Angelo Cau

Relationship of feeding, reproductive cycle and bathymetric distribution in Conger conger

A study on the alimentary ethology of conger eels was carried out over a period of four years. Individuals were captured at a depth ranging from 10 to 800 m. The parameters analysed lead to the following observations: (a) in the Central Mediterranean basin the feeding of Conger conger (L.) populations was mainly based on Osteichthyes, Crustacea and Cephalopoda; (b) the neritic population fed on a higher number of species than the epimesobathyal. The high percentage of empty stomachs in the bathyal population was due to the fact that the neritic females, at the end of trophic phase, set out on a reproductive migration towards the bathyal level.

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.

Population structure, demographic history, and selective processes: Contrasting evidences from mitochondrial and nuclear markers in the European spiny lobster Palinurus elephas (Fabricius, 1787)

The European spiny lobster Palinurus elephas (Fabricius, 1787) is an ecologically and economically important species inhabiting a wide geographic range that extends from the North-east Atlantic and Azores to the Eastern Mediterranean. We investigated the population structure and evolutionary history of this species by both mitochondrial and microsatellite markers. Ten population samples covering a large part of the species distribution range (three samples from the Atlantic Ocean and seven from the Mediterranean Sea) were analyzed for a portion of the mitochondrial control region and seven polymorphic microsatellite loci. Both markers rejected the hypothesis of panmixia identifying two differentiated gene pools. The control region clearly distinguished the Atlantic and Mediterranean populations in two genetically separated groups. Microsatellites, also revealed two groups roughly associated to the Atlantic-Mediterranean separation, however, the Azores sample did not conform to this geographic scheme. Discrepancy between mitochondrial and nuclear markers emerged also when reconstructing the history of the species. Neutrality tests of the mitochondrial sequences indicated a departure from mutation-drift equilibrium that, combined to the mismatch analysis, pointed toward a sudden population expansion in both Atlantic and Mediterranean gene pools. Unexpectedly, microsatellites did not identify any signal of population expansion neither in the Atlantic pool nor in the Mediterranean one.

Major and 5S ribosomal sequences of the largemouth bass Micropterus salmoides (Perciformes, Centrarchidae) are localized in GC-rich regions of the genome

Major and 5S ribosomal genes have been localized in the chromosomes of Micropterus salmoides. By C-banding, Ag-staining, CMA3-staining and 45S and 5S fluorescence in-situ hybridization (FISH), we demonstrate that the 45S and 5S ribosomal genes are clustered in two different chromosome pairs and both are located in heterochromatic GC-rich regions. PCR amplification and sequencing of the 5S intergenic non-transcribed sequences have allowed us to identify variability essentially due to a trinucleotide tandem repeat (GCT).

Analyses of Nuclear ldhA Gene and mtDNA Control Region Sequences of Atlantic Northern Bluefin Tuna Populations

There has been considerable debate about whether the Atlantic northern bluefin tuna exist as a single panmictic unit. We have addressed this issue by examining both mitochondrial DNA control region nucleotide sequences and nuclear gene ldhA allele frequencies in replicate size or year class samples of northern bluefin tuna from the Mediterranean Sea and the northwestern Atlantic Ocean. Pairwise comparisons of multiple year class samples from the 2 regions provided no evidence for population subdivision. Similarly, analyses of molecular variance of both mitochondrial and ldhA data revealed no significant differences among or between samples from the 2 regions. These results demonstrate the importance of analyzing multiple year classes and large sample sizes to obtain accurate estimates when using allele frequencies to characterize a population. It is important to note that the absence of genetic evidence for population substructure does not unilaterally constitute evidence of a single panmictic population, as genetic differentiation can be prevented by large population sizes and by migration.

Community structure of the decapod crustaceans in the middle bathyal zone of the Sardinian Channel

A series of experimental catches between 500 and 1050 m was carried out in the Sardinian Channel (mid-western Mediterranean sea) to obtain information on the distribution of several species of decapod crustaceans. The collections were made by bottom trawls in two different periods, summer and winter, during the years 1989, 1990, and 1991. Forty-seven species of Decapoda were collected. The most common species caught in all the strata examined are Aristeus antennatus, Plesionika martia, P. acanthonotus, and Polycheles typhlops. Acanthephyra eximia and Cymonomus granulatus have been caught in this area for the first time. Thirty-four percent of the species show a seasonal variation in bathymetric distribution. Below 650-700 m the species-composition changes and the number of species decreases. RIASSUNTO

SIZE AT SEXUAL MATURITY OF THE SPIDER CRAB ANAMATHIA RISSOANA (DECAPODA: MAJOIDEA) FROM THE SARDINIAN SEA

Abstract This study relates to the size at morphological and physiological sexual maturity of the deep sea crab Anamathia rissoana. Between August 1997 to July 2000, 469 specimens were collected at depths of between 400 and 620 m off the western coast of Sardinia (Mediterranean Sea). On the basis of cheliped morphology, the males were classified into three demographic categories: immature, adolescent, or adult. In addition, a discriminant function analysis was performed in order to classify the males (post hoc prediction) using the biometric data relating to the four distal segments of the endopod of the right cheliped. For the females, only two demographic categories were detected: juvenile females with flat abdomen and adult females with domed abdomen. Morphological maturity was estimated from the allometric relationships between carapace width and propodus length in males or maximum abdomen width in females. For both sexes, allometric relationships were established in the specimens of each of the demographic categories. Physiological maturity was determined by observing testes or ovary size, colour, morphology, and development. Functional maturity was presumed to be the minimum size at which each sex was morphologically and physiologically able to reproduce. In males, the size at physiological maturity was clearly earlier than the size at morphological maturity, unlike in females where such values were similar.

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.

Egg clutch, sperm reservoirs and fecundity of Neorossia caroli (Cephalopoda: Sepiolidae) from the southern Sardinian sea (western Mediterranean)

First observations on reproduction of Neorossia caroli from the southern Sardinian sea are reported, based on the analyses of an egg clutch and specimens collected by bottom trawl on sandy and muddy grounds. The egg clutch, consisting of 13 white eggs of 9 mm length with embryos at an advanced developmental stage, was found at 1200 m depth, attached to a piece of hard substrate. Adult specimens were collected in a depth range between 400 and 1600 metres. DNA sequences indicated that embryos, spermatangia and adults belonged to the same species, the carol bobtail squid, N. caroli. Fecundity analysis made on 40 females showed a variable number of eggs (20-611) in the ovaries, with the combined presence of advanced and developing oocytes, and few smooth eggs ready to be spawned in the oviducts of mature females. Several sperm reservoirs (spermatangia) were embedded in the mantle of some of the females, in the anterior ventral area overlying the oviduct.