Alessandro Cau

The characterization of Muraena Helena L. mitotic chromosomes: karyotype, C-banding, nucleolar organizer regions, and in situ digestion with restriction endonucleases

We investigated the chromosome complement of Muraena Helena L. using C-banding, nucleolar organizer region silver staining, and restriction endonuclease digestion. We found a diploid number identical to that previously found in other Muraenidae (2n = 42). C-banding revealed the presence of constitutive heterochromatin in the centromeres of all chromosomes as well as in most telomeres of acrocentric chromosomes. Nucleolar organizer regions were detected only on the short arm of chromosome 7. Digestion with either HaeIII, MboI, or DdeI restriction endonucleases produced a clearcut, specific banding pattern for each enzyme and indicated the existence of at least two different classes of highly repetitive DNAs. The short arm of chromosome 7 varied in size and staining characteristics.

Distribution and assessment of marine debris in the deep Tyrrhenian Sea (NW Mediterranean Sea, Italy).

Marine debris is a recognized global ecological concern. Little is known about the extent of the problem in the Mediterranean Sea regarding litter distribution and its influence on deep rocky habitats. A quantitative assessment of debris present in the deep seafloor (30-300 m depth) was carried out in 26 areas off the coast of three Italian regions in the Tyrrhenian Sea, using a Remotely Operated Vehicle (ROV). The dominant type of debris (89%) was represented by fishing gears, mainly lines, while plastic objects were recorded only occasionally. Abundant quantities of gears were found on rocky banks in Sicily and Campania (0.09-0.12 debris m(-2)), proving intense fishing activity. Fifty-four percent of the recorded debris directly impacted benthic organisms, primarily gorgonians, followed by black corals and sponges. This work provides a first insight on the impact of marine debris in Mediterranean deep ecosystems and a valuable baseline for future comparisons.

Persistence of Pristine Deep-Sea Coral Gardens in the Mediterranean Sea (SW Sardinia)

Leiopathes glaberrima is a tall arborescent black coral species structuring important facies of the deep-sea rocky bottoms of the Mediterranean Sea that are severely stifled by fishing activities. At present, however, no morphological in vivo description, ecological characterization, age dating and evaluation of the possible conservation actions have ever been made for any population of this species in the basin. A dense coral population was reported during two Remotely Operated Vehicle (ROV) surveys conducted on a rocky bank off the SW coasts of Sardinia (Western Mediterranean Sea). L. glaberrima forms up to 2 m-tall colonies with a maximal observed basal diameter of nearly 7 cm. The radiocarbon dating carried out on a colony from this site with a 4 cm basal diameter revealed an approximately age of 2000 years. Considering the size-frequency distribution of the colonies in the area it is possible to hypothesize the existence of other millennial specimens occupying a supposedly very stable ecosystem. The persistence of this ecosystem is likely guaranteed by the heterogeneous rocky substrate hosting the black coral population that represents a physical barrier against the mechanical impacts acted on the surrounding muddy areas, heavily exploited as trawling fishing grounds. This favorable condition, together with the existence of a nursery area for catsharks within the coral ramifications and the occurrence of a meadow of the now rare soft bottom alcyonacean Isidella elongata in small surviving muddy enclaves, indicates that this ecosystem have to be considered a pristine Mediterranean deep-sea coral sanctuary that would deserve special protection.

Improving the Conservation of Mediterranean Chondrichthyans: The ELASMOMED DNA Barcode Reference Library

Cartilaginous fish are particularly vulnerable to anthropogenic stressors and environmental change because of their K-selected reproductive strategy. Accurate data from scientific surveys and landings are essential to assess conservation status and to develop robust protection and management plans. Currently available data are often incomplete or incorrect as a result of inaccurate species identifications, due to a high level of morphological stasis, especially among closely related taxa. Moreover, several diagnostic characters clearly visible in adult specimens are less evident in juveniles. Here we present results generated by the ELASMOMED Consortium, a regional network aiming to sample and DNA-barcode the Mediterranean Chondrichthyans with the ultimate goal to provide a comprehensive DNA barcode reference library. This library will support and improve the molecular taxonomy of this group and the effectiveness of management and conservation measures. We successfully barcoded 882 individuals belonging to 42 species (17 sharks, 24 batoids and one chimaera), including four endemic and several threatened ones. Morphological misidentifications were found across most orders, further confirming the need for a comprehensive DNA barcoding library as a valuable tool for the reliable identification of specimens in support of taxonomist who are reviewing current identification keys. Despite low intraspecific variation among their barcode sequences and reduced samples size, five species showed preliminary evidence of phylogeographic structure. Overall, the ELASMOMED initiative further emphasizes the key role accurate DNA barcoding libraries play in establishing reliable diagnostic species specific features in otherwise taxonomically problematic groups for biodiversity management and conservation actions.

Homing and orientation of Palinurus elephas (Fabricius) in three no-take areas of the central-western Mediterranean: implications for marine reserve design

The homing and orientation skills of Palinurus elephas were investigated in three no-take areas of the central-western Mediterranean in order to inform future reserve design. In general, P. elephas did not show a particular ability to orient homeward. A considerable portion of tagged lobsters were recaptured in the same direction as the capture point but, the points of capture and recapture were at such a distance from each other as to exclude any possible return to the original den. Homing ability seemed to be constrained to where lobsters were only displaced a short distance. For distances longer than 0.5km, the lobster movements seem to become nomadic, without a particular direction. The movement pattern suggests that it will be important that any restocking of marine reserves must be performed with lobsters collected in adjacent zones at distance more than 0.5km. Lobsters captured in a fishing zone <0.5km outside the reserve will return to the point of capture whilethose collected from further away will not go back to their original place. Our results indicate that, for species like P. elephas, small reserves can protect most small subpopulations with a consequent benefit for the surrounding commercial areas.

Habitat constraints and self-thinning shape Mediterranean red coral deep population structure: implications for conservation practice.

The Mediterranean red coral, Corallium rubrum, is one of the most precious corals worldwide. Below 50 m depth, C. rubrum populations are generally characterised by large and sparse colonies, whereas shallow populations (above 50 m depth) show high densities of small colonies. We show here instead that populations dwelling between 80 and 170 m depth exhibited a continuous range of population density (from 2 to 75 colonies per 0.25 m2), with less than 1% of variance explained by water depth. An inverse relationship between maximum population density and mean colony height was found, suggesting that self-thinning processes may shape population structure. Moreover, demographically young populations composed of small and dense colonies dominated along rocky vertical walls, whereas mature populations characterised by large and sparsely distributed colonies were found only in horizontal beds not covered by sediment. We hypothesise that, in the long term, shallow protected populations should resemble to present deep populations, with sparsely distributed large colonies. Since the density of red coral colonies can decay as a result of self-thinning mechanisms, we advise that future protection strategies should be based also on a measure of red coral spatial coverage instead of population density.

Replication banding in two Mediterranean moray eels: chromosomal characterization and comparison

Early and late replication bandings have been obtained by in vitro BrdU incorporation in the Mediterranean Muraenidae species Muraena helena and Gymnothorax unicolor, and used to characterize their karyotypes. A comparative analysis of the banding patterns allowed to point out high karyotype similarity as well as chromosome rearrangements that occurred in karyotype evolution between these species.

Genetic characterization and artificial reproduction attempt of endemic Sardinian trout Salmo trutta L., 1758 (Osteichthyes, Salmonidae): Experiences in captivity

Abstract Native species of Sardinian brown trout (Salmo trutta) have declined drastically because of the introduction of non-native salmonids, overharvesting, and habitat degradation. One approach to conservation of declining species is to establish new populations through repopulation with genetically certified fish. In this study, samples of brown trout from seven rivers in Sardinia were analysed to look for the presence of pure individuals of the endemic Sardinian trout. Analyses of the mitochondrial DNA control region and the LDH-C1* gene revealed the presence of non-endemic and hybrid individuals in four of the seven rivers analysed. In addition, we reared a stock of native Sardinian trout at the experimental fish farm of Sadali and had them reproduce artificially. This experiment provided more knowledge about the incubation phase, hatching, reabsorption of the vitelline sac and the initial phases of growth, which can be used to develop more optimal management of this resource.

Deep-water red coral from the island of Sardinia (north-western Mediterranean): a local example of sustainable management

Since 1979, red coral harvesting in Sardinia has been regulated by regional laws. The regulations, including a minimum take size of 10-mm basal diameter, were imposed to limit and control harvesting. Our study indicated that >75% of the red coral colonies harvested in 2007–08 in the north-western coast were above the legal minimum size for exploitation. Moreover, extensive surveys with remotely operated vehicles allowed us to document the real structure of wild populations. Large colonies (>10 mm) represented a big portion of the population (~38% of the total), suggesting that harvesting effort did not affect yet the maximum size of colonies. All these results seem to be confirmed by the application of the model of Beverton and Holt. This model shows that the fishery of red coral in Sardinia reaches its maximum yield at an age at first capture of 20 years, an age significantly lower than the average age of 30 years calculated for the colonies actually harvested in the Sardinian coast. Our data confirmed that the measures enacted in the Sardinian regulations provide for an adequate management of this resource and, in addition, can represent a guideline for other countries that still lack a valid management plan.

Reproduction strategy of the deep-sea hermit crabs Pagurus alatus and Pagurus excavatus of the Central-Western Mediterranean Sea

Some aspects of the reproductive biology of two hermit crabs Pagurus alatus (Fabricius, 1775) and P. excavatus (Herbst, 1791) were studied. Specimens were collected monthly from April 2000 to March 2001 on the continental shelf and the upper-middle slope off the Southwestern coasts of Sardinia, in the central-western Mediterranean Sea. Crab size (minimum and maximum shield length) was 1.7 and 9.5 mm for 1150 females of P. alatus; 4.0 and 10.4 mm for 347 females of P. excavatus, respectively. Females of P. alatus with ripe ovaries were only found in February-April and ovigerous females were observed throughout the year except in March, with the highest incidence in summer. Females of P. excavatus with fully developed ovaries were collected during all months of the year reaching a peak from April to June. Ovigerous females of P. excavatus occurred throughout the year and the main spawning period occurred in March and April. Fecundity of both species was calculated to assess seasonal variation of reproductive intensity and was positively correlated with the size of the individuals. Monthly fecundity did not reveal significant differences in P. alatus ovigerous females, whereas P. excavatus exhibited significant differences in monthly fecundity depending on the time of year. Difference in fecundity among P. alatus and P. excavatus can be related to the size of the ovigerous females and species of hermit crab, but their different reproductive strategies suggest that they are specifically related to different environmental conditions.