Parabathyesola calida, Kim & Kim & Lee, 2025

Parabathyesola calida gen. et sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3 , 4 View Figure 4 , 5 View Figure 5 , 6 View Figure 6

Type material.

Holotype. • intact female preserved in alcohol ( MABIK CR 00259486 ), Indian Ocean, Onnuri Vent Field located on the Central Indian Ridge ( CIR), 11°24'52.99"N, 66°25'25.45"E, depth 2018.6 m; 24 June 2018, J. Lee leg. GoogleMaps Paratypes. • one intact female ( MABIK CR 00259487 ), (whose antennules lost after drawing of habitus) and one intact male ( MABIK CR 00259488 ) preserved in alcohol, dissected and figured female ( MABIK CR 00259489 ) and male ( MABIK CR 00259490 ) mounted onto three slides, respectively. Five dissected females ( MABIK CR 00259491 – CR 00259495 ) and three dissected males ( MABIK CR 00259496 – CR 00259498 ) mounted onto a slide, respectively. Other intact two females and two males preserved together in alcohol ( HNIBRIV 25084 ) GoogleMaps . Sampling data of all paratypes as for the holotype.

Description.

Female (based on paratypes MABIK CR 00259487 and CR 00259489 ). Total body length ranged from 457–519 μm (mean = 490.1 μm, n = 7), excluding length of caudal setae. Body (Fig. 1 A, B View Figure 1 ) subcylindrical, slightly tapering posteriorly, approximately 4 × as long as wide; maximum width ~ 130 μm long measured at posterior end of cephalothoracic shield in dorsal view; demarcation between prosome and urosome inconspicuous, but flexible dorsally. Integument on all body somites reticulated (Fig. 1 C View Figure 1 ), covered with fine spinules.

Rostrum (Fig. 1 D View Figure 1 ) well-developed, bell-shaped, defined at base, subapically with one mid-ventral pore and one pair of lateral pores; apical tip blunt, with two sensilla.

Prosome (Fig. 1 A, B View Figure 1 ) composed of cephalothorax and three free pedigerous somites (bearing P 2 – P 4); first pedigerous somite completely incorporated into cephalosome. Cephalothoracic shield bell-shaped, ~ 1.2 × as wide as long, with one mid-dorsal pore, and one unpaired sensillum (in central) and several paired sensilla; pleural areas rounded, with lobate posterior angles; posterior and ventro-lateral margins fringed with long fine setules. Free pedigerous somites gradually tapering posteriorly, with one dorsal row of fine spinules near posterior margin, one pair of dorsal sensilla, and five (in P 2 -, P 4 - bearing somites) or six (in P 3 - bearing somites) pairs of posterior sensilla; posterior and ventro-lateral margins fringed with long spinules; P 2 - bearing somite with one mid-dorsal pore.

Urosome (Fig. 1 A, B View Figure 1 ) five-segmented, comprising P 5 - bearing somite, genital double-somite, three free abdominal somites. All urosomites except for anal somite ornamented with one row of dorsal spinules posteriorly and two or three groups of long spinules laterally. P 5 - bearing somite with remarkably boarder posterior half and dorsal posterior margin ornamented with four pairs of sensilla and one pair of rows of long spinules. Genital double-somite completely fused ventrally (Fig. 2 A View Figure 2 ), but original division marked by bilateral constriction and dorsal transverse suture, 0.77 × as long as wide; anterior somite (genital somite) with border posterior half bearing three pairs of dorsal posterior sensilla; posterior somite gradually bordering towards posterior margin, with one pair of lateral tube pores (arrowed in Fig. 1 A View Figure 1 ) and four pairs of dorsal posterior sensilla; genital gonopores and minute mid-copulatory pore covered by single opercula derived from sixth legs; P 6 represented by two small setae on small lobes; midventral surface with one pair of pores and one pair of small sensilla. First free abdominal somite (fourth urosomite) comprising narrower anterior one-third and broadened posterior two-thirds, with one pair of lateral tube pores (arrowed in Fig. 1 A View Figure 1 ) and three pairs of dorsal posterior sensilla. Second free abdominal somite (fifth urosomite) with almost straight lateral margins without sensillum and tube pore ornamentation. Anal somite smaller than preceding somite, with one pair of lateral tube pores (arrowed in Fig. 1 A View Figure 1 ), one pair of ventral tube pores (arrowed in Fig. 1 A View Figure 1 ), ornamented by posterior spinules laterally and ventrally; median cleft deep, ornamented by rows of lateral spinules on each side; semi-circular operculum ornamented with two rows of spinules, flanked by two sensilla. Caudal rami distinctly separated from each other, cylindrical, slightly swollen proximally, 3.4 × as long as wide, ~ 1.4 × longer than preceding somite, with one dorsal tube pore proximally and one row of inner spinules subdistally; set of setae I and II arising from distal one-fourth of lateral margin, seta I very small and seta II 4 × as long as seta I; ventro-lateral seta III subdistal, posterior to set of setae I and II, ~ 1.6 × as long as seta II; setae IV and V bi-serrate, with fracture plane, seta IV ~ 1.7 × as long as ramus, seta V as long as urosome (including caudal rami); seta VI issuing at inner distal corner, small; dorsal seta VII arising from insertion level of seta III, longer than seta II.

Antennule (Fig. 2 B View Figure 2 ) six-segmented, elongate. First segment with one small spinous projection on outer margin and two rows of inner spinules. Second segment longest. Third segment slightly shorter than preceding segment. Fourth segment with distal pedestal bearing aesthetasc fused to adjacent seta. Fifth segment smallest. Sixth segment shorter than third segment, with acrothek composed of one aesthetasc and two setae. Armature formula as follows: 1 - [1], 2 - [8], 3 - [6], 4 - [1 + (1 + ae)], 5 - [1], 6 - [9 + acrothek]. All setae bare except for one spinulose seta on second segment; five outer setae on sixth segment bi-articulate basally.

Antenna (Fig. 3 A View Figure 3 ) composed of coxa, allobasis, one-segmented endopod, and one-segmented exopod. Coxa small, ornamented with two rows of spinules. Allobasis largest, 2.1 × as long as wide, with one spinulose abexopodal seta. Free endopodal segment, longest, gradually broadening towards distal end; inner margin armed with long spinules proximal two-thirds, with one stout spine and two serrated setae; outer margin with surface frill composed of spinules. Distal armature comprising two spines, three geniculate setae, and one delicate seta; longest geniculate seta fused basally to delicate seta at inner distal corner. Exopod small, gradually broadening towards distal end, armed with one row of lateral spinules, with four plumose setae.

Mandible (Fig. 3 B View Figure 3 ). Coxa well-developed, with one row of stout spinules, one blunt median protrusion; gnathobase comprising one uni-cuspidate, two bi-cuspidate, one multicuspid teeth, and one uni-serrate seta. Palp composed of broad basis and one-segmented endopod; basis with two plumose setae distally and one plumose seta proximally (representing exopod); endopod small, with one lateral and two distal plumose setae.

Maxillule (Fig. 3 C View Figure 3 ). Parecoxa broad, with two rows of spinules on outer margin; arthrite well-developed, armed with one bare anterior seta and four posterior spinules; with two bare and two spinulose spines, one pinnate and three bare setae. Coxa small, armed with several outer spinules; endite cylindrical, with one bare seta and one spinulose spine. Base transversally elongate with two plumose setae laterally and one spinulose spine and two bare setae distally. Endopod small, 1.7 × longer than wide, ornamented with lateral spinules, with two plumose setae distally.

Maxilla (Fig. 3 D View Figure 3 ). Syncoxa robust, ornamented with two stout spinules and one row of spinules on outer margin, one row of setules on surface, with three endites; proximal endite smallest, with one bare seta; middle endite largest, with one bare seta and two spinulose setae; distal endite, as large as middle endite, with one spinulose seta and two bare setae. Allobasis drawn out into stout claw accompanying one bare and one pinnate seta. Endopod very small, with one weakly plumose seta and two bare setae.

Maxilliped (Fig. 3 E View Figure 3 ) subchelate, composed of syncoxa, basis and endopod. Syncoxa ornamented with two groups of spinules and one row of spinules on surface, one row of spinules near outer margin, with two plumose setae distally. Basis largest, 2.4 × as long as wide; outer margin convex, with two rows of long spinules, inner (palmar) margin almost straight, with two rows of long spinules. Endopod one-segmented, claw-like, uni-serrated, accompanying one small seta and one small denticle.

P 1 (Fig. 4 A View Figure 4 ). Praecoxa unexamined. Intercoxal sclerite transversely elongate, wide, slightly arched, without ornamentation. Coxa large, slightly longer than greatest width; outer margin slightly swollen proximal two-thirds bearing two groups of long spinules; anterior surface with one row of stout spinules and three rows of minute denticles. Basis elongated by development of pedestal for insertion of endopod, longer than coxa, ~ 1.7 × as long as wide, ornamented with one row of inner spinules, one row of anterior spinules and one anterior tube pore; long and plumose outer seta issuing from pedestal positioned proximal one-fourth of outer margin and accompanying several anterior spinules; plumose inner seta shorter than outer seta, arising from distal one-fourth of anterior surface. Exopod 3 - segmented, slightly less than midlength of ENP 1; all segments subequal in length, ornamented with two rows of outer spinules and several inner setules (absent in EXP 3); EXP 1 with one long and plumose outer seta slightly beyond midlength of EXP 3; EXP 2 with one bare outer spine; EXP 3 with two bare outer spines and two geniculate distal setae. Endopod prehensile, 2 - segmented; ENP 1 robust, elongate, ~ 5.5 × as long as wide, ornamented with outer spinules and inner setules; ENP 2 small, ornamented with outer setules and inner spinules (gradually increasing towards inwardly), distally with one delicate seta and one stout and uni-serrate spine.

P 2 (Fig. 4 B View Figure 4 ). Praecoxal small, ornamented with distal spinules. Intercoxal sclerite wide, arched, unornamented. Coxa large, ornamented with two rows of outer spinules and four rows of anterior spinules. Basis smaller than coxa, with one anterior tube pore near outer margin; inner margin ornamented with one group of setules and outer margin ornamented with one row of spinules; outer seta long and pinnate. Exopod longer than endopod, 3 - segmented; EXP 1 ornamented with five rows of outer spinules and one row of inner setules, with one pinnate outer spine; EXP 2 smallest, with three groups of outer spinules and one row of inner setules, with one pinnate outer spine and one inner plumose seta; EXP 3 as long as EXP 1, ornamented with four rows of outer spinules, with three pinnate outer spines, one distal spine (ornamented with outer spinules and inner setules), one plumose distal seta, and one plumose inner seta. Endopod reaching distal one-third of EXP 2; ENP 1 slightly beyond midlength of EXP 1, ornamented with outer setules, with one anterior tube pore and one plumose inner seta; ENP 2 ~ 1.5 × as long as ENP 1, ornamented with outer setules, with one outer seta, two distal setae, and two inner setae; outer seta and distal inner seta with additional spinular ornamentation.

P 3 (Fig. 4 C View Figure 4 ) as in P 2 except for setal armatures and ornamentations. Coxa with two rows of anterior spinules. Basis with one bare outer seta. Exopod same as setal armature of P 2, but inner seta on EXP 3 extremely long, 2.4 × as long as EXP 3. Endopod also slightly less than distal end of EXP 2; ENP 2 ~ 2 × as long as ENP 1; ENP 2 with one anterior pore and inner setules; armature of ENP 2 comprising one outer spine being plumose proximally and pinnate subdistally, two plumose distal setae and three plumose inner setae; two subdistal inner setae ornamented additional outer spinular ornamentation.

P 4 (Fig. 2 C View Figure 2 ) as in P 2 and P 3 except for setal armatures and ornamentations. Coxa with one row of anterior spinules. Outer seta on basis bare and smaller than those of P 2 and P 3. EXP 1 ornamented with six rows of outer spinules; EXP 3 with same setal armature of P 2 EXP 3, but inner seta extremely long, ~ 2.6 × as long as EXP 3. Endopod also slightly less than distal end of EXP 2; ENP 1 lacking anterior tube pore; ENP 2 ~ 2.8 × as long as ENP 1, ornamented with setules in proximal half on both sides, one row of outer spinules in distal half; anterior tube pore present; setal armature of ENP 2 as in P 2, but outer seta exceeding distal end of EXP 3; spinular ornamentation observed in outer seta and two inner setae.

P 5 (Fig. 2 D View Figure 2 ). BENP elongate, ~ 3.3 × as long as wide, with one anterior tube pore; outer setophore distinctly prolonged, with one long bare seta, and ornamented with spinules anteriorly and posteriorly; endopodal lobe well-developed, beyond midlength of exopod, slightly tapering towards distal end, with one tube pore, three long pinnate inner setae and two small pinnate distal setae; all margins of endopodal lobe ornamented with spinules. Exopod elongate, ~ 4.8 × as long as wide; distal margin produced as tubular extension, with one long bare seta; inner margin ornamented with spinules and subdistal pinnate seta; outer margin ornamented with three groups of spinules and four pinnate setae; proximal two setae on outer margin displaced in same insertion position.

Male (based on paratype MABIK CR 00259490 ). Habitus (Fig. 5 A View Figure 5 ) slightly smaller than female. Body length ranged from 440 to 462 μm (mean = 448.8 μm, n = 5); length / width ratio ~ 4.3 and prosome / urosome (including caudal rami) length ratio 1.0. Urosome (Figs 5 A View Figure 5 , 6 A View Figure 6 ) six-segmented; P 5 bearing-somite trapezoidal in dorsal aspect; genital somite free, slightly broadening towards posterior margin; first and second postgenital somites as in female, with two pairs and one pair of ventral tube pores, respectively.

Antennule (Fig. 5 B View Figure 5 ) seven-segmented, subchirocerate, with geniculation between fifth and sixth segments; first segment armed with one row of weak spinules and two rows of stout spinules; second segment longest, 2.3 × as long as wide, subdistally with incomplete suture line; fourth segment represented by small sclerite bearing one seta; fifth segment swollen, with peduncle bearing one long seta and aesthetasc fused basally to adjacent another seta; sixth segment with one bare seta and three teeth-like projections; seventh segment conical, slightly recurved, subdistally with one acrothek as female. Armature formula as follows: 1 - [1], 2 - [9], 3 - [6], 4 - [1], 5 - [10 + (1 + ae)], 6 - [1 + 3 teeth], 7 - [8 + acrothek]. All setae bare except for one spinulose seta on second segment and uni-serrate seta on fifth segment; six outer setae on distal segment bi-articulate.

P 3 (Fig. 6 B, B View Figure 6 ’). Endopod probably 3 - segmented, with incomplete anterior division between distal two segments; ENP 1 as in that of female; ENP 2 with one recurved and pinnate outer spine and one short and plumose inner seta; ENP 3 with two inner and two distal plumose setae.

P 5 (Fig. 6 C View Figure 6 ) two-segmented; left and right BENP fused to sclerite; BENP with one anterior and two inner tube pores; outer setophore cylindrical, flanked with one row of anterior spinules, with one long bare seta. Exopod elongate, 2.3 × as long as wide, ornamented with anterior spinules; with two outer, one distal, and two inner setae.

P 6 (Fig. 6 A View Figure 6 ). asymmetrical, right membrane basally articulated from ventral surface of genital somite; leg represented by small cylindrical protrusion bearing one plumose seta.

Etymology.

The species name is derived from the Latin adjective calidus meaning ‘warm’ or ‘hot’, and refers the hydrothermal habitat of its type locality. Gender: feminine.