Haplostomella biseta, 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 : 188-190

Haplostomella biseta sp. nov.

( Fig. 121 )

Type material. Holotype ♀ (MNHN-IU-2014-21535), 2 ♀♀ paratypes (MNHN-IU-2014-21536), and 1 ♀ paratype (dissected, MNHN-IU-2014-17395) from Apl ẚdẚum falklandẚcum Millar, 1960; E. Kerguelen Is., MD04 -BENTHOS cruise, R. V. “Marion Dufresne”, Stn CP 13 (49°32-33’S, 70°57’E), depth 149-155 m, Boury-Esnault coll., 22 February 1975.

Additional material. 3 ♀♀ (MNHN-IU-2014-21537) from Apl ẚdẚum cẚrcumvçlutum (Sluiter, 1900), NW Kerguelen Is., MD03 -ICTHYO cruise, RV ”Marion Dufresne”, Stn 18-52-CP11, (47°42’S, 68°07’E), depth 243 m, 15 April 1974 .

Etymology. The specific name refers to the presence of 2 setae on the mandible.

Description of female. Body ( Fig. 121A, B ) eruciform, consisting of cephalosome, metasome, and genitoabdomen. Body length 1.74 mm; maximum width 0.51 mm. Cephalosome incompletely defined from metasome, 190×284 μm, distinctly narrower than metasome, and dorsoventrally depressed. Metasome cylindrical, comprising first to fifth pedigerous somites, unsegmented, without any trace of division, bearing 3 pairs of weak dorsolateral folds, at levels of legs 2-4, respectively ( Fig. 121B ). Genitoabdomen ( Fig. 121C ) wider than long, consisting of genital somite and 2-segmented abdomen. Genital somite much wider than long; genital apertures large, positioned dorsolaterally; genital operculum bearing 3 teeth on medial margin. Abdomen clearly defined, much narrower than genital somite; first abdominal somite short; second abdominal somite incompletely articulated from first, as long as wide. Caudal rami widely divergent ( Fig. 121C, D ), not articulated from somite, narrowing distally, about 1.8 times longer than wide (58×32 μm), armed with 3 distal setae and 1 subdistal, dorsal seta (at least twice as long as other setae).

Rostrum absent. Antennule ( Fig. 121E ) 150 μm long, 2.4 times longer than wide, 2-segmented; articulation incomplete between segments; proximal segment bearing 11 small setae; distal segment distinctly shorter and narrower than proximal segment, bearing 9 small setae. Antenna ( Fig. 121F ) 3-segmented; first segment longest, unarmed; second segment slightly longer than wide, with 1 seta at inner distal corner; third segment as long as second, bearing 2 unequal setae distally and 1 small, blunt seta and 1 lobe subdistally.

Labrum ( Fig. 121G ) simple, with concave posterior margin. Mandible ( Fig. 121H ) as rectangular lobe bearing 2 equal setae distally. Maxillule absent. Maxilla unsegmented ( Fig. 121I ), but divisible into broad proximal part and narrower distal part, bearing 1 seta apically, and ornamented with 3 patches of minute spinules distally. Maxilliped ( Fig. 121J ) 3-segmented; first segment broad, unarmed; second segment with prominent mediodistal projection bearing minute spinules distally and 1 spine on medial margin; third segment short and narrow, unarmed; terminal claw short and simple.

Leg 1 ( Fig. 121K ) with broad protopod bearing 1 seta on outer margin; exopod narrow, distally bilobed; anterior lobe claw-like, bearing pale, blunt lobe subdistally; posterior lobe tipped with 1 seta. Endopod wider than exopod, with mediodistal corner protruded. Legs 2-4 same as leg 1, but mediodistal corner of endopod of legs 2 and 3 more prominent than in legs 1 and 4.

Leg 5 ( Fig. 121L ) short, much broader than long, with 1 apical and 2 subapical setae; all setae equal in length.

Male. Unknown.

Remarks. The mandible of females of the genera eaplçstçmẚdes and eaplçstçma is typically armed with 1 to 3 distal setae. In contrast to these two genera, the mandible of female eaplçstçmella is variable in its armature, depending on species; it can be a spine, or a claw, or a seta. In five species of eaplçstçmella the distal element of the female mandible is a seta. These species are e. dubẚa, e. magellanẚca, e. malacçcera, e. tuberculata, and e. crassa sp. nov. However, no species has hitherto been reported with a pair of setae on the mandible, as in e. bẚseta sp. nov. Therefore, the new species can be differentiated from its congeners by the unique setation of its mandible alone.

The combination of three other features also serves of differentiate e. bẚseta sp. nov. from its congeners. These are: (1) the caudal ramus is armed with 4 distinct setae (as in e. tuberculata), (2) the antennule is 2-segmented (as in e. bẚlçbata sp. nov. and eK crassa sp. nov.), and (3) leg 5 is tipped with 3 setae (as in e. dubẚa, e. tuberculata, and e. crassa sp. nov.). No other species share all three of these diagnostic features.

Figures

FIG. 121. eaplçstçmella bẚseta sp. nov., female. A, habitus, dorsal; B, habitus, right; C, genitoabdomen, ventral; D, left caudal ramus, dorsal; E, antennule; F, antenna; G, labrum; H, mandible; I, maxilla; J, maxilliped; K, leg 1; L, leg 5. Scale bars: A, B, 0.2 mm; C, 0.1 mm; D-L, 0.02 mm.