Salvatore Casu

The freshwater planarian Dugesia sicula Lepori from Sardinia (Platyhelminthes, Tricladida)

Fissiparous strains of freshwater triclads of the Dugesia gonocephala group were collected from 12 localities in Sardinia all situated not more than 5 kilometers from the coast. Some environmental factors and the sexual status of the specimens were noted at the time of collection. During the laboratory rearing 30% of individuals of each strain became sexual (ex-fissiparous individuals). All the examined strains showed common karyological and morphological characteristics suggestive of the species Dugesia sicula Lepori. The chromosome complement, which was a constant 27+2–3 B chromosomes, was classified as aneutriploid, due to its clearly documented characteristics. The fissiparous populations of D. sicula appear to have a high degree of tolerance to variations in environmental factors, especially temperature. Within the D. gonocephala group this species has the broadest distribution in the Mediterranean region.

A new species of freshwater planarian belonging to the genus Dugesia (Platyhelminthes, Tricladida) from Sardinia

Abstract Dugesia leporii sp. n. from SW Sardinia is described. It is characterised by a comparatively small copulatory apparatus, the shape of the penial papilla, and the course and opening of the ejaculatory duct. The penial papilla, which has a penial valve, protrudes into an undivided atrium and is not provided with accessory structures. The taxonomic position of the new species within the D. gonocephala group is discussed.

African planarians: Morphology and karyology of Dugesia maghrebiana sp. n. (Platyhelminthes, Tricladida) from Tunisia

Extensive surveys were made of Tunisian freshwaters, yielding freshwater planarians at only one locality in southeastern Tunisia, representing a new species. Dugesia maghrebiana sp. n. is characterized by the presence of the following features: ventral course of the ejaculatory duct, terminal opening of the ejaculatory duct, double diaphragm, symmetrical openings of the oviducts into the bursal canal, and by a typical condition of mixoploidy with a double aneuploidic chromosome complement. The taxonomic position of the new species is discussed in relation to other African and Mediterranean species.

Endemic freshwater planarians of Sardinia: Redescription of Dugesia hepta (Platyhelminthes, Tricladida) with a comparison of the Mediterranean species of the genus

The endemic freshwater planarian Dugesia hepta from Sardinia was described mainly by karyology and karyotype analysis and by geographic distribution. The present paper reports on the detailed morphological study of the copulatory apparatus and highlights the fact that the exclusive diagnostic characters of D. hepta are the shape of the penis papilla, the course and opening of the ejaculatory duct and the openings of the shell glands. A neotype is designated on the basis of a detailed description, and the geographic range of the species is better defined. The two phylogenetically important traits represented by the course and opening of the ejaculatory duct show an unknown condition in the genus Dugesia, diverging from the typical one displayed by the other 69 species. A comparative analysis of morphological traits of the 20 Mediterranean species of the genus Dugesia was made.

Karyology and karyotype analysis of diploid freshwater planarian populations of the Dugesia gonocephala group (Platyhelminthes, Tricladida) found in Sardinia

Karyology and karyotype analysis were carried out on freshwater planarian populations of the Dugesia gonocephala group. The strains studied were all diploid with chromosomic number 2n = 16; n = 8. They came from 12 sites mainly localized on the west of the island of Sardinia. Three karyotypes indicated with the letters A, B and C were found in which eight homomorphic pairs of chromosomes were easily identified. In karyotype A all chromosomes are metacentric. Ten populations of the twelve examined showed this karyotype which appears to be the most common. In karyotype B the seventh pair of chromosomes is submetacentric. This karyotype is quite common having been previously found in another eight Sardinian localities. Karyotype C differs from the others in having submetacentric third and seventh pairs of the chromosome complement. It was found in only one locality. The differences observed between these three karyotypes could be interpreted either as sign of differentiation at species level, or as an intraspecific variation due to chromosome mutations (pericentric inversions).

Chromosomes and genetic organization of rdna in planarians of the genus schmidtea (platyhelminthes, tricladida)

Abstract The genus Schmidtea includes four planarian species characterized by karyological differentiation. Different levels of ploidy also define various biotypes, typically associated with sexual or pseudogamic forms of reproduction. The present paper gives a karyological survey of somatic cells and unfertilized oocytes of specimens collected from natural populations. With the aim of integrating classical karyological analyses with molecular data, the molecular structure of ribosomal DNA (rDNA), in individuals of different species and biotypes is also compared, using restriction enzyme analysis. The results reveal the presence of species‐specific rDNA restriction patterns. In spite of the occurrence of poly‐ploid forms, a high level of structural intraspecific homogeneity of these genes was also observed among different populations.