Bruno Sabelli

Rapid miocene-pliocene dispersal and evolution of Mediterranean rajid fauna as inferred by mitochondrial gene variation.

Rajidae (colloquially known as skates and rays) experienced multiple and parallel adaptive radiations allowing high species diversity and great differences of species composition between regional faunas. Nevertheless, they show considerable conservation of bio‐ecological, morphological and reproductive traits. The evolutionary history and dispersal of North‐east Atlantic and Mediterranean rajid fauna were investigated throughout the sequence analysis of the control region and 16S rDNA mitochondrial genes. Molecular estimates of divergence times indicated recent origin and rapid dispersal of the present species. Compared with the ancient origin of the family (Late Cretaceous), the present species diversity arose in a relatively narrow time‐window (12 Myr) from Middle Miocene to Early Pleistocene, likely by speciation processes related to dramatic geological and climatic events in the Mediterranean. Nucleotide substitution rates and phylogenetic relationships indicated Mediterranean endemic skates derived from sister species with wider distribution during Late Pliocene–Pleistocene. Skate phylogeny and systematics obtained using mitochondrial gene variation were largely consistent with those based on morpho‐anatomical data.

Development of molecular and morphological markers to improve species-specific monitoring and systematics of Northeast Atlantic and Mediterranean skates (Rajiformes)

The Northeast Atlantic and Mediterranean skates (Rajidae) showed remarkable species diversity but with high morphological and ecological conservatism. Since skates are particularly vulnerable to the bottom trawl fishery, species-specific demographic surveys as well as studies defining life history and evolutionary traits are important in prioritising conservation programs. However, the identification of juveniles and adults of some species may be difficult using referenced guidelines and identification keys. Therefore, we attempt to develop markers for species identification through the parallel analysis of a 16S rDNA gene sequence and of several morphological characters on 135 individuals collected by trawl surveys in the Adriatic Sea and putatively assigned to six taxa. Species-specific haplotypes were defined for Raja miraletus, Raja montagui, Dipturus oxyrinchus, since a solid accordance between species boundaries and well-differentiated haplotypes was observed. Comparative analysis of 16S rDNA sequences allowed the identification of three juvenile specimens of Leucoraja circularis, a species that rarely occurs in the Adriatic Sea. On the contrary, morphological traits and haplotype distribution were largely discordant in Raja asterias and R. clavata. While all putative R. clavata individuals showed a unique haplotype (H-CLA), only 8 of 30 putative R. asterias individuals possessed a second weakly divergent haplotype (H-AST). The remaining 22 R. asterias carried the H-CLA. The multivariate analyses of morphometric and meristic characters in putative R. clavata and R. asterias revealed the clustering of individuals regardless of haplotypes. However, a bimodal distribution of R. asterias and R. clavata samples would suggest that two separated taxa might exist, both sharing the two 16S rDNA haplotypes. The haplotype distribution appeared to be significantly correlated only to the standardised disc length/total length (DL/TL) variation. Three alternative explanations may support this scenario: (i) an incomplete lineage sorting process in two morphologically yet distinct taxa; (ii) a recent hybridisation between the two taxa; (iii) the two taxa are morphologically plastic species and all considered morphological characters may be misleading in discriminating between them at all maturity stages, except for the DL/TL. However, further analyses on larger data sets and using molecular key markers (i.e. nuclear genes) will be needed to definitely resolve the status of these taxa. Molecular relationships among rajid taxa are largely consistent with systematics based on internal and external anatomical features. This multidisciplinary study contributed to defining the pattern of species diversity and abundance of rajids in the Adriatic Sea.

On the identity and origin of Anadara demiri (Bivalvia: Arcidae)

Anadara demiri (Piani, 1981) is an alien species in the Mediterranean Sea extending its range from Turkey westernly to the Adriatic Sea, where it is locally abundant. The species was first identified as Arca amygdalum Philippi, 1847 in the 1970s. The locus typicus of A. amygdalum is China. This first identification has never been discussed and the species has been thought to be of Indo-Pacific origin to date. However, in the Indo-Pacific province no Anadara shows any similarity with A. demiri. Morphological and molecular data suggest A. demiri is closely related to Anadara transversa (Say, 1822), a common species of the eastern coasts of North America. Anadara demiri is hence considered a junior synonym of A. transversa and the origin of this immigration has to be searched in the southern range of this species, maybe the Gulf of Mexico coasts of Florida.

Reproductive biology and substitution of two species of Nassariidae

Reproductive biology of Nassarius reticulatus is well known, but informations about Nassarius mutabilis are scarce; we have so undertaken a macroscopical and histological study to clear the reproductive biology of this species.

Comparative aspects of habenulae in some species of Chondrohycthes and Ostehycthes

Diencephalic habenular nuclei of several species of Chondrohycthes and Ostehycthes fishes were investigated in order to ascertain their asymmetry. Raja asterias, Squalus acanthias, Mustels mustelus, Scyliorhinus canicula and Scyllium stellare show the left habenula larger than the right, as occurs in the elasmobranchs till now investigated. Among the six species of teleostean fishes we studied, the habenulae of Liza aurata, Anguilla anguilla and Trisopterus minutus are symmetrical, while in Lepidorhombus boscii, Platichthys flesus and Solea vulgaris the habenulae are slightly asymmetrical. This finding might suggest a relation, to be better investigated, among bentic life and habenular asymmetry in teleostean.

Osservazioni sull'ultrastruttura della parete della gonade di Goniodiscus rotundatus (Gasteropodi, Polmonati)

Abstract The wall of the gonad of Goniodiscus rotundatus, according to ultrastructural observations, may be subdivided in functional unities similar to the acina of Limnaea stagnalis. Every U shaped functional unity has cuboidal cells (cells 1) at the proximal ends, and flattened cells (cells 2) at the bottom. The transitional zone between the two cells types is just the same as the “germinal epithelial ring”. Ultrastructural study confirms the subdivision of the gonad in a series of periferically located female compartments and a central male one, which are separated by “somatic” cells.

Il genere Chiton in Mediterraneo, osservazioni al microscopio elettronico a scansione

Abstract Some doubtful taxonomic structure of three mediterranean species of the Genus Chiton (C. olivaceus, C. corallimts and C. phaseolinus) are comparatively examined by means of scanning electron microscope. Radula and aesthetes show rather uniform morphology and so are useless as diagnostic features. Only the upper scales of the girdle appear different enough to be considered an useful character in taxonomic studies.