Parvocalanus leei, Moon, Seong Yong, Youn, Seok-Hyun & Soh, Ho Young, 2014

Moon, Seong Yong, Youn, Seok-Hyun & Soh, Ho Young, 2014, Description of Parvocalanusleei sp. n. (Copepoda, Calanoida, Paracalanidae) in Western Korea, with comments on the taxonomic position of Paracalanusarabiensis Kesarkar & Anil, 2010, ZooKeys 456, pp. 29-47 : 30-35

Taxon classification Animalia Calanoida Paracalanidae

Parvocalanus leei sp. n. Figs 2, 3, 4, 5, 6

Type material.

Adult female holotype, 0.93 mm (NIBRIV0000302101) and adult male allotype, 0.62 mm (NIBRIV0000302102) preserved undissected in 70% ethanol, collected from the Yellow Sea, Korea (34°46'10"N, 126°20'24"E). Paratypes: 20 females (NIBRIV302103) and 10 males (NIBRIV302104) preserved in 70% ethanol, 21 August 2013. Dissected paratypes (5 females, 3 males) are kept in collection of the senior author. Description below is based on paratypes.

Type locality.

Shallow waters of Mokpo (34°46'10"N, 126°20'24"E), Western Korea.

Etymology.

The species is named after Mrs. Jungah Lee, wife of senior author (S.Y. Moon), as a small token of appreciation for her encouragement and support to senior author.

Description.

Female. (Based on female paratype). Body (Fig. 2A, B) 0.92 mm, plump. Prosome length 2.7 times as long as urosome including caudal rami, 3.6 times as long as urosome excluding caudal rami. Prosome 5-segmented: cephalosome and first pedigerous somite completely fused, 1.49 times longer (467 µm) than wide (313 µm); fourth and fifth pedigerous somites completely separated (Fig. 2A, B). Proportional length (%) of prosomites as 68.2:11.6:10.4:5.5:4.3=100. Rostrum (Fig. 3A) short, broad, about 23 µm long. Urosome 4-segmented (Figs 2A, B, 3B): genital double-somite symmetrical, swollen anterolaterally, 1.12 times wider (81 µm) than long (72 µm); genital system remarkably symmetrical with paired gonopores located each side, genital operculum (Fig. 3C) located midventrally, rounded, about one-third as long as genital double-somite. Caudal rami (Figs 2A, B, 3B) nearly symmetrical, 2.4 times longer (66 µm) than wide (27 µm), each with row of hairs on anterior inner margin and 5 caudal setae: seta II and VI spiniform; III, IV, and VII setiform and plumose. Proportional length (%) of urosomites and caudal rami as 28.3:9.5:10.4: 27.2: 24.6 = 100.

Antennule 25-segmented (Fig. 2C); extending to midlength of anal somite; ancestral segments II to IV and XXVII-XXVIII completely fused. Segmentation and setation pattern as follows: I-2s + 1ae, II-IV - 4s + 1ae, V - 1s + 1ae, VI - 1s, VII - 1s + 1ae, VIII - 1s, IX - 1s + 1ae, X - 1 spine + 1s, XI - 1s + 1ae, XII - 1s + 1ae, XIII - 1s, XIV - 1 spine+ 1ae, XV - 1s, XVI - 1s + 1ae, XVII - 1s, XVIII - 1s + 1ae, XIX - 1s + 1ae, XX - 1s, XXI - 1s + 1ae, XXII - 1s + 1ae, XXIII - 1s, XXIV - 1s + 1s, XXV - 1s + 1s, XXVI - 1s + 1s, XXVII-XXVIII - 5s + 1ae. Ancestral segments I to XXV with row of spinules on posterior surface. Ancestral segment X and XIV with short spiniform process on distal margin of dorsal surface.

Antenna (Fig. 3D) biramous; coxa with two setae; basis with single seta; endopod 2-segmented, first endopodal segment with 2 setae; second endopodal segment with 8 setae about midway of inner margin, 7 setae terminally, and oblique row of tiny spinules midway and subdistally on outer margin; exopod 7-segmented, setal formula 1, 3, 1, 1, 1, 1, 4.

Mandible (Fig. 3E, F): gnathobase well developed, cutting edge with short teeth and dorsal single seta (Fig. 3F). Mandibular palp biramous; basis with 4 setae; exopod 5-segmented, setal formula 1, 1, 1, 1, 2; endopod 2-segmented, proximal and distal segments with 4 and 11 setae, respectively; oblique row of tiny spinules subterminally on distal segment.

Maxillule (Fig. 3G): praecoxa and coxa partially fused; praecoxal arthrite with 14 elements, and with several rows of spinules on anterior surface; coxal endite with 3 setae, coxal epipodite with 9 setae; proximal basal endite with 3 setae, distal basal endite with 4 setae; endopod 3-segmented, setal formula 3, 3, 7; exopod unsegmented with 11 marginal setae.

Maxilla (Fig. 3H): precoxa and coxa completely fused, each with two endites, posteromedial surface furnished with setules; proximal praecoxal endite with 6 setae, distal endite with 3 setae; coxal endites each with 3 setae; coxal epipodite seta present; basis with 4 setae and row of spinules subterminally; endopod 4-segmented, first and second segments incompletely separated with setal formula of 1, 2, 2, 3.

Maxilliped (Fig. 4A): syncoxa robust with setal formula 1, 2, 3, 4 and oblique rows of spinules on anterior surface; basis with 3 setae and setules on medial surface; endopod 6-segmented, first and second segments completely separated with setal formula 2, 3, 4, 3, 3+1, 4.

P1 (Fig. 4B): coxa with spinules anterolaterally and subterminally; basis with inner seta; exopod 3-segmented, first to third exopodal segments with spinules subterminally and terminally; endopod unsegmented, with row of spinules anteriomedially.

P2 (Fig. 4C): coxa with spinules on posterior magin; basis unadorned; exopod 3-segmented, first and second segments with row of spinules on anterodistally, third exopodal segment with denticles on outer proximal edge; endopod 3-segmented, first segment smooth; second segment with spinules anterodorsally and posterodistally; third endopodal segment with row of spinules posterolaterally.

P3 (Fig. 4D): coxa with spinules posteromedially; basis unadorned; exopod 3-segmented, first segment smooth; second segment with row of spinules anterodistally and posterodistally; third exopodal segment with denticles on outer proximal edge and spinules on anterior margin; endopod 3-segmented, first segment smooth; second segment with spinules anterodorsally and posterodistally; third endopodal segment with row of spinules anterolaterally.

P4 (Fig. 4E): basis unadorned; exopod 3-segmented, first segment with row of spinules posterodistally; spinules absent on anterior margin of third exopodal segment; endopod 3-segmented, first segment smooth; second segment with spinules posterodistally; third endopodal segment with row of spinules anteromedially.

Armature formula of swimming legs 1-4 (P1-P4) as follows (Roman numerals indicate spines, Arabic numerals indicate setae):

P 5 (Fig. 2D) 2-segmented, proximal segment smooth, unarmed; distal segment 2.15 times as long (31 µm) as wide (14 µm) with row of spinules subdistally and with two unequal terminal spines, inner distal spine longest, denticulated along distal part of outer margin.

Male. (Based on male paratype): Body (Fig. 5A, B) 0.53 mm, plumper than female. Prosome length 2.6 times as long as urosome including caudal rami. Prosome 5-segmented: cephalosome without dorsal hump and first pedigerous somite completely fused, 1.31 times longer (281 µm) than wide (213 µm); fourth and fifth pedigerous somites completely separated (Fig. 5A, B). Proportional length (%) of prosomites 60.5:13.5:13.5:12.5=100. Rostrum as in female. Urosome 5-segmented; first urosomal somite longest; proportional length (%) of urosomites 25.2: 20.3: 16.6: 14.6: 23.3=100. Caudal rami nearly symmetrical, about 2.2 times longer than wide, each with 5 setae, setae I and II wanting.

Antennule (Fig. 5C) 19-segmented, extending to distal part of third urosomite; ancestral segments I-IV, V-VIII, IX-X, XI-XII, and XXVII-XXVIII completely fused. Segmentation and setation as follows: segment 1 (fused ancestral segments I-IV), 7s+5ae; segment 2 (fused V-VIII), 3s+7ae; segment 3 (fused IX-X), 1s+1 spine+1ae; segment 4 (fused XI-XII), 1s+ 2ae; segments 5 (XIII) and 6 (XIV), 1s+1ae each; segment 7 (XV), naked; segment 8 (XVI), 1s+1ae; segment 9 (XVII), naked; segment 10 (XVIII), 1s+1ae; segment 11 (XIX), naked; segment 12 (XX), 1s+1ae; segment 13 (XXI), 1s; segment 14 (XXII), 1s+1ae; segment 15 (XXIII), 1s+1ae; segment 16(XXIV)1s+1s; segment 17 (XXV), 1s+1s+1ae; segment 18 (XXVI), 1s+1ae; segment 19 (XXVII-XXVIII), 5s+1ae.

Antenna (Fig. 5D) biramous but vestigial; coxa and basis completely fused, both unarmed; endopod 2-segmented, proximal endopodal segment naked; distal segment with 5 setae about midway of inner margin and with 6 terminal setae; exopod 5-segmented, setal formula 0, 1, 1, 1, 2.

Mandible (Fig. 5E) coxal gnathobase lacking; basis unarmed; exopod 5-segmented, setal formula 1, 1, 1, 1, 2; endopod 2-segmented, first endopodal segment with single seta, second endopodal segment with 8 setae.

Maxillule (Fig. 5F) vestigial presumed coxal epipodite with 5 setae.

Maxilla (not figured) vestigial.

Maxilliped (Fig. 5G): comprising robust syncoxa, basis, and 3-segmented endopod; syncoxa with a single seta and row of tiny spinules on inner distal edge; basis medially with single stout seta; proximal endopodal segment with 6 setae, of which distal seta robust; second segment with single seta; distal segment with 3 setae.

Swimming legs seta and spine formula and ornamentation (Fig. 6 A–D) generally as in female, but with some differences, as follows: P1 (Fig. 6A) lacks posterior spinules on coxa, the basis and endopod are unadorned, and the third exopodal segment lacks of row of spinules on posterior surface; P2 (Fig. 6B) has the second and distal endopodal segments with denticles on outer edge; distal endopodal segment without row of spinules on mediolateral margin; P3 (Fig. 6C) has the second and distal endopodal segments with denticles on outer edge; second exopodal segment without row of spinules on the posterodistal margin; and P4 (Fig. 6D) has the second and distal endopodal segments with denticles on outer edge; and first exopodal segment without row of spinules on the anterodistal margin.

P5 (Fig. 6E) strongly asymmetrical and uniramous: right P5 5-segmented and longer than second urosomal segment; basis and first exopodal segment unarmed; second exopodal segment with pointed process on distomedial angle; distal segment with two pointed processes, inner tiny. Left leg 3-segmented; distal segment with tiny outer apical spine, inner apical spine long, 9 times as long as outer spine.

Variation.

Body length ranged from 0.75-0.92 mm (mean ± sd, 0.84 ± 0.05, N=10) in females and 0.49-0.69 mm (mean ± sd, 0.55 ± 0.07, N=6) in males. Variability was found in number of spinules on posterior surface of P1-P4 in both sexes, on posterodistal margin of female P5, on the length/width ratio of second segment of female P5 (2.15-2.54 times as long as wide; mean ± sd; 2.31 ± 0.12, N=5), and on ornamentation of denticles on the second and distal exopodal segments of P2-P4 in female.

Distribution.

Parvocalanus leei sp. n. generally occurred together with other paracalanids, such as Bestiolina coreana Moon, Lee & Soh, 2010, Parvocalanus crassirostris , and Paracalanus parvus s. l. at the collection sites in the Yellow Sea, Korea on 21 August 2013. This new species is predominantly found in shallow waters with temperature above approximately 20 °C and 32 psu in the Mokpo Harbor, Western Korea.

Remarks.

The adult female of Parvocalanus leei sp. n. is very similar to Parvocalanus arabiensis (Kesarkar & Anil, 2010), Parvocalanus crassirostris , Parvocalanus latus Andronov, 1972, and Parvocalanus scotti ( Früchtl, 1923). All them share the short and blunt rostrum and the elongate distal segment of P5, with the inner terminal spine less than three times the length of the outer terminal spine. Nevertheless, the new species differs from Parvocalanus arabiensis as follows: (1) the body length is higher than 0.7 mm in the new species, but less than 0.7 mm in Parvocalanus arabiensis ; (2) the antennule extends up to the medial margin of third urosomite in the new species, but only to the posterior margin of genital double-somite in Parvocalanus arabiensis ; (3) the endopod of P1 is unsegmented in the new species, but 2-segmented in Parvocalanus arabiensis ; (4) the inner spine of P5 is less than 1.7 times longer than outer terminal spine of P5 in the new species, but more than 1.7 times longer than in Parvocalanus arabiensis ; and (5) there is no ornamentation of denticles on the distal edge of the third exopodal segment of P4 in the new species, vs. denticles present in Parvocalanus arabiensis .

The female of Parvocalanus leei closely resembles Parvocalanus crassirostris , but is larger (more than 0.7 mm in length compared to less than 0.7 mm); the fourth and fifth pedigerous somites are separated (vs. partially fused in Parvocalanus crassirostris ); the antennules extend to the medial margin of anal somite (vs. approximately to second urosomite in Parvocalanus crassirostris ); the length/width ratio of the distal segment of P5 is lower than 2.5 (vs. more than 3 in Parvocalanus crassirostris ); and there is a row of spinules on the distal end of the second segment of P5 (vs. row absent in Parvocalanus crassirostris ).

The new species shares with Parvocalanus latus the similar body shape and the P5 ornamentation in the female, but differs in the following features: (1) the body is more than 0.7 mm in length (vs. less than 0.7 mm in Parvocalanus latus ); (2) the antennule is comparatively shorter, reaching only the medial margin of anal somite (vs. reaching the end of caudal rami in Parvocalanus latus ); and (3) the genital double-somite is swollen anterolaterally in the new species (vs. somite not swollen in Parvocalanus latus ).

The female of Parvocalanus leei can be readily differentiated from Parvocalanus scotti based on the following features: (1) the body is more than 0.7 mm (vs. less than 0.7 mm in Parvocalanus scotti ); (2) the antennule extends only to the medial margin of anal somite (vs. to the distal margin of caudal rami in Parvocalanus scotti ); (3) the length/width ratio of caudal rami is higher than 2 in the new species (vs. less than 2 in Parvocalanus scotti ), and (4) the length/width ratio of second segment of P5 is less than 3 (vs. more than 3 times in Parvocalanus scotti ).