Haplosaccus ardius, 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 : 169-171

Haplosaccus ardius sp. nov.

( Fig. 110 )

Type material. Holotype ♀ (MNHN-IU-2014-21523), 6 ♀♀ paratypes (MNHN-IU-2014-21524) and 2 ♀♀ para- types (dissected, MNHN-IU-2014-17388) from aẚdemnum mçlle (Herdman, 1886); near Ouaco , Koumac Sector, New Caledonia, LAGON cruise, RV “Alis”, Stn DW 919 (20°52.2’S, 164°25.2’E), depth 17 m, B. Richer de Forges- IRD coll., 26 April 1988.

Etymology. The name is derived from the Greek ard (=arrowhead), reflecting the arrowhead-like rostrum of the new species.

Description of female. Body ( Fig. 110A ) vermiform, unsegmented, gradually narrowing anteriorly; body length 2.96 mm, maximum width 0.64 mm (at level of leg 4). Cephalosome not defined from metasome; 4 metasomites recognizable by weak lateral constrictions. Genitoabdomen ( Fig. 110B ) 164×297 μm, not articulated from metasome, but defined by abrupt narrowing, unsegmented but divisible into broader anterior two-thirds and narrower posterior third, with convex rear margin. Caudal ramus ( Fig. 110C ) vestigial, 12×6 μm, constricted in middle, tipped with 1 minute seta. Egg sac containing 10 rows of eggs; each egg about 160 μm in diameter.

Cephalic appendages very small. Rostrum ( Fig. 110D ) 24×13 μm, minute, but well-sclerotized, arrowheadshaped with pointed apex. Antennule ( Fig. 110E ) 19 μm long, shorter than wide, 2-segmented, armed with 2 and 8 setae on first and second segments, respectively. Antenna ( Fig. 110F ) 2-segmented; proximal segment slightly longer than wide, unarmed; distal segment 2.25 times longer than wide (18×8 μm), armed distally with 1 inner claw and 1 outer spine.

Labrum ( Fig. 110G ) strongly tapering posteriorly towards rounded apex. Mandible ( Fig. 110G ) represented by broad seta lateral to labrum. Maxillule and maxilla absent. Maxilliped ( Fig. 110H ) consisting of 4 segments plus terminal claw; first segment unarmed, second segment as long as wide, with 2 small setae; narrower third and fourth segments unarmed; terminal claw acutely pointed, slightly longer than fourth segment.

Leg 1 ( Fig. 110I ) consisting of protopod, short exopod and semicircular endopod; protopod lacking outer seta; exopod incompletely defined from protopod, armed with 1 seta on outer margin and strong claw distally; endopod unarmed but with pair of minute sensilla. Legs 2-4 exactly same as leg 1 in shape and armature.

Leg 5 ( Fig. 110B ) represented by 1 minute seta located ventrolaterally on posterior part of metasome. Leg 6 ( Fig. 110J ) represented by 1 spine and 1 larger, spiniform process on genital operculum; 5 spiniform internal elements accompanying leg 6.

Male. Unknown.

Remarks. In having a strong terminal claw on the antenna and on the exopods of legs 1-4, the new species belongs to the genus eaplçsaccus which currently consists of only two known species, e. sacculus and e. elçngatus. The most significant diagnostic features of eK ardẚus sp. nov. are: the antenna is armed terminally with 1 strong claw and 1 spine, and the exopods of legs 1-4 are armed with 1 outer seta and 1 strong terminal claw. These features clearly differentiate the new species from its two congeners (see Table 5 for more detailed comparison).

Genus Haplostomella Chatton & Harant, 1924

Diagnosis. Female: Body eruciform or vermiform, usually unsegmented, but occasionally indistinctly divisible into cephalosome, metasome, and genitoabdomen. Cephalosome discernible by weakly developed cephalic shield. Metasome incorporating fifth pedigerous somite, sometimes with lobate dorsolateral folds in same plane as legs 1-5. Genitoabdomen not articulated from metasome, consisting of broad genital and narrow abdominal regions. Genital apertures large, positioned dorsolaterally; genital operculum bearing 3 teeth on inner side of distal border. Caudal rami distinct, armed with up to 5 setae. Rostrum not developed. Antennule small, 1- or incompletely 2-segmented, but exceptionally 4-segmented in eaplçstçmella magellanẚca ( Chatton & Brément, 1910). Antenna basically 3-segmented, with unarmed first segment, 1 seta on second segment, and 3 setae and 1 lobate element on third segment. Labrum broad, simple, or occasionally with lobes on posterior margin. Mandible absent or consisting of lobe tipped with distal element(s); distal element(s) variable with species, either spine, claw, or 1 or 2 setae. Maxillule absent. Maxilla indistinctly 2-segmented; proximal segment unarmed; distal segment with 1 or 2 setae. Maxilliped broad, chelate, and consisting of 2 segments plus terminal claw; proximal segment (syncoxa) unarmed; distal segment (basis) bearing inner distal protrusion and acute spine on anteromedial surface; terminal claw short, directed between distal protrusion and spine of second segment. Legs 1-4 consisting of unsegmented protopod, exopod and endopod; protopod with seta on outer margin; exopod distally bilobed, with sclerotized, claw-like anterior lobe and rounded posterior lobe tipped with 1 setule; endopod not articulated from protopod, unarmed. Ventrolateral surface of body lateral to legs 1-4 sometimes with 1 to 5 tubercles. Leg 5 as small lobe tipped with 2 or 3 setae.

Male: Body cyclopiform, distinctly segmented, clearly divisible into prosome and urosome. Prosome consisting of cephalosome and first to fourth pedigerous somites. Urosome 6-segmented, consisting of fifth pedigerous somite, genital somite, and 4 abdominal somites. Caudal ramus with 6 setae; 2 median terminal setae (setae IV and V) long, fringed with membrane along both margins. Antenna 7- or 8-segmented; proximal segments each with 1 large aesthetasc. Antenna and labrum as in female. Mandible, maxillule, and maxilla vestigial or absent. Maxilliped similar to that of female. Legs 1-4 biramous, consisting of coxa, basis, exopod, and endopod. Setation variable with species: coxa with or without inner seta: basis with outer seta; inner distal element on leg 1 present or absent. Exopod 3-segmented. Endopod 1- to 3-segmented in leg 1, and 3-segmented in legs 2-4. Leg 5 consisting of 1 lateral seta on fifth pedigerous somite and free or lobate exopod tipped with 2 setae. Leg 6 represented by 1 or 2 setal elements on genital operculum

Type species. eaplçstçmella malacçcera Chatton & Harant, 1924, by original designation.

Remarks. Marchenkov & Boxshall (2003) recognised 11 valid species in the genus eaplçstçmella, including their new species, e. bçrealẚs Marchenkov & Boxshall, 2003. Boxshall & Halsey (2004) regarded eaplçstçmella as the first offshoot within the family Botryllophilidae because its male lacks many of the synapomorphies that are shared by the males of Bçtryllçphẚlus, eaplçstçma and eaplçstçmẚdes, such as the presence of the rosette of densely packed aesthetascs on the proximal segment of the antennule. The female of eaplçstçmella is distinctive within the family in the form of its antenna, maxilliped, and swimming legs.

Figures

FIG. 110. eaplçsaccus ardẚus sp. nov., female.A, habitus, ventral; B, urosome, ventral; C, caudal ramus; D, rostrum; E, antennule; F, antenna; G, labrum and left mandible; H, maxilliped; I, leg 1; J, genital aperture. Scale bars: A, 0.2 mm; B, 0.1 mm; C-J, 0.01 mm.