ( Gooding 1957), while C. lobatus possesses a dorsomedian lobe on the female genital double-somite, highly divergent caudal rami, and an ovoid, distinctly smaller spermatophore (129 × 50 Μm, according to Humes & Cressey (1958), compared to 227 × 83 Μm in the large male or 190 × 63 Μm in the small male of C. dispar ).