Polyankylis ovilaxa Kim 2014, n. sp.
Creators: name: Kim, Il-Hoi
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Hexanauplia
Cyclopoida
Polyankyliidae
Polyankylis
Polyankylis ovilaxa

description: Polyankylis ovilaxa n. sp. (Figs. 11-13)
Material examined. 17 from the terebellid polychaete Thelepus japonicus Marenzeller collected from a tidal flat (34 49′54′′N, 128 02′08′′E), Namhae Island on the southern coast of Korea, 22 July 2001. Holotype (00286634), and paratypes (14 00286635) have been deposited in the National Institute of Biological Resources (NIBR), Incheon, Korea. Dissected paratypes (2 of the author.
Female. Body (Fig. 11A) 838 Μm long, excluding caudal seta, in dissected paratype. Prosome 512 Μm long and strongly tapering posteriorly. Cephalothorax 333 343 Μm, divided by faint dorsal suture line into cephalosome and first pedigerous somite. Cephalosome with apical, rostral prominence and slight lateral constriction indicating division between oral and maxillipedal areas. Second to fourth pedigerous somites with distinct epimera. Fourth pedigerous somite small. Urosome (Fig. 11B) 5-segmented. Fifth pedigerous somite 62 Μm wide and distinctly narrower than genital double-somite. Genital double-somite 92 77 Μm, consisting of broader anterior 70% and narrower posterior 30%, ventrally divided by transverse line into anterior and posterior halves (Fig. 11C). Three free abdominal somites narrow, unornamented, 37 40, 35 38, and 46 40 Μm, respectively. Anal region large. Caudal rami rather slender, slightly divergent, and widely separated from each other by ramus width; each ramus 66 15 Μm (ratio 4.40: 1), with 6 naked setae; outer lateral seta locating slightly proximal to midlength of ramus; largest caudal seta (seta V) 206 Μm long, more than twice as long as next longest nearby seta (seta VI); all caudal setae naked. Egg sac containing loosely aggregated eggs (Fig. 11A); each egg about 40 Μm in diameter. Rostrum tapering posteriorly, slightly wider than long, with round posterior apex (Fig. 11D). Antennule (Fig. 11E) slender, 202 Μm long, and 6-segmented; all setae naked; armature formula: 2, 6, 6, 4+aesthetasc, 2+aesthetasc, and 7+aesthetasc; 2 proximal setae on third segment obscurely positioned between second and third segments, therefore armature formula of first 3 segments may be interpreted as 2, 7, and 5 (or 2, 8, and 4). Antenna (Fig. 12A) 4-segmented, consisting of coxobasis and 3-segmented endopod; coxobasis narrow proximally and broadened distally, with 1 distal seta medially; first endopodal segment the longest segment, gradually broadening distally, with 1 seta in middle of medial margin; second endopodal segment short, armed with 1 claw and 2 setae (proximal seta very small); third endopodal segment 2.5 times as long as wide and armed with 3 claws and 2 naked outer setae; 2 medial claws strongly curved and smaller than outer one, the latter with subdistal spinule on medial margin.
Labrum (Fig. 12B) narrow and covering only part of mandible, with large posterior lobes, and deep and narrow median incision. Mandible (Fig. 12C) with short, strongly tapering blade and 2 spines (or spiniform scales) on convex side (proximal one distinctly longer than distal one); blade terminating in blunt tip, with more than 20 teeth along convex outer margin and wavy row of small, densely arranged spinules on concave medial margin. Paragnath not seen. Maxillule (Fig. 12D) lobate, slightly longer than wide, and armed with 4 setae (2 lateral and 2 distal); 2 middle ones of these 4 setae weakly pinnate unilaterally. Maxilla (Fig. 12E) 2-segmented; proximal segment ornamented proximally with patch of setules on posterior surface; distal segment drawn out into short, acutely tapering process bearing with 4 large and 1 small teeth on convex side; medial seta (seta I) large, longer than segment, with 1 row of large spines and 1 row of small spinules on distal (outer) margin and several setules on proximal (medial) margin; anterior seta (seta II) spiniform, unilaterally spinulose along medial margin; outer proximal seta (seta III) lacking. Maxilliped (Fig. 12F) 3- segmented. First segment (syncoxa) unarmed. Second segment (basis) inflated medially, with two large, spiniform setae; proximal seta much longer than segment, with 4 long setules on medial margin and 2 shorter setules on outer margin; distal seta slightly shorter than segment, almost straight, with minute spinules along outer margin and minute setules along medial margin. Terminal segment (endopod) forming distally slender, elongate claw and proximally with 1 spinulose spine, 1 small seta, and 1 spiniform process.
Legs 1-3 (Figs. 12G, 13A, B) with 3-segmented exopod and 2-segmented endopod. Leg 4 (Fig. 13C) uniramous, with 2-segmented exopod. Endopods of legs 1-3 longer than exopods; distal endopodal segment of these legs much longer than wide and with small, pointed process on outer margin. Three spines on outer and distal margins of exopod of leg 4 setiform, elongate and distally barbed. Armature formula of legs 1-4 as follows:
CoxaBasisExopodEndopodLeg 1:0-1;1-0;I-0; I-1; III, 4;0-1; I, 1, 5Leg 2:0-1;1-0;I-0; I-1; III, 5;0-1; II, I, 4Leg 3:0-1;1-0;I-0; I-1; III, 5;0-1; II, I, 3Leg 4:0-0;1-0;I-0; II, I, 3;(missing)
Leg 5 consisting of 1 dorsolateral seta on fifth pedigerous somite and 1-segmented, free exopod; exopod (Fig. 13D) small, 19 10 Μm (ratio 1.90: 1), carrying terminally 1 setiform spine and 1 long seta, both naked. Leg 6 represented by large seta on ventral surface of genital double-somite (Fig. 11C).
Male. Body (Fig. 13E) similar to that of female. Body length 702 Μm in dissected paratype. Urosome (Fig. 13F) 6-segmented. Fifth pedigerous somite narrow, less than half width of genital somite. Genital somite longer than wide, 102 Μm, with pronounced posterolateral corners. Four abdominal somites 26 and 33 33 Μm, respectively. All abdominal somites smooth, without ornamentation. Caudal ramus 51 13 Μm (ratio 3.92: 1).
Antennule segmented and armed as in female except for addition of 2 aesthetascs on second segment and 1 aesthetasc on third segment, as indicated by dark dots in Fig. 11E. Antenna ornamented with spinules on outer margin of second segment (basis).
Labrum, Mandible, maxillule, and maxilla as in female. Maxilliped (Fig. 13G) 4-segmented. First segment with large, acutely pointed process distally. Second segment with 1 longitudinal row of setules (3 distal ones enlarged) on outer surface, and 2 expanded, heavily barbed, transformed setae; proximal one of latters longer than distal one, gradually narrowing distally, with spinules on proximal half of proximal margin; distal seta blunt, short, with 1 setule proximally and spinules distally. Third segment small and unarmed. Terminal segment forming large, arched claw bearing proximally 1 large and 1 small setae. Legs 1-4 not different from those of female. Leg 5 similar to that of female, but exopod 14 6 Μm (ratio 2.33: 1), more slender, and armed with 2 unequal, distal setae.
Etymology. The specific name ovilaxa is a combination of Latin words ovum (egg) and laxus (loose). It alludes to the loose aggregation of the eggs of the new species.
Remarks. Polyankylis orientalis Ho and Kim, 1997 was discovered from a tide pool on a mudflat in the Yellow Sea (Ho and Kim, 1997). The second species Polyankylis australis Karanovic, 2008 was found interstitially from South Australia (Karanovic, 2008). Although the two species were found in different hemispheres, they could be distinguished only by a few morphological details (Karanovic, 2008). P. ovilaxa n. sp. reveals no striking differences from the two congeners, either. However, they are distinguishable from one another and major differences are shown in the segmentation of leg 4 exopod and the armature of antenna. These and other morphological differences are summarized in Table 1.
description: Published as part of Kim, Il-Hoi, 2014, Six new species of Copepoda (Clausiidae, Pseudanthessiidae, Polyankyliidae) associated with polychaetes from Korea, pp. 95-122 in Journal of Species Research 3 (2) on pages 111-115, DOI: 10.12651/JSR.2014.3.2.095, http://zenodo.org/record/8120272