Biospeedotrema biospeedoi Bray, Waeschenbach, Dyal, Littlewood & Morand, 2014, n. sp.

Biospeedotrema biospeedoi n. sp.

(Fig. 3)

urn:lsid:zoobank.org:act:8381CFB8-5EA9-4FD7-A9DE-A161B7C0E664

Type host. Thermichthys hollisi (Cohen, Rosenblatt & Moser) (Ophididiiformes: Bythitidae ), Hollis brosmekvabbe.

Site. Small and large intestine.

Type locality. South East Pacific Rise, hydrothermal vent site Hobbs, 17°35.20’S, 113°14.75’W; Biospeedo cruise, PL 1588, depth 2598 m, baited trap, 29 Apr. Biospeedo labels: 1588–3, 1588–6, 1588–8.

Type specimens. MNHN holotype 1 slide MNHN HEL 391, paratypes 6 wholemount slides MNHN HEL 392 393 394 395 396 397, 4 section slides. MNHN HEL 398 399 400 401; BMNH paratypes 2013.12.3.7-10.

GenBank number. rDNA KF733986.

TABLE 1. Measurements and ratios of digeneans of hydrothermal vent fishes.

Width as % of body-length 39.3–51.1 (43.6) 57.7–82.2 (67.9) 60.6 104–133 (121) 47.6–85.6 (71.6) 22.5–53.9 (37.2)

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TABLE 1. (Continued)

Ventral sucker to ovary as % of body- 2.20–17.8 (7.41) 0–2.11 (0.40) 0 0–7.68 (2.21) 0–6.85 (1.88) 0–2.27 (0.75)

length

Etymology. This species is named after the Biospeedo expedition on which the material was collected

Description. Based on 11 wholemounts and 2 sets of serial sections. Measurements and ratios in Table 1. Body small, oval to fusiform, widest at level of ventral sucker (Fig. 3). Tegument unarmed, but thrown into numerous denticulate annular folds. Oral sucker shallow cup-shaped, almost terminal. Ventral sucker rounded, larger than oral sucker, just pre-equatorial. Prepharynx short. Pharynx oval. Oesophagus long, thin-walled. Intestinal bifurcation dorsal to ventral sucker. Caeca blind, divergent, narrow, reaching just into hindbody or just to testis.

Testes lobate, symmetrical, separated by uterus, in anterior hindbody. Cirrus sac elongate claviform, reaching into hindbody, proximal extremity in sinistral anterior hindbody, curves dorsally to ventral sucker. Internal seminal vesicle saccular. Pars prostatica narrow, surrounded by gland-cells. Ejaculatory duct? Genital atrium small. Genital pore median to slightly submedian, just anterior to ventral sucker.

Ovary oval, between dextral testis and cirrus sac. Seminal receptacle uterine. Laurer’s canal opens dorsally in mid post-testicular region. Mehlis’ gland not clearly seen. Uterus mainly post-testicular but also intertesticular. Eggs large, operculate, tanned, few. Metraterm not clearly differentiated. Vitellarium follicular, follicles small, irregular, lateral fields reaching from anterior part of ventral sucker to anterior part of testes, confluent in narrow band dorsally to ventral sucker, lateral and dorsal to caeca.

Excretory pore terminal, to dorsally subterminal. Vesicle I-shaped, reaches between testes to ovary.

Remarks. In basic morphology this species is similar to B. jolliveti, but differs in being generally smaller. The vitelline fields are shorter, filling a smaller proportion of the body-length, and the cirrus sac is relatively larger (Table 1). The uterus tends to extend further posteriorly, relative to the testes. The morphological similarity between B. jolliveti and this species is also reflected in the molecular data; 1300 base pairs of lsrDNA differ only in two positions.

Biospeedotrema parajolliveti differs in body-shape and the ratios of vitelline field length and ventral sucker size to body-length. The uterus tends to extend further posteriorly, relative to the testes.