Meggittina numida n. sp. (Cyclophyllidea: Catenotaeniidae), a parasite of the Shaw's jird Meriones shawi (Duvernoy) (Rodentia: Gerbillinae) in Tunisia

New data on the catenotaeniid cestode Gerbillitaenia psammomi (Mikhail and Fahmy, 1968) parasitizing Fat sand rats, Psammomys obesus (Muridae: Gerbillinae), in Tunisia

The cestode Gerbillitaenia psammomi (Cyclophyllidea: Catenotaeniidae: Skrjabinotaeniinae) was found parasitizing fat sand rats (Psammomys obesus) in the south of Tunisia. The species was found previously in P. obesus from Egypt and in Meriones shawi from Morocco. The present finding constitutes the first record of the species in Tunisia. In the present study, G. psammomi was morphologically characterized using light microscopy and compared to previous records of the species. The main differentiating morphological features of G. psammomi with respect to other skrjabinotaenines of North African Gerbillinae murids are, in particular, the shape of strobila, size of suckers, number of testes, absence of an antero-poral ovarian lobe, length of the central uterine stem, and number of primary uterine branches. Negative density-dependent growth (crowding effect) has also been reported. Molecular analysis based on 28S rDNA was performed for G. psammomi and for Skrjabinotaenia oranensis. Thus, both species are grouped in a clade with other species of the subfamily Skrjabinotaeniinae and are clearly separated from the clade that includes species of the subfamily Catenotaeniinae. The molecular study confirmed the previously postulated synonymy of Meggittina numida with S. oranensis.

Taxonomic review of Skrjabinotaenia Akhumyan, Meggittina Lynsdale and Gerbillitaenia gen. nov. (Cestoda: Catenotaeniidae), parasites of rodents

The present study concerns the classification and morphologic features of species variously assigned to the genera Skrjabinotaenia Akhumyan, 1946 and Meggittina Lynsdale, 1953 (Cestoda: Cyclophyllidea: Catenotaeniidae), particularly those characterized by a widely divided testicular field. The latter feature together with the typical structure of the ovary and uterus give grounds for assigning Skrjabinotaenia oranensis (Joyeux & Foley, 1930), Meggittina baeri Lynsdale, 1953, M. cricetomydis (Hockley, 1961) and M. gerbilli (Wertheim, 1954) to the genus Skrjabinotaenia sensu stricto ("s. s."). Skrjabinotaenia s. s. is characterized by an ovary without anterior lobules and with a prominent unbranched "antero-poral lobe" as well as a uterus with a short anterior trunk and a few long primary branches. Skrjabinotaenia s. s. is divided here into two subgenera (Skrjabinotaenia and Meggittina) based on the size and shape of the strobila and characteristics of the uterus. The present study provides amended diagnoses for Skrjabinotaenia s. s., subgenus Meggittina and redescriptions of their type species. In addition, a new genus (Gerbillitaenia gen. nov.) is erected for G. psammomi (Mihkail & Fahmy, 1968) n. comb. The phylogenetic position of G. psammomi, a species with a widely-divided testicular field, is unknown but it lacks the distinguishing features of Skrjabinotaenia s. s. concerning the structure of the ovary and uterus. Based on phylogenetic and morphologic evidence, Skrjabinotaenia sensu lato includes at least three additional lineages, which should be further examined as putative new genera.

Spermatological Characterization of the Cestode Meggittina gerbilli (Cyclophyllidea: Catenotaeniidae), a Parasite of Gerbils, Gerbillus gerbillus and Gerbillus campestris (Rodentia: Muridae) in Tunisia

Ultrastructural characters of spermiogenesis and the mature spermatozoon of the cestode Meggittina gerbilli (Cyclophyllidea: Catenotaeniidae), a parasite of the Lesser Egyptian gerbil (Gerbillus gerbillus) and the North African gerbil (Gerbillus campestris) (Rodentia: Muridae) in the Djebel Dahar (South of Tunisia), were studied using transmission electron microscopy. The spermiogenesis of M. gerbilli is of Bâ and Marchand's type III, which is mainly characterized by a proximodistal fusion of a single flagellum with a cytoplasmic extension. In this catenotaeniid, the proximal fusion is preceded by a 90° rotation of the flagellum. The spermatozoon is a Levron et al. type VI, which presents a single axoneme with the 9 + '1' trepaxonematan pattern, a periaxonemal sheath, two crest-like bodies, twisted cortical microtubules, and a spiraled nucleus. The obtained results show similarities with the remaining studied catenotaeniids, namely Catenotaenia pusilla and Skrjabinotaenia lobata. The results are compared and discussed according to several characteristics found in the catenotaeniids and other studied cyclophyllideans.