Haplostomella crassa, 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 : 186-188

Haplostomella crassa sp. nov.

( Fig. 120 )

Type material. Holotype ♀ (MNHN-IU-2014-21534) and 1 ♀ paratype (MNHN-IU-2014-17394, dissected) from Synçẚcum flçrẚferum Monniot, F. & Monniot, C., 2006 (MNHN-IT-2018-18 = MNHN A1 / SYN/116 ); Sainte Luce, SW Îlot Souillac, Madagascar, ATIMO VATAE expedition, Stn TA36 (24°45´S, 47°12´E), MNHN coll., 04 June 2010.

Etymology. The specific name is derived from the Latin crass (= thick) and alludes to the relatively broad body of the female.

Description of female. Body ( Fig. 120A, B ) eruciform, relatively small and stout, distinctly segmented; body length 957 μm; maximum width 330 μm. Cephalosome nearly triangular, 158×231 μm, incompletely articulated from metasome. First to fifth pedigerous somites well-defined from one another, similar in width. Genitoabdomen ( Fig. 120C ) distinctly articulated from fifth pedigerous somite, 4-segmented, consisting of genital somite and indistinctly 3-segmented abdomen. Genital somite much wider than long; genital apertures large, positioned dorsolaterally; genital operculum bearing 3 teeth on mediodistal margin. First abdominal somite broad; second and third abdominal somites much narrower than first. Caudal rami ( Fig. 120D ) divergent, about 2.2 times longer than wide (69×31 μm), bearing 4 small setae distally.

Rostrum absent. Antennule ( Fig. 120E ) indistinctly 2-segmented, 107 μm long, twice as long as wide; proximal segment unarmed, but ornamented with 2 rows of minute spinules proximally; short distal segment occupying about 20% length of antennule, obscurely articulated from first segment, but defined by abrupt narrowing; armed with 11 slender setae of unequal lengths (4 on anterior margin and 7 on distal and posterior margins). Antenna ( Fig. 120F ) 2-segmented; proximal segment 28×12 μm, unarmed; distal segment 25×13 μm, slightly shorter than first, bearing 4 setae (2 on inner margin and 2 on distal margin) and 1 lobe bearing minute spinules, and ornamented with short row of spinules proximally.

Labrum ( Fig. 120G ) with deeply concave posterior margin. Mandible ( Fig. 120G ) as small lobe tipped with 1 seta. Maxillule absent. Maxilla ( Fig. 120H ) incompletely 2-segmented; broad proximal segment unarmed; narrow distal segment tipped with 1 naked seta and ornamented with 2 rows of minute spinules. Maxilliped ( Fig. 120I ) robust, 2-segmented; proximal segment much wider than long, unarmed but ornamented with 2 transverse rows of minute spinules on anterior surface; distal segment bearing medial spine, but lacking mediodistal protrusion; terminal claw robust, strongly tapering, with trace of suture line at proximal third, 1 small seta in middle of anterior surface; apex of terminal claw simple, not bicuspid.

Leg 1 ( Fig. 120J ) consisting of protopod, exopod, and endopod. Protopod short, unarmed, but ornamented with rows of minute spinules on anterior surface. Exopod divisible into broader proximal part and abruptly narrower distal part; distal part distally bilobed, with pointed, spinule-like anterior lobe and rounded posterior lobe lacking seta. Endopod much broader than exopod, truncate, with rounded distal corners. Ventral surface of body lateral to legs 1-4 lacking any tubercles or protrusions. Leg 2 ( Fig. 120K ) similar to leg 1; exopod same as that of leg 1, but endopod distally bilobed, with inner lobe more prominent than outer lobe. Legs 3 and 4 same as leg 2.

Leg 5 ( Fig. 120L ) as lobe bearing 3 unequal setae.

Male. Unknown.

Remarks. The caudal ramus in eaplçstçmella is typically armed with 5 setae. The recorded exceptions to this are: the presence of 4 setae in e. tuberculata, although this species has a rudimentary additional seta on the outer margin of the caudal ramus (as redescribed in the present work), 1 in e. magellanẚca, as described by Chatton and Brément (1910), and none in e. sycçzçae (Salfi, 1926). In having 4 caudal setae, e. crassa sp. nov. is similar only to e. tuberculata. These two species also share the possession of 3 setae on leg 5, a feature shared only with e. dubẚa and e. bẚseta sp. nov. described below. However, e. crassa sp. nov. is readily distinguishable from e. tuberculata by its 3-segmented abdomen (vs. abdomen unsegmented in e. tuberculata) and a 2-segmented antenna (vs. 3-segmented in e. tuberculata), and by the absence of the dorsolateral folds on the metasomal region (vs. the folds are present in e. tuberculata).

The small body size (0.96 mm in length) of e. crassa sp. nov. is noteworthy because it is the smallest species known: the range of known body lengths in eaplçstçmella is from 1.01 mm recorded in the present work for e. bẚnçdçsa sp. nov. to 11.7 mm recorded by Kim I.H. (2012) for e. halçcynthẚae.

Figures

FIG. 120. eaplçstçmella crassa sp. nov., female.A, habitus, dorsal; B, habitus, ventral; C, genitoabdomen, dorsal; D, abdomen, ventral; E, antennule; F, antenna; G, labrum and left mandible; H, maxilla; I, maxilliped; J, leg 1; K, leg 2; L, leg 5. Scale bars: A, B, 0.1 mm; C, D, 0.05 mm; E, G, H, J-L, 0.02 mm; F, I, 0.01 mm.