Skrjabinotaenia (Meggittina) gerbilli ( Wertheim, 1954 ) Tenora, Mas-Coma, Murai & Feliu, 1980

Skrjabinotaenia (Meggittina) gerbilli ( Wertheim, 1954) Tenora, Mas-Coma, Murai & Feliu, 1980

( Fig. 6 View FIGURE 6 .)

Synonyms: Rajotaenia gerbilli Wertheim, 1954 , Catenotaenia gerbilli ( Wertheim, 1954) Ortlepp, 1962 , Meggittina gerbilli ( Wertheim, 1954) Tenora, Mas-Coma, Murai & Feliu, 1980 , Catenotaenia aegyptica Wolfgang, 1956 , Skrjabinotaenia aegyptica ( Wolfgang, 1956) Tenora, 1964 , Meggittina aegyptica ( Wolfgang, 1956) Tenora, Mas-Coma, Murai & Feliu, 1980 .

The holotype of S. (M.) gerbilli is deposited in HCHU and the paratype in NHM (1955.7.20.95). The holotype of S. (M.) aegyptica is deposited in USNM (1338138).

Material examined: Five specimens from Gerbillus pyramidum Geoffroy and five from Pachyuromys duprasi Lataste ( Gerbillinae ) from Egypt (see Elmahi 2012 and Elmahy 2022). Because the specimens from the two host species differed with respect to the body size and number of testes, the following description is based on the specimens from G. gerbillus , with some quantitative data for the specimens from P. duprasi shown in brackets. For additional morphometric data, see Elmahi (2012).

Deposited voucher specimens (slides): FMNH: KN.47860- KN.47862 from G. pyramidum, KN. 47863- KN.47865 from P. duprasi .

Description: Fully gravid strobila with four [three] proglottids, length 5.5 mm [1.5–1.8 mm]. Anterior part of strobila widens rapidly. Depending on state of contraction, strobila (without gravid proglottid) either elongate or as long as wide, attaining triangular shape in latter case. Terminal gravid proglottid 5 mm [4.5–5.5 mm] wide, distinctly wider than previous pregravid proglottid, partly split along midline forming elongate “wings”. Lateral proglottid margins convex; margins between proglottids first convex, then straight and finally concave. Scolex dome-shaped, not distinctly separate from neck region. Diameter of suckers 125–150 (x̅=135, n=14) [160–185, x̅=168]. Genital pores usually regularly alternating, positioned near anterior margin of proglottid.

Testes 138–156 (x̅=148, n=4) [69–105, x̅=88] in total number, positioned as two widely separate lateral groups. Testes more numerous on antiporal side (80–90, x̅=84, n=4) [44–59, x̅=52] than on poral side (54–70, x̅=64, n=4) [25–46, x̅=36]. Cirrus sac slender, 250–330 [110] long, slightly curved. Distinct internal and external seminal vesicles absent.

Ovary median, massive, 1.3–2.1 mm (x̅= 1.6 mm, n=3) [450–700] wide, distinctly lobulate and slightly branched, lateral lobules longer than median ones; anterior lobules lacking, prominent unbranched antero-poral lobe extending anterior to median lobe of vitellarium. Vitellarium bilobed, lateral lobe larger than median one; width 630–850 (x̅=727, n=3) [140–240, x̅=183). Longitudinal axis of vitellarium inclined posteriorly with respect to longitudinal axis of proglottid (inclination may be obscure in transversely elongate mature proglottids).Vagina slender, slightly curved, of uniform width; length 550–770 (n=2) [230] or 1.8–2.3 (x̅=2.1, n=3) [2.1] times longer than cirrus sac. Seminal receptacle ovoid, larger diameter 140–160 (n=2) [60–70]. Uterus in pregravid proglottids with two primary branches, of which posterior one more prominent that anterior one and with multiple short secondary lobules directed “posteriad”; anterior appendage of uterus lacking. Eggs deformed.

Remarks. Skrjabinotaenia (M.) gerbilli has usually a slightly elongate anterior strobila, which differentiates it from the other species in the subgenus Meggittina , the latter with a transversely elongate strobila. However, it is assigned here to Meggittina due to the reduced number of proglottids and the deeply split, somewhat transversely elongate terminal gravid proglottids.The structure of the uterus in S. (M.) gerbilli (massive “posterior” primary branch with multiple short secondary branches directed “posteriorly”) also affiliates it with the subgenus Meggittina .

In the present material, there are evidently two forms of S. (M.) gerbilli -like cestodes occurring in different host species and genera ( G. gerbillus , P. duprasi ). They are distinguished mainly by the size of the fully gravid strobila and number of testes ( Fig. 6 View FIGURE 6 ). However, Elmahi (2012) did not find significant differences in the body length, diameter of suckers and dimensions of various genital organs between the two collections (the number of testes was not provided).

With respect to their general morphology, the two forms resemble S. (M.) gerbilli and S. (M.) aegyptica . Skrjabinotaenia (M.) aegyptica , another species described from gerbils ( Gerbillus spp. ) in the Middle East, has been considered a junior synonym of S. (M.) gerbilli (see Ortlepp 1962), although the description of the latter species lacks the number of testes and some other measurements. However, due to the overall qualitative similarity of these forms, we agree with the action of Ortlepp (1962). Based on the number of testes, the present type from G. gerbillus is more similar to S. (M.) aegyptica than the one from P. duprasi . Because the present material suggests a possibility that there exist at least two S. (M.) gerbilli -like species, this complex should be revised, ideally utilizing materials from the various genera of gerbils in which this species has been reported ( Gerbillus , Meriones Illiger , Pachyuromys , Dipodillus Lataste ) ( Table 1 View TABLE 1 ).

Skrjabinotaenia (M.) gerbilli is a parasite of gerbils in North Africa and the Middle East ( Table 1 View TABLE 1 ), except that it was described from the murid rodents Hybomys univittatus (Peters) ( Murinae ) and Lophuromys sikapusi (Temminck) ( Deomyinae ) in the Central African Republic ( Quentin 1971). The latter specimens fit in most respects to the original descriptions of S. gerbilli and S. aegyptica but they have distinctive lappets in the margins of the suckers, which are present in all three specimens from two host species illustrated by Quentin (1971). Because this feature appears to be constant and has not been described in other species of Skrjabinotaenia , it is probable that the S. (M.) gerbilli of Quentin (1971) represents a distinct, new species. No voucher specimens were designated by Quentin (1971).