Cristina Porcu

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.

Gonad development of the deep-sea lobster Polycheles typhlops (Decapoda: Polichelidae) from the Central Western Mediterranean

Abstract In this paper, we report data related to the reproductive biology of a cosmopolitan mesobathyal lobster, Polycheles typhlops (Decapoda: Polychelidae), caught in the Sardinian waters between 400 and 1400 m of depth. Macroscopic and microscopic analyses were performed on 1104 females and 895 males. The observation on the gonads leads us to conclude that there are seven and four stages of development for the females and for males, respectively. Monthly variations of the percentage distribution related to various stages of development of the ovary and the presence of ovigerous females indicated that the species does not seem to follow a marked seasonal reproductive model, with a long main period for egg hatching that seems to occur between spring and autumn.

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.

Gonad Development and Reproduction in the Monoecious Species Chlorophthalmus Agassizi (Actinopterygii: Aulopiformes: Chlorophthalmidae) from the Sardinian Waters (Central-Western Mediterranean)

The shortnose greeneye, Chlorophthalmus agassizi Bonaparte, 1840, is a circumglobal species found in temperate and tropical regions. This species is distributed in the Western Atlantic from Canada to northern South America, in the Eastern Atlantic from Spain to Senegal, and in the Mediterranean Sea (Bini 1970, Robins and Ray 1986, Scott and Scott 1988). Young stages are pelagic, living near the surface, while the adults are demersal, near the mud and clay bottoms, at the 50 to 1000 m depth range, mainly between 350 and 450 m (Fischer et al. 1987). C. agassizi lives between 150 m and 700 m in the Italian seas (Relini et al. 1999). Recently, it has been caught between 70 m to 1163 m in the South Sardinian waters (Follesa et al. 2010). The knowledge of the biology of C. agassizi is poor out of the Mediterranean Sea. Mead (1959) observed an adult specimen captured in the Gulf of Mexico indicating that this species is monoecious and the gonad appears in the form of a combined gonad (ovotestis), with neither component mature. In the Mediterranean, although in some areas, such as the Sardinian and Sicilian seas, it is among the most abundant commercial fish (Cau and Mura 1978, Relini et al. 1999, Follesa et al. 2004b) few studies have been carried out. These studies are mainly related to distribution, population structure, life strategies (Anastasopoulou et al. 2006, D’Onghia et al. 2006) and diet in the Ionian Sea, the Aegean Sea, and Sardinian waters (Kabasakal 1999, Cabiddu et al. 2005, Anastasopoulou and Kapiris 2007). In Sardinian seas, some aspects of the reproductive biology of C. agassizi, based only on histological criteria, such as the identification of oocyte and male sex cells were studied by Follesa et al. (2004a). ACTA ICHTHYOLOGICA ET PISCATORIA (2010) 40 (2): 167–177 DOI: 10.3750/AIP2010.40.2.10

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.

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.

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.