Haplostomella bilobata, 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 : 172-176

Haplostomella bilobata sp. nov.

( Figs. 112 , 113 )

Type material. Holotype ♀ (MNHN-IU-2014-21526), 2 ♀♀ paratypes (MNHN-IU-2014-21527), and 2 ♀♀, 1 ♂ paratypes (dissected, MNHN-IU-2014-17389) from Apl ẚdẚum sp.; Kerguelen Islands, no other collection data.

Etymology. The specific name alludes to the presence of a pair of lobes on the labrum of the new species.

Description of female. Body ( Fig. 112A, B ) eruciform, consisting of unsegmented anterior part and short abdomen. Body length 2.04 mm; maximum width 496 μm (across region of leg 4). Anterior half of body slightly tapering anteriorly; cephalosome narrower than metasome, incompletely defined from metasome by posterolateral margins of cephalic shield. Cylindrical metasomal region incorporating leg 5, with 5 pairs of small dorsolateral folds; last pair at level of leg 5 much smaller than anterior 4 pairs. Genital somite completely fused to metasome; paired genital apertures ( Fig. 112L ) positioned dorsolaterally. Genital operculum bearing 3 teeth inside. Abdomen ( Fig. 112C ) tapering, 3-segmented, but articulation incomplete between last 2 somites. Caudal ramus ( Fig. 112D ) about 2.9 times longer than wide (69×24 μm), slightly longer than anal somite, with 5 subequal, naked setae (1 lateral and 4 distal); lateral seta positioned at 63% of ramus length. Egg sac ( Fig. 112B ) 1.40× 0.34 mm; each egg about 115 μm in diameter.

Rostrum absent. Antennule ( Fig. 112E ) 100 μm long, 2-segmented; proximal segment with 9 setae; distal seg- ment small, only 17 μm long, subdivided in middle, with 5 setae and 1 short aesthetasc; all setae naked. Antenna ( Fig. 112F ) indistinctly 2-segmented; proximal segment unarmed; distal segment with 1 seta on inner margin, 1 short, blunt seta plus 1 lobate process subdistally, and tipped with 1 seta.

Labrum ( Fig. 112G ) short and broad, characteristically with pair of large lobes on posterior margin. Mandible and maxillule absent. Maxilla ( Fig. 112H ) distinctly 2-segmented; broad proximal segment unarmed; distal segment shorter and narrower than proximal segment, distally armed with 2 setae; outer seta pinnate, small medial seta naked and located on tip of digitiform process of segment. Maxilliped ( Fig. 112I ) consisting of 2 segments plus terminal claw; proximal segment broad and unarmed; distal segment as long as wide, with short medial margin and longer outer margin, bearing 1 broad, plate-like process and 1 acute spine near mediodistal corner; terminal claw stout with bicuspid tip.

Leg 1 ( Fig. 112J ) consisting of protopod, exopod, and endopod; protopod obscurely defined at medial side, with 1 seta on outer margin; exopod distally bilobed, anterior lobe claw-like, with bicuspid tip, posterior lobe tipped with 1 small seta; endopod large, semicircular, more than twice as wide as exopod, and ornamented with rows of minute spinules. Legs 2-4 same as leg 1.

Leg 5 ( Fig. 112A, K ) as rudimentary lobe tipped with 2 small setae.

Description of male. Body ( Fig. 113A ) narrow, cyclopiform, clearly segmented, with distinct prosome-urosome division. Body length 809 μm. Maximum width of body 205 μm across third pedigerous somite. Prosome consisting of cephalosome and 4 pedigerous somites. Urosome ( Fig. 113B ) 6-segmented, consisting of fifth pedigerous somite, genital somite and 4-segmented abdomen. Genital somite as long as wide. Four abdominal somites 50× 70m 50×61, 36×50, and 23×43 μm, respectively. Caudal ramus ( Fig. 113C ) rectangular, 2.24 times longer than wide (38×17 μm), armed with 6 setae (1 small outer, 1 dorsal, and 4 broad distal).

Rostrum absent. Antennule 7-segmented; armature on segments uncertain due to many setae missing. Antenna as in female. Labrum, mandible, maxillule, and maxilla absent. Maxilliped ( Fig. 113D ) 2-segmented; proximal segment short and unarmed; distal segment 1.5 times longer than wide, with 1 spine subdistally and 1 small lobe at mediodistal corner; terminal claw strongly curved, with bicuspid tip.

Legs 1-4 ( Fig. 113 E-H) biramous, consisting of coxa, basis, exopod, and endopod. Coxa unarmed; basis with outer seta; basis of leg 1 additionally with inner distal spine. Exopods 3-segmented in all swimming legs. Endopods 1-segmented in leg 1, but 3-segmented in legs 2-4. All setae on swimming legs geniculate proximally, and all spines fringed with broad membranes bilaterally. Endopod of leg 1 and third exopodal segment of leg 2 with bicuspid outer distal corner. Third exopodal segment of legs 3 and 4 with tricuspid outer distal corner.

Leg 5 ( Fig. 113B ) represented by free exopod tipped with 2 unequal setae. Leg 6 represented by 1 seta on distolateral apex of genital operculum.

Remarks. Species of ealçstçmella seldom bear any lobes on the labrum in the female. The only known exception is eK magellanẚca ( Chatton & Brément, 1910) in which the labrum bears 2 pairs of lobes, as illustrated by Chatton & Brément (1910). Therefore, eK bẚlçbata sp. nov. can be distinguished from all other species of the genus by the possession of a single pair of lobes on the female labrum. Other diagnostic features of the female of e. bẚlçbata sp. nov. include: (1) the abdomen is 3-segmented, a feature shared only with e. australẚensẚs Gotto, 1970; (2) the antennule is distinctly 2-segmented, which is a unique feature of the new species; (3) the mandible is absent, a feature shared only with e. reducta Ooishi & Illg, 1977; and (4) the maxilla is distinctly 2-segmented and armed with 2 setae on its distal segment, a feature shared only with e. bçrealẚs. The combination of these diagnostic features serves to characterize the new species.

Figures

FIG. 112. eaplçstçmella bẚlçbata sp. nov., female. A, habitus, right; B, habitus, dorsal; C, genitoabdomen, dorsal; D, right caudal ramus, ventral; E, antennule; F, antenna; G, labrum; H, maxilla; I, maxilliped; J, leg 1; K, leg 5; L. genital aperture. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D-K, 0.02 mm; L, 0.05 mm.

FIG. 113. eaplçstçmella bẚlçbata sp. nov., male. A, habitus, dorsal; B, urosome, ventral; C, right caudal ramus, dorsal; D, maxilliped; E, leg 1; F, leg 2; G, leg 3; H, leg 4. Scale bars: A, 0.1 mm; B, 0.05; C-H, 0.02 mm.