Andrea Sabatini

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.

Dystrophy effects on the LIZA RAMADA (Risso, 1826) (Pisces, Mugilidae) population in the Cabras lagoon (Central-Western Sardinia)

Fish samples were collected between 1999 and 2002 in the Cabras lagoon, the largest brackish area in Sardinia and one of the most important areas for the artisanal lagoon fishery in the Mediterranean area. Because of its natural connection with both the Oristano Gulf and the ‘Mare e Foghe’ river, in which pollution problems are frequent, this area suffers from dystrophic crises linked to phytoplanktonic or macrophytes blooms. The effect of the 1999 dystrophy on the fish population was studied by analysing the commercial landings variations and the modification of the demographic structure of the most important species, Liza ramada. Because of the dystrophy, the yields have decreased by about 90% since 1998. These effects are most likely attributable to the reduction in recruitment as the VPA analysis on L. ramada suggests. The calculated growth parameters of Thinlip mullet, which are the first reported for a Sardinia lagoon, are useful for fishery management of these areas. The study leads us to conclude that the trophic conditions probably changed, causing the reduction in the natural lagoons ‘call-effect’ of recruits from the sea.

Assemblages in a submarine canyon: influence of depth and time

In this work we have studied the assemblages from Quirra canyon (Sardinia). We analysed data from 25 trawl samples from the canyon, made at different times and depth. A total of 71 demersal species (38 teleosts, 5 cartilaginous fishes, 13 molluscs and 15 crustaceans) were examined. We found four groups using cluster analysis; each group is characterised by a certain depth or time. In particular we have shown that the time of the day appears to have a role in the movement of shrimps and other species. This phenomenon seems to be linked to trophic need and by the consequent different food availability into the Canyon.

Antennular Morphology and Contribution of Aesthetascs in the Detection of Food-related Compounds in the Shrimp Palaemon adspersus Rathke, 1837 (Decapoda: Palaemonidae)

Shrimp are an essential ecological component of marine ecosystems, and have commercial importance for human consumption and aquaculture. Like other decapod crustaceans, shrimp rely on chemical senses to detect and localize food resources by means of chemosensilla that are located mainly on the cephalothoracic appendages. Using the shrimp Palaemon adspersus, a model organism with omnivorous feeding behavior, we aimed to provide comparative information on the role of aesthetascs, antennular sensilla, and flicking behavior in food detection. To this end, we examined i) the morphology of antennular sensilla by field emission scanning electron microscopy, ii) the shrimp’s sensitivity to a number of food-related compounds (amino acids and sugars) by means of whole-animal bioassays, and iii) the contribution of the aesthetasc sensilla to food detection. Our results showed that, aside from the aesthetascs, only three other main morphotypes of setae with chemoreceptive features were present in the antennules, thus accounting for relatively simple sensillar equipment. Nevertheless, we found broad-spectrum sensitivity of the shrimp to a number of amino acids (i.e., isoleucine, leucine, methionine, phenylalanine, glycine, tryptophan, cysteine, and tyrosine) and carbohydrates (trehalose, maltose, cellobiose, and fructose) that was consistent with the omnivorous or scavenging habits of the animal. Although aesthetasc ablation attenuated flicking behavior in a chemical stimulus-independent manner, success in detection and short-range localization of food did not rely on the presence of aesthetasc sensilla. This finding confirms the existence of a non-aesthetasc alternative pathway for feeding, with functional redundancy in simple generalist feeder models such as shrimp.

Karyotype, ribosomal genes, and telomeric sequences in the crayfish Procambarus clarkii (Decapoda: Cambaridae)

Mitotic and meiotic chromosomes of the crayfish Procambarus clarkii (Girard, 1852) were characterized by means of heterochromatin staining techniques (C-, DAPI- and CMA3-bandings), and FISH of major ribosomal genes and telomeric pentameric repeat (TTAGG)n. Nucleolar organizer regions have been located on four chromosome pairs. GC-rich heterochromatin was mostly associated with NORs, and brightly fluorescent centromeric/pericentromeric AT-rich bands were present in most chromosomes. Telomeric pentameric repeats (TTAGG)n, occurred in all the P. clarkii telomeres and in the interstitial region of the largest chromosome pair, not co-located to ribosomal genes; as possible explanation of the origin of this chromosome, a fusion event was hypothesized.

Demersal assemblages in two trawl fishing lanes located on the Baronie Seamount (Central Western Mediterranean)

This work focuses on the species associations of the Baronie Seamount (north-eastern Sardinia, Italy), according to variations in depth and time of day. The aim was to highlight the potential vertical movements of the species and to compare these results to existing data from a submarine canyon. Twenty-two samples were taken at different depths and times along two trawl lines over the seamount. A total of 94 species were caught; among these, 4 8 bony fish, 9 cartilaginous fish, 13 molluscs and 24 crustaceans were selected for analysis. Cluster analysis showed 3 groups in which both depth and time of day play an important role in grouping. Nine species showed some daily and nocturnal movement, probably linked to trophic requirements. The daily movements according to size and sex of the shrimps Aristaeomorpha foliacea and Aristeus antennatus were also studied. For these two populations, the analysis showed an uneven distribution and the diel cycle appears to involve only the females. These species seem to adapt their life cycle to the geomorphology of the sea bottom. The diurnal movements from the base of the seamount to the edge of the continental shelf increase the range of the species distribution. In fact, the seamount, due to its geomorphological conformation, offers these species the opportunity to very quickly span a considerable range of depths. These movements are known to occur in the continental shelf and slope, but in the seamount they are broadened and can be studied more easily.

Larval Helminth Parasites of Fishes and Shellfishes from Santa Gilla Lagoon (Sardinia, Western Mediterranean), and Their Use as Bioecological Indicators

Qualitative and quantitative data of the larval stages of 30 helminth species infecting fish and shellfish in the Santa Gilla lagoon (southern Sardinia, western Mediterranean Sea) were collected and analysed to determine their usefulness as biological and ecological indicators. Parasitological data were collected from 2001 to 2011 from 12 fish species, from the families Anguillidae, Atherinidae, Cyprinodontidae, Gobiidae, Moronidae, Mugilidae, Soleidae and Sparidae and from bivalve molluscs of the families Cardiidae, Mytilidae and Veneridae. Digenean metacercariae dominated the larval parasitofauna; nevertheless, the most abundant parasite species was a nematode, i.e. the third-stage larvae of the anisakid Contracaecum rudolphii. Based on their life cycle, the species detected were divided into autogenic or allogenic parasites, which have fishes and birds/mammals as their definitive hosts, respectively. Data on the prevalence, intensity and abundance of infections and the parasitic diversity in each host species were combined with previous knowledge on the life history of the parasites detected, to build a model food web based on the different trophic relations, especially predator–prey interactions between hosts marked by the transmission of parasites. The results will contribute to the knowledge of species diversity and to the evaluation of general environmental changes occurring in brackish Mediterranean ecosystems. In combination with other analytic tools in a multidisciplinary approach, this will enable us to better understand the functioning of other Mediterranean brackish waters that are comparable to the Santa Gilla lagoon.

Sensing with the legs: contribution of pereiopods in the detection of food-related compounds in the red swamp crayfish Procambarus clarkii

The red swamp crayfish Procambarus clarkii (Girard, 1852) is one of the most hazardous invasive alien species of freshwater habitats. Like other decapod crustaceans, crayfish rely on chemical senses to detect and localize food resources. By way of extracellular nerve recordings coupled with behavioural bioassays, we investigated the sensitivity spectra of the walking leg chemoreceptors of P. clarkii in response to different food-related compounds. Recordings from isolated legs confirmed a marked sensitivity of the legs to trehalose, cellobiose, sucrose, maltose, glycine, and leucine. Some sensitivity to glucose, fructose, asparagine, and taurocholic acid was also found. Under confined experimental conditions, the behavioural bioassays excluded involvement of antennules in the detection of food-related compounds, thus emphasizing the role of the legs as the main short-distance, broad-spectrum sensors involved in feeding. Such information could be valuable for the identification of key chemicals aimed at the future development of strategies for crayfish population control programs.

Morphological description and intraspecific variability of Mullus surmuletus (Teleostea, Mullidae) vertebral column

Morphological aspects of the vertebral column of Mullus surmuletus from the Sardinian Channel are highlighted. The total number of vertebrae proved to be constant (24) in all examined individuals and the most correct morphological subdivision appears to be into three regions (abdominal, caudal, and intermediate). A difference in the number of abdominal and intermediate vertebrae can be noted: respectively, 7+3 in 39% of individuals and 6+4 in the remaining 61%. The number of caudal vertebrae, however, is always constant (14). These differences were not influenced by size or sex. The present paper shows the first observations of variability, independently of depth or latitude, in the vertebral column of a species with subcarangiform swimming. Since variations in the vertebral composition are determined in the very early stages of ontogenesis, the observed differences might be caused by groups of individuals born in different periods of the same year, in which there could be differences in environmental parameters sufficient to determine variations in the vertebral morphology, but not in the number of vertebrae.

First record of the alien polychaete Naineris setosa (Scolecida; Orbiniidae) in Tyrrhenian Sea (Western Mediterranean)

During a survey in Santa Gilla, a Tyrrhenian lagoon located in southern Sardinia, several specimens of the alien polychaete Naineris setosa were found. 1) A brief description of the specimens is presented; they possess the rounded prostomium and the crenulated capillary chaetae typical of the genus, but they are characterized by the absolute lacking of uncini or subuluncini in thoracic neuropodia, which is unique trait within Naineris; 2) some environmental characteristics of the collection site are measured; 3) the description and the distribution of the specimens are also provided.