Ontogenetic change in the body length–mass relationship concomitant to the onset of vitellogenesis in female blackmouth catshark Galeus melastomus (Chondrichthyes: Scyliorhinidae)

The examination of the total length (L) vs. body mass (W) relationship in the blackmouth catshark from the southern Adriatic Sea showed the occurrence of two development phases or growth stanzas in females. The passage from the first stanza (L range: 22.8-37.4cm) to the following one (L range: 39.7-51.4cm) was marked by an inflection in the power equation correlating body mass to total length, occurring at about 38.6cm of length (change point). After the change point, growth became positively allometric. This catshark is a lecitotrophic oviparous continuous spawner, and follicles in different stages of development are simultaneously present in the ovary. The histological analysis of the ovary showed that the smallest vitellogenic follicles were about 2mm in diameter; the diameter of the largest observed oocyte was 18mm. The change point occurred slightly before the onset of vitellogenesis (smallest vitellogenic female L=41.0cm) and appeared to be related to the activation of the reproductive axis

Multiple-phase biometric relationships and sexual maturity in the atlantic bluefin tuna, thunnus thynnus (Osteichthyes: Scombridae)

Most fish undergo distinct growth phases during ontogenesis. An extremely important passage from the juvenile to adult phase occurs at the onset of sexual maturity, which shows in body proportion and/or growth rate changes. These can be detected as change-points in biometric relationships. In this paper, the Atlantic bluefin tuna was analyzed to verify whether its somatic proportions show any sign of discontinuity during growth, i.e., whether any change-points may be detected in its somatic proportions. This fish has never been examined in this respect, and single-phase models, which are indeed easier to both compute and apply, are used in stock analyses. The following somatic relationships were analyzed in Atlantic bluefin tuna captured in the Mediterranean Sea between 1998 and 2010: “fork length–weight” regression, the von Bertalanffy growth equation, and “first dorsal spine cross section surface–fork length” regression. All of the examined relationships were found to be best modelled by multiple-phase regression equations, and all of them showed a change-point within the range of 101–110 cm fork length, which corresponds to 3–4 years of age. The present results, based on reproductive state-independent analyses, corroborate the disputed hypothesis that Atlantic bluefin tuna from the eastern stock in fact reproduce for the first time at this age

Epibiontic and endobiontic polychaetes of Geodia cydonium (Porifera, Demospongiae) from the Mediterranean Sea

Polychaete assemblages associated to the sponge Geodia cydonium were investigated at two sampling sites in the Mediterranean Sea: Porto Cesareo Basin (Apulia) and Marsala Lagoon (Sicily), both characterized by sheltered hydrodynamic conditions. Samples were seasonally performed during 1997, in order to compare the assemblages coming from the two localities studied, considering separately the internal and external tissues of the sponge, and with the aim of evaluating the influence of sponge size on polychaete colonization. The examined sponge is characterized by a peculiar stratification of its tissues: an external thick and hard layer, the cortex, and an internal softer one, the choanosome. Statistical analysis showed that this was the main factor controlling polychaete assemblage, with the internal tissue, less rich and diversified, appearing impoverished with respect to the external layer. A similarity in species composition was observed between sites, even though some differences were evidenced in the abundance of some species, mainly reflecting differences in local environmental conditions. Species richness and density increased with the increasing sponge size. Such a situation is particularly evident at Porto Cesareo, where sponges are covered by an algal layer which is particularly rich on the largest specimens, thus suggesting that most of the species of polychaetes were linked more to the neighbouring environment than to the sponge itself

Protandric hermaphroditism in the bivalve Arca noae (Mollusca: Arcidae)

Following the histological analysis of Arca noae samples from the south-western Adriatic Sea, five hermaphroditic specimens were found out of 168 sexed individuals (3.0%). The hermaphrodite gonads showed the co-occurrence of male and female germ cells within the same acini, i.e. both spermatozoa in the lumen and oogonia lining its wall. Oogonia increased in size through winter, thus suggesting that the direction of sex change is from male to female. Both the biometrical analyses and theoretical considerations strongly suggest that A. noae is an obligate protandric species

Protandric hermaphroditism in the bivalve Arca noae (Mollusca: Arcidae)

Following the histological analysis of Arca noae samples from the south-western Adriatic Sea, five hermaphroditic specimens were found out of 168 sexed individuals (3.0%). The hermaphrodite gonads showed the co-occurrence of male and female germ cells within the same acini, i.e. both spermatozoa in the lumen and oogonia lining its wall. Oogonia increased in size through winter, thus suggesting that the direction of sex change is from male to female. Both the biometrical analyses and theoretical considerations strongly suggest that A. noae is an obligate protandric species

Large-Scale Distribution of the European Seahorses (Hippocampus Rafinesque, 1810): A Systematic Review

Human pressures on marine ecosystems have caused extensive degradation of marine habitats and several local extinctions. Overexploitation and destructive fishing practices are responsible for biodiversity loss in many coastal ecosystems. The definition of conservation programs in marine fish requires comprehensive knowledge on large-scale geographical distribution, while considering distribution/abundance patterns in relation to key environmental variables. Due to their life-cycle traits, the two European seahorses (Hippocampus guttulatus and H. hippocampus), as with other congeneric species, are particularly sensitive to the effects of anthropogenic activities and habitat changes. However, information on the ecological distribution of these two species is scattered, patchy, and mainly focused on small-scale studies. In this paper, we followed an international standard protocol for systematic reviews (the PRISMA protocol) to provide a detailed assessment of the two species’ geographical distribution in relation to the environmental characteristics. According to the 134 analyzed studies, Hippocampus guttulatus is more common in confined areas, while H. hippocampus is found in marine shelf waters. With several interspecific differences, seagrasses were the most used holdfasts of both species. The EUNIS codes (European nature information system) referring to a specific and unique habitat were discussed as a potential tool for defining the ecological distribution of the two species. The obtained results and their future implementation could help plan conservation actions

Biological variations in a long-term ex situ cultivation: a Mediterranean demosponge as model system

The demosponge Tethya citrina Sarà & Melone was subjected to long-term aquarium farming, considering that several species belonging to this genus are a rich source of useful bioactive metabolites. The rearing method in the present research was mainly based on applying parameters taken from the current literature. The sponge's biological activity was assessed in terms of survival and growth over time; status of filtering apparatus; protein banding profiles. Farmed sponges showed a high survival rate and marked reduction in size. In addition, they were frequently affected by massive production of asexual buds. Histological and ultrastructural observations showed a gradual disorganization of the sponge choanocyte chambers, with a drastic reduction in choanocytes and a progressive increase in spherulous cells. Comparative electrophoretic analysis of the protein profiles of wild and reared specimens showed differences in protein composition and abundance between the tested groups. Such data are consistent with the increase in spherulous cells whose content was markedly electron-dense, a feature stressing the proteinaceous nature of these inclusions. Experimental tank-rearing of Tethya provided promising responses in terms of high survival rate of the species and easy reproduction, though the rearing protocol used led to profound morpho-functional changes in the sponge. This confirms the inadequate state of knowledge on farming techniques for this taxon, while also highlighting potential applications in biotechnology of ex situ breeding techniques, in order to modify the sponges' biological responses

Osservazioni sulla mortalita di ircinia spinosula (schmidt) ed ircinia sp. (porifera, demospongiae) nell’insenatura della strea di porto cesareo

EnA long-term investigation (1994-1996) was carried out on two species of Ircinia, I. spinosula and Ircinia sp., coexisting in a Mediterranean coastal basin (Porto Cesareo, South-Western Apulia). During 1994 both species were affected by a disease which caused a decrease of their density. In I. spinosula the maximum decrement was observed in January 1996 (about 27%), while, in the same period Ircinia sp. was almost completely disappeared from the investigated area. In July1996 a successive slow restarting of the two species was observed. SEM observations of the skeleton of damaged specimens showed a decay of spongine fibres. Even though these ones were frequently broken, they did not show grooves in their external surface, nor they seemed excavated inside. Tissue reparation processes were observed; they seemed to consist in the isolation of affected areas, permitting a recovery and regeneration of many specimens.ItE’ stato condotto un monitoraggio temporale (1994-1996) su due specie del genere Ircinia, I. spinosula e Ircinia sp,, coesistenti in un bacino costiero mediterraneo (Porto Cesareo, Puglia Sud-Occidentale). Ne1 1994 entrambe le specie sono state colpite da una malattia che ha provocato un decremento della loro densita. In I. spinosula il decremento massimo è stato osservato in gennaio 1996 (circa il27%), mentre nello stesso periodo Ircinia sp è quasi del tutto scomparsa dall’area d’indagine. Nel luglio 1996 è stata osservata una successiva e lenta ripresa delle due specie. Le indagini ultrastrutturali (SEM) hanno permesso di osservare che in entrambe le specie lo scheletro degli esemplari danneggiati presentava una trama discontinua con le fibre di spongina frequentemente spezzate. Sebbene tali fibre risultassero sfaldate non apparivano mai erose al loro interno. Sono stati osservati, inoltre, probabili meccanismi di riparo dei tessuti; tali meccanismi, consistenti nell'isolamento delle aree affette da malattia, sono probabilmente alla base dei processi di ripresa e di rigenerazione di molti esemplari

Site fidelity of Hippocampus guttulatus Cuvier, 1829 at Mar Piccolo of Taranto (Southern Italy; Ionian Sea)

Lack of detailed knowledge on ecological niche, life cycles, spatial distribution, reproductive biology and space use strongly affects the selection of useful tools and measures in the conservation of threatened marine species. Especially for sedentary and slow species, behaviour and movement capacities are supposed to be the most important functional traits. Indeed, behavioural variability concerning available space and the close presence of individuals is considered a crucial trait for the population dynamics assessments, especially when disturbances of various causes are present in the environment. The present study aimed to investigate the site fidelity and degree of movement of Hippocampus guttulatus, an emblematic and threatened Mediterranean seahorse species. With this aim, a number of seahorses were tagged and monitored throughout two years within a limited area of the lagoon of Mar Piccolo of Taranto (Southern Italy). The studied individuals were initially morphometrically measured for size, sex and life-cycle stage and subsequently monitored through repeated four-month surveys each year. Obtained results indicated high site fidelity regardless of habitat type. Movement pattern was in line with the data on congeneric species, although values were slightly higher. The analyses showed differences in movement degree among different sexes and life-cycle stages and indicated greater mobility of adult females compared to males and juveniles. The investigated parameters showed a great variability suggesting that even small-scale environmental factors can influence the species mobility. Finally, a change in the population structure has been observed, with the loss of large individuals in 2016 and reduced recruitment in 2017. These findings indicated the possible presence of stressors that could lead to the alteration of the seahorse population at Mar Piccolo of Taranto