Heterolaophonte discophora

Heterolaophonte discophora (Willey, 1929) Figs 6, 7, 8, 9 Laophonte discophora Willey, 1929: 531, Abb. 2, 3, 6; Willey 1930: 607, pl. XVIII, figs 16 ~ 18 (cited from Itô 1974); Willey 1931: 5. Heterolaophonte discophora Lang, 1948: 1375, fig. 557-1; Lang 1965: 480, figs 262–265; Itô 1974: 628–638, figs 42–47; Song 2000: 83–86, fig. 25; Kim 2013: 25–27, fig. 9. Heterolaophonte rotundipes Chappuis, 1958: 420, figs 23–34. Material examined. (1) • Gohado (34°45'56.04"N, 126°22'22.38"E), Mokpo, Jeollanam-do, marine rope debris; 01 April 2021; leg. OH Yu, SL Kim and SM Kang: 1 ♀ (MinRB-Hr 105-L 001), 3 ♀♀ (MABIK CR 00258880), 1 ♂ (MinRB-Hr 105-L 002) and 3 ♂♂ (MABIK CR 00258881), preserved separately in a vial with 95 % ethanol; 1 ♀ (MinRB-Hr 105-S 003), 2 ♀♀ (MABIK CR 00258882–00258883), 1 ♂ (MInRB -Hr 105-S 006) and 2 ♂♂ (MABIK CR 00258884 –00258885), each dissected and mounted on 1 or 2 H-S slides. (2) • Naechi Beach (34°53'17.94"N, 126°00'05.68"E), Sinan, Jeollanam-do, expanded polystyrene buoy; 14 September 2022; leg. GH Han: 1 ♀ (MABIK CR 00258877), dissected and mounted on 2 H-S slides. • Same locality, fishing net; 01 February 2024; leg. SL Kim and SJ Gwak: 5 ♀♀ (MinRB-Hr 105-L 003), preserved in a vial with 95 % ethanol. (3) • Masan-ri (36°00'58.99"N, 129°29'05.55"E), Pohang, Gyeongsangbuk-do, green algae; 27 February 1997; leg. J Lee; 1 ♂ (MinRB-Hr 105-L 004), preserved in a vial with 95 % ethanol. • Same area, coralline algae (36°00'59.90"N, 129°28'58.32"E); 23 April 2005; leg. J Lee: 1 ♀ (MABIK CR 00258878, asymmetry in the number of setae on P 2 enp - 2), dissected and mounted on 2 H-S slides and 1 ♀ (MABIK CR 00258879), preserved in a vial with 95 % ethanol. • Same area (36°00'59.90"N, 129°28'58.32"E), coralline algae; 26 April 2005; leg. J Lee: 2 ♀♀ (MinRB-Hr 105-L 005, asymmetry in the number of setae on P 2 enp - 2), preserved in a vial with 95 % ethanol. Redescription. Female. Body length 827–1,098 μm (n = 17; measured from anterior margin of rostrum to posterior margin of caudal rami). Habitus slender, cylindrical, and gradually tapering posteriorly in dorsal view, separation between prosome and urosome indistinct (Fig. 6 A). Cephalothorax with diminutive spinules and several sensilla dorsally; posterior margin smooth, bearing several sensilla. Free pedigerous somites with diminutive spinular rows on dorsal surface, and one or two rows of spinules and several sensilla along posterior margin. Ventrolateral margins of cephalothorax fringed with a closely set of spinules (Fig. 6 a). Urosomites (Figs 6 A, 7 G) with spinules along posterior margin (except anal somite); dorsal and ventral surfaces with patterns of diminutive spinules. Genital double-somite with a transverse spinular row dorsally and laterally, indicating original segmentation; ventrally completely fused. Genital field located near anterior margin of genital double-somite; each side covered by lobe derived from P 6, bearing one inner vestigial and one outer long seta; small triangular process present medially on each lobe. Anal somite as long as caudal rami, ornamented with tiny dorsal spinules and lateral / ventral spinules along posterior margin; semicircular operculum ornamented with marginal spinules and pair of sensilla. Caudal rami (Figs 6 A, 7 G) ~ 1.7 × longer than wide; with seven setae: seta I bare, diminutive, identified at high magnification; setae II and III bare, the former shorter than the latter; setae IV and V well-developed, fused basally to each other, and bipinnate; seta VI bare, shorter than seta II, seta VII tri-articulate, arising dorsally in distal 1 / 3 of ramus. Rostrum (Fig. 6 A) completely defined basally, triangular, with pair of sensilla near apex; midventral tube pore in subapical position (not figured). Antennule (Fig. 7 A) 7 - segmented; segments 1–5 covered with minute spinules on dorsal view. First segment short, with several spinular rows; second segment with outer distal spinules; third segment longest; fourth segment with one seta fused basally to an aesthetasc on a distal peduncle; seventh segment tapering distally, with apical acrothek composed of one aesthetasc and two long setae. Armature formula: 1 - [1], 2 - [8], 3 - [7], 4 - [1 + (1 + ae)], 5 - [1], 6 - [2], 7 - [7 + acro]. Antenna (Fig. 7 B) 3 - segmented, comprising coxa, allobasis, and 1 - segmented endopod. Coxa small, with a row of spinules. Allobasis with 1 abexopodal seta located approximately midway along outer margin of segment, and with long setules near base of exopod. Endopod as long as allobasis, ornamented with long spinules along inner proximal margin and rows of spinules along outer distal margin; lateral armature consisting of two pinnate spines and one slender seta; distal armature composed of two strong spines and three geniculate setae (of which most outer one basally fused to short seta). Exopod small, 1 - segmented, with three slender setae, middle one shortest inner one longest. Mandible (Fig. 7 C). Coxa transversely elongated; gnathobase with one bicuspidate, three multicuspidate teeth, and one pinnate spine around distal margin and one pinnate seta at distal corner. Palp small, uniramous, with four bare (1 exopodal, 3 endopodal) lateral setae and one pinnate apical (basal) seta; with few small spinules present at base of proximal lateral seta. Maxillule (Fig. 7 D). Praecoxa with a row of outer spinules; arthrite with one subdistal and eight distal elements; posterior surface with a row of spinules. Coxa with a row of long spinules on anterior surface and few spinules around inner distal margin; cylindrical endite bearing one spinulose and one slender seta. Basis with one anterior spinular row; endite with one spinulose and two slender setae. Endopod nearly incorporated into basis, represented by three bare setae, of which middle one smaller than others. Exopod small, 1 - segmented, with two long apical setae. Maxilla (Fig. 7 E). Syncoxa with a long spinular row around outer margin and two rows of small spinules on surface; with three endites: proximal endite (praecoxal) bearing one pinnate seta; middle endite with one serrate spine and two pinnate setae, of which spine fused basally to segment; distal endite with one spine and two pinnate setae. Allobasis drawn out into a stout claw, with one spine (bearing three spinules near midlength) and two slender setae. Endopod represented by three bare setae (1 short, 2 long). Maxilliped (Fig. 7 F) 3 - segmented, comprising syncoxa, basis, and 1 - segmented endopod. Syncoxa with two distal plumose setae and several spinular rows. Basis longer than preceding segment, outer margin slightly convex, with two rows of spinules; inner margin with a row of strong spinules in distal half. Endopod 1 - segmented, with a long, curved claw; with one short bare seta anteriorly and a tube pore posteriorly (as in P. setadefectus sp. nov., Fig. 2 F); concave inner margin bearing row of spinules. P 1 (Fig. 8 A). Intercoxal sclerite transversely elongated and narrow. Praecoxa damaged (not shown). Coxa large, proximal outer margin protruded, with spinular rows along inner and outer margins. Basis with three spinular rows; one outer and one inner seta (displaced anteriorly). Exopod shorter than enp - 1, 3 - segmented, each segment with outer spinules; exp - 1 and exp - 2 with one outer spine; exp - 2 longest; exp - 3 with two outer spines and two geniculate apical setae. Endopod 2 - segmented, enp - 1 elongated, ~ 2 × as long as entire exopod; enp - 2 short, bearing one strong, serrate claw and one small seta, and several spinules along outer margin. P 2 and P 3 (Fig. 8 B, C). Intercoxal sclerites subrectangular. Praecoxae transversely elongated triangular, with outer spinular rows. Coxae and bases ornamented with spinular rows along outer margin and on anterior surface. Bases each with one bare outer seta and one anterior tube pore. Exopods 3 - segmented, longer than endopods; each segment ornamented with strong spinules as illustrated; exp - 2 shortest, exp - 3 longest; exp - 1 with one outer spine; exp - 2 with one outer spine and one inner seta; exp - 3 with three outer spines, one apical spine, one apical seta, and one inner seta. Endopods 2 - segmented, enp - 1 as long as enp - 2 in P 2, but much shorter than enp - 2 in P 3, with long inner spinules and short outer spinules, with (P 2) or without (P 3) one tube pore on outer corner; enp - 2 with spinules along outer margin and on anterior surface (P 3); with one tube pore located proximally (P 2) or distally (P 3), bearing two inner (occasionally 3 in P 3), two apical and no outer (P 2) or one (P 3) outer seta. P 4 (Fig. 8 D). Intercoxal sclerite elongated and narrow (see Fig. 9 E). Praecoxa small, transversely elongated and triangular. Coxa and basis with spinular rows along outer margins and on anterior surface. Basis with one bare outer seta and one anterior tube pore. Exopod 3 - segmented, gradually tapering distally, longer than endopod; exp - 1 broad, with several spinular rows on anterior surface; exp - 2 shortest, with one outer, slender, and elongated spine and one inner seta; exp - 3 with three outer, slender, and elongated spines, and two apical elements. Endopod 2 - segmented, enp - 1 with long inner spinules; enp - 2 ~ 2.5 × as long as enp - 1, with spinules on anterior surface, bearing one inner, two apical, and one outer seta. Armature formula of P 1 – P 4 as follows: P 5 (Fig. 8 E) with baseoendopod and 1 - segmented exopod, both surfaces covered with fine spinules. Baseoendopod with one bare basal seta arising from long cylindrical setophore; endopodal lobe extending to distal third of exopod, bearing spinules along inner margin, and armed with three inner and two distal bipinnate setae. Exopod widely subquadrate with slightly convex inner margin, strongly sclerotized and dented between innermost distal seta and longest seta; with three bare and three pinnate setae. Male. Body (Fig. 6 B) generally similar to that of female,