G. Gandolfi

Breeding ecology and male spawning success in two hill-stream populations of the freshwater goby, Padogobius martensi

SynopsisThis investigation was carried out at two study sites to examine the influence of shelter availability, nest site quality and male body size on spawning success of malePadogobius martensi. At Stirone Stream (first study site) individuals were not randomly distributed with respect to usable stones; larger males and females were consistently found to occupy larger stones. Laboratory experiments showed that the bottom surface area of the shelter was the relevant cue for the choice. The number of nesting males settled in a given area increased with increasing availability of local stone cover; inter-nest distance was directly correlated with male size. At Rivarolo Stream (second study site), which was characterized by lower nest density and a greater shortage of large stones, the pattern of shelter occupation was similar. These results suggest the presence of competition among individuals for the possession of larger-sized shelter sites. At both sites, the number of eggs in the nest increased as stone size increased; however, at the first study site, male body size played a major role in male spawning success as it concerns both the numbers of females mated and the number of eggs, while at the second study site, male body size was not shown to influence male spawning success. Factors responsible for between-site differences in male spawning success are discussed.

A quantitative analysis of the occurrence of visual and acoustic displays during the courtship in the freshwater goby, Padogobius martensi (Günther, 1961) (Pisces, Gobiidae)

Abstract Seventeen pairs of Padogobius martensi were observed to compare the relative occurrence of the acoustic and visual displays performed by the male during courtship. The results show that the visual display, which gradually decreases when the male approaches the nest, is the main signal to orient and attract the female towards the males nest; sound production, on the other hand, becomes more frequent when the male approaches and enters his nest. So, the acoustic signal has an important role when the visual one becomes ineffectual, when the male is hidden in the shelter. Visual and acoustic signals seem to have a complementary role and the male P.martensi uses the most effective signal in each particular situation.

Molecular phylogeny of the blind cavefish Phreatichthys andruzzii and Garra barreimiae within the family Cyprinidae

The phylogenetic relationships of two cavefish, Phreatichthys andruzzii and Garra barreimiae, belonging to the family Cyprinidae, were investigated by sequencing the mitochondrial cytochrome b gene. These cavefish species are native to Somalia (eastern Africa) and Oman (southeastern Arabian peninsula), respectively, and so far no molecular support to their taxonomy and phylogenetic position was ever provided. The analysis of cytochrome b sequences showed that the species are monophyletic taxa, closely related to each other and to other species of the genus Garra. Molecular clock calculations allowed to date the origin of these hypogaean species back to the Plio-Pleistocene and support the hypothesis that African cyprinids originated from Miocenic immigrations of Asian ancestors.

Mitochondrial DNA variability in Anguilla anguilla and phylogenetical relationships with congeneric species

Abstract To obtain genetic molecular markers, valuable for the explanation of intraspecific variability, we have sequenced and compared a region of the mitochondrial cytochrome b (Cyt‐b) of seven European eels, Anguilla anguilla (L.), from four different Italian sites. The alignment of the seven sequences shows the existence of 14 variable sites, due to nucleotidic substitutions which are evolutively neutral. Alignment of the A. anguilla Cyt‐b sequences with the corresponding sequences from A. rostrata and A. japonica (both available in the EMBL DNA database) identifies some interspecific differences. A phylogenetic analysis by the neighbour‐joining method clearly confirms the genetic separation and the monophyletic origin of the three species. Six and twenty base substitutions, which are common to all the samples of A. anguilla, can be diagnostic candidates for the interspecific differences of this species with A. rostrata and A. japonica, respectively.

Mitochondrial DNA sequences in three genera of Italian lampreys

Abstract The genetic diversity obtained by comparing mitochondrial DNA regions (the slowly evolving protein‐coding gene cytochrome b and the tRNAGlu gene) of three lamprey species belonging to different genera, Petromyzon marinus, Lethenteron zanandreai, and Lampetra planeri, is reported. The low degree of intergeneric variability detected, as compared with differences described for other fish taxa, supports the view of a recent evolutive separation of both Lethenteron and Lampetra from Petromyzon.

Social learning in non-primate animals

(1975). Social learning in non-primate animals. Bollettino di zoologia: Vol. 42, No. 4, pp. 311-329.

Ascent of elvers, Anguilla anguilla (L.), and prospects for their use in aquaculture

Abstract An overall picture of the European elvers behaviour during coastward migration and entrance into inland waters emerges from a survey of the literature. The factors influencing trophic migration are discussed. In particular, the data relevant to the Mediterranean area are taken into account. The observations by the authors over the course of one year at the outlet of the River Arno confirm that the behaviour of elvers there is similar to that described for the North Atlantic coast. The ascent of the elvers at the sampling point (located approximately 1100 m upstream from the outlet) is greater in the hours immediately following sunset. A clear-cut influence upon the amount of the ascent is due to tidal movements, and catches are larger after the peaks registered with flood tide. Temperature of the waters appears to have some effect, but no fluctuations in the ascent are attributable to the flow of the river and to the phases of the moon. The increase in the demand for elvers to replace stocks and...

Feeding habits of mullet fry in the Arno River (Tyrrhenian coast). I. Daily feeding cycle

Abstract The daily feeding rhythms of five species of mullet fry (Liza ramada, Liza aurata, Liza saliens, Mugil cephalus and Chelon labrosus) were investigated by analyzing their stomach fullness during 24‐hour cycles. Light is the major abiotic factor influencing the feeding rhythm of the fry. Feeding activity occurs prevalently during day‐time with a clear unimodal feeding cycle. Only L. saliens fry show a bimodal feeding cycle, with a secondary peak around sunset. Differences in the feeding activity rhythm are probably due to larger individuals which, unlike the smaller individuals, show preferential twilight feeding. Tides and temperature play a secondary role and their influence is probably masked by the light effect.

Phylogenetic relationships among two Atlantic and three Indo‐Pacific Anguilla species (Osteichthyes, Anguillidae)

Abstract Mitochondrial DNA (mt‐DNA) of three eel species (the Atlantic eels Anguilla anguilla and A. rostrata, and the African eel A. mossam‐bica), was sequenced and compared with mt‐DNA of other Indo‐Pacific eels (A. japonica and A. marmorata, obtained from the EM‐BL data library), with the aim of analysing their phylogenetic relationships. Maximum parsimony analysis of 475 bp alignable sequences (partial Cyt‐b, tRNAThr and tRNAPro) showed a single most parsimonious tree, which was in agreement with the phylogeny ex pected on the basis of their breeding grounds distribution. UPGMA analysis resulted in a similar tree. Pairwise comparison of the se quences confirmed te genetic separation of the Atlantic species and showed a small evolutive distance between them. Nucleotide diver sities between Indo‐Pacific species equaled the diversities between these and the two grouped Atlantic species, suggesting that the three Indo‐Pacific species could have had an evolutive origin almost con temporary with a common an...

RE-DESCRIPTION OF THE EXTERNAL MORPHOLOGY OF SOMNIOSUS ROSTRATUS (RISSO, 1826), WITH SPECIAL REFERENCE TO ITS SQUAMATION AND CUTANEOUS SENSORY ORGANS, AND ASPECTS OF THEIR FUNCTIONAL MORPHOLOGY (PISCES SELACHII SQUALIDAE)

SUMMARY The availability of a new S. rostratus (Risso, 1826) specimen (Pisces Selachii Squalidae), the re-examination of two museum collections and a survey of literature on the subject has provided the opportunity to clarify some problems concerning this shark and other species of the genus Somniosus. The main topics investigated were morphometric characters, squamation morphogenesis, distribution of cutaneous sensory organs and modified scales. Morpho-functional problems are discussed, with special reference to hydrodynamic aspects. The little sleeper, S. rostratus, has a typical squaloid morphology. In all ontogenetic stages, a peculiar short keel occurs in the caudal peduncle, above the ventral hypochordal lobe. The function of the keel could be to improve turning ability and/or to act as a stabilizer. The caudal morphology belongs to the squaloid type (THOMSON & SIMANEK, 1977) and differs from that of the strictly benthic species. On this basis we therefore believe that S. rostratus is a benthopelagi...