Dugesia benazzii Lepori, 1951

The new species D. benazzii was described by Lepori (1951) as a taxon endemic to the two islands Sardinia and Corsica. However, further studies carried out in the Tuscany Archipelago enlarged the geographic range of this species to include also Capraia Island (Benazzi & Benazzi Lentati, 1976).

Dugesia benazzii is represented by sexual and mixed natural populations, the latter characterized by the coexistence of sexual and fissiparous individuals (see Stocchino & Manconi 2013). This species has a haploid chromosome complement of n=8, which is the most common set of chromosomes among Dugesia species, with several biotypes that can be distinguished by the ploidy level and by the type of development (amphimixis or gynogenesis): (1) diploid, amphimictic (2n = 16; n = 8); (2) triploid, amphimictic (3n = 24; n = 8); (3) triploid, gynogenetic synaptic (3n = 24; n = 8); (4) tetraploid, gynogenetic asynaptic (4n = 32; n = 8) (Lepori, 1948a; Benazzi & Benazzi Lentati, 1976; Vacca et al., 1988, 1993; Pala et al., 1999). Moreover, a tetraploid, gynogenetic synaptic karyoptype (4n = 32; n = 8) and a hexaploid karyotype (6n = 48; n = 8) in a sexual population were also found in Sardinia (M. Pala, pers. comm.); the type of development of this last population is unknown.

Dugesia benazzii is widely distributed in Sardinia both in small rivers and in large hydrographic basins (Lepori, 1951; Benazzi & Deri, 1988; Vacca et al., 1988; 1993; Pala et al., 1999; M. Pala, pers. comm.). A single population has been found also in a spring (Su Cantaru Spring) (Stocchino et al., 2013c) (Fig. 1).

Until the 1960s D. benazzii was considered to be the only species of the genus Dugesia present in Sardinia (Benazzi, 1969). However, researches carried out by Lepori, Pala and co-workers since the 1970s led to the discovery of four other species, while in-depth investigations on their biology were also performed (see below).