Skrjabinotaenia Akhumyan, 1946

Haukisalmi, Voitto & Elmahy, Rasha A., 2025, Taxonomic review of Skrjabinotaenia Akhumyan, Meggittina Lynsdale and Gerbillitaenia gen. nov. (Cestoda: Catenotaeniidae), parasites of rodents, Zootaxa 5590 (2), pp. 185-208 : 189-190

Skrjabinotaenia Akhumyan, 1946 sensu stricto

( Figs. 2 , 4–6 )

Diagnosis: Strobila of varying shape and size, from longitudinally elongate and relatively long to transversely elongate and short. Proglottids usually few but more numerous in type species. Scolex gradually merging with neck region or embedded in strobila. Neck (unsegmented region) short or absent. Proglottids acraspedote, of varying shape; terminal gravid proglottid deeply divided along midline in subgenus Meggittina . Lateral proglottid margins convex. Genital pores irregularly alternating in short series or (appearing as) unilateral in species with few proglottids, positioned near anterior margin of proglottid; genital atrium indistinct. Longitudinal osmoregulatory canals numerous, anastomosing, in type species forming complex ventral and dorsal plexus; transverse canals absent. In type species, lateral genital ducts run between plexuses. Testes numerous, appearing as two widely separate lateral groups extending throughout proglottid in antero-posterior plane (absent in region occupied by lateral genital ducts). Cirrus sac slender, curved, usually poorly delimited from vas deferens.Vas deferens sinuous or slightly coiled distally. Distinct internal and external seminal vesicles absent. Ovary median, extensive, flabelliform, with several long branches pointing posteriorly and postero-laterally (but not anteriorly); prominent unbranched “antero-poral lobe” extending anterior to median lobe of vitellarium. Vitellarium poral, elongate in transverse plane, slightly curved; bilobed, poral lobe usually more prominent than median one. Longitudinal axis of vitellarium inclined posteriorly with respect to longitudinal axis of proglottid (inclination may be obscure in subgenus Meggittina ). Vagina long and slender, usually distinctly longer than cirrus sac, of uniform width, slightly curved, opening posterior or postero-ventral to cirrus sac. Large ovoid or spherical seminal receptacle present. Uterus first appears as transverse band or tube near anterior margin of mature proglottids. Developed uterus with short longitudinal trunk in anterior part of proglottid and few long, furcating branches forming two groups divided in midline of proglottid. Eggs small, ovoid or elongate, with delicate wall; embryophore elongate. In murid ( Murinae , Gerbillinae and Deomyinae ) and nesomyid ( Nesomyinae and Cricetomyinae ) rodents.

Type species: S. oranensis ( Joyeux & Foley, 1930) Akhumyan, 1946 .

Other species: S. baeri ( Lynsdale, 1953) Tenora, 1964 , S. cricetomydis Hockley, 1961 , S. gerbilli ( Wertheim, 1954) Spasskii, 1955 [syn. S. aegyptica ( Wolfgang, 1956) ].

Remarks. The genus Skrjabinotaenia in the present sense (hereafter sensu stricto, “ s. s. ”) is confined to species with a widely divided testicular field in two fairly narrow lateral groups, a characteristically fan-shaped ovary without anterior branches and with a prominent, unbranched antero-poral lobe, and a uterus with a short longitudinal anterior trunk and a small number of long primary branches, which form two groups divided along the midline of the proglottid. The structure of the ovary in the species with a strongly reduced, transversely elongate strobila (subgenus Meggittina ) has not been adequately described but it is shown here to be qualitatively similar to the ovary of S. oranensis (below).

Compared with Skrjabinotaenia s. s., the genera Spasskijela (sometimes with a partly divided testicular field) and Neoskrjabinotaenia Bilqees, 1982 have a longer strobila with more numerous proglottids, an ovary of different structure (anterior lobules present, antero-poral lobe absent) and a uterus with a longer trunk and more numerous, relatively short branches ( Figs. 2 , 3 ). In addition, the longitudinal axis of the vitellarium in the latter genera is inclined anteriorly with respect to the longitudinal axis of the proglottid (posteriorly in Skrjabinotaenia s. s.). The above features also differentiate Skrjabinotaenia sensu lato (“ s. l.”) capensis ( Ortlepp, 1940) (with a divided testicular field), Skrjabinotaenia (s. l.) indica ( Parihar & Nama, 1977) and the undescribed species of Skrjabinotaenia s. l. in subclade “A” from Skrjabinotaenia s. s. ( Figs. 1–3 ).

Morphologic differences between Skrjabinotaenia and Gerbillitaenia gen. nov., both with a widely divided testicular field, will be described in the Remarks section for the latter genus.

Figures

FIGURE 1. Summary of statistically significant phylogenetic relationships of the “African clade” of catenotaeniid cestodes (i.e. subfamily Skrjabinotaeniinae) based on two DNA markers (Haukisalmi et al. 2018). Branch lengths are arbitrary. Host subfamilies: M, Murinae; G, Gerbillinae; N, Nesomyinae; C, Cricetomyinae. Distribution of testes: L, lateral; P, posterior.

FIGURE 2. Mounted specimens of Skrjabinotaenia oranensis (Joyeux & Foley, 1930) (A), Gerbillitaenia psammomi (Mikhail & Fahmy, 1968) n. comb. (B), Spasskijela kratochvili Tenora, 1959 (C) and Skrjabinotaenia (s. l.) media Quentin, 1971) (D). Specimens are not in scale.

FIGURE 3. Mature proglottid and anterior strobila of Skrjabinotaenia (s. l.) capensis (Ortlepp, 1940) (A, B), Spasskijela lobata (Baer, 1925) (C), Spasskijela kratochvili Tenora, 1959 (D) and Skrjabinotaenia (s. l.) media Quentin, 1971 (E, F).

FIGURE 4. Skrjabinotaenia oranensis (Joyeux & Foley, 1930) from Meriones shawi from Algeria (A, D, G, H; syntypes) and Tunisia (B, C, E, F; material of Jrijer & Neifar 2014).A, B, mature proglottid; C, D, scolex and anterior strobila; E, lateral genital ducts and osmoregulatory canals; F, G, pregravid proglottid; H, gravid proglottid.AP, “antero-poral lobe” of the ovary.

FIGURE 5. Skrjabinotaenia (Meggittina) cf. baeri (Lynsdale, 1953) from Rhabdomys spp. from South Africa. A, pregravid strobila; B, gravid strobila; C, pregravid uterus; D, lateral genital ducts; E, scolex. AP, “antero-poral lobe” of the ovary.

FIGURE 6. Skrjabinotaenia (Meggittina) gerbilli (Wertheim, 1954) from Gerbillus pyramidum (A, D) and Pachyuromys duprasi (B, C) from Egypt (material of Elmahi 2012 and Elmahy 2022). A, C, gravid strobila; B, anterior strobila; D, lateral genital ducts. AP, “antero-poral lobe” of the ovary.