Haplostomella uniseriata, 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 : 177

Haplostomella uniseriata sp. nov.

( Fig. 114 )

Type material. Holotype ♀ (MNHN-IU-2014-21528) and 1 ♀ paratype (MNHN-IU-2014-17390, dissected) from bxçstçma ẚanthẚnum (Sluiter, 1909); Chuuk Island , OCDN 0900 -M (07°25.29’N, 151°49.02’E), depth 4 m, CRRF coll., 11 November 1992.

Etymology. The name of the new species refers to the uniseriate arrangement of eggs within its egg sac.

Description of female. Body ( Fig. 114A ) vermiform, cylindrical, curved dorsally, and unsegmented; body length 1.53 mm, maximum width 250 μm. Cephalosome ( Fig. 114B ) 136×163 μm, narrower than metasomal re- gion, and incompletely defined from metasomal region by posterolateral margins of cephalic shield. Metasomal region bearing 5 pairs of dorsolateral folds at levels of legs 1-5, respectively, last pair smaller than anterior 4 pairs. Genitoabdomen ( Fig. 114C ) not defined from metasome; genital apertures large, positioned dorsolaterally; genital operculum with 3 teeth distally and 1 small palm-like element bearing 6 digits on ventral side ( Fig. 114N ). Abdomen ( Fig. 114C ) not articulated from, but distinctly defined from metasomal region by its narrowness, slightly longer than wide (67×62 μm). Caudal ramus ( Fig. 114D ) 1.9 times longer than wide (30×16 μm), almost rectangular, armed with 5 naked setae, 1 at middle of outer margin and 4 distally; largest distal seta 28 μm long, about twice as long as other 3. Egg sac ( Fig. 114E ) 590×155 μm, containing 5 or 6 uniseriate eggs; each egg about 125 μm in diameter.

Rostrum absent. Antennule ( Fig. 114F ) small, unsegmented, 64 μm long, armed with 7 setae on anterior margin and 6 setae plus 3 short aesthetascs on distal margin; 1 seta on distal margin more than twice length of other setae. Antenna ( Fig. 114G ) unsegmented, slender, curved, with 1 process-like seta subdistally on inner margin, plus 1 blunt process, 1 spinulose lobe and 1 seta distally.

Labrum ( Fig. 114H ) simple, semicircular. Mandible ( Fig. 114I ) unsegmented, lobate, tipped with elongate, acutely pointed spine. Maxilla ( Fig. 114J ) unsegmented, but consisting of short and broad proximal part and narrow digitiform distal part bearing 1 weakly pinnate seta subdistally. Maxilliped ( Fig. 114K ) 2-segmented; proximal segment unarmed; distal segment with 1 spine and 1 blunt process mediodistally; and ornamented with several rows of minute spinules on posterior surface; terminal claw simple.

Leg 1 ( Fig. 114L ) consisting of protopod, exopod, and endopod. Intercoxal plate ( Fig. 114L ) present between left and right legs, not sclerotized but distinct and broad, ornamented with several rows of minute spinules on anterior surface. Protopod bearing 1 seta on outer margin and 1 tubercle at inner distal corner. Exopod small, distinctly articulated from protopod, and distally bilobed; anterior lobe sclerotized and distally bifurcate; posterior lobe subcircular, tipped with 1 seta. Endopod well-defined, almost rectangular, longer than wide, with truncate and slightly bilobed distal margin. Legs 2-4 same as leg 1, but distal margin of endopods weakly trilobed. Legs 1-4 accompanied by small tubercle on ventral surface of body just lateral to each leg ( Fig. 114A, L ).

Leg 5 ( Fig. 114M ) as small lobe bearing 1 minute seta subdistally and 2 naked setae on distal margin.

Male. Unknown.

Remarks. The distal armature element on the mandible of e. unẚserẚata sp. nov. is a slender, straight spine by which the new species can be distinguished from its congeners, since in other species of eaplçstçmella the distal element is a robust claw in e. bçrealẚs; a curved spine in e. dẚstẚncta Ooishi & Illg, 1977 and e. çceanẚca Ooishi & Illg, 1977; a strong, spinulose blade in e. halçcynthẚae (Fukui, 1965); a single seta in e. dubẚa Ooishi & Illg, 1977, e. magellanẚca, e. malacçcera, and e. tuberculata; and it is absent in e. reducta. The mandible of eK australẚensẚs is unknown, but it has a large body size, 6.5 mm long in the female, a 3-segmented abdomen, and 2 distal setae on the maxilla ( Gotto, 1970), which serve to distinguish it from the new species.

Egg sacs are known in only five species of the genus eaplçstçmella, and all of these species have a multiseriate arrangement of eggs. The uniseriate arrangement of eggs in the egg sac of eK unẚserẚata sp. nov. also seems to be an unusual feature within the genus.

Figures

FIG. 114. eaplçstçmella unẚserẚata sp. nov., female.A, habitus, right; B, cephalosome, dorsal; C, posterior part of body, dorsal; D, left caudal ramus, dorsal; E, egg sac; F, antennule; G, antenna; H, labrum; I, mandible; J, maxilla; K, maxilliped; L. leg 1; M, leg 5; N, genital aperture. Scale bars: A, E, 0.1 mm; B, C, 0.05 mm; D, K. L. N, 0.02 mm; F-J, M, 0.01 mm.