Labidocera churaumi, Hirabayashi, Takeshi & Ohtsuka, Susumu, 2014

Hirabayashi, Takeshi & Ohtsuka, Susumu, 2014, A new species of Labidocera (Copepoda, Calanoida, Pontellidae) collected from Okinawa, southwestern Japan, with establishment of five Indo-West Pacific species groups in the L. detruncata species complex, ZooKeys 447, pp. 21-34 : 22-28

Taxon classification Animalia Calanoida Pontellidae

Labidocera churaumi sp. n. Figs 1, 2, 3, 4

Material examined.

Tokashiki Port, Tokashiki Island, Okinawa Prefecture, Japan, (26°12'0.98"N; 127°22'8.77"E), 21 May 2011 (8 ♀♀, 3 ♂♂); (26°12'1.21"N; 127°22'10.20"E), 27 May 2012 (21♀♀, 11♂♂). Naha New Port, Okinawa Prefecture, Japan, (26°14'8.22"N; 127°40'47.56"E), 20 May 2011, (1 ♀, 6 ♂♂).

Types.

Holotype: 1♀, Tokashiki Port, 27 May 2012, whole specimen (KMNH IvR 500,759). Allotype: 1♂ Tokashiki Port, 27 May 2012, whole specimen (KMNH IvR 500,783). Paratypes: 1♀, 6♂♂, Naha New Port, 20 May 2011, whole specimen (♀ KMNH IvR 500,734; ♂♂ KMNH IvR 500,764-KMNH IvR 500,769); 8 ♀♀, 3 ♂♂, Tokashiki Port, 21 May 2011 partly dissected and mounted on 11 glass slides (♀♀KMNH IvR 500,735-KMNH IvR 500,742; ♂♂KMNH IvR 500,770-KMNH IvR 500,772); 20 ♀♀, 10♂♂, Tokashiki Port, 27 May 2012, whole specimen (♀♀KMNH IvR 500,743-KMNH IvR 500,758 and KMNH IvR 500,760-KMNH IvR 500,763; ♂♂KMNH IvR 500,773-KMNH IvR 500,782).

Type locality.

Tokashiki Port, Tokashiki Island, Okinawa Prefecture, Japan (26°12'1.21"N; 127°22'10.20"E).

Female.

Body (Fig. 1A, B) length of females ranging between: 2225 and 2790 µm (average 2475 µm, n=29), measured from frontal margin of cephalosome to end of caudal rami excluding caudal setae. Ratio of prosome to urosome lengths 4:1, prosome length to width ratio 2.85:1. Cephalic profile rounded in dorsal view, without lateral cephalic hooks. Paired dorsal eyes with cuticular lenses; protuberant ventral eye extending anteroventrally between rostral processes (Fig. 1C). Rostrum bifid, directed posteroventrally. Posterior margins of prosome almost symmetrical in dorsal view, tapering to simple abbreviated, pointed process at each lateral corner. Urosome 2-segmented of highly characteristic shape. Genital compound somite strongly asymmetrical; anterior left surface with posteriorly-directed rod-like process and posterior right smoothly rounded. Spermatophore (Fig. 1D) attached dorsally to genital compound somite.

Antennules (Fig. 1E) symmetrical, 23-segmented: segments armed as follows (Arabic numbers=setae; sp=spines, aes=aesthetasc): (I) 2+aes, (II-IV) 4+aes, (V) 2+aes, (VI) 2, (VII) 2+aes, (VIII-IX) 4+aes, (X) 2, (XI) 2+aes, (XII) 1+sp, (XIII) 1+sp+aes, (XIV) 1+sp+aes, (XV) 2+aes, (XVI) 2+aes, (XVII) 1+sp+aes, (XVIII) 2+aes, (XIX) 1+sp+aes, (XX) 2+aes, (XXI) 2+aes, (XXII) 1, (XXIII) 1, (XXIV) 1+sp, (XXV) 1+sp+aes, (XXVI-XXVIII) 6. Larger and longer setae on segments 3-6. Antenna (Fig. 1F) biramous: coxa with short plumose distal seta, basis and first endopodal segment fused to from elongate allobasis, setation formula 2, 2. Compound distal endopodal segment with 9 and 7 setae on proximal and distal lobes, respectively; exopod 5-segmented, setation formula 0, 0, 2, 2, 3. Mandible (Fig. 2A) with wide, heavily chitinized gnathobase; mandibular palp biramous, basis robust, armed with 4 inner setae. Endopod 2-segmented, first segment armed with 1 short and 3 long setae; second segment with 7 terminal setae. Exopod 2-segmented, first segment unarmed, second segment with 6 terminal setae. Mandibular gnathobase distal edge bearing 8 teeth comprising: from ventral margin 1 apical, 1 subapical, 3 compound medial, and 3 basal (see Fig. 2A); medial teeth with bifurcated cusps; dorsal end of gnathobase with 1 seta. Maxillule (Fig. 2B) praecoxal arthrite with 15 setal elements, 4 on posterior surface; coxal endite with 2 long and 1 short elements on endite and 9 setae on epipodite; basis with 3 setae on proximal and distal endites; and 1 large seta on basal exite; proximal endopod segment and endpod segment 2 incorporated into basis, proximal endopod segments with 2 setae, endopod segment 2 with 2 setae and distal endopod segment with 5 apical setae; exopod with 10 setae. Maxilla (Fig. 2C) with first praecoxal endite bearing 6 setae, second with 3 seta; coxa with 3 setae each on proximal and distal endites. Basis with 3 setae; endopod 3-segmented, setal formula of endopod: 1, 1, 4. Maxilliped (Fig. 2D) with praecoxa and coxa fused, three syncoxal endites well developed, with setal formula 2, 2, 4; endite setae strong, spinulose. Basis fringed with medial row of spiniform processes and 2 distal setae. Endopod 4-segmented, setal formula of endopod as: 2, 1, 1, 2.

Legs 1-4 (Fig. 3 A–D) with 2-segmented endopods and 3-segmented exopods. Coxae with plumose inner seta. Seta and spine formula (Arabic numbers=setae, Roman numerals=spines) of legs 1-4 as follows:

Leg 5 (Fig. 3E) biramous, slightly asymmetrical; coxa and intercoxal sclerite fused. Basis subrectangular, with posterior seta. Endopod rounded distally, about 0.3 times as long as exopod. Exopods of both legs 1-segmented, bifurcated tip and with 2 outer spines; outer process on left slightly larger than right and with small spine-like process on proximal part.

Male.

Body (Fig. 4A, B) slightly smaller than female (1819-2531 µm, average: 2219 µm, n=20). Prosome about 4 times as long as urosome, Urosome (Fig. 4A) symmetrical with 5 somites; anal somite and caudal rami asymmetrical.

Right antennule (Fig. 4C) with 15 segments geniculate between segments 11 and 12, reaching middle of third pedigerous somite. Antennular segments armed as follows (Arabic numbers=setae; sp=spines, aes=aesthetasc): (I) 2+aes, (II-IV) 4+aes, (V) 2+aes, (VI) 2, (VII) 2+aes, (VIII-XIV) 8+6sp+4aes, (XV-XVI) 4+2aes, (XVII) 2+aes, (XVIII) 2+aes, (XIX) 1+aes, (XX) 1+aes, (XXI-XXIII) 2+aes, (XXIV) 2, (XXV) 2+aes, (XXVI-XXVIII) 6; Segments 11 and 12 with row of teeth.

Left antennule, antenna, mouthparts and swimming legs as in female.

Leg 5 (Fig. 4D) asymmetrical. Left leg 5 short; intercoxal sclerite and left coxa fused. Basis cylindrical with seta near base. Exopod 2-segmented: first segment cylindrical; second segment triangular short with protruding hairy medial surface and 3 distal and 1 lateral spines, one of them long. Right leg 5 basis with seta. Exopod 2-segmented, forming chela; thumb of chela large, triangular, arising near base of first exopodal segment. First exopodal segment with 2 small setae. Second exopodal segment elongate and curved, with 3 slender marginal setae.

Remarks.

The present new species is similar to Labidocera madurae Scott, 1909 and Labidocera tasmanica Taw, 1974 in having the following features: (1) the posterolateral margins of the prosome are symmetrical, each triangular with a sharply pointed tip; (2) the female urosome is moderately or markedly asymmetrical; (3) the caudal rami are symmetrical and not highly modified; (4) the endopods of female leg 5 are nearly symmetrical, short, conical, and not bifid at the tip; (5) the thumb of the right leg 5 of the male is triangular with a broad base, and is slightly recurved; (6) the distal part of terminal segment of the left leg 5 of the male bears 3 spines, the outermost of which is the longest. These 3 species constitute a species group within the Labidocera detruncata species complex (see Discussion). Labidocera churaumi sp. n. can be distinguished from Labidocera madurae and Labidocera tasmanica by: (1) the presence of right postero-lateral and left antero-lateral processes on the female genital compound somite; (2) the exopod of the female leg 5 is very short, only as long as the basis, and has a bifurcated tip on both sides; (3) the inner margin of the terminal segment of the male left leg 5 has a protrusion at mid-length.

Etymology.

The new specific name “churaumi” is from an Okinawan dialect, meaning the beautiful seas around the type locality Okinawa.