Early fasting does not impact gonadal size nor vasa gene expression in the European seabass Dicentrarchus labrax.

Primordial germ cells (PGCs) play a crucial role in sexual development in fish, with recent studies revealing their influence on sexual fate. Notably, PGC number at specific developmental stages can determine whether an individual develops as male or female. Temperature was shown to impact PGC proliferation and the subsequent phenotypic sex in some fish species.

Male triploid oysters of Crassostrea gigas exhibit defects in mitosis and meiosis during early spermatogenesis.

The Pacific oyster, Crassostrea gigas, is a successive irregular hermaphrodite mollusk which has an annual breeding cycle. Oysters are naturally diploid organisms, but triploid oysters have been developed for use in shellfish aquaculture, with the aim of obtaining sterile animals with commercial value. However, studies have shown that some triploid oysters are partially able to undergo gametogenesis, with numerous proliferating cells closed to diploids (3n alpha) or a partial one with an accumulation of locked germ cells (3n beta).

Gonadal transcriptomes associated with sex phenotypes provide potential male and female candidate genes of sex determination or early differentiation in Crassostrea gigas, a sequential hermaphrodite mollusc.

Background: In the animal kingdom, mollusca is an important phylum of the Lophotrochozoa. However, few studies have investigated the molecular cascade of sex determination/early gonadal differentiation within this phylum. The oyster Crassostrea gigas is a sequential irregular hermaphrodite mollusc of economic, physiological and phylogenetic importance.

Cg-SoxE and Cg-β-catenin, two new potential actors of the sex-determining pathway in a hermaphrodite lophotrochozoan, the Pacific oyster Crassostrea gigas.

Sex determination is poorly known in mollusks, lophotrochozoa and most hermaphrodites. In the oyster Crassostrea gigas, an irregular successive hermaphrodite, sex determination may occur at the end of a gametogenetic cycle to prepare the next cycle. To investigate further into these aspects we have focused on orthologs of SoxE and β-catenin, key players of the male and female gonadic differentiation respectively in mammals.

Oyster sex determination is influenced by temperature - first clues in spat during first gonadic differentiation and gametogenesis.

The sex-determining system of Crassostrea gigas is still poorly known, especially regarding the potential influence of temperature. In order to address this question, mRNA expressions of actors of the molecular cascade (Cg-DMl, Cg-SoxE, Cg-β-catenin, Cg-Foxl2/Cg-Foxl2os) and of Oyvlg, a germ cell marker, were investigated by real-time PCR in spat grown at different temperatures (18, 22, 25 and 28°C). In parallel, gonadic differentiation, gametogenesis and sex ratios were assessed by histology at each of these temperatures.

Molecular cloning and gene expression of Cg-Foxl2 during the development and the adult gametogenetic cycle in the oyster Crassostrea gigas.

A Foxl2 ortholog has been identified in a lophotrochozoa, the pacific oyster, which is a successive irregular hermaphrodite mollusc. Its cDNA has been called Cg-Foxl2 (Crassostrea gigas Foxl2) and the deduced protein sequence is 367aa long. This sequence contains the conserved domain Forkhead box and its gene is devoid of intron at least in the first 926 bp of the cDNA, as found for Foxl2 factors.

Identification and expression of a factor of the DM family in the oyster Crassostrea gigas.

The Pacific oyster Crassostrea gigas is a successive not systematic protandric hermaphrodite. Searching for an ortholog to Dmrt1, a conserved sex determinism factor, we have identified the first complete cDNA of a DM factor in Lophotrochozoa which we have called Cg-DMl (Crassostrea gigas DMRT-like). It is 359aa long, with the DM domain common to all the family factors, and one DMA domain specific to members such as Dmrt4 and Dmrt5.

Study of the potential spermatogonial stem cell compartment in dogfish testis, Scyliorhinus canicula L.

In the lesser-spotted dogfish (Scyliorhinus canicula), spermatogenesis takes place within spermatocysts made up of Sertoli cells associated with stage-synchronized germ cells. As shown in testicular cross sections, cysts radiate in maturational order from the germinative area, where they are formed, to the opposite margin of the testis, where spermiation occurs. In the germinative zone, which is located in a specific area between the tunica albuginea of the testis and the dorsal testicular vessel, individual large spermatogonia are surrounded by elongated somatic cells.

The role of aquaporin 3 in teleost fish.

The aquaporin isoform, AQP3 has now been identified in a number of different teleost fish species, with additional DNA sequence information on AQP3 genes in further fish species available in genome databases. In zebrafish (Danio rerio), the AQP3 gene is present as two duplicate isoforms resulting from a teleostean fish genome-wide duplication. A further splicoform/isoform has also been identified in rainbow trout (Oncorhynchus mykiss).

Effect of cortisol on aquaporin expression in the esophagus of the European eel, Anguilla anguilla.

Long-term cortisol infusion into freshwater (FW)-adapted eels induced a significant increase in aquaporin-1 (AQP1) mRNA expression within the esophageal epithelium of migratory "silver" eels, but not in nonmigratory, immature "yellow" eels. Cortisol treatment had no significant effect on the mRNA abundance of a second aquaporin-1 isoform, termed AQP1dup, which exhibited a highly variable expression profile among individual members of all fish groups. These results suggest that cortisol, at plasma concentrations similar to that found during FW/seawater (SW) acclimation, induces upregulation in AQP1 expression and thus increases esophageal water permeability during the migration of eels to the SW environment.

Cloning and expression of guanylin-like peptides in teleost fish.

Homologues of the guanylin peptide family are expressed in teleost fish. Using the eel as a model euryhaline species, cDNAs for three peptides, guanylin, uroguanylin, and renoguanylin, were cloned and found to be expressed within both renal and intestinal epithelia. Seawater (SW) acclimation resulted in upregulation of uroguanylin mRNA expression in the intestinal epithelia of both immature "yellow" and sexually mature "silver" eels.

Cloning and expression of three aquaporin homologues from the European eel (Anguilla anguilla): effects of seawater acclimation and cortisol treatment on renal expression.

Background Information: The European eel (Anguilla anguilla) is able to osmoregulate over a wide range of environmental salinities from FW (freshwater) to hyperconcentrated SW (seawater). Successful acclimation is associated with strict regulation of ion and water transport pathways within key osmoregulatory epithelia to enable animals to survive the dehydrating or oedematous conditions. These observations suggested that homologues of the AQP (aquaporin) water channel family were expressed in the eel and that these proteins may contribute to the water transport and osmoregulation in all euryhaline teleosts.

Branchial chamber tissues in two caridean shrimps: the epibenthic Palaemon adspersus and the deep-sea hydrothermal Rimicaris exoculata.

The structure of the epithelia of the branchial chamber organs (gills, branchiostegites, epipodites) and the localization of the Na(+),K(+)-ATPase were investigated in two caridean shrimps, the epibenthic Palaemon adspersus and the deep-sea hydrothermal Rimicaris exoculata. The general organization of the phyllobranchiate gills, branchiostegites and epipodites is similar in P. adspersus and in R.

Regulation of expression of two aquaporin homologs in the intestine of the European eel: effects of seawater acclimation and cortisol treatment.

Complementary DNAs encoding homologs of the mammalian aquaglyceroporins (termed AQPe) and aquaporin-1 isoforms (termed AQP1) were isolated from the European eel. The AQP amino acid sequences share 35-54% identity with other known human AQPs. Although AQPe mRNA expression was approximately equivalent along the entire length of the gut, AQP1 expression was the highest in the posterior/rectal segment.

Does sulphide detoxication occur in the gills of the hydrothermal vent shrimp, Rimicaris exoculata?

Ultrastructural observations of the gills of the hydrothermal vent shrimp Rimicaris exoculata reveal that the epithelial cells contain numerous mitochondria clustered around unusual organelles (diameter of 0.7 to 2.5 microns) containing membrane stacks.