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Octopus maya endemic to the Yucatan Peninsula, Mexico, is an ectotherm organism particularly temperature-sensitive. Studies in O. maya females show that temperatures above 27°C reduce the number of eggs per spawn, fertilization rate and the viability of embryos. High temperatures also reduce the male reproductive performance and success. However, the molecular mechanisms are still unknown. The transcriptomic profiles of testes from thermally stressed (30°C) and not stressed (24°C) adult male octopuses were compared, before and after mating to understand the molecular bases involved in the low reproductive performance at high temperature. The testis paired-end cDNA libraries were sequenced using the Illumina MiSeq platform. Then, the transcriptome was assembled de novo using Trinity software. A total of 53,214,611 high-quality paired reads were used to reconstruct 85,249 transcripts and 77,661 unigenes with an N50 of 889 bp length. Later, 13,154 transcripts were annotated implementing Blastx searches in the UniProt database. Differential expression analysis revealed 1,881 transcripts with significant difference among treatments. Functional annotation and pathway mapping of differential expressed transcripts revealed significant enrichment for biological processes involved in spermatogenesis, gamete generation, germ cell development, spermatid development and differentiation, response to stress, inflammatory response and apoptosis. Remarkably, the transcripts encoding genes such as ZMYND15, KLHL10, TDRD1, TSSK2 and DNAJB13, which are linked to male infertility in other species, were differentially expressed among the treatments. The expression levels of these key genes, involved in sperm motility and spermatogenesis were validated by quantitative real-time PCR. The results suggest that the reduction in male fertility at high temperature can be related to alterations in spermatozoa development and motility.

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The octopus optic glands are the source of multiple signalling molecules that control the transitions through different physiological stages, such as maturation, ageing and death. This study focused on the role of the optic glands during the reproductive phase of Octopus maya, investigating the molecular mechanisms that prevent reproduction at elevated temperatures. RNA sequencing was used to analyse and compare optic gland transcriptomic profiles of female O. maya before, during and after egg-laying under optimal and thermal stress (elevated temperature) conditions. Each stage showed well-defined transcriptomic patterns, and all were strongly affected by thermal stress. At optimal temperature, the optic glands contribute importantly to regulating the energetic balance, as suggested by the expression of genes that modulate the metabolic rate, arterial blood pressure and the management of ATP sources in response to food deprivation. At elevated temperatures, the optic glands of mated females (before egg-laying) showed upregulation of genes encoding neuropeptides (FMRF-amide, APGW-amide, PRQFV-amide, FCAP, buccalin and myomodulin) and the dopamine beta-hydroxylase gene. During egg-laying at elevated temperatures, the neuropeptide receptor capaR and the sex peptide receptor were upregulated whereas homologs of fetuin-B and oviduct-specific glycoprotein genes, crucial for fertilization, were downregulated. These changes in optic gland gene expression in O. maya may be the basis for the high-temperature inhibition of egg-laying, previously observed from this octopus species. Furthermore, after egg-laying, during egg incubation thermal stress affected the expression of genes involved in steroid and thyroid hormone biosynthesis and in inflammatory and apoptotic pathways.

The Gulf of Mexico is an important crude oil reserve worldwide, and the oyster Crassostrea virginica is an excellent candidate to study the oil spill impacts on marine invertebrates. In this work, the concentrations of polycyclic aromatic hydrocarbons (PAHs) and aliphatic hydrocarbons (AHs) from eight productive oyster areas in the Gulf of Mexico were measured on sediment, water, and tissues from C. virginica. In water, the highest AHs concentration was detected in Tamiahua (0.50 ng/mL), while for PAHs, the highest concentration was > 0.10 ng/mL in Tampamachoco. In sediment, Tamiahua and Tampamachoco lagoons had the highest AHs concentrations with values near 2.5 μg/g dry weight. Considering the PAHs, Tamiahua, Carmen, and Tampamachoco lagoons registered the highest levels, with values > 60 ng/g dry weight. In tissues from C. virginica, La Pesca, Cármen and Mecoacán presented the highest PAHs concentrations with values between 0.20 and 0.25 μg/g dry weight. Furthermore, from the molecular analysis of genes related with different phases of the xenobiotic detoxification process such as hypoxia inducible factor (hif-1a), cytochrome P450 10 (cyp10), flavin mono-oxygenase (fmo), glutathione S-transferase (gstΩ1), multidrug resistant protein (mdrd1), catalase (cat), among others, the differences between lagoons were significant (P< 0.05) and generally with Las Enramadas showing the highest expression levels. From genes evaluated in this study, hif-1a, cyp10, fmo, mdrd1 and cat presented the highest expression differentials between lagoons. The above allowed us to validate the utility of molecular markers in the assessment of the hydrocarbons effect on oyster under the conditions from the Southern Gulf of Mexico.