Pronoprymna ventricosa ( Rudolphi, 1819 ) Poche, 1926

Sokolov, S. G., Shchenkov, S. V. & Gordeev, I. I., 2021, A phylogenetic assessment of Pronoprymna spp. (Digenea: Faustulidae) and Pacific and Antarctic representatives of the genus Steringophorus Odhner, 1905 (Digenea: Fellodistomidae), with description of a new species, Journal of Natural History 55 (13 - 14), pp. 867-887 : 870-872

Pronoprymna ventricosa ( Rudolphi, 1819) Poche, 1926 ( Figure 1 (a))

Host. Alosa volgensis .

Site of infection. Intestine.

Locality. Obzhorovo channel in the Volga River Delta , Russia (46°10ʹN, 49°13ʹE) .

Prevalence. 1 of 1 host specimen.

Intensity of infection. 3 worms in the single infected host.

Deposited material. Paragenophore (IPEE RAS 14296).

Representative DNA sequences. A partial 28S rRNA gene sequence was deposited in Genbank (NCBI) as MT872203 .

Description (based on a slightly macerated paragenophore). Body elongate oval, length 1,499, maximum width 350 at level of ventral sucker, 24.2% of length. Tegument unarmed. Oral sucker subglobular, 161 × 175, length 11.1% of body length; oral opening subterminal. Ventral sucker 189 × 196, length 13.0% of body length. Sucker width ratio 1:1.12. Forebody 30.9% of body length. Prepharynx very short. Pharynx 56 × 49, length 3.9% of body length. Oral sucker to pharynx width ratio 1:0.28. Oesophagus 126, 8.7% of body length. Intestinal bifurcation in posterior quarter of forebody. Caeca terminating at level of testes; post-caecal distance 48.8% of body length.

Testes two, entire, opposite, in anterior third of hindbody, separated from ventral sucker; left 140 × 77, length 9.7% of body length, right 133 × 77, length 9.2% of body length. Post-testicular region length 40.1% of body length. Cirrus-sac clavate, thin-walled, extending posteriorly slightly beyond middle of ventral sucker, enclosing bipartite seminal vesicle, very small vesicular pars prostatica, and ejaculatory duct, 154 × 49, length 10.6% of body length. Genital atrium tubular. Genital pore median, anterior to ventral sucker.

Ovary trilobed, median, post-testicular, 114 × 114, length 7.9% of body length. Laurer’s canal not detected. Mehlis’ gland anterior to ovary. Uterus filling most of hindbody. Eggs 22 × 15. Vitellarium from two compact oval masses, postero-lateral to ventral sucker, partly overlapping testes ventrally, left 147 × 84, length 10.1% of body length, right 168 × 70, length 11.6% of body length. Vitelline ducts wide, running towards median line of body, ventral to testes.

Excretory vesicle almost V-shaped; excretory pore terminal.

Remarks. Pronoprymna ventricosa (as Distoma ventricosum Rudolphi, 1819 ) was originally described from Alosa alosa (Linnaeus, 1758) (Clupeidae) caught in the Italian part of the Adriatic Sea ( Rudolphi 1819). Poche (1926) erected for this species an independent genus Pronoprymna . Kurochkin (1964), who was the first to discover this parasite in the Caspian Sea, described it as a new species Orientophorus caspialosae Kurochkin, 1964 . Bray and Gibson (1980) synonymised O. caspialosae with P. ventricosa .

The morphology of our specimens corresponds to the description of P. ventricosa by Bray and Gibson (1980), i.e. body elongate oval, oral sucker subglobular, sucker-ratio 1:1.12 caeca terminating at level of testes, the testes entire and symmetrically opposed, the cirrus-sac thin-walled and lying dorsal to ventral sucker and extending posteriorly to about midlevel of it, internal seminal vesicle bipartite, genital atrium tubular, ovary trilobed and post-testicular, vitellarium from two compact masses, located posterolateral to ventral sucker.

Figures

Figure 1. Paragenophores of Pronoprymna spp. (a) Pronoprymna ventricosa, ventral view; (b) Pronoprymna petrowi, ventral view. Scales: (a) 400 µm; (b) 200 µm.