Paramesochra similis Kunz, 1936

Back, Jinwook & Lee, Wonchoel, 2013, Three new species of the genus Paramesochra T. Scott, 1892 (Copepoda: Harpacticoida: Paramesochridae) from Yellow Sea, Korea with a redescription of Paramesochra similis Kunz, 1936, Journal of Natural History 47 (5 - 12), pp. 769-803 : 791-794

Paramesochra similis Kunz, 1936

(Figures 13, 14)

Material examined

One ♀ (a loan from the Natural History Museum London) dissected on three slides and sealed with transparent nail varnish, from type locality, collected by Kunz on 22 May 1985.

Description of female

Body (Figure 13A,B). Cylindrical and depressed dorsoventrally; body length 400 µm (n = 1, measured from tip of rostrum of cephalic shield to posterior margin of caudal rami); largest width measured at posterior margin of cephalic shield (75 µm); gradually tapering posteriorly; body somites connected by arthrodial membranes, several sensilla on dorsal surface.

Rostrum. Diminutive, bare, and fused to cephalosome (Figure 13A).

Prosome (Figure 13A,B). Four-segmented, comprising cephalothorax (bearing first pedigerous somite) and three free pedigerous somites; cephalothorax bell-shaped, with few sensilla, and one pair of pores; pleural areas weakly developed and posterolateral angles rounded; posterior margin smooth; three prosomites with one pair of pores located each lateral side.

Urosome (Figures 13A,B, 14A). Five-segmented, comprising P5-bearing somite, genital double-somite, and three free abdominal somites; genital somite and first abdominal somite completely fused forming genital double-somite with one large median pore dorsally; gonopores covered on both sides by P6; P6 represented by plate, with one pinnate seta each; middle of plate flattened. Anal operculum not present, pseudoperculum well developed, round and bare.

Caudal rami (Figure 13C). Oblong and approximately 3.8 times as long as wide; each ramus armed with six setae and one dorsal pore; seta I obscure; seta II bare at proximal

Figure 13. Paramesochra similis Kunz , (♀). (A) Habitus, dorsal; (B) habitus, lateral; (C) caudal rami, dorsal; (D) P5.

Figure 14. Paramesochra similis Kunz , (♀). (A) Urosome, ventral; (B) segment-1 and –2 of antennule; (C) antenna; (D) mandible (D 1, gnathobase; D 2, palp); (E) maxillule; (F) maxilla (F 1, maxilla except for second endite; F 2, second endite); (G) maxilliped.

half; seta III pinnate on outer lateral corner; seta IV bare; seta V longest and bare; seta VI smallest and bare; seta VII triarticulated at base on dorsal surface.

Antennule. Damaged during observation (Figure 14B), however clearly eightsegmented, short; segment 1 with one small bare seta; segment 2 with seven bare and one pinnate; other segments damaged.

Antenna (Figure 14C). Four-segmented, comprising coxa, basis, and free twosegmented endopod. Exopod one-segmented with five bare setae. Endopod twosegmented; enp-1 with one abexopodal pinnate seta; enp-2 armed with three bare setae, four geniculate setae, and one geniculate seta fused basally to one bare seta.

Mandible (Figure 14D 1,D 2). Gnathobase well developed, bearing several teeth overlapping each other around distal margin and one bare seta at distal corner; mandibular palp biramous: basis widening distally. Exopod one-segmented, with two lateral and two distal bare setae. Endopod two-segmented, enp-1 longest as long as exopod, with two bare setae at distal margin, enp-2 with five basally fused setae.

Maxillule (Figure 14E). Praecoxa trapezoidal; arthrite well developed with one bare seta on lateral margin, seven curved distal spines, and two juxtaposed bare setae on anterior surface; coxa with cylindrical process bearing two bare setae; basis bearing cylindrical process with one pinnate and five bare setae; exopod one-segmented, square, and with two pinnate setae; endopod one-segmented, elongate, rectangular and with six distal bare setae.

Maxilla (Figure 14F 1,F 2). Syncoxa with chitinous outer margin, and three cylindrical endites; proximal endite bilobed, with two bare setae on each lobe; second and third endites close to each other, with three bare setae, respectively; allobasis with two stout setae; endopod one-segmented, indistinctly subdivided, square, and with five bare setae.

Maxilliped (Figure 14G). Four-segmented; syncoxa bare; basis elongate approximately 2.3 times as long as width without ornamentation; endopod two-segmented; enp-1 with one small bare seta laterally and one geniculate seta distally; enp-2 small with two geniculate distal setae.

Remarks

There are several discrepancies between Kunz’s original description ( Kunz 1936) and the observations presented in the present study: (1) A2 exopod armed with five setae; (2) endopod of maxilliped two-segmented; (3) P6 armed with one unipinnate seta; and (4) segment-1 of A1 with one small bare seta (Figure 14B). All these characters were confirmed from observation of the specimens collected by Kunz from the type locality.