Transcriptomic response and hydrocarbon accumulation in the eastern oyster (Crassostrea virginica) exposed to crude oil.

The adverse effect of crude oil on marine invertebrates is well known. To have a better understanding of its effects on marine invertebrates, Crassostrea virginica was exposed to different concentrations (50, 100 and 200 µg/L) of a mixture of super-light and light crude oil for two weeks, evaluating the transcriptomic response of the digestive gland using RNA-Seq and their accumulation in soft tissues. A total of 33,469,374 reads were assembled, which resulted in 61,356 genome assemblies ('Genes'). Trinotate was used for transcript annotation. At the end of this process, 86,409 transcripts were maintained, comprising a broad set of enzymes from xenobiotics metabolism, oxidative stress, stress and immune responses, and energetic metabolism. The enrichment analysis revealed a change in biological processes and molecular functions, finding from 100 to 200 µg/L. Moreover, the differential gene expression analysis showed a dose-dependent transcriptional response, generally up to 100 µg/L and in some cases up to 200 µg/L, which suggested that oysters' response decreased after 100 µg/L; the analysis of crude oil presence in soft tissues indicated that C. virginica is a suitable candidate for ecotoxicology. Finally, these results should contribute to expanding current genomic resources for C. virginica. Furthermore, they will help to develop new studies in aquatic toxicology focused on knowledge in depth of metabolic pathways, jointly with other approaches (such as proteomics) to allow obtaining a complete idea about the eastern oyster response to crude oil.

Octopus maya white body show sex-specific transcriptomic profiles during the reproductive phase, with high differentiation in signaling pathways.

White bodies (WB), multilobulated soft tissue that wraps the optic tracts and optic lobes, have been considered the hematopoietic organ of the cephalopods. Its glandular appearance and its lobular morphology suggest that different parts of the WB may perform different functions, but a detailed functional analysis of the octopus WB is lacking. The aim of this study is to describe the transcriptomic profile of WB to better understand its functions, with emphasis on the difference between sexes during reproductive events. Then, validation via qPCR was performed using different tissues to find out tissue-specific transcripts. High differentiation in signaling pathways was observed in the comparison of female and male transcriptomic profiles. For instance, the expression of genes involved in the androgen receptor-signaling pathway were detected only in males, whereas estrogen receptor showed higher expression in females. Highly expressed genes in males enriched oxidation-reduction and apoptotic processes, which are related to the immune response. On the other hand, expression of genes involved in replicative senescence and the response to cortisol were only detected in females. Moreover, the transcripts with higher expression in females enriched a wide variety of signaling pathways mediated by molecules like neuropeptides, integrins, MAPKs and receptors like TNF and Toll-like. In addition, these putative neuropeptide transcripts, showed higher expression in females' WB and were not detected in other analyzed tissues. These results suggest that the differentiation in signaling pathways in white bodies of O. maya influences the physiological dimorphism between females and males during the reproductive phase.

Allotriploid genotypic assignment in abalone larvae by detection of microsatellite-recombinant genotypes.

Abalone species are different from most mollusks utilized in aquaculture as they are known to hybridize in laboratory-induced matings. Allotriploidization of hybrid abalone has not yet been studied, and methodology useful in verifying the genotypic condition of such allotriploids do not exist. Genotypic verification of hybridization and allotriploidization in a cross of Haliotis fulgens and Haliotis rufescens was performed utilizing 6 crossamplifying microsatellite loci. Five H. rufescens spawns were used in this experiment, dividing each spawn into control and experimental hybrid groups and further into diploids and triploids. Two microsatellite loci developed for H. fulgens and H. rufescens allowed for the genotypic identification of hybrids within diploid and triploids. To further verify the percentage of allotriploids within the genotypic hybrids in the triploid hybrid groups, microsatellite loci originally developed in Haliotis corrugata and Haliotis kamtschatkana were tested for crossamplification in H. fulgens and H. rufescens. Of 21 loci, 4 were chosen for this study based on their crossamplification, heterozygosity in the females, and centromere recombination frequencies. Allotriploids in triploid-hybrid larvae were then detected by identifying larvae with recombinant genotypes at any of those loci. One family had low success verification associated with reduced recombination frequencies for all loci in that family. These results demonstrate that allotriploid verification at larval stages is feasible but depends on the number of loci available, their crossamplification in the species, and their recombination frequencies.