Dr. Urzua-Osorio, Angel

In the Southeast Pacific Ocean, Xiphias gladius migrates through the Chilean coastal zone for feeding. Here, it forages for different prey items from autumn to spring, acquiring a great variety of energy and nutritional reserves. We evaluated seasonal variations in the biochemical reserves (i.e., contents of lipids, proteins, and glucose), total energy content and fatty acid profile of specimens captured during the austral autumn, winter, and spring. Our results show that higher amounts of lipids were found in the winter and spring, while protein and glucose were higher in the autumn. Thus, the energy content showed significant differences, with higher levels in winter and spring. Furthermore, the fatty acid profile was more diverse in the spring than the autumn and winter and was characterized by higher amounts of polyunsaturated fatty acids. These findings suggest that temporal changes in the biochemical reserves, total energy content and fatty acid profile support the idea of a “trophic migration” (i.e., the feeding period) established by the dynamics of fishery fleets. The high amounts of lipids and diverse fatty acid profile found in the spring could indicate the end of the trophic migration during this season. Thus, X. gladius may reach an optimum nutritional condition in the spring and make energetic adjustments to carry out its reproductive migration during the austral summer. Therefore, this species seems to meet the high energy demands of the reproductive season by foraging for a wide range of prey items from autumn to spring and storing an increased amount of lipids at the end of the feeding period. Overall, our data provides crucial baseline knowledge for future research on the ecophysiology of X. gladius, as well as for the management and conservation of this fishery resource under an ecosystem approach.

In this brief, non-exhaustive essay, we review major adaptive changes in reproductive and developmental traits of decapod crustaceans, which have passed through evolutionary transitions from ancestral life in coastal marine environments to brackish, limnic, polar, or deep-sea habitats. Two major approaches can be recognised in studies of life-history evolution, focussing on: (1) developmental changes in adaptive physiological or biochemical traits of successive ontogenetic stages, comparing, for instance, osmoregulatory capabilities in larvae, juveniles, and adults (“ontogeny of adaptations” perspective); (2) adaptive changes in the modes of reproduction and development, e.g., enhanced maternal energy investment in egg production, abbreviated, non-feeding larval development (“adaptations in ontogeny”). Using both scientific approaches, Christoph D. Schubart has significantly contributed to our understanding of evolutionary transitions in crustaceans. In our essay, we pay particular attention to the significance of nutritional selection factors in relation to presumably adaptive developmental, physiological, and biochemical traits in different life-history stages. In this context, we highlight the key roles of lipids and carotenoid pigments, in particular of essential polyunsaturated fatty acids (PUFAs) and astaxanthin. While PUFAs and other lipid compounds have received wide scientific attention, we propose that future studies should further analyse also the potential role of astaxanthin and other essential carotenoids.

Changes in environmental conditions play an important role in essential biological processes such as reproduction, which is partially driven by an organism’s diet. Here, we evaluate spatio-temporal variations in the bioenergetic reserves (lipids and fatty acids) of the fishery resource Concholepas concholepas (Loco), a prominent benthic carnivorous gastropod. We used data from summer (January) and winter (July) from two coastal localities that shown contrasting environmental conditions in central Chile (Quintay and Las Cruces). The results indicate that there is a correlation between the fatty acid profiles and the interactions between seasonality and locality. This was particularly evident among the fatty acid concentrations of docosahexaenoic (DHA, C22:6n-3), eicosapentaenoic (EPA, C20:5n-3) and arachidonic (ARA, C20:4n-6) acids, which were high in winter, in both localities. Contrastingly, palmitic (C16:0) and stearic (C18:0) acids were present among all comparisons at stable concentrations. These findings suggest an influence of environmental conditions on the availability and quality of the prey of C. concholepas, in both localities. Moreover, the high concentration of essential fatty acids during winter, could suggest an adaptive physiological response, to ensure reproductive success. This knowledge is indispensable to improve regulatory measures for the extraction periods of marine resources, towards a more sustainable fishery, in the Humboldt Current System.