Haplostomides scotti Chatton & Harant, 1924

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 : 132

Haplostomides scotti Chatton & Harant, 1924

( Figs. 85 , 86 )

Material examined. 4 ♀♀ (MNHN-IU-2018-1986, 2 ♀♀ dissected) from mçlyclẚnum aurantẚum Milne Edwards, 1841; Saint-Vaast-la-Hougue, Atlantic coast of France, Monniot coll.

Supplementary redescription of female. Body ( Fig. 85A ) maggot-shaped, narrowing anteriorly, consisting of cephalosome, incompletely 5-segmented metasome and 2-segmented genitoabdomen. Body length 1.48 mm; maximum width 0.46 mm (across middle). Anterior half of metasome narrowing anteriorly; cephalosome 150×235 μm, much narrower than first pedigerous somite. Pedigerous somites defined by constrictions. Genitoabdomen ( Fig. 85B ) distinctly bipartite with parts defined by deep constriction; anterior part strongly tapering posteriorly, subdivided by trace of transverse suture line; posterior part (anal somite) narrowing anteriorly. Caudal ramus ( Fig. 85C ) conical, not articulated from anal somite, as long as wide, armed with 1 triangular spine distally plus 4 setae (2 outer, 1 dorsal, and 1 inner subdistal); distal spine broader than long.

Rostrum ( Fig. 85D ) wider than long (19×32 μm), nearly triangular, with blunt apex, ornamented with 5 or 6 denticles subdistally on lateral margins. Antennule ( Fig. 85E ) unsegmented, but with traces of 2 articulations, distinctly tapering, with large protuberance on proximal ventral margin, and armed with 13 small setae (arranged as 3, 3, and 7). Antenna ( Fig. 85F ) 3-segmented, consisting of coxa, basis, and endopod; coxa and basis unarmed; endopod slightly longer than basis, bearing 4 spines (2 proximal spines smaller, not articulated at base, dentiform).

Labrum small, unornamented, with convex posterior margin. Mandible ( Fig. 85G ) incompletely 2-segmented, digitiform, with 3 blunt setae on distal segment. Maxillule ( Fig. 85H ) 2-segmented; proximal segment (precoxa) with 4 blunt setae on mediodistal surface, distalmost seta broad, leaf-like; distal segment (palp) originating on outer margin of proximal segment, broadening distally, bearing 5 bluntly tipped setae of unequal lengths, innermost shortest. Maxilla ( Fig. 85I ) lobate, tapering distally, with 2 setae (1 lateral and 1 distal). Maxilliped ( Fig. 85J ) consisting of 4 segments plus terminal claw; first segment (syncoxa) much wider than long, unarmed; second segment (basis) with 1 distal and 1 subdistal setae; third segment unarmed; fourth segment with pointed inner distal corner; terminal claw stout, shorter than fourth segment.

Leg 1 ( Fig. 86A ) consisting of protopod, exopod, and endopod. Protopod unarmed, with transverse sclerotized band. Exopod armed with 1 seta on outer margin, 2 small spines on subdistal outer margin, and 1 bifurcate spine distally. Endopod prominent, not articulated from protopod, unarmed and unornamented, as long as wide, with rounded distal margin. Leg 2 ( Fig. 86B ) broader than leg 1. Exopod armed with 1 seta, 1 small spine on subdistal outer margin and bifurcate distal spine. Endopod narrower than that of leg 1. Legs 3 and 4 same as leg 2 in form and armature. Leg 5 ( Fig. 85K ) consisting of 3 small equal setae on lateral margin of fifth pedigerous somite (2 located on small lobe). Leg 6 ( Fig. 85L ) represented by 1 spine and 1 larger, spiniform process on genital operculum; 5 tooth-like elements present on surface medial to leg 6.

Male. Ooishi (2002a) described the male of this species.

Remarks. eaplçstçmẚdes scçttẚ, the type species of the genus and first described by Chatton & Harant (1924b), was redescribed by Ooishi (2002a) on the basis of specimens taken from the mçlyclẚnum aurantẚum Milne Edwards, 1841. There are some minor discrepancies between our specimens and Ooishi’s redescription. Firstly, Ooishi (2002a) did not figure or mention the presence of denticles on the lateral margins of the rostrum, which are quite distinct in our specimens. Secondly, the setae on the maxillule of our specimens are blunt and the distalmost seta on its proximal segment (precoxa) is broad, leaf-like, but in Ooishi’s specimens the setae are generally attenuated and the distalmost seta on the first segment is vestigial. Thirdly, we observed 1 spine and 4 setae on the caudal ramus in our specimens whereas Ooishi described and figured 1 spine and 2 setae on the ramus. Because of the numerous similarities between the two sets of material, we consider that these discrepancies are likely to be due either to the state of the material observed or to variation. The similarities between Ooishi’s specimens and ours include: (1) the shape of the genitoabdomen is consistent, i.e., the anterior and posterior parts are clearly demarcated by a deep constriction; (2) they both have a large proximal protuberance on the ventral margin of the antennule; and (3) the distalmost seta on the distal segment (palp) of the maxillule is much smaller than the proximal setae. In addition, both sets of material were found in the same host species, mçlyclẚnum aurantẚum, in the Northeast Atlantic.

Figures

FIG. 85. eaplçstçmẚdes scçttẚ Chatton & Harant, 1924, female. A, habitus, dorsal; B, genitoabdomen, dorsal; C, right caudal ramus, dorsal; D, rostrum; E, antennule; F, antenna; G, mandible; H, maxillule; I, maxilla; J, maxilliped; K, leg 5; L, genital aperture. Scale bars: A, 0.2 mm; B, 0.1 mm; C-L, 0.01 mm.

FIG. 86. eaplçstçmẚdes scçttẚ Chatton & Harant, 1924, female. A, leg 1; B, leg 2. Scale bars: 0.02 mm.