Preferential habitats prediction in syngnathids using species distribution models

Syngnathids are considered as flagship species for marine conservation. Seahorses and pipefish are highly vulnerable to anthropogenic and environmental disturbances, but most species are currently considered Data Deficient by IUCN, requiring more biological and ecological research. Although syngnathids are well known for their unusual breeding biology, some aspects on the ecology of this family have rarely received attention. The knowledge on the factors governing syngnathids distribution is limited to some species and geographical regions. The present study is the first approach to predict syngnathid habitat preference in Spanish coasts, particularly in a marine National Park. In this study, Species Distribution Models (SDMs) were implemented to investigate the preferential habitat and distribution of the pipefish Syngnathus acus in Cíes Archipelago (Atlantic Islands of Galicia National Park, PNIA). Occurrence data of the species obtained from 2016 to 2018 surveys in PNIA were modeled as a function of bathymetric (depth, slope), substrate (sediment texture) and oceanographic (waves exposure) variables, using GAM, Random Forest and Maxent algorithms. From those SDMs, prediction models were built and the ensemble map of predictions was performed. The variables that most determined the distribution of the species were depth and wave exposure. The results of this study provide information on (1) habitat preference in the most dominant species in PNIA, the pipefish S. acus, towards sustainable management of this species in the National Park, and (2) predictive statistical tools for proper spatial conservation plans of this syngnathid species.

Regulation of growth-related genes by nutrition in paralarvae of the common octopus (Octopus vulgaris)

The common octopus (Octopus vulgaris) is a species of great interest to the aquaculture industry. However, the high mortalities registered during different phases of the octopus lifecycle, particularly the paralarvae stage, present a challenge for commercial aquaculture. Improvement of diet formulation is seen as one way to reduce mortality and improve growth. Molecular growth-markers could help to improve rearing protocols and increase survival and growth performance; therefore, over a hundred orthologous genes related to protein balance and muscle growth in vertebrates were identified for the common octopus and their suitability as molecular markers for growth in octopus paralarvae explored. We successfully amplified 14 of those genes and studied their transcription in paralarvae either fed with artemia, artemia + zoea diets or submitted to a short fasting-refeeding procedure. Paralarvae fed with artemia + zoea had higher growth rates compared to those fed only with artemia, as well as a significant increase in octopus mtor (mtor-L) and hsp90 (hsp90-L) transcription, with both genes also up-regulated during refeeding. Our results suggest that at least mtor-L and hsp90-L are likely linked to somatic growth in octopus paralarvae. Conversely, ckip1-L, crk-L, src-L and srf-L had expression patterns that did not match to periods of growth as would be expected based on similar studies in vertebrates, indicating that further research is needed to understand their function during growth and in a muscle specific context.

Temperature-independent genome-wide DNA methylation profile in turbot post-embryonic development

The morphological and biological characteristics of ectothermic vertebrates are known to be strongly influenced by environmental conditions, particularly temperature. Epigenetic mechanisms such as DNA methylation have been reported to contribute to the phenotypic plasticity observed in vertebrates in response to environmental changes. Additionally, DNA methylation is a dynamic process that occurs throughout vertebrate ontogeny and it has been associated with the activation and silencing of gene expression during post-embryonic development and metamorphosis. In this study, we investigated genome-wide DNA methylation profiles during turbot metamorphosis, as well as the epigenetic effects of temperature on turbot post-embryonic development. Fish growth and rates of development were greatly affected by rearing temperature. Thus, turbot raised at ambient temperature (18 °C) achieved greater body weights and progressed through development more quickly than those reared at a colder temperature (14 °C). Genome-wide DNA methylation dynamics analyzed via a methylation-sensitive amplified polymorphism (MSAP) technique were not significantly different between animals reared within the two different thermal environments. Furthermore, comparisons between phenotypically similar fish revealed that genome-wide DNA methylation profiles do not necessarily correlate with specific developmental stages in turbot.

Effect of triploidy on digestive enzyme activity of early stages of turbot (Scophthalmus maximus)

In the present work, growth and digestive enzyme activities of total acid and alkaline proteases, pepsin, trypsin, lipase, and α-amylase, as well as partial characterization of enzyme activity, were studied in diploid and triploid turbot. Growth was similar between both groups. Acid protease activity increased consistently during the experiment, for both diploid (2n) and triploid (3n) fish. The alkaline protease activity was always higher for triploids throughout the experiment. Proteolytic acid activity (pH 2) was generally higher for diploids, at all temperatures tested. Higher activity was at pH 2 and 3 for 2n and 3n fish, respectively. Regarding temperature, acid and alkaline protease activity was higher at 37 °C and 60 °C, respectively, for both groups. The general increase in pancreatic enzymes (trypsin and amylase) before 35 days after hatching (DAH) and posterior decrease until 60 DAH. There was a marked effect on enzyme activity when changing from live prey to pellets (35 DAH), especially on triploids.