Haplostoma fusiforme, 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 : 158

Haplostoma fusiforme sp. nov.

( Figs. 102 , 103 )

Type material. Holotype ♀ (MNHN-IU-2014-21518) and 1 ♀ paratype (dissected, MNHN-IU-2014-17386) from mareugyrẚçẚdes galatheae (Millar, 1959) (MNHN-IT-2008-6004 = MNHN S3 / PAR.A/11); Kerguelen Is., SW Heard I., MD03 -ICTHYO cruise, RV ”Marion Dufresne”, Stn 12-36-CP08, Bassin de Crozet (55°49.5’S, 69°35.7’E), depth 4200-4225 m, 11 April 1974.

Etymology. The name of the new species alludes to its fusiform body.

Description of female. Body ( Fig. 102A, B ) large, fusiform, tapering anteriorly and posteriorly. Body length 3.80 mm and maximum width 1.30 mm in holotype; dissected paratype 3.35 mm long. Cephalosome not defined from first metasomite, but indistinct trace of suture present between them dorsally. Four metasomites distinctly defined by 3 deep constrictions; last metasomite compound, consisting of fused fourth and fifth pedigerous somites, narrowing posteriorly. Genitoabdomen ( Fig. 102C ) tapering posteriorly, about 500 μm long, occupying about 15% of body length, 2-segmented; anterior somite 1.33 times wider than long, with broad dorsal stripe between genital apertures; genital apertures large, positioned dorsolaterally; posterior somite (free abdomen) about 1.3 times wider than long, half as long as anterior somite. Caudal ramus ( Fig. 102D ) conical, about 1.47 times longer than wide (91×62 μm), 0.63 times as long as free abdominal somite; armed with 2 small setae (1 subdistal dorsal and 1 on outer margin) and 1 distal spine bearing small subsidiary denticle on outer margin.

Rostrum small, semicircular, unornamented. Antennule ( Fig. 102E ) incompletely 3-segmented, tapering; armed with 1, 5, and 12 small setae on first to third segments, respectively; second seta of second segment with enlarged base fused to segment. Antenna ( Fig. 102F ) 3-segmented; first segment (coxa) short and unarmed; second segment (basis) slightly longer than wide, unarmed; third segment (endopod) swollen proximally, narrowing distally; armed with 4 spines, becoming gradually larger from proximal to distal; distal spine bearing 3 or 4 spinules.

Labrum ( Fig. 102G ) short and broad, with simple convex posterior margin. Mandible ( Fig. 102H ) elongate, tapering, with 1 distal seta and 1 small subdistal seta. Maxillule and maxilla absent. Maxilliped 4-segmented; first and third segments unarmed; second segment with 2 small setae; fourth segment with 1 small seta distally; terminal claw short, bearing small dentiform process proximally on inner margin.

Legs 1-4 each consisting of protopod, exopod, and endopod; protopod lacking outer seta; endopod not clearly defined from protopod, but extending to distal end of exopodal segment. Exopod of leg 1 ( Fig. 102I ) armed with 1 seta and 4 spines (3 small proximal and 1 larger distal). Exopod of leg 2 ( Fig. 103A ) armed with 1 seta and 3 spines (2 small proximal and 1 larger distal). Exopod of legs 3 ( Fig. 103B ) and 4 armed with 1 seta and 2 distal spines. In legs 3 and 4, two distal spines on exopod fused at base. Larger distalmost spine on exopods of legs 1-4 distally trifurcate or quadrifurcate.

Leg 5 ( Fig. 102J ) small, papilla-like ( Fig. 102A, B ), bearing 2 minute setae distally. Leg 6 represented by 1 spine and 1 spiniform process (at low magnification).

Male. Unknown.

Remarks. The combination of armature elements on the exopods of legs 1-4 of eK fusẚfçrme sp. nov. is 5, 4, 3, and 3. This combination is shared by six other species of eaplçstçma; e. albẚcatum, e. dentatum, e. elegans, e. mẚnutum, e. eruca, and e. depressum sp. nov.

eaplçstçma fusẚfçrme sp. nov. can be distinguished from e. dentatum, e. eruca and e. depressum sp. nov. by the absence of any lobes or processes on the posterior margin of the labrum (cf. 8 pointed lobes in e. dentatum, 6 lobes in e. eruca, and 4 lobes in e. depressum sp. nov.), and from e. albẚcatum, e. elegans, and e. mẚnutum by the absence of an outer seta on the protopod of legs 1-4. The new species can be differentiated further from e. albẚcatum and eK mẚnutum by the narrower caudal ramus which is about 1.5 times longer than wide (cf. wider than long in e. albẚcatum and e. mẚnutum) and from e. elegans by the possession of 2 setae on the mandible (cf. 3 setae in e. elegans).

Figures

FIG. 102. eaplçstçma fusẚfçrme sp. nov., female.A, habitus, dorsal; B, habitus, right; C, genitoabdomen, dorsal; D, left caudal ramus, outer; E, antennule; F, antenna; G, labrum; H, mandible; I, leg 1; J, leg 5. Scale bars: A, B, 0.5 mm; C, 0.2 mm; D-F, H, I, 0.02 mm; G, J, 0.05 mm.

FIG. 103. eaplçstçma fusẚfçrme sp. nov., female. A, leg 2; B, leg 3. Scale bars: 0.05 mm.