Paramesochra pungdoensis, Back & Lee, 2013

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 : 777-783

Paramesochra pungdoensis sp. nov.

(Figures 5–8)

Type locality

Off Pungdo Island , subtidale zone, coast of Korea, Yellow sea (37 ◦ 6 ′ 39 ′′ N, 126 ◦ 24 ′ 27 ′′ E), depth 20–25 m, sand, salinity 31 psu .

Material examined

Holotype 1 ♀ dissected on seven slides ( NIBRIV0000261348 ) . Paratypes 3 ♀♀ (CR00173701) in 70% ethanol, 26 February 2008, Leg. J. Back.

Description of female

Body (Figure 5A,B). Cylindrical and depressed dorsoventrally; body length 325 µm (n = 4, mean = 320, measured from tip of rostrum of cephalic shield to posterior margin of caudal rami); largest width measured at posterior margin of cephalic shield (85 µm); gradually tapering posteriorly; entire surface covered with tiny denticles as illustrated (inserted in the rectangle of Figure 5A).

Rostrum. Diminutive (Figure 5A) bare, fused with cephalic shield.

Prosome. Four-segmented (Figure 5A,B), comprising cephalothorax (bearing first pedigerous somite) and three free pedigerous somites; cephalothorax bell-shaped with few sensilla and two pores laterally; pleural areas weakly developed and posterolateral angles rounded.

Figure 5. Paramesochra pungdoensis sp. nov. (♀). (A) Habitus, dorsal; (B) habitus lateral; (C) antennule.

Urosome. Five-segmented (Figures 5A, 6A), comprising P5-bearing somite, genital double-somite, and three free abdominal somites; genital somite and first abdominal somite completely fused forming genital double-somite; genital field with copulatory

Figure 6. Paramesochra pungdoensis sp. nov. (♀). (A) Urosome, ventral; (B) caudal rami, dorsal (B 1, caudal rami; B 2 seta IV and V); (C) P5.

pore located in median depression; gonopores obscure, presumably single genital slit covered on both sides by opercula derived from P6; P6 represented by plate, each side with one long pinnate seta laterally and two inner, small, and bare setae; anal somite with row of spinules along ventral posterior margin; anal operculum not present,

however, pseudoperculum well developed and multiple dimpled pattern on surface near posterior margin (Figure 6B 1).

Caudal rami (Figure 6A,B 1,B 2). Oblong, approximately 4.2 times as long as wide; with spinular row along distal margin ventrally; each ramus armed with six setae; seta I obscure, presumably represented by one lateral pore; seta II bare, situated on proximal half near outer edge; seta III plumose, situated at outer corner; seta IV well developed, with short row of small setules; seta V longest, pinnate; seta VI small, bare, situated at inner distal corner; dorsal seta VII triarticulated at base.

Antennule (Figure 5C). Eight-segmented, short, robust; segment 1 largest, with one short bare seta; segment 3 and segment 4 with sub-cylindrical pedestal; armature formula: 1–[1 bare], 2–[5 bare + 3 pinnate], 3–[5 bare + 1 pinnate], 4–[3 bare + (1+ae)], 5–[1 pinnate], 6–[1 bare], 7–[3 bare], 8–[5 bare + acrothek], apical acrothek consisting of small aesthetasc fused basally to two bare setae.

Antenna (Figure 7A). With basis approximately 2.5 times as long as wide; exopod onesegmented, with one bifurcate modified apical element, one bare seta distally at inner corner, and three lateral bare setae. Endopod two-segmented; enp-1 with one pinnate abexopodal seta; enp-2 with three bare lateral setae, one geniculate seta fused basally to one bare seta, and four geniculate apical elements.

Mandible (Figure 7B 1,B 2). With well-developed gnathobase bearing several cuspidate teeth distally and one pinnate seta at dorsal corner; mandibular palp biramous and well developed; basis widening distally, with two bare setae; exopod one-segmented, with one apical bare, and three lateral bare setae; endopod two-segmented, enp-1 twice as long as enp-2; enp-1 with two bare setae distally; enp-2 with five basally fused distal setae.

Maxillule (Figure 7C). With trapezoidal praecoxa; arthrite well developed with three lateral bare setae, six distal spines, and two long bare setae on anterior surface; coxa with cylindrical endite bearing one stout, and two bare setae; basis with five bare setae; exopod one-segmented with two bare setae; endopod one-segmented, rectangular, with five bare distal setae.

Maxilla (Figure 7D). Syncoxa with chitinous outer margin, and three cylindrical endites; proximal endite bilobed, with two bare setae on proximal lobe, and one bare and one pinnate seta on distal lobe; second and third endites closed to each other, each endite with three bare setae; allobasis with one claw-like pinnate spine and one stout bare seta; endopod one-segmented, square, with five bare setae distally.

Maxilliped (Figure 7E). Four-segmented; syncoxa bare; basis elongate, approximately three times as long as wide, without ornamentation; endopod two-segmented; enp-1 with one small bare seta laterally and one geniculate seta on distal margin; enp-2 small, with one small bare seta laterally and two geniculate setae distally.

P1–P4 (Figure 8A–D). Well-developed coxae and bases with setules and spinules row on anterior surface as illustrated; P2–P4 exopod three-segmented and endopod twosegmented; P2–P4 with spinular row along outer margin of exopod and endopod.

Figure 7. Paramesochra pungdoensis sp. nov. (♀). (A) Antenna; (B) mandible (B 1, gnathobase; B 2, palp); (C) maxillule; (D) maxilla; (E) maxilliped.

Figure 8. Paramesochra pungdoensis sp. nov. (♀). (A) P1; (B) P2; (C) P3; (D) P4.

pungdoensis sp. nov.

P1 (Figure 8A). Basis with one inner and one outer bare setae; exopod twosegmented and much shorter than endopod; exp-1 longer than exp-2, with one outer bare seta; exp-2 with four pinnate setae. Endopod two-segmented; enp-1 elongate, approximately six times as long as wide, with spinular row along outer margin; enp-2 small and squarish, with one bare seta and one geniculate seta on distal margin.

P2–P3 (Figure 8B,C). Basis with one outer small bare seta; exopod longer than endopod; exp-1 with one outer spine; exp-2 with one outer spine and inner corner forming spinous projection; exp-3 with two outer spines, one stout seta apically, and one thin bare seta at distal inner corner; enp-1 without seta (P2) or with one inner seta (P3); enp-2 with one apical, pinnate and small seta, and with row of spinules distally.

P4 (Figure 8D). Basis with one outer small bare seta; exp-1 with one strong outer spine; exp-2 with one outer spine, inner corner forming spinous projection; exp-3 with one outer spine and one stout bare seta apically; enp-1 with one pinnate inner seta; enp-2 with one stout unipinnate seta. Armature formula of P1 to P4 is shown in Table 2.

P5 (Figure 6C). Baseoendopods confluent, forming large plate, furnished with one basal bare seta each; endopodal lobe expanding beyond exopod, and bilobed along median distal margin, with one long outer pinnate and one shorter inner pinnate setae; exopod small, distinct, with one bare and two pinnate setae, with rows of spinules along inner and outer margin.

Etymology

The species is named after its type locality, off Pungdo Island , in the west coast Korea .

Remarks

This new species superficially resembles P. similis and P. parasimilis in the structure of shape of caudal rami and armature formula of P1–P5. However P. pungdoensis is clearly distinguishable from its congeners by the combination of the following characters: (1) antennary exopod with five setae; (2) it possesses the longest caudal seta IV among the congeners, the caudal setae IV of P. similis and P. parasimilis are shorter than their supporting ramus, and, the caudal seta IV of P. pungdoensis is approximately 1.8 times as long as the length of caudal ramus; (3) both sides of P6 fused forming a thin plate, and represented by one long outer pinnate seta and two small inner naked setae at each side (Figure 6A), P. similis and P. parasimilis have only one long outer seta on the female P6; and (4) the inner seta of P5 baseoendopod is shorter than the outer one in P. pungdoensis , whereas it is sub-equal in length in the two other congeners (Figures 2B, 13D).