#### Description

[Based on adult specimens from off Crimean coasts.] Gravid specimens small, 2.13–6.43 (4 ± 0.4, n = 16) mm long, with 6–11 (9 ± 0.5, n = 15) segments in gravid specimens (Fig. 6); maximum width of strobila 200–700 (291 ± 13, n = 23). Scolex acraspedote, 550–850 (691 ± 19, n = 23) long; maximum width 85–190 (134 ± 9, n = 13) in pars bothridialis (Fig. 7); pars bothridialis 100–250 (159 ± 7, n = 23) long; two elongate sub-cordiform bothridia without distinct margins or a distinct posterior indentation, width of bothridium 50–200 (116 ± 7, n = 23) (Fig. 7). Pars vaginalis 225–550 (362 ± 19, n = 13) long; tentacular sheaths slightly sinuous. Bulbs elongate 300–563 (366 ± 13, n = 23) long, 25–100 (47 ± 3, n = 23) wide. Ratio of bulb length to width 5–14.8 (8.4 ± 0.5, n = 23) (Fig. 8). Prominent prebulbar organ at junction of sheath with bulb (Fig. 8); retractor muscle originates at base of bulb, posterior part of retractor surrounded within bulb by linear array of gland cells; bulbs project into pars proliferans scolecis. Scolex-ratio (Pbo : Pv : Pb) 1 : 2.4 : 2.4.

Tentacles elongate, up to 500–700 (568 ± 21, n = 4) long when maximum of everted; tentacles without basal swelling, 10–40 (20 ± 2, n = 15) in diameter at base, 8–30 (15 ± 1.3, n = 21) in metabasal region. Armature heteroacanthous, atypical; hooks solid. Basal armature consists of 2-3 rows of hooks arranged in ascending rows beginning on internal surface (Fig. 1); terminating on external surface (Fig. 3); initial hooks in rows 1.7–10.01 (5.54 ± 0.2, n = 23) long, base 1.1–8.5 (3.7 ± 0.2, n = 23), diminishing in size gradually along row towards external surface (Fig. 3). Metabasal armature composed of half rows of 6 hooks arranged in ascending half circles (Fig. 2); small space between hooks 1 (1’) on internal surface of tentacle, hooks beginning on internal surface, terminating on external surface (Fig. 2). Hooks 1 (1’) large, uncinate, with long thickened base, 12–16 (14.8 ± 0.1, n = 23) long, base 10–15 (13 ± 0.2, n = 23) (Fig 4). Hooks 2 (2’) uncinate, slightly longer than the hook 1(1’), but with shorter base, 15–20 (16 ± 0.1, n = 23) long, base 7–10 (9.7 ± 0.1, n = 23). Hooks 3 (3’) erect, falcate, blade long, but with short and narrower base, 14–16 (15 ± 0.1, n = 23) long, base 5–10 (8 ± 0.3, n = 23). Hooks 4 (4’) slightly falcate, shorter than 3 (3’), with less curved blade and slightly narrower base, 10–13 (12 ± 0.2, n = 23) long, base 4–10 (6 ± 0.3, n = 23). Hooks 5 (5’) similar to previous hooks, considerably shorter than 4(4’), 7–12 (10 ± 0.2, n = 23) long, base 4–7 (5 ± 0.1, n = 23). Hooks 6 (6’) small, erect, 7–10 (9 ± 0.2, n = 23) long, base 3–6 (4 ± 0.1, n = 23). Single row of intercalary hooks between each principal row (Fig. 3); intercalary hooks 1.25–5.82 (2.66 ± 0.1, n = 23) long, base 0.7–3.04 (1.63 ± 0.08, n = 23). No intercalary row in basal region; initial intercalary row appear under principal row 1, composed of 2–4 hooks (Figs. 3); the next intercalary row located between principal row 1 and 2, composed of 6 hooks arranged in arc, beginning at level of hooks 4 (4’), sometimes at the level of hooks 3 (3’), extending beyond principal row to middle of external surface (Fig. 3). No additional hooks on external surface of tentacle apart from intercalary hooks. Hooks of each intercalary row initially spiniform; final hooks (e(e’), f(f’)) of enlarged, uncinate, with broad base and short broad blade (Fig. 5).

Segments acraspedote; mature segments 1–3 (2 ± 0.1; n = 16) in number, 300–750 (527 ± 24, n = 23) long, maximum width 120–450 (230 ± 14, n = 23) (Fig. 10); gravid segments 1–4 (2.4 ± 0.2; n = 16) in number, 0.53–1.4 (0.97 ± 0.05, n = 16) mm long, 0.15–0.4 (0.29 ± 0.01, n = 16) mm wide; terminal segment 0.95–1.95 (1.4 ± 0.1, n = 10) mm long, 0.24–0.7 (0.38 ± 0.05, n = 10) mm wide (Fig. 11). Genital pores alternate irregularly, in shallow depression of segments margin, 0.3–1.05 (0.51 ± 0.04, n = 23) from anterior extremity. Testes preovarian, arranged in two parallel columns in segment (Fig. 10); total number of testes 20–24 (22 ± 0.2, n = 16), arranged as 10–13 (12 ± 0.2, n = 16) antiporal, 9–12 (10 ± 0.2, n = 16) poral, with 5–8 (7 ± 0.2, n = 16) anterior to cirrus sac, 3–5 (4 ± 0.1, n = 16) posterior to cirrus sac; testis dimensions 25–60 (45 ± 2, n = 16) by 25–85 (57 ± 3.6, n = 16). Cirrus sac 50–100 (68 ± 5.5, n = 13) by 50–100 (74 ± 5.5, n = 13); cirrus everted in two segment, unarmed (Fig. 9). Cirrus sinuous, leads to crescentic internal seminal vesicle adjacent to proximal pore; adnate external seminal vesicle on antero-median aspect of cirrus sac (Fig. 9); vas deferens coils posteriorly from external seminal vesicle towards ovarian isthmus. Vagina opens to genital atrium at same level as cirrus sac, runs medially then posteriorly towards ovary. Ovary in posterior part of segment, 4-lobed, H-shaped in dorsoventral view, 75–160 (124 ± 7, n = 17) long, 75–200 (114 ± 8.5, n = 17) wide. Vitelline follicles 13–30 (21 ± 0.8, n = 16) in diameter, cortical, scattered around margin of segment. Uterus simple, tubular, extending in midline almost to anterior extremity of segment; gravid uterus saccate, filled with eggs (Fig. 11). Eggs spherical, 20–40 (26 ± 1.2, n = 16) in diameter.

Plerocercus: (Figures 12–22). [Based on 6 specimens from off Crimean coasts.] Total length 0.7–1.05 (0.85 ± 0.05, n = 5); scolex acraspedote, SL 480–600 (538 ± 23, n = 5) (Fig. 18); maximum width in the region of pars vaginalis, 160–180 (171 ± 4.3, n = 4) (Fig. 12, 17); pbo 80–175 (143 ± 17, n = 5); two elongate sub-cordiform bothridia without distinct margins or a distinct posterior indentation, width of bothridium 80–125 (101 ± 7, n = 5); pv 300–450 (385 ± 29, n = 5); tentacular sheaths slightly sinuous. Bulbs elongate, BL 260–280 (272 ± 3.4, n = 5), BW 40–50 (42 ± 5, n = 5), BR 5.6–6.9 (6.5 ± 0.2, n = 5); prominent prebulbar organ at junction of sheath with bulb (Fig. 12); retractor muscle originates at base of bulb, posterior part of retractor surrounded within bulb by linear array of gland cells; bulbs project into pars proliferans scolecis; SP 1 : 2.9 : 2.1. Plerocercoids examined by SEM were covered with numerous microtriches of two different shapes: elongated filifiorm microtriches (Fig. 21) covered the internal bothrial surface and short filiform microtriches with a rounded tip (Fig. 22), covered the pars bothridialis, scolex peduncle and body surface.

Tentacles without basal swelling (Fig. 13, 15); TL 350–650 (470 ± 58, n = 5), TW 20–25 (24 ± 1, n = 5) in diameter at base, 13–20 (16 ± 1.2, n = 5) in metabasal region. Armature heteroacanthous, atypical; hooks solid (Fig. 13–15). Basal armature consists of 2–3 rows of uncinate hooks with sharply recurved blades and elongate bases, arranged in ascending rows beginning on internal surface; initial hooks in rows 3.8–8.9 (6 ± 0.5, n = 6) long, base 1.5–8.5 (3.5 ± 0.8, n = 6), diminishing in size gradually along row towards external surface (Fig. 13, 15, 20). Metabasal armature composed of half rows of 6 hooks arranged in ascending half circles (Fig. 14, 19); small space between hooks 1 (1’) on internal surface of tentacle, hooks beginning on internal surface, terminating on external surface (Fig. 15). Hooks 1 (1’) large, uncinate, with long base, 10–16 (14 ± 0.4, n = 6) long, base 7.2–15 (12 ± 0.6, n = 6) (Fig 16, 19). Hooks 2 (2’) slightly longer than the hook 1(1’), but with shorter base, 12–17 (14 ± 0.3, n = 6) long, base 5.7–10.8 (9 ± 0.3, n = 6). Hooks 3 (3’) erect, falcate, blade long, base short, 12–17 (15 ± 0.4, n = 6) long, base 5–10 (7.6 ± 0.3, n = 6). Hooks 4 (4’) slightly falcate, shorter than 3 (3’), with narrower base, 8–15 (12 ± 0.5, n = 6) long, base 4–10 (6 ± 0.5, n = 6). Hooks 5 (5’) similar to previous hooks, 8.2–12 (10 ± 0.4, n = 6) long, base 4–8 (5.3 ± 0.4, n = 6). Hooks 6 (6’) very small, erect, 6–10 (7 ± 0.5, n = 6) long, base 2–5 (3.4 ± 0.4, n = 6). Single row of intercalary hooks between each principal row (Fig. 15); intercalary hooks 4–7 (5.4 ± 0.5, n = 5) long, base 2 (n = 2). No intercalary row in basal region; initial intercalary row appear under principal row 1, composed of 2–3 hooks (Fig. 15); remaining intercalary row composed of 6 hooks arranged in arc, beginning at level of hooks 4 (4’), extending beyond principal row to middle of external surface (Fig. 15). No additional hooks on external surface of tentacle apart from intercalary hooks.