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 Author Moon, Seong Yong Author Kim, Il-Hoi text Zootaxa 2014 3760 3 471 478 journal article 46516 10.11646/zootaxa.3760.3.14 b3666e33-629d-46f6-adf9-3a80c082c18c 1175-5326 231474 25B7F2BD-709C-4CE8-8B31-58ADA7A2EC97 Conchyliurus dispar n. sp. ( Figs 1–4 ) 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 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 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 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 A). Antennule ( Fig. 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 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 E) with shallow median incision, paired spinular rosettes and tapering processes near midline; posterior margin with minute spinules. Mandible ( Fig. 1 F) with spinulate lash and 2 basally articulated, spinulate elements. Paragnath ( Fig. 1 G) bilobate distally, densely spinulate. Maxillule ( Fig. 1 H) armed with 8 stiff setae, one located laterally, others distally. Maxilla ( Fig. 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 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. FIGURE 1 . Conchyliurus dispar n. sp. , female. A, habitus, dorsal; B, urosome, dorsal; C, antennule; D, antenna; E, labrum; F, mandible; G, paragnath; H, maxillule. Scale bars: A, 0.2 mm; B, 0.1 mm; C–D, 0.05 mm; E–F, H, 0.02 mm; G, 0.1 mm. 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 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 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 C–F) as follows:

Coxa	Basis	Exopod	Endopod
Leg 1	0-1	1-I	I-0; I-1; III,I,4	0-1;0-1;II,4
Leg 2	0-I	1-0	I-0; I-1; III,I,5	0-1; 0-2; III,3
Leg 3	0-I	1-0	I-0; I-1; III,I,5	0-1; 0-2; IV,2
Leg 4	0-I	1-0	I-0; I-1; III,I,5	0-I; 0-2; IV,1

FIGURE 2 . Conchyliurus dispar n. sp. , female. A, maxilla; B, maxilliped; C, leg 1; D, leg 2; E, third endopodal segment of leg 3; F, leg 4; G, free exopod segment of leg 5. Scale bars: A–B, 0.02 mm; C–G, 0.05 mm. FIGURE 3 . Conchyliurus dispar n. sp. , male (A −F) and Conchyliurus quintus Tanaka, 1961 , male (F). A, habitus of large male, dorsal; B, habitus of small male, dorsal; C, urosome of small male, ventral; D, spermatophore; E, maxilliped of large male; F, maxilliped of small male; G, urosome of small male, ventral. Scale bars: A −B, 0.2 mm; C, G, 0.1 mm; D −F, 0.05 mm. Leg 5 ( Fig. 1 B) consisting of free exopod and 1 seta near base of exopod. Exopod ( Fig. 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 B) represented by digitiform process tipped with small seta on disto-median surface of genital double-somite. Large male. Body ( Fig. 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 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 D) elongate, sac-like, 227 × 83 Μm. Maxilliped ( Fig. 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 C) represented by 1 weak plumose seta on posterior part of genital operculum. Small male. Body ( Fig. 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 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 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 A), unlike in C. quintus where the rami are in contact with each other proximally ( Fig. 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 A, 4C), unlike those of C. quintus which usually bear accessory spine(s) ( Fig. 4 D–E). FIGURE 4 . Conchyliurus dispar n. sp. (A, C) and Conchyliurus quintus Tanaka, 1961 (B, D–E). A, anal somite and caudal rami of female, ventral; B, anal somite and caudal rami of female, ventral; C, distal segment of female maxilla; D, distal segment of female maxilla; E, distal segment of male maxilla. Scale bars: A −B, 0.05 mm; C −E, 0.02 mm. 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 ).