Antonello Mulas

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.

Diet and feeding habits of two skate species, Raja brachyura and Raja miraletus (Chondrichthyes, Rajidae) in Sardinian waters (central‐western Mediterranean)

The diet and inter‐ and intraspecific interactions of two shallow‐water skates, Raja brachyura and R. miraletus, caught at depths between 30 and 162 m during trawl surveys carried out in 2005 and 2006 in the seas surrounding Sardinia (central‐western Mediterranean), were analysed. The low values of Levin and Shannon indexes (Bi = 0.37 and 0.42, respectively, for the former, and H′ = 1.31 and 1.62, respectively, for the latter) showed that these two species are specialized predators. An ontogenetic analysis of the diets of three size groups showed that they adopted similar trophic habits. Young R. brachyura specimens (Bi = 0.27; H′ = 1.05) feed mainly on Crustacea (% IRI = 74) (mainly Mysidiacea and Amphipoda Gammaridea), which were replaced in the diet of medium‐large specimens principally by Osteichthyes (mainly Gymnammodytes cicerelus). Multidimensional scaling analysis indicated a high level of intraspecific competition between medium and large individuals. In R. miraletus, Crustacea represented the main prey in all size groups (% IRI = 99.5, 99.6, and 88, respectively). Amphipoda Gammaridea were the predominant prey for small individuals, and were replaced in medium and large specimens by decapods. Low levels of interspecific competition were generally found.

First record of Chilomycterus reticulatus (Osteichthyes: Diodontidae) in the Mediterranean Sea

The spotfin burrfish Chilomycterus reticulatus (405 mm standard length) is recorded for the first time on the shoreline of the Mediterranean Sea. The adult specimen was found dried on a beach near the south Sardinian Sea (S. Antiocos Island). Photographs and morphometrics of the specimen are given.

Oviducal gland microstructure of Raja miraletus and Dipturus oxyrinchus (Elasmobranchii, Rajidae).

We studied the morphology and histology of the oviducal gland (OG) in the brown ray (Raja miraletus) and the long‐nosed skate (Dipturus oxyrinchus) to understand its functional role in the reproductive strategy of these species. The external morphology of the gland was similar in both species, with lateral extensions like those found in other members of the Rajidae. Microscopic analysis showed a similar internal organization in both species. Immature and developing glands did not react to histochemical techniques. On reaching maturity, the OG had the largest width due to an increase in the production of secretory materials. In both species, the club zone of the gland showed a strong reaction to Periodic acid‐Schiff (PAS) and alcian blue (AB) stains, indicating production of neutral and sulfated acid mucins. The secretory material produced by the papillary zone varied greatly between the two species. Both displayed tubular glands similar to those observed in the club zone, but in D. oxyrinchus the region near the lumen was intensely PAS+, whereas the last row of tubules of the brown ray stained intensely for a mixture of neutral and sulfated mucins. The baffle zone was the most conspicuous and extensive segment of all OGs, and it did not react to PAS/AB. The terminal zone, which is responsible for production of hair filaments, differed between the two species in terms of composition and organization of serous and mucous glands. This difference probably is related to the different substrates in which they release the egg capsules. Individual sperm detected in the brown ray baffle lamellae could be the result of a recent mating, whereas their presence in the deep recesses of the baffle and in the terminal zone of the long‐nosed skate might indicate sperm storage. J. Morphol. 276:1392–1403, 2015.

XX/XY sex chromosome system and chromosome markers in the snake eel Ophisurus serpens (Anguilliformes: Ophichtidae)

ABSTRACT We report evidence of an XX/XY sex chromosome system in the snake eel Ophisurus serpens (Anguilliformes: Ophichthidae). We characterized the male and female karyotypes by C-, replication- and HaeIII-bandings. The 45S and 5S ribosomal gene families were located using dual fluorescence in situ hybridization, which showed that the 5S rDNA sites were present on the X chromosome, beside an autosome pair. FISH with a telomeric peptide nucleic acid probe enabled recognition of Interstitial Telomeric Sequences (ITSs), likely remnants of chromosomal rearrangements, in five chromosome pairs, including the rDNA-bearing ones. Possible mechanisms of the origin of sex chromosomes in this species are discussed, considering the presence of a sex-linked marker and ITSs.

Life‐history traits of the long‐nosed skate Dipturus oxyrinchus

This work investigates life-history traits of the long-nosed skate Dipturus oxyrinchus, which is a common by-catch in Sardinian waters. The reproductive variables were analysed from 979 specimens sampled during scientific and commercial hauls. Females (10·4-117·5 cm total length, LT ) attained larger sizes than males (14·5-99·5 cm LT ). To evaluate age and growth, a sub-sample of 130 individuals (76 females and 54 males) were used. The age was estimated by annuli counts of sectioned vertebral centra. Four models were used for the length-at-age data: the von Bertalanffy, the exponential, the Gompertz and the logistic functions. According to the Akaikes information criterion, the Gompertz model seemed to provide the best fitting curve (L∞ mean ± s.e.: 127·55 ± 4·90 cm, k: 0·14 ± 0·09, IP: 3·97 ± 0·90 years). The oldest female and male were aged 17 (115·5 cm LT ) and 15 years (96·0 cm LT ), respectively. Lengths at maturity were 103·5 cm for females and 91·0 cm for males, corresponding to 90% of the maximum observed length in both sexes. The monthly distribution of maturity stages highlighted an extended reproductive cycle, with spawning females and active males being present almost throughout the year, as confirmed by the gonado-somatic index. Ovarian fecundity reached a maximum of 26 yolked follicles with a mean ± s.e. size of 19·7 ± 6·5 mm.

Amount and distribution of benthic marine litter along Sardinian fishing grounds (CW Mediterranean Sea)

Reports of marine litter pollution first appeared in scientific literature of the early 1970s; yet, more than 40 years later, no rigorous estimates exist of the amount of litter existing in the marine environment. To cope with this global urgency, this study reports the status of marine litter abundance along fishing grounds surrounding the island of Sardinia (CW Mediterranean Sea; FAO Geographical Sub-Area 11) through three years of trawl surveys. A total of 302 hauls, covering a total of 18.4 km2 of trawled surface were carried out in the framework of the MEDITS campaign, at depths comprised between 0 and 800 m. A total of 918 items were collected and sorted, with the highest concentration observed above 200 m depth. Overall, plastic was the dominant component of litter, followed by glass and metal. Comparing our results with other areas from the Mediterranean basin, Sardinian waters showed a lower impact, possibly as a consequence of multiple factors such as the lower human population density and the low flow of the main rivers, among others. In addition, fishermen behaviour with respect to marine litter was investigated by mean of anonymous questionnaires, emphasizing the necessity to further develop management policies and infrastructures supporting litter disposal.

Natural history and molecular evolution of demersal Mediterranean sharks and skates inferred by comparative phylogeographic and demographic analyses

Background The unique and complex paleoclimatic and paleogeographic events which affected the Mediterranean Sea since late Miocene deeply influenced the distribution and evolution of marine organisms and shaped their genetic structure. Following the Messinian salinity crisis and the sea-level fluctuations during the Pleistocene, several Mediterranean marine species developed deep genetic differentiation, and some underwent rapid radiation. Here, we consider two of the most prioritized groups for conservation in the light of their evolutionary history: sharks and rays (elasmobranchs). This paper deals with a comparative multispecies analysis of phylogeographic structure and historical demography in two pairs of sympatric, phylogenetically- and ecologically-related elasmobranchs, two scyliorhinid catsharks (Galeus melastomus, Scyliorhinus canicula) and two rajid skates (Raja clavata, Raja miraletus). Sampling and experimental analyses were designed to primarily test if the Sicilian Channel can be considered as effective eco-physiological barrier for Mediterranean demersal sympatric elasmobranchs. Methods The phylogeography and the historical demography of target species were inferred by analysing the nucleotide variation of three mitochondrial DNA markers (i.e., partial sequence of COI, NADH2 and CR) obtained from a total of 248 individuals sampled in the Western and Eastern Mediterranean Sea as well as in the adjacent northeastern Atlantic Ocean. Phylogeographic analysis was performed by haplotype networking and testing spatial genetic differentiation of samples (i.e., analysis of molecular variance and of principal components). Demographic history of Mediterranean populations was reconstructed using mismatch distribution and Bayesian Skyline Plot analyses. Results No spatial genetic differentiation was identified in either catshark species, while phylogeographic structure of lineages was identified in both skates, with R. miraletus more structured than R. clavata. However, such structuring of skate lineages was not consistent with the separation between Western and Eastern Mediterranean. Sudden demographic expansions occurred synchronously during the upper Pleistocene (40,000–60,000 years ago) in both skates and G. melastomus, likely related to optimal environmental conditions. In contrast, S. canicula experienced a slow and constant increase in population size over the last 350,000 years. Discussion The comparative analysis of phylogeographic and historical demographic patterns for the Mediterranean populations of these elasmobranchs reveals that historical phylogeographic breaks have not had a large impact on their microevolution. We hypothesize that interactions between environmental and ecological/physiological traits may have been the driving force in the microevolution of these demersal elasmobranch species in the Mediterranean rather than oceanographic barriers.

Dumping to the abyss: single-use marine litter invading bathyal plains of the Sardinian margin (Tyrrhenian Sea)

This study reports data on benthic litter abundance, composition and distribution obtained during deep-sea trawl surveys conducted along the Sardinian continental margin down to the bathyal plain, at depths comprised from 740 to 1740 m. None of the investigated sites was litter free. Density ranged from a minimum of 4 to a maximum of >1300 litter items per km2, with a mean value of 258 ± 59 items. Plastic accounted for 56% of the total collected items, followed by glass (24%), metal (10%). Most items, irrespectively of the category, were single-use items. Fish abundance in all of the investigated catches was significantly higher than the number of litter items, the weight of which was similar to the reared fish biomass. Our results confirm that anthropogenic waste has reached the deep Mediterranean Sea, and that the most recent EU legislation banning single-use plastic tools represents a timely and necessary measure.

Ovary development in the deep-sea shrimp Acanthephyra eximia Smith, 1884 in Sardinian waters

We report data regarding the gonad development in females of Acanthephyra eximia Smith, 1884. Specimens were caught during experimental surveys carried out in Sardinian waters between 500 and 1880 m. We employed for our analysis of the ovary development both macroscopic observation and histologic analysis. According to the macroscopic observations, carried out on 491 specimens, six developmental stages of the ovaries were identified. These were validated by histologic analysis, performed on a sample of 10 specimens per stage, that allow us to describe different cell types. A table whith both macroscopic and histologic stages of the female gonad of A. eximia are briefly summarized.