Haplostomides partitus, Kim & Boxshall, 2021

Kim, Il-Hoi & Boxshall, Geoff A., 2021, Copepods (Cyclopoida) associated with ascidian hosts: Ascidicolidae, Buproridae, Botryllophilidae, and Enteropsidae, with descriptions of 84 new species, Zootaxa 1, pp. 1-286 : 138-140

Haplostomides partitus sp. nov.

( Fig. 90 )

Type material. Holotype ♀ (MNHN-IU-2018-1991, dissected and mounted on a slide) from Apl ẚdẚum benhamẚ (Brewin, 1946) (MNHN-IT-2018-19 = MNHN A1 / APL.B/547); Madagascar, Îlot des Roches, ATIMO VATAE expedition, Stn TA56 (24°58´S, 47°03´E), depth 1-8 m, MNHN coll., 14 June 2010.

Etymology. The name is derived from the Latin partẚt (=divided), referring to the segmented body of the female of the new species.

Description of female. Body ( Fig. 90A ) maggot-shaped, well-segmented, consisting of cephalosome, 4-segmented metasome, and 4-segmented genitoabdomen. Body length 1.15 mm; maximum width 0.37 mm across second pedigerous somite. Body somites clearly defined from one another by deep constrictions and distinct suture lines. Genitoabdomen indistinctly articulated from metasome, consisting of genital somite and 3-segmented abdomen. Genital apertures positioned dorsally. Abdomen strongly tapering. Caudal rami ( Fig. 90B ) convergent, originating on dorsal surface of anal somite, not articulated from somite; each ramus ( Fig. 90C ) tapering, longer than wide, divided into larger proximal part bearing 1 seta distally and lobate distal part bearing 1 small, claw-like distal spine.

Rostrum absent. Antennule ( Fig. 90D ) 3-segmented; first segment expanded, about twice as long as distal part of antennule, armed with 4 small setae; second segment incompletely articulated from first, armed with 1 small and 1 large, extremely expanded seta; third segment armed with 10 setae (3 proximal and 7 distal and subdistal). Antenna ( Fig. 90E ) 2-segmented, consisting of coxobasis and endopod; coxobasis unarmed; endopod about 3.1 times longer than wide (50×16 μm), longer than coxobasis, armed with 4 claw-like spines, all articulated at base, and ornamented with many minute spinules along outer surface.

Labrum ( Fig. 90F ) pale, much wider than long, strongly tapering towards truncate apex. Mandible ( Fig. 90G ) lobate, with convex medial margin; armed with 2 broad setae distally. Maxillule ( Fig. 90H ) unsegmented, lobate, armed with 5 broad setae (2 posterodistal, 2 anterodistal, and 1 subdistal). Maxilla ( Fig. 90I ) also unsegmented and lobate, armed with 9 setae (6 slender and 1 broad setae distally and 2 expanded setae on posterior margin). Maxilliped ( Fig. 90J ) 4-segmented; first segment much larger than other segments, as long as wide, unarmed; second segment with 2 small, transparent setae (1 mediodistal and 1 outer distal), third and fourth segments small, unarmed, with similar lengths; terminal claw small, with strongly curved, acute tip.

Leg 1 ( Fig. 90K ) biramous, but both rami not articulated from protopod; protopod unarmed, lacking outer seta; exopod with 1 swollen, transparent seta in middle of outer margin and 2 distal spines of unequal lengths, ornamented with several minute spinules near bases of distal spines; endopod short, broad, appearing as convex inner protuberance on protopod. Legs 2-4 exactly same as leg 1 in form and armature.

Leg 5 as unarmed posterolateral lobe on compound fourth metasomite ( Fig. 90A ). Leg 6 ( Fig. 90L ) represented by 1 spine and 1 large, blunt process covered with transparent material. Five dentiform internal elements present near leg 6.

Male. Unknown.

Remarks. eaplçstçmẚdes partẚtus sp. nov. can be differentiated from its congeners by three diagnostic features, as follows: (1) the maxillule is unsegmented (in all previously known species of the genus the maxillule is 2-segmented, consisting of the proximal precoxa and the distal palp); (2) the maxilla is armed with 9 setae, compared to a maximum of 4 setae in all congeners (as for example in e. luteçlus Ooishi & Illg, 1977); and (3) the outer seta on the exopod of legs 1-4 is markedly swollen and distinctly broader than the distal spines (another unique feature of the new species).

Genus Haplostoma Canu, 1886

Diagnosis. Female: Body eruciform, unsegmented or indistinctly segmented.Genitoabdomen fused with or obscurely defined from metasome.Caudal rami armed with1 to6 armature elements(spines plus setae), or occasionally unarmed. Rostrum not developed.Antennule small, 1- to 5-segmented.Antenna 2- or 3-segmented; terminal segment bearing 3 to 5 armature elements (usually 4 spines). Labrum simple or with 2 or 3 pairs of lobes on posterior margin. Mandible absent or small, mostly 1-or 2-segmented, tipped with 1 to3 setae.Maxillule and maxilla absent.Maxilliped consisting of 4 segments plus terminal claw.Legs 1-4 usually consisting of protopod,exopod and endopod.Protopods unsegment- ed, with or without outer seta. Exopods with up to 5 armature elements; in some species distal spines fused at base to form bifurcate spine; exopod occasionally with single, claw-like distal element. Endopods represented by inner distal protuberance on protopod, sometimes absent. Leg 5 variously reduced, usually lobate and bearing 1 to 3 small setae. Male: Body cyclopiform with distinct prosome-urosome division. Prosome consisting of cephalosome and first to fourth pedigerous somites. Urosome 6-segmented. Caudal rami armed with 5 setae. Rostrum not developed. Antennule 4-segmented; first segment bearing numerous aesthetascs.Antenna 3-segmented with 3 or 4 armature elements on terminal segment. Labrum simple. Mandible 1- to 3-segmented, with 1 to 3 setae distally. Maxillule absent. Maxilla as a lobe, unarmed or armed with 1 apical seta. Maxilliped consisting of 4 segments plus terminal claw. Leg 1 with 3-segmented exopod; endopod 1- or 2-segmented, with transformed setal elements. Legs 2 and 3 with 3-segmented rami. Leg 4 with 3-segmented exopod and 2-segmented endopod. First exopodal segment of legs 1-4 lacking inner seta. Leg 5 consisting of 1 lateral seta on fifth pedigerous somite and exopodal segment tipped with 2 setae, Leg 6 represented by 2 setae on genital operculum.

Type species. eaplçstçma brevẚcauda (Canu, 1886) by original monotypy.

Remarks. Ooishi (2009b) recognized 18 species of eaplçstçma as valid. In seven of these species, which she recognized as “subgroup 2”, the exopods of legs 1-4 are armed only with spines and lack setae (the proximal seta is transformed to a spine). In the present work 12 new species are described, including three belonging to Ooishi’s subgroup 2 and nine placed in subgroup 1.

Figures

FIG. 90. eaplçstçmẚdes partẚtus sp. nov., female. A, habitus, dorsal; B, distal part of genitoabdomen, ventral; C, left caudal ramus, ventral; D, antennule; E, antenna; F, labrum; G, mandible; H, maxillule; I, maxilla; J, maxilliped; K, leg 1; L, genital aperture. Scale bars: A, 0.1 mm; B, K, 0.02 mm; C-J, L, 0.01 mm.