Haloschizopera cheni, Liu & Ma & Li, 2021

Liu, Qinghe, Ma, Lin & Li, Xinzheng, 2021, Review of the genus Haloschizopera (Harpacticoida: Miraciidae, Diosaccinae) with description of a new species, Zootaxa 4927 (4), pp. 525-538 : 526-531

Haloschizopera cheni sp. nov.

Material examined. Holotype: 1 adult female, dissected on 6 slides ( MBM189248 ), soft mud, depth 52 m, 122.51°E, 28.95°N, 18 December 2016 . Paratypes: 2 adult females, dissected on 11 slides ( MBM189249-189250 ) ; 3 adult males, dissected on 12 slides ( MBM189251-189253 ) ; 1 adult female and 2 adult males ( MBM189254 ) preserved in alcohol, collecting information as holotype.

Diagnosis. Body subcylindrical, widest at posterior margin of cephalothorax, prosome slightly tapering anteriorly and posteriorly, cephalothorax and three free somites subequal, prosome slightly wider and longer than urosome. Rostrum defined at base, elongate, triangular, semi-hyaline distally, with central reinforcement, extending beyond second antennular segment, pair of small lateral sensilla in distal half length. Somatic ornamentation simple and slight, dorsal and lateral surface without spinules except one dorsal-lateral row of spinules on first abdominal somite in male. Antennule eight-segmented in female, nine-segmented in male; with aesthetascs on fourth and terminal segments. Allobasis of antenna with one seta at inner middle margin; exopod three-segmented, second segment with one plumose seta; endopod with seven terminal elements. Mandibular basis with three plumose setae; exopod two-segmented, with 1:3 setae; endopod one-segmented, with two middle and six terminal setae. Maxillulary coxal endite with one seta; basis with five setae; endopod and exopod one-segmented with four naked setae and two plumose setae, respectively. Maxilla with three coxal endites, with 2:2:3 elements (proximal to posterior); allobasal endite with three elements; endopod with seven naked setae. Maxilliped with three setae on syncoxa; basis with one seta and one small spine; endopod one-segmented, with a terminal claw and one accessory seta. P1 endopod and exopod three-segmented; endopod not prehensile, enp-1 not extending to the middle of exp-2, sexual dimorphism characterized by two hyaline apophyses and reinforcement at inner margin of male basis. P2-P4 rami three-segmented, except enp-2 of P 2 in male; P2 enp-2 modified in male, with two inner setae, one apical spine and two outer spines, inner one of outer spine with two teeth at tip; exp-3 of P3 without inner seta, P4 with two inner setae. Caudal rami longer than broad, with one dorsal, two ventral, one inner distal, one outer lateral and two terminal setae.

Description of adult female. Body length: 251–296 μm. Body subcylindrical ( Fig. 1A ), tapering slightly pos-teriorly, widest at posterior margin of cephalothorax. Rostrum defined at base, elongate, triangular, semi-hyaline distally, extending beyond second antennular segment, with central reinforcement and pair of small lateral sensilla in half length. Cephalothorax tapering anteriorly, with scattered sensilla, metasome with paired sensilla; cephalothorax slightly longer than metasome. Genital double-somite dorsally and laterally subdivided by subcuticular rib; genital area as in Fig. 1E ; vestigial sixth swimming leg bearing one long seta and two small smooth setae. Anal somite deeply divided in dorsal view with inner margins bearing complex rows of small spinules; operculum flabellate, near median dorsal anterior border with hyaline frills. Caudal rami ( Fig. 1 ) longer than broad (length/width: 1.3), carrying seven setae: one smooth and three-segmented seta near inner margin of dorsal surface, one strong seta on outer lateral surface, one fine seta on inner distal corner, one short and one fine setae on posterior part of ventral surface and two well developed terminal setae with outer one been smaller and shorter than the inner one.

Somatic ornamentation. ( Fig. 1 D-F) Body ornamentation simple and slight. Prosome same as in male with sensilla and pores. Dorsal surface of urosome smooth except with several sensilla; ventral surface with one continuous row of spinules on penultimate somite and short ventral-lateral row of spinules on third abdominal somite. Anal somite with lateroventral row of spinules around caudal rami. Posterior margin of cephalothorax and free thoracic somites, hyaline frill of urosomites with inconspicuous incision.

Antennule. ( Fig. 2A ) Eight-segmented, first segment with setulose seta; second segment with two unipinnate setae, one large on outer margin and one small on distal inner corner; third segment with two plumose setae on distal corner; aesthetascs on fourth and terminal segments; armature formula: 1 [1], 2 [11], 3 [6],4 [4 + aes], 5 [2], 6 [3], 7 [3], 8 [7 + aes].

Antenna. ( Fig. 2C ) Coxa with spinules at outer subdistal corner. Allobasis with one pinnate seta at proximal half of abexopodal margin. Exopod three-segmented, first segment and second segment both with one plumose seta; second segment short; third segment slender with spinules around subterminal margin, one plumose seta on middle inner margin, and three setae on distal margin, one plumose and two naked. Endopod with rows of spinules along proximal inner margin; subterminal inner corner with two setae, one spinulose, surrounded by one row of strong spinules; outer distal corner with one row of setules on posterior surface; outer margin with several spinules; distal end with seven elements: one pinnate seta, one slender seta, four geniculate setae, posterior one of which strongly spinulose around point of inflexion and sharing base with slender seta, one short fine seta inserted inside terminal edge.

Mandible. ( Fig. 2D ) Gnathobase armed with one large tricuspid tooth, two bicuspid, four unicuspidal teeth, one smooth and one pinnate setae at outer distal corner. Basis broad, with row of setules on surface and scattered setules along outer margin. Endopod one-segmented, with two lateral and six terminal setae, all smooth. Exopod two-segmented, approximately half length of endopod; proximal segment with one smooth seta on distal corner, terminal segment with one plumose seta and two smooth setae.

Maxillule. ( Fig. 2E ) Praecoxa with row of short setules on anterior surface; arthrite with one smooth seta and row of setules on anterior surface, distal margin with eight stout, one slender and one spinulose spines. Coxa with two setae on distal margin, one stout, one slender. Basis with two slender subterminal setae, one smooth and two pinnate apical setae. Exopod one-segmented, with two plumose setae. Endopod one-segmented, with four smooth apical setae.

Maxilla. ( Fig. 2F ) Syncoxa with two rows of spinules at outer proximal edge; inner edge with three endites, proximal endite armed with two spines, middle endite with one spine and one seta, distal endite with three spines (one pinnate). Allobasal endite with two spines (one dentate) and one naked seta fused at base of endite. Endopod one-segmented, with seven unequal smooth setae, longest one stout.

Maxilliped. ( Fig. 2G ) Syncoxa with rows of spinules on proximal edge and on anterior surface at subdistal margin; two small pinnate setae and one large plumose seta on distal margin. Basis with row of spinules on proximal surface; subdistal distal margin with one slender seta and middle inner margin with one short spine. Endopod onesegmented, with one terminal claw and one accessory seta.

P1. Intercoxal sclerite long, rectangular ( Fig. 3A ). Coxa with four rows of setules on anterior face. Basis with several stout spinules at distal outer corner; inner spine peculiar, rather strong and stout with long spinules on distal part, basis reinforced and armed with row of spinules; outer spine pinnate. Exopod and endopod three-segmented, all segments with row of stout spinules along outer margin and on the anterior face of exp-1; both exp-1 and -2 with one long pinnate spine at outer distal corner; exp-3 with two pinnate spines at outer distal corner and two apical plumose setae without geniculation; enp-1 and -2 each with one plumose seta at subdistal inner margin; enp-3 with two apical setae (one large, plumose and another slender, smooth), and one pinnate spine at outer subdistal corner. Exopod shorter than Endopod, first and third segments subequal, slightly longer than middle segment; Endopod not prehensile, enp-1 subequal with enp-2, not extending to the middle of exp-2.

P2-P4. Intercoxal sclerite bulbous, with two conical projections, unornamented ( Figs. 3B , 4 A-B). Coxa with two rows of setules on anterior surface. Basis with one row of setules at inner distal corner and several long spinules on inner margin. Outer proximal corner of basis in P3 and P4 each with one smooth seta borne on short peduncle. All rami three-segmented, terminal segments longest; P2 and P3 enp-3 longer than enp-1 and enp-2 together; P2-P4 with hyaline plate between exp-1 and exp-2 on posterior face, enp-2 with conspicuous apophysis at outer distal corner; P2 and P3 enp-1 with small apophysis at inner distal corner ( Figs. 4D & 5A-B). Endopod slightly longer than exopod in P2 and P3, shorter in P4. Terminal setae of distal segments well-developed, plumose and longer than the whole length of each ramus. Setal formulae of P1-P4 as follows:

P5. ( Fig. 4D ) Baseoendopods not fused medially, separated with exopod. Baseoendopodal lobe extending to the end of exopod. Baseoendopod with one small pinnate inner seta, one subterminal unipinnate seta and three apical pinnate setae (middle one more than two times as long as others); outer margin with few spinules, hyaline area near base of exopod. Exopod slightly oval in shape, approximately 1.3 times as long as broad, with one rows of spinules on distal inner margin, and five setae (one inner, one apical, three outer); inner seta well developed and pinnate, about four times as long as apical seta, apical seta fine, naked, and borne on short peduncle; distal outer seta naked, slightly shorter than inner seta; middle outer seta smooth, about half length of distal outer seta; outermost seta small and naked.

Description of adult male. Similar to female except for following features:

Body. Shorter than females, 240–260 μm long, first two abdominal somites distinct.

Somatic ornamentation. Ornamentation on urosome more complete than female. Dorsal surface with dorsolateral row of spinules and sensilla on first abdominal somite; second and third abdominal somites both with one continuous ventral row of spinules at posterior margin, one ventral row of short spinules on anterior part of second abdominal somite; fourth abdominal somite with discontinuous ventral rows of spinules on posterior margin.

Antennule. ( Fig. 2B ) Haplocer, nine-segmented, with major articulation between sixth and seventh segments; aesthetascs on fourth segment and terminal segment. Armature formula: 1 [1], 2 [11], 3 [6], 4 [4 + aes], 5 [1], 6 [1], 7 [1], 8[3], 9 [6+aes].

P1. ( Fig. 3C ) Inner margin of basis reinforced with two chitinous projections at proximal corner and distal inner corner respectively; inner spine well-developed with strong spinules.

P2. ( Fig. 3D ) Endopod two-segmented. First segment ornamented with row of setules on outer margin. Second segment modified; proximal inner margin with one long plumose seta, arising from small cuticular projection; distal inner seta well-developed, plumose, arising from basis of terminal spine; terminal spine geniculate at distal margin, with long and narrow basis; outer margin with one stout spine, thick at proximal end, and one slender spine, with two teeth at distal end.

P3. ( Fig. 4C ) Distal segment of exopod with small hyaline tube pore issuing from anterior surface, next to inner margin, nearly parallel with most proximal outer spine.

P5. ( Fig. 4E ) Endopodal lobe extending beyond end of exopod, with two stout pinnate terminal setae and few spinules along outer margin, hyaline spot at base of exopod. Exopod separate, subcircular, with five setae; inner seta stout and pinnate; apical seta pinnate, longer than half length of inner seta, ornamented with one spinule at base; distal outer seta smooth, about twice as long as apical one; other two outer lateral setae small and naked.

P6. ( Fig.1C ) Plate with one inner large seta and two small outer setae. One leg larger than another.

Etymology. The species is named after Dr. Qingchao Chen, in recognition of his numerous contributions to marine planktonic copepods of China.

Variation. No obvious variation was noticed among the specimens examined except body length (251–296 μm). Urosome and prosome often bent at an angle, which may lead the shrinking of urosomites and variation in length/ width ratio of abdominal somites.

Figures

FIGURE 1. Haloschizopera cheni sp. nov., male (A-C), female (D-F); (A) Habitus, dorsal view; (B) abdomen, lateral view; (C) abdomen, ventral view; (D) abdomen, dorsal view; (E) abdomen, lateral view; (F) abdomen, ventral view.

FIGURE 2. Haloschizopera cheni sp. nov., (A) antennule of female; (B) antennule of male; (C) antenna; (D) mandible; (E) maxillule; (F) maxilla G maxilliped.

FIGURE 3. Haloschizopera cheni sp. nov., (A) P1 female; (B) P2 female; (C) P1 basis of male; (D) endopod of male P2.

FIGURE 4. Haloschizopera cheni sp. nov., (A) P3 female; (B) P4 female; (C) exp-3 of Male P3; (D) female P5; (E) male P5.