Influence of Storage Time on the DNA Integrity and Viability of Spermatozoa of the Spider Crab Maja brachydactyla.

Natural populations of the spider crab Maja brachydactyla constitute a fishery resource of great economic importance in many countries. As in the rest of eubrachyurans, the females of this species have ventral-type seminal receptacles where they store sperm from copulations. Sperm can be stored in these structures for months and even years before egg fertilisation, with the consequent degradation of the sperm cells during the time. In this work, we analyse the viability and the possible genetic damage in sperm accumulated in the seminal receptacles of M. brachydactyla females as a function of the storage time (from 0 to 14 months) using the comet assay technique. On one hand, we developed an algorithm for comet image analysis that improves the comet segmentation compared with the free software Open comet v1.3.1 (97% vs. 76% of detection). In addition, our software allows the manual modification of the contours wrongly delimited via the automatic tool. On the other hand, our data show a sharp decline in sperm viability and DNA integrity in the first four months of storage, which could lead to a decrease in the fecundity rate and/or viability of the embryos or larvae from the second and third clutches of the annual cycle if the repair capacity in these gametic cells is low.

High incidence of heteroplasmy in the mtDNA of a natural population of the spider crab Maja brachydactyla.

Mitochondria are mostly inherited by maternal via, that is, only mitochondria from eggs are retained in the embryos. However, this general assumption of uniparentally transmitted, homoplasmic and non-recombining mitochondrial genomes is becoming more and more controversial. The presence of different sequences of mtDNA within a cell or individual, known as heteroplasmy, is increasingly reported in several taxon of animals, such as molluscs, arthropods and vertebrates. In this work, a considerable frequency of heteroplasmy were detected in the COI and 16S genes of the spider crab Maja brachydactyla, possibly associated to hybridisation with the congeneric species Maja squinado. This finding is a fact to keep in mind before addressing molecular analyses based on mitochondrial markers, since the assumption of maternal inheritance could lead to erroneous results. As M. brachydactyla is a commercial species, heteroplasmy is an important aspect to take into account for the fisheries management of this resource, since effective population size could be overestimated.

Assessing the spatial variability, level and source of organic chemical contaminants in bivalve fishing grounds on the Galician coast (NW Spain).

Polychlorinated biphenyls, organochlorine pesticides, organotin compounds and triazines were quantified in sediments and bivalves collected in four areas on the Galician coast. One or several species were analysed at each site depending on their availability, including mussels (Mytilus galloprovincialis), cockles (Cerastoderma edule), clams (Venerupis pullastra and Ruditapes decussatus) and razor shells (Ensis siliqua). The general spatial distribution of contaminants was consistent in spite of the different sources of contamination. High inter-species variability was also observed. M. galloprovincialis and V. pullastra showed the highest levels of contaminants and intra-spatial variability, which highlights them as suitable species to be used as sentinel organisms. The area of O Burgo showed some worrisome results: PCB sediment concentrations were within the range that could cause biological effects. Also the level of heptachlor observed in V. pullastra was above limits accepted on edible seafood. Finally TBT concentration in mussels correlated with concentrations causing imposex in snails.