The common whelk Buccinum undatum (Neogastropoda, Buccinidae) is widespread along the north Atlantic coasts of France. In west Cotentin (Normandy), an important local fishery exists that depends exclusively on this marine resource and represents about 90% of French whelk production. Despite successive restrictive measures, fishing yields have decreased since 2000. Shell length frequency distributions of Buccinum undatum caught in west Cotentin were studied in 2005 (N = 2910), in 2007 (N = 2032) and in 2009 (N = 4145) ranging from 7 to 85 mm. In order to preserve this fishery and to characterise the whelk stock at this site, the reproductive biology of this species was studied in relation to age, sex and size, for whelks of commercial size (45 to 61 mm) over the complete annual cycle in 2008. Age was determined by reading the number of operculum striae: animals between 45 and 59 mm had 2 to 4 striae. Four reproductive stages were defined for males and females on the basis of histological analysis. The time course of reproductive events was described according to size and sex: the highest percentages of ripe stages were found in October for both sexes. Spawning events occurred between October and December. The shell length that corresponded to 50% of animals having mature gonads (49 mm and 52 mm for males and females, respectively, corresponding to 3 and 4 years old animals) exceeded the minimal landing size (45 mm). Fifty percent maturity was reached for males in their third year and for females in their fourth year. Reproductive investment was evaluated by quantitative analysis of the gonadal thickness or surface and was found to be proportional to shell size. We found that less than 20% of females under 49 mm in length were sexually mature and that these produced only a few eggs. This information, collected in a major fishing area, should assist fishery management decisions.

The following paper gives a detailed description of the oogenesis cycle for the European Plaice (Pleuronectes platessa), from oogonia to post-ovulatory follicle, including ovarian follicle and zona pellucida sizes. Noteworthy particularities were the difficulty in identifying cortical alveoli due to their very small size. Quantitative histology (stereology) on histological slides was used to determine a first size at maturity for females from the English Channel, which was found to be smaller compared to the literature (19 cm). Stereology also determined a first spawning event starting in January, with a peak in February and ongoing until March. Moreover, the use of stereology showed misclassifications for individuals categorized into a maturity phase using a macroscopic visual method. Misclassifications were found with individuals that had spawned (D) but were put under the immature (A) phase, and individuals in development (B) classified under D.

In bilaterian species, the amino acid sequence conservation between Insulin related peptides is relatively low except for the cysteine residues involved in the disulphide bonds. In the A chain, the conserved cystein residues are included in a signature motif. Investigating the variations in this motif would give insight into the phylogenetic history of the family. The table presented in this paper contains a large set of insulin-related peptides in bilateral phylogenetic groups (deuterostomian, ecdysozoan, lophotrochozoan). NCBI databases in silico wide screening combined with bibliographic researches provided a framework for identifying and categorising the structural characteristics of these insulin related peptides. The dataset includes NCBI IDs of each sequence with hyperlinks to FASTA format. Moreover, the structural type (α, β or γ), the A chain motif, the total number of cysteins, the C peptide cleavage mode and the potential additional domains (D or E) are specified for each sequence. The data are associated with the research article "Molecular evolution and functional characterisation of insulin-related peptides in molluscs: contributions of Crassostrea gigas genomic and transcriptomic-wide screening" [1]. The table presented here can be found at http://dx.doi.org/10.17632/w4gr8zcpk5.4#file-21c0f6a5-a3e3-4a15-86e0-e5a696458866.

A technique was developed for dissection and isolation of male germ cells in the oyster Crassostrea gigas. This procedure can provide cells for the exploration of processes involved in the reproductive physiology of bivalves. Spermatogonia were chosen because of their essential role in spermatogenesis and the impact of gonia proliferation on reproductive effort. A non lethal method for determining sex and reproductive cycle stage was first validated in oysters. This first step was essential in order to constitute a homogeneous pool of oysters at the same stages of gametogenesis. Germ cell fractions were then obtained from a density gradient, and enrichment of each fraction was ratified by electron microscopy and by means of a 2-parameter flow cytometry procedure (DNA and mitochondrial staining). A significant enrichment in spermatogonia and spermatocytes was confirmed by the increased expression of markers of proliferative cells (proliferative cell nuclear antigen, PCNA) and early germ cells (oyster vasa-like gene). A preliminary cell sorting procedure is also reported, which was applied to fractions enriched in spermatogonia.