Haplostomella ooishiae Kim & Boxshall 2021, sp. nov.

Haplostomella ooishiae sp. nov.

(Figs. 115, 116)

Type material. Holotype ♀ (MNHN-IU-2014-21529), 3 ♀♀ paratypes (MNHN-IU-2014-21530), and 2 ♀♀ para- types (dissected, MNHN-IU-2014-17391) from Apl ẚdẚum calẚfçrnẚcum (Ritter & Forsyth, 1917) (MNHN-IT-2008- 242 = MNHN A1 / APL.B/200); British Columbia, Canada, Pennachetti coll.

Etymology. This new species is named in honor of the late Dr. Shigeko Ooishi, who contributed enormously to the taxonomy of ascidicolous copepods.

Description of female. Body (Fig. 115A, B) vermiform, unsegmented, slightly compressed laterally, with 5 pairs of dorsolateral folds at levels of legs 1-5. Body length 2.80 mm; maximum width 0.48 mm (in middle); maximum dorsoventral depth 0.58 mm. Body surface ornamented with numerous rows of fine spinules (Fig. 115C). Cephalosome weakly defined from rest of body by dorsolateral constriction. Posterior third of body straight or curved dorsally, gradually narrowing posteriorly; abdominal part variable in relative length. Genitoabdomen or abdomen not defined. Genital apertures (Fig. 116E) large; genital operculum with 3 small internal teeth distally and row of 6 denticles on ventral side. Caudal rami (Fig. 115C) divergent, nearly rectangular, about 2.35 times longer than wide (54×23 μm); armed with 5 setae (1 on outer margin and 4 distally; outer margin seta shorter than others and positioned at 58% of ramus length).

Rostrum absent. Antennule (Fig. 115D) strongly tapering, 90×48 μm, incompletely 2-segmented; proximal seg- ment with 3 vestigial suture lines along posterior side and armed with 10 setae (including 2 large setae) plus 2 aesthetascs; small distal segment armed with 4 setae, distal seta longer and broader than other 3. Antenna (Fig. 115E) 3-segmented; first segment longest but unarmed; second segment quadrate, incompletely articulated from first, with 1 seta at inner distal corner; third segment distinctly articulated from second, bearing 2 short, nipple-shaped setae, 1 spinulose lobe and 1 naked seta.

Labrum (Fig. 115F) simple, unornamented, with slightly concave posterior margin. Mandible (Fig. 115G) consisting of short segment and whip-like (but not flexible) distal spine. Maxillule absent. Maxilla (Fig. 115H) 2-segmented; proximal segment unarmed; distal segment shorter and narrower than proximal, tipped with 1 weakly pinnate seta. Maxilliped (Fig. 115I, J) 2-segmented; proximal segment much wider than long, unarmed; distal segment slightly longer than wide, with 1 blunt process and 1 pointed spine mediodistally; terminal claw with bicuspid tip.

Leg 1 (Fig. 116A) consisting of unsegmented protopod, exopod and endopod. Protopod with seta on outer margin, plus large mediodistal protrusion with bilobed apex. Exopod distally bilobed; anterior lobe claw-like and bicuspid at tip; posterior lobe flexible, unarmed. Endopod longer than wide, distally bilobed. Legs 2 and 3 similar to leg 1, but distal margin of endopod trilobed (Fig. 116B). Leg 4 similar to leg 1, but with 1 seta on tip of posterior lobe of exopod (this seta absent in legs 1-3). Legs 1-4 each accompanied laterally by 2 or 3 tubercles (1 anterior and 2 posterior) on ventral surface of body (Figs. 116 A-C), posterior 2 lobes always present, but anterior lobe present or absent, and variable in size.

Leg 5 (Fig. 116D) as small lobe tipped with 2 setae of unequal length.

Male. Unknown.

Remarks. In species of eaplçstçmella the inner distal corner of the protopod of legs 1-4 can be variously protruded, as follows: (1) a large expansion in e. australẚensẚs, which Gotto (1970) interpreted as representing an inner lobe of the endopod; (2) a broad protrusion in e. dẚstẚncta Ooishi & Illg, 1977, which was also interpreted as an inner lobe of the endopod by Ooishi & Illg (1977) and by Marchenkov & Boxshall (2003); (3) a bilobed protrusion in e. malacçcera, which was illustrated by Chatton & Harant (1924a); and (4) a tubercle in e. unẚserẚata sp. nov. In eK ççẚshẚae sp. nov. the inner distal corner of the protopod of legs 1-4 bears a large, distally-bilobed protrusion, similar to that of e. malacçcera. The latter species is known from the Mediterranean and differs from e. ççẚshẚae sp. nov. in having a clearly defined abdomen, as illustrated by Chatton & Harant (1924a), a 2-segmented antenna, and no dorsolateral folds on the metasomal region.

The presence in leg 4 only of a distal seta on the posterior lobe of the exopod (the seta is absent in legs 1-3) seems to be the most remarkable distinguishing feature of e. ççẚshẚae sp. nov., because all known eaplçstçmella species possess this seta on the posterior lobe of the exopods of legs 1-4. In addition, the shape of the distal spine on the mandible is characteristically distally attenuated, curved, and whip-like, although it is stiff, not flexible.