Haplostoma brevicaudum (Canu, 1886)

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 : 153-155

Haplostoma brevicaudum (Canu, 1886)

( Fig. 99 )

Material examined. 3 ♀♀ (MNHN-IU-2018-1999, 1 ♀ dissected) in Apl ẚdẚum turbẚnatum (Savigny, 1816), Dinard, Atlantic coast of France ; 2 ♀♀ (MNHN-IU-2018-2000, 1 ♀ dissected) in A. turbẚnatum, Roscoff , France .

Supplementary description of female. Body ( Fig. 99 ) eruciform, fleshy, curved dorsally, consisting of cephalosome, 4-segmented metasome, and 1-segmented genitoabdomen. Body length 1.93 mm. Cephalosome ( Fig. 99B ) narrowing anteriorly, narrower than metasome, indistinctly defined from first metasomite. Metasome gradually broadening posteriorly, incompletely 4-segmented; last metasomite compound, consisting of fused fourth and fifth pedigerous somites. Genitoabdomen tapering posteriorly, subdivided by weak constriction ( Fig. 99C ). Caudal ramus ( Fig. 99C ) tapering, about 1.6 times longer than wide (50×31 μm), obscurely defined from genitoabdomen; armed with 1 distal spine and 2 small setae (1 dorsal and 1 on outer margin).

Rostrum ( Fig. 99D ) as small anterior protuberance of cephalosome, characteristically bearing 2 saw-like transverse rows of denticles. Antennule ( Fig. 99E ) tapering, unsegmented, but with 3 partial suture lines along posterior side, armed with 17 setae, several on anterior margin broadened. Antenna ( Fig. 99F ) 3-segmented; first segment (coxa) short and unarmed; second segment (basis) also unarmed; third segment (endopod) slightly longer than second and ornamented with several minute spinules near base of distalmost spine; armed with 4 simple spines, all articulated at base, distalmost spine smaller than second distal spine.

Labrum ( Fig. 99G ) with convex posterior margin produced into 3 very weak lobes (appearing as wavy portions of posterior margin) on each side. Mandible ( Fig. 99G ) represented by single seta tipped on small papilla-like lobe. Maxillule and maxilla absent. Maxilliped ( Fig. 99H ) stout, 4-segmented; first segment much wider than long, unarmed; second segment wider than long, with 2 small setae on medial side; third segment unarmed; fourth segment with 1 minute seta on anterior surface; terminal claw small, with blunt dentiform protuberance proximally on medial margin.

Legs 1-4 consisting of protopod, exopod, and endopod; protopods lacking outer seta; exopods not articulated from protopod; endopods present as semicircular mediodistal protuberance on each protopod. Exopod of leg 1 ( Fig. 99I ) with 1 seta and 4 spines (3 small and 1 larger distal). Exopod of leg 2 ( Fig. 99K ) with 1 seta and 3 spines, proximal spine markedly smaller than distal 2. Leg 3 shaped and armed as leg 2. Exopod of leg 4 ( Fig. 99J ) with same armature formula as in legs 2 and 3, but proximal spine larger than distal.

Leg 5 ( Fig. 99A ) as blunt tubercle on last metasomite bearing 3 minute setae (1 proximal and 2 distal). Leg 6 ( Fig. 99L ) represented by 1 spine and 1 spiniform process on genital operculum; 9 dentiform internal elements accompanied with leg 6.

Male. Unknown.

Remarks. In her redescription of eK brevẚcauda, Ooishi (2004b) mentioned and figured the presence of an outer seta on the protopod of legs 1-4 of this species. Although we failed to observe that seta, we were able to confirm close agreement between Ooishi’s redescription and our specimens, including the same combination of the armature on the exopods of leg 1-4, the small, blunt leg 5, the presence of 6 weak lobes on the labrum, the presence of 9 dentiform internal elements near leg 6, and, most of all, the presence of 2 rows of 9 denticles on the ventral surface of the rostrum. On this basis our material from France is identified as conspecific with Ooishi’s material. The suffix – stçma is neuter so eK brevẚcauda (Canu, 1886) is here amended to e. brevẚcaudum (Canu, 1886).

Figures

FIG. 99. eaplçstçma brevẚcaudum (Canu, 1886), female. A, habitus, right; B, cephalic region, dorsal; C, abdomen, dorsal; D, rostral area, ventral (A1 indicating base of antennule); E, antennule; F, antenna; G, labrum and mandibles; H, maxilliped; I, leg 1; J, leg 4; K, leg 2; L, genital aperture. Scale bars: A, 0.1 mm; B, 0.1 mm; C-L, 0.02 mm.