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

The cestode <i>Gerbillitaenia psammomi</i> (Cyclophyllidea: Catenotaeniidae: Skrjabinotaeniinae) was found parasitizing fat sand rats (<i>Psammomys obesus</i>) in the south of Tunisia. The species was found previously in <i>P. obesus</i> from Egypt and in <i>Meriones shawi</i> from Morocco. The present finding constitutes the first record of the species in Tunisia. In the present study, <i>G. psammomi</i> was morphologically characterized using light microscopy and compared to previous records of the species. The main differentiating morphological features of <i>G. psammomi</i> 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 <i>G. psammomi</i> and for <i>Skrjabinotaenia oranensis.</i> 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 <i>Meggittina numida</i> with <i>S. oranensis.</i>