Dugesia sicula Lepori, 1948

Stocchino, Giacinta Angela, 2018, 80 years of research on planarians (Platyhelminthes, Tricladida) from Sardinia, Italy: an annotated checklist, Zootaxa 4532 (4), pp. 539-552 : 541

Dugesia sicula Lepori, 1948

Dugesia sicula was first reported for Sardinia on the basis of fissiparous populations, in which a certain percentage of individuals underwent a sexualization process, from 12 Sardinian localities, including 2 small nearby islets (spring and wells on the Tavolara Island Protected Area and watercourses on the S. Antioco Island) (Pala et al., 1995) ( Fig. 1 ). After several years other fissiparous populations were found in two other watercourses, one in the northwestern Asinara Island National Park (Rio d’Auteri reservoir) ( Stocchino, 2003) and another in southeastern Sardinia (Fiume Quirra) (M. Pala, pers. comm.) ( Fig. 1 ). All Sardinian populations showed a coastal distribution with a high degree of tolerance to variations in environmental factors, especially temperature and watercourses hydrological regime e.g. temporary water (Pala et al., 1995; G.A. Stocchino, pers. obs.).

Dugesia sicula has a pan-Mediterranean geographic range where it is mostly represented by fissiparous populations with only a few sexual populations being present in Mallorca, Algeria, Tunisia and Israel. Two mixed populations, including both sexual and fissiparous individuals, were reported from Sicily (Stocchino & Manconi 2013 and references therein). A recent reassessment of the taxonomic status of D. biblica Benazzi & Banchetti, 1973 from Israel and Turkey, based on morphological and molecular studies, considered this species to be a junior synonym of D. sicula ( Solà et al., 2015) .

As for karyology, numerous studies confirmed a diploid condition for sexual populations with a chromosome complement of 2n = 18; n = 9, and a triploid condition for fissiparous populations with a chromosome complement of 3n = 27; n = 9 + 1-5 B-chromosomes (see Stocchino et al., 2012 and references therein).

Among Dugesia species, the haploid complement of nine chromosomes of D. sicula is shared with only five other species: D. maghrebiana Stocchino et al., 2009 , from North Africa; D. arabica Harrath & Sluys, 2013 from Yemen; D. aethiopica Stocchino et al., 2002 and D. afromontana Stocchino & Sluys, 2012 from the Afrotropical region; D. bifida Stocchino & Sluys, 2014 from Madagascar ( Stocchino et al., 2002, 2004, 2009, 2012, 2014; Harrath et al., 2013).

Although D. sicula is extremely widespread, a molecular analyses on many fissiparous populations from its entire distributional range revealed a remarkable pattern of low interpopulation genetic variability, which was interpreted as the result of recent anthropochore colonizations after triploidization of sexual diploid populations ( Lazaro et al., 2009).

Figures

FIGURE 1. Geographic distribution of species of the genus Dugesia recorded from Sardinia. 1, Rio d’Auteri reservoir, Asinara Island National Park; 2, Rio Mannu di Portotorres; 3, Fiume Silis; 4, Rio Lu Bagnu; 5, Fiume Coghinas; 6, Fiume Liscia; 7, spring and wells on the Tavolara Island Protected Area; 8, springs and unnamed rivulets on the Molara Island Protected Area; 9, Rio Su Lernu; 10, Rio Cuga; 11, Rio de sa Pazzosa; 12, Rio Torre Argentina; 13, Fiume Temo; 14, Sa Ucca ‘e su Peltusu Cave; 15, Rio S’Abba Mala; 16, Rio Mannu di Scano di Montiferro; 17, Rio Santa Caterina; 18, Fiume Tirso; 19, Su Cantaru Spring, Rio di Siniscola basin; 20, Fiume Cedrino; 21, Rio Osalla; 22, Rio Mannu di Milis; 23, Rio di Monte Arci; 24, Fiume Flumendosa; 25, Rio Mannu di Cagliari; 26, Fiume Quirra; 27, Rio Acqua ‘e sa Murta, S. Antioco Island; 28, Rio Triga, S. Antioco Island; 29, Rio ‘e sa Canna, S. Antioco Island; 30, Rio Flumentepido; 31, Rio Gutturu Mannu; 32, Rio Geremeas. New records are indicated by asterisks.