Deep-Dwelling Populations of Mediterranean Corallium rubrum and Eunicella cavolini: Distribution, Demography, and Co-Occurrence.

Corallium rubrum and Eunicella cavolini are two octocorals, reported as co-occurring species in the deep rocky habitats of the Mediterranean Sea with a high hydrodynamic and moderate eutrophication. Their spatial distribution and demography in the deep sea are mainly affected by temperature and direct and indirect anthropogenic activities; however, knowledge of the factors that potentially influence their co-existence is scarce. This paper provides novel data on the distribution and demography of these two species, at depths between 50 and 290 m in the Western Mediterranean Sea, providing insights on their co-occurrence. Both species exhibited the highest population density at deeper sites (>150 m), showing an inverse size-density relation. Density values ranged from 0.03 colonies m-2 to 32 and 80 col. m-2 for yellow gorgonian and red coral, respectively. The two species co-occurred in 13% of the total frames examined, mostly dwelling between 120 and 160 m depth. Distance-based linear modeling (DistLM) emphasized that when co-occurring the variability of the two species' densities were significantly driven by the density-rather than the morphology (i.e., height)-of the other species. We stress the need for further studies to elucidate the possible mutual effects of suspension feeders and to test the role of different environmental factors potentially influencing inter-specific relationships.

Chromosome Mapping of 5S Ribosomal Genes in Indo-Pacific and Atlantic Muraenidae: Comparative Analysis by Dual Colour Fluorescence In Situ Hybridisation.

The Muraenidae is one of the largest and most complex anguilliform families. Despite their abundance and important ecological roles, morays are little studied, especially cytogenetically, and both their phylogenetic relationships and the taxonomy of their genera are controversial. With the aim of extending the karyology of this fish group, the chromosomal mapping of the 5S ribosomal gene family was performed on seven species belonging to the genera Muraena and Gymnothorax from both the Atlantic and Pacific oceans. Fluorescence in situ hybridisation (FISH) experiments were realized using species-specific 5S rDNA probes; in addition, two-colour FISH was performed to investigate the possible association with the 45S ribosomal gene family. Multiple 5S rDNA clusters, located either in species-specific or in possibly homoeologous chromosomes, were found. Either a syntenic or different chromosomal location of the two ribosomal genes was detected. Our results revealed variability in the number and location of 5S rDNA clusters and confirmed a substantial conservation of the number and location of the 45S rDNA.

Comparative cytogenetics in four species of Palinuridae: B chromosomes, ribosomal genes and telomeric sequences.

The evolutionary pathway of Palinuridae (Crustacea, Decapoda) is still controversial, uncertain and unexplored, expecially from a karyological point of view. Here we describe the South African spiny lobster Jasus lalandii karyotype: n and 2n values, heterochromatin distribution, nucleolar organizer region (NOR) location and telomeric repeat structure and location. To compare the genomic and chromosomal organization in Palinuridae we located NORs in Panulirus regius, Palinurus gilchristi and Palinurus mauritanicus: all species showed multiple NORs. In J. lalandii NORs were located on three chromosome pairs, with interindividual polymorphism. In P. regius and in the two Palinurus species NORs were located on two chromosome pairs. In the two last species 45S ribosomal gene loci were also found on B chromosomes. In addition, the nature and location of telomeric repeats were investigated by FISH in J. lalandii, P. gilchristi, P. mauritanicus Palinurus elephas, and P. regius (Palinuridae, Achelata), and in Scyllarus arctus (Scyllaridae, Achelata): all these Achelata species showed the (TTAGG)n pentameric repeats. Furthermore, in J. lalandii these repeats occurred in all the telomeres and in some interstitial chromosomal sites, associated with NORs.

Striped mullet (Mugil cephalus) hemoglobin system: multiplicity and functional properties.

The most frequent (90%) phenotype of the hemoglobin system of M. cephalus presented two major hemoglobins, the more anodal HbI accounting for approximately 70% of the total. The two hemoglobin components separated by ion-exchange chromatography were analyzed by reverse-phase HPLC and electrospray ionization-mass spectrometry which revealed a more complex pattern: HbI consists in four different globins, two ß (named ß1 and ß3) and two co-eluting α chains (α1 and α2); HbII consists in three globins, one ß chain (named ß2) and the same α1 and α2 present in HbI. The oxygen-binding properties of both hemoglobin components purified by DEAE cellulose were almost identical to those of the hemolysate: stripped hemoglobin showed a large Bohr effect which was enhanced by chloride ions and, at a larger extent, by organic phosphates which, at acidic pH values gave rise to the Root effect. A series of oxygen-binding experiments at increasing GTP concentrations was carried out in order to compare GTP-binding activities in the absence and presence of physiological amounts of chloride. The results indicated that hemoglobin do have two sites for GTP binding. In the absence of chloride, the two sites cannot be discriminated, whereas in the presence of chloride, a competition between the two anions occurred for both GTP-binding sites. The presence of multiple hemoglobin components with identical properties confirms that hemoglobin heterogeneity that often occurs in fish cannot be only explained as an evolutionary response to the physiological and/or environmental needs of the species.

The oxygen-binding modulation of hemocyanin from the Southern spiny lobster Palinurus gilchristi.

Arthropod hemocyanins transport and store oxygen and are composed of six subunits, or multiples thereof depending on the species. Palinurus gilchristi hemocyanin is found only as 1 x 6-mers, as normally occurs in spiny lobsters. An alkaline pH and removal of calcium ions induce a wholly reversible dissociation into monomers. The oxygen-binding properties of 1 x 6-meric hemocyanin from P. gilchristi were investigated with respect to pH and modulating effect exerted by calcium, lactate and urate. The oxygen affinity was highly affected by pH in the presence of calcium ions, while in its absence the Bohr coefficient became 60% lower. The protein is insensitive to lactate, but affected by urate which markedly increased hemocyanin-oxygen affinity, acting as the physiological major positive effector. Calcium ions decrease oxygen affinity at low concentration range (0-1 mM), while as concentration becomes higher than 100 mM, the oxygen affinity increases, indicating the presence of two independent types of calcium-binding sites with high and low affinity, respectively. The previous hypothesis, that the presence of high-affinity binding sites in addition to low affinity ones could be a characteristic feature of Palinuran hemocyanins, has been tested by analyzing, with respect to calcium-hemocyanin interaction, three other species belonging to Palinura.

Isolation and characterization of 14 polymorphic microsatellite markers for the blue and red shrimp, Aristeus antennatus (Crustacea, Decapoda).

Eighteen microsatellite loci were isolated and characterized from the blue and red shrimp, Aristeus antennatus Risso 1816, a commercially exploited marine crustacean widely distributed throughout the Mediterranean Sea and in the eastern Atlantic. Polymorphism was assessed in a population (n = 20) from the southwestern Sardinian seas; 14 loci resulted polymorphic and showed from three to 13 alleles. The observed heterozygosity ranged from 0.2 to 0.85. These microsatellites will be potentially useful for the study of A. antennatus population genetic structure.

Oxygen-binding modulation of hemocyanin from the slipper lobster Scyllarides latus.

The oxygen-binding properties of hexameric hemocyanin (Hc) from Scyllarides latus were investigated with respect to pH, temperature, and modulating effect exerted by calcium, lactate, and urate. The oxygen affinity decreased at higher temperature, was slightly affected by pH, and was insensitive to lactate. Nevertheless, urate markedly increased Hc-oxygen affinity and its temperature sensitivity, acting as the physiological major positive effector: four urate sites per hexamer with an overall affinity constant of 1 x 10(4) M(-1) were found and the exothermic contribution of their binding was found to be about 30 kJ mol(-1). Calcium ions largely influenced oxygen affinity: their effect, which has an opposite sign at low (0-1 mM) and high (0.1-1 M) concentration ranges, indicates the presence of two independent types of binding sites with high and low affinity, respectively; however, only the former ones seem to be operative in vivo because, at physiological calcium concentrations, they are already saturated and the oxygen affinity is reduced.