Clausia parva, Kim, 2014

Kim, Il-Hoi, 2014, Six new species of Copepoda (Clausiidae, Pseudanthessiidae, Polyankyliidae) associated with polychaetes from Korea, Journal of Species Research 3 (2), pp. 95-122 : 100-104

Clausia parva n. sp. ( Figs. 4-6 )

Material examined. 15, 3 from the polychaete Hydroides ezoensis Okuda epizoic on the shell of the oyster Crassostrea gigas (Thunberg) , Gangneung Port (37 46′15′′N, 128 57′08′′E), depth about 50 cm, 21 November 2012. Holotype (, NIBRIV0000286627 ) , allotype (, NIBRIV 0000286628), and paratypes (11, NIBRIV 0000286629) have been deposited in the National Institute of Biological Resources ( NIBR), Incheon, Korea. Dissected paratypes (2 retained in the collection of the author.

Other material examined. 2 from washings of Hydroides ezoensis Okuda epizoic on the shell of Crassostrea gigas, Yangpo Port (35 15′54′′N, 129 31′28′′E), 31 July 2007.

Female. Body ( Fig. 4A ) elongate, cylindrical, and relatively small. Body length of dissected paratype 1.49 mm. Prosome indistinctly segmented, but 4 prosomal somites well-defined from one another by constrictions and thin exoskeletons between them. Maximum width of prosome 278 Μm across second pedigerous somite. All prosomal somites with rounded lateral margins. Cephalothorax 275 Μm wide and as long as wide, with truncated rostral protuberance. Second to fourth pedigerous somites similar in length and width, with rudimentary dorsal tergite ( Fig. 4B ). Urosome slightly shorter than prosome and 6- segmented. Fifth pedigerous somite 272 Μm wide, as wide as prosomal somites. Genital somite 135 219 Μm; genital apertures locating dorsolaterally in subdistal region of somite. Abdomen distinctly narrower than preceding somites, 96 126, 87 125, 67 110, and 108 102 Μm, respectively; all abdominal somites smooth, without ornamentation. Caudal rami ( Fig. 4C ) small and widely separated from each other; each ramus 51 27 Μm (ratio 1.89: 1) and weakly tapering in distal half, with 6 naked setae; largest terminal seta (seta V) 250 Μm long, markedly larger than other 5 setae; outer lateral seta located at midlength of ramus. Egg sac ( Fig. 4D ) uniserial, containing several eggs, and longer than urosome; each egg about 200 Μm in diameter.

Rostrum as anterior protuberance of cephalothorax ( Fig. 4A ). Antennule ( Fig. 4E ) short, 142 Μm long and 5-segmented, with armature formula 5, 23, 4, 2+aesthetasc, and 7+aesthetasc; all setae naked; first segment with proximal patch of minute spinules on anterior surface; second segment the longest, longer than combined distal 3 segments. Antenna ( Fig. 4F ) 3-segmented; first segment (basis) with 1 distal seta and patches of spinules on medial and outer surfaces; second segment (first endopodal segment) unarmed, with 2 patches of minute spinules; terminal segment (second endopodal segment) with 4 distal claws of unequal lengths, 2 small, subdistal claws (proximal one of them being setiform) on medial margin, 2 weakly pinnate setae on outer margin, and minute spinules on medial margin and middle of outer margin.

Labrum unornamented, with tapering posterior lobes, and deep and broad posteromedian invagination ( Fig. 5A ). Mandible with 2 very unequal, distal spines; larger anterior one of them with 5 teeth distally ( Fig. 5A ). Maxillule as lobe bearing 3 outer setae, 1 inner seta, and on ventral surface patch of minute spinules ( Fig. 5A ). Maxilla ( Fig. 5B ) 2-segmented; proximal segment broad, unarmed but with 1 small patch of minute spinules on dorsal (anterior) surface; distal segment forming distally obliquely expanded spinulose pad, with 2 small setae (each on anterior and posterior surface) and scattered minute spinules. Maxilliped ( Fig. 5C ) 3-segmented; first segment broad but short and unarmed; second segment the longest, with 2 small medial setae at proximal third of medial margin; terminal segment short, stout, and distally forming spinulose pad, with 1 subdistal spine.

Legs 1 and 2 ( Fig. 5D, E ) with 2-segemented rami; inner seta on coxa small, blunt and naked; basis with patch of spinules on posterior region near base of endopod; outer seta on basis thick and stiff; outer surfaces of rami covered with spinules; medial surface of first endopodal segment of leg 1 also covered with spinules; outer spines on leg 2 exopod with subdistal setule. Leg 3 ( Fig. 5F ) as small lobe bearing 2 setae. Leg 4 absent. Armature formula of legs 1-3 as follows:

	Coxa	Basis	Exopod	Endopod
Leg 1:	0-1;	1-0;	I-0; II, I, 0;	0-0; 0, II, 2
Leg 2:	0-1;	1-0;	I-0; III, I, 1;	0-0; 0, I, 2
Leg 3:	2 (on lobe)

Leg 5 ( Fig. 5G ) consisting of protopod and distal exopod; protopod 108 69 Μm, articulated at base from somite, with 1 small outer seta. Exopod distinctly smaller than protopod, 51 Μm (ratio 1.59: 1); with 2 patches of minute spinules and 4 setae; these 4 setae smooth or weakly setulose, and 120, 172, 55, and 105 Μm long, respectively, from outer to inner. Leg 6 represented by 1 small setule in genital aperture ( Fig. 4A ).

Male. Body ( Fig. 6A ) cylindrical as in female. Body length 0.89 mm in dissected paratype. Prosome well-segmented. Cephalothorax 221 Μm, longer than wide. Three metasomites distinctly shorter than cephalothorax and 72 Μm, respectively. Fifth pedigerous somite 72 Μm. Genital somite 94 140 Μm, with weakly convex lateral margins. Four abdominal somites 62 81 Μm, respectively. Caudal ramus 48 25 Μm (ratio 1.92: 1), not different from that of female in shape ( Fig. 6B ).

Rostrum, antennule and antenna as in female. Maxilliped ( Fig. 6C ) 3-segmented as in female; first segment small and unarmed; second segment strongly protuberant medially, with 2 naked setae on tapering medial protuberance; terminal segment forming strong, smooth, distally curved claw. Other mouthparts as in female.

Legs 1 and 2 ( Fig. 6D, E ) with 2-segmented rami as in female but with different armature formula; setae on coxa and rami well-developed and pinnate, unlike those of female. Terminal spine on distal exopodal segment in legs 1 and 2 larger than that of female, with subterminal setule. Second endopodal segment of leg 1 with 2 spinulose bulges on medial side posterior to base of medial seta ( Fig. 6D ). Leg 3 as lobe bearing 2 setae, as in female. Leg 4 absent. Armature formula of legs 1-3 as follows:

Coxa Basis	Exopod		Endopod
Leg 1: 0-1; 1-0; Leg 2: 0-1; 1-0; Leg 3: 2 (on lobe)	I-0; III, I, 3 (or II, I-0; II, I, 3;	I, 2);	0-0; I, 1, 1 0-0; 0, I, 3

Leg 5 similar to that of female; exopod 48 31 Μm (ratio 1.55: 1). Leg 6 represented by 1 rudimentary seta on genital operculum ( Fig. 6B ).

Etymology. The specific name parva refers to the relatively small body size of the new species (the Latin parvus means “small”).

Remarks. Kim et al. (2013) synonymized Clausia uniseta Bocquet and Stock, 1960 with the type species C. lubbockii Claparède, 1863 . Therefore, the genus comprised only a single species ( Kim et al., 2013). Major differences between C. parva n. sp. and C. lubbocki are found in the antennular segmentation and leg armature. The antennule of C. parva n. sp. is 5-segmented (vs. 6-segmented in C. lubbockii ). The armature formulae of legs 1 and 2 of C. parva are I-0; II, I, 0 (vs. I-0; II, II, 1 in C. lubbocki ) for leg 1 exopod; 0-0; 0, II, 2 (vs. 0-1; 0, I, 1 in C. lubbocki ) for leg 1 endopod; I-0; III, I, 1 (vs. I-0; II, I, 1 in C. lubbocki ) for leg 2 exopod; and 0-0; 0, I, 2 (vs. 0-1; II, I, 0 in C. lubbocki for leg 2 endopod).

The body of C. parva n. sp. (1.49 mm long in the female) is significantly smaller than that of C. lubbocki which was measured by Bocquet and Stock (1960) to be 2.25 mm and 2.4 mm (the latter as C. uniseta ) or by Kim et al. (2013) to be 2.04 mm. Other minor morphological differences between the two species are noticed in the setation of the antennule, the form of the labrum and the distal segment of the maxilla, and the egg arrangement (uniserial in C. clindrata vs. biserial in C. lubbocki ).

Figures

Fig. 4. Clausia parva n. sp., female. A. habitus, dorsal. B. anterior part of prosome, right. C. caudal rami, dorsal. D. egg sac. E. antennule. F. antenna. Scales: A, B. 0.1 mm. C. 0.05 mm. D. 0.2 mm. E, F. 0.02 mm.

Fig. 5. Clausia parva n. sp., female. A. labrum, mandibles, and left maxillule. B. maxilla. C. maxilliped. D. leg 1. E. leg 2. F. leg 3. G. leg 5. Scale bars: A-F. 0.02 mm. G. 0.05 mm.

Fig. 6. Clausia parva n. sp., male. A. habitus, dorsal. B. urosome, ventral. C. maxilliped. D. leg 1. E. leg 2. Scale bars: A, B. 0.1 mm. C-E. 0.02 mm.