Itostenhelia golikovi (Chislenko, 1978) comb. nov.

(Figs. 43–47)

Type locality. Russia, Primorsky Krai, Posyet Bay, Minonosok inlet, benthic sands at 3–4 m depth, 42.609258°N 130.861661°E .

Specimens examined. Two females dissected on one slide each (collection numbers NIBRIV0000232699 and NIBRIV0000232700), male dissected on one slide (collection number NIBRIV0000232701), one male and five females together on one SEM stub (collection number NIBRIV0000232702), 10 females (four ovigerous) and two copepodids together in ethanol (collection number NIBRIV0000232703), 10 females together in ethanol (collection number NIBRIV0000232704), four males and 40 females (10 ovigerous) together in ethanol (collection number NIBRIV0000232705), 10 females destroyed for DNA sequence (five amplifications successful, Codes 0734, 0832, 0631, 0330 & 0433), type locality, 06 May 2012, leg. J. Trebyakova.

Redescription. Female (based on ten specimens). Body length from 545 to 648 µm. Body segmentation, nauplius eye, hyaline fringes, integument thickness, surface appearance of somites, and all somite ornamentation as in Itostenhelia polyhymnia sp. nov., including all sensilla and pores, and minute dorso-lateral rows of spinules on urosomites. However, colour of preserved specimens more translucent. Habitus (Figs. 43A, B, 46A) more robust than in Itostenhelia polyhymnia, with prosome/urosome length ratio about 1.1, body length/width ratio 3.4, and cephalothorax 1.8 times as wide as genital double-somite. Five specimens with paired egg-sacs, each containing between seven and 10 eggs.

Rostrum (Fig. 43C) as in Itostenhelia polyhymnia, including apical bunch of spinules, dorsal suture, position of anterior pair of sensilla no. 1; only slightly smaller in comparison to cephalothorax.

Cephalothorax (Figs. 43A, B, 46B, 47C) about 0.9 times as long as wide; comprising 26% of total body length. Surface of cephalothoracic shield ornamented exactly as in Delavalia polyhymnia (all homologous pores and sensilla indicated with Arabic numerals, geometric shapes or Roman numerals in illustrations).

Pleuron of second pedigerous somite (Figs. 43A, B, 46C, 47D), pleuron of third pedigerous somite (Figs. 43A, B, 46C, 47D), and pleuron of fourth pedigerous somite (Figs. 43A, B, 46C, 47D) ornamented exactly as in Itostenhelia polyhymnia .

First urosomite (Figs. 34A, B) as in Itostenhelia polyhymnia, except slightly narrower both in dorsal and lateral view.

Genital double-somite (Figs. 43A, B, 44A, 46D) as in Itostenhelia polyhymnia, except internal structure slightly narrower (arrowed in Fig. 44A).

Third urosomite (Figs. 43A, B, 44A, 46D) and preanal somite (Figs. 43A, B, 44A, 46E) as in Itostenhelia polyhymnia .

Anal somite (Figs. 43A, B, 44A, 46E) also as in Itostenhelia polyhymnia, except lateral pore no. 80 present.

Caudal rami (Figs. 43A, B, 44A, 46E) as in Itostenhelia polyhymnia, except additional field of small spinules present on anterior ventral surface close to inner margin, in addition to large inner spinules.

Antennula (Figs. 43D, 47C) as in Itostenhelia polyhymnia, except sixth and seventh segments completely fused.

Antenna, labrum (Figs. 43E, 47A), paragnaths (Fig. 47A), mandibula, maxillula (Fig. 47A), maxilla (Fig. 47B), maxilliped (Fig. 47B), first swimming leg, second swimming leg, third swimming leg (Fig. 44B), and fourth swimming leg (Fig. 44C) as in Itostenhelia polyhymnia .

Fifth leg (Figs. 43A, B, 44D, 46F) as in Itostenhelia polyhymnia, except pore on basis missing and endopodal lobe slightly more convex. Length ratio of endopodal setae, starting from inner side, 1: 1.3: 2.9: 1.8. Length ratio of exopodal setae, starting from inner side, 1: 0.5: 0.15: 0.7: 0.3.

Sixth leg (Figs. 44A, E, 46F) as in Itostenhelia polyhymnia, except for additional spiniform process next to plumose seta.

Male (based on three specimens). Body length from 548 to 604 µm. Habitus, colour, rostrum, shape and all ornamentation of cephalothorax, shape and ornamentation of second, third, and fourth pedigerous somites, ornamentation of first urosomite (Figs. 45A, B, 47E), caudal rami (Figs. 45A, B, 47F), antenna, labrum, paragnaths, mandibula, maxillula, maxilla, maxilliped (Fig. 45C), first swimming leg, third swimming leg, and fourth swimming leg as in female.

Genital somite (Figs. 45A, B, 47E) as in Itostenhelia polyhymnia, except lateral pore no. # missing; relatively small spermatophore visible inside, positioned longitudinally on right side, about 3.5 times as long as wide, its neck reaching slightly beyond anterior margin of first urosomite.

Third urosomite (Fig. 45A, B) as in Itostenhelia polyhymnia .

Fourth urosomite (Fig. 45A, B) as in Itostenhelia polyhymnia, except ventral pair of pores no. VI missing (arrowed in Fig. 45A).

Preanal and anal somites (Figs. 45A, B, 47F) as in Itostenhelia polyhymnia .

Caudal rami (Figs. 45A, B, 47F) as in Itostenhelia polyhymnia, except slightly shorter (arrowed in Fig. 45A, B) and with additional patch of ventral spinules (arrowed in Fig. 45A), about four times as long as wide in ventral view, with two rows of relatively short inner spinules in anterior third.

Antennula (Fig. 44F) as in Itostenhelia polyhymnia, except less clasped; general shape and segmentation as in Wellstenhelia calliope; only ornamentation proximal row of spinules on first segment and two dorsal spinules on sixth segment; aesthetascs on third and fourth segments long and slender, no aesthetasc on ninth segment; setal formula 1.10.6+ae.8+ae.1.2.2.4.5.

Second swimming leg coxa, basis, and exopod as in female; endopod (Fig. 45D) as in Itostenhelia polyhymnia, except inner spiniform process marking ancestral boundary between second and third segment missing (arrowed in Fig. 45D), proximal seta on ancestral second segment proportionately longer (arrowed in Fig. 45D), and inner spiniform element on ancestral third segment also proportionately longer (arrowed in Fig. 45D).

Fifth leg (Figs. 45A, B, 47E) as in Itostenhelia polyhymnia, except outer endopodal spine proportionately much longer (arrowed in Fig. 45A).

Sixth legs (Figs. 45A, B, 47E) as in Itostenhelia polyhymnia .

Variability. One male has the inner spine on left sixth leg curled, while the same element on right sixth leg is straight (Fig. 45A, B).

Remarks. Chislenko (1978) reports a different armature formula of the swimming legs for this species than what we have found, with the minute inner distal setae missing on the third endopodal and exopodal segments of the fourth leg, as well as no inner seta on the first and second exopodal segments of the second leg. We examined all newly collected specimens from the type locality for these characters and found these setae always present. This implies that Chislenko (1978) either overlooked these setae (perhaps they were broken off on his specimen), or he was dealing with an aberrant specimen. We are inclined to favour the former, as Chislenko (1978) also provides a drawing of a maxilliped with only two setae on the basis, while all stenheliins have three setae here. Given the similarity of other features between our specimens and those studied by Chislenko (1978), the fact that our specimens were collected exactly from the type locality, and the apparent low diversity of stenheliins there, we believe that there is no chance that were are dealing with a different biological species.

Itostenhelia golikovi (Chislenko, 1978) comb. nov. shows very few morphological differences from its Korean congener, Itostenhelia polyhymnia sp. nov., and they are all pointed out in the affinities of the latter species (see above) and also indicated with arrowheads in Figs. 43, 44, 45.