Helicometra sp.

Sokolov, Sergey G., Shchenkov, Sergei V., Khasanov, Fuat K., Kornyychuk, Yuliya M. & Gordeev, Ilya I., 2022, Redescription and phylogenetic assessment of Helicometra antarcticae Holloway & Bier, 1968 (Trematoda, Opecoelidae), with evidence of non-monophyletic status of the genus Helicometra Odhner, 1902, Zoosystema 44 (15), pp. 423-433 : 428

Helicometra sp.

( Fig. 2 )

MATERIAL EXAMINED. — Northwest Pacific • 3 strongly deformed adult whole-mounted, 1 sequenced specimens; Simushir Island area ; intestine of Lycodes cf. brunneofasciatus ; 47°11’8”N, 152°17’7”E; 21.III.2017; IPEE RAS 14318; GenBank: OK644195 (28SrRNA gene) .

DESCRIPTION

General morphology and digestive system

Body elongate-oval, length 2.890 -2.940, maximum width 1.042 -1.142 in posterior half of body.Tegument unarmed. Pre-oral lobe absent. Oral sucker funnel-shaped, 385-414 / 357-414, mouth opening terminal. Ventral sucker rounded, 442-499 / 457-514. Oral sucker to ventral sucker width ratio 1:1.10-1.44. Forebody strongly contracted, about 30% of body length. Prepharynx short, distinct. Pharynx well-developed, 170-177 / 127-155. Oesophagus 212 in one specimen and strongly contracted in others. Pharyngeal and oesophagus glands distinct. Intestinal bifurcation distinctly anterior to anterior margin of ventral sucker. Caeca blind; distance from caecal ends to posterior end of body reaching 481-537.

Male reproductive system

Two testes, variously lobed, slightly overlapping, almost tandem, post-equatorial; anterior testis slightly sinistrosubmedian, 442-742 / 542-628, posterior testis median, 557-571 / 400-571. Post-testicular region 14.8-18.0% of body length. Cirrus-sac well-developed, 607-685 / 183- 205, overlapping 77.1-85.7% of ventral sucker. Internal seminal vesicle long, tubular, folded. Pars prostatica tubular, surrounded by numerous prostatic gland-cells. Ejaculatory duct distinct, cirrus not visible. Genital atrium indistinct. Genital pore strongly dextro-submedian, at level of intestinal bifurcation.

Female reproductive system

Ovary variously lobed, dextro-submedian, antero-dextral to and contiguous with anterior testis, 228-214 / 343-542. Ovarian complex not visible. Uterus pre-ovarian, coiled, intercaecal. Metraterm not visible. Eggs operculate, with long, unipolar filament; length without filament 66.7-72.7, width 30.3-36.4. Vitellarium follicular; follicles, in two lateral fields, extending from distinctly anterior to intestinal bifurcation to near posterior end of body; fields overlapping caeca dorsally at level of their distal ends and in pre-ovarian region and ventrally in ovary area and post-ovarian region, extracaecal or encroach caecain post-ovarian regionon dorsal side of body and in pre-ovarian region on ventral side of body, not confluent.

Excretory system

Excretory pore terminal. Excretory vesicle saccular or clavate with lobated anterior end, extending to ovary; posterior end surrounded by numerous glands and small subterminal muscular sphincter.

Figures

FIG. 2. — Helicometra sp. from intestine of tawnystripe eelpout, Lycodes cf. brunneofasciatus Suvorov, 1935, Northwest Pacific; whole mount, ventral view. Scale bar: 1 mm.