Dr. Urzua-Osorio, Angel

The temporal dynamics of energy reserves are associated with the physiological processes (i.e., reproduction) in marine fishes, in which storage organs play a key role for efficient energy investment. We evaluated the temporal (i.e., seasons) and intra-individual (i.e., organs) dynamics of adult female swordfish (Xiphias gladius) during its feeding period off the Chilean coast in the southeastern Pacific Ocean (SEPO). The biochemical composition (i.e., lipids, proteins, and glucose), energy content and fatty acid profile of the muscle, liver and gonad were evaluated during the austral autumn, winter, and spring. Our results showed principally an intra-individual effect in both the muscle and liver in the autumn and spring. Herein, a trend of higher amounts of lipids and total energy were found in the muscle, while the liver showed greater protein and glucose contents. Consequently, the muscle showed a higher saturated, monounsaturated, and polyunsaturated fatty acid contents than the liver. Although the gonad showed no significant temporal effect in the lipids and proteins contents, an increasing trend of each biochemical constituent, fatty acid group and gonadosomatic index were found from autumn to winter. Consistently, the glucose and total energy content as well Fulton's condition factor were significantly higher in winter. These findings reflect the spatial-temporal physiological dynamic of swordfish based on the storage of energy reserves in different organs during its feeding period. In this way, the products obtained from swordfish could have an added value depending on the season and capture zone, which could benefit the exploitation and regulation measures of this resource under an ecological approach of conservation and sustainability in the SEPO.

Upwelling oceanographic phenomenon is associated with increased food availability, low seawater temperature and pH. These conditions could significantly affect food quality and, in consequence, the growth of marine species. One of the most important organismal traits is somatic growth, which is highly related to skeletal muscle. In fish, skeletal muscle growth is highly influenced by environmental factors (i.e. temperature and nutrient availability) that showed differences between upwelling and downwelling zones. Nevertheless, there are no available field studies regarding the impact of those conditions on fish muscle physiology. This work aimed to evaluate the muscle fibers size, protein content, gene expression of growth and atrophy-related genes in fish sampled from upwelling and downwelling zones. Seawater and fish food items (seaweeds) samples were collected from upwelling and downwelling zones to determine the habitat's physical-chemical variations and the abundance of biomolecules in seaweed tissue. In addition, white skeletal muscle samples were collected from an intertidal fish to analyze muscular histology, the growth pathways of protein kinase B and the extracellular signal-regulated kinase; and the gene expression of growth- (insulin-like growth factor 1 and myosin heavy-chain) and atrophy-related genes (F-box only protein 32 and muscle RING-finger protein-1). Upwelling zones revealed higher nutrients in seawater and higher protein content in seaweed than samples from downwelling zones. Moreover, fish from upwelling zones presented a greater size of muscle fibers and protein content compared to downwelling fish, associated with lower protein ubiquitination and gene expression of F-box only protein 32. Our data indicate an attenuated use of proteins as energy source in upwelling conditions favoring protein synthesis and muscle growth. This report shed lights of how oceanographic conditions may modulate food quality and fish muscle physiology in an integrated way, with high implications for marine conservation and sustainable fisheries management.

Porcelain crabs that inhabit contrasting environments along the Southeastern Pacific coast have developed physiological adaptive responses to the harsh environmental conditions. However, it is not yet known if these responses are already present in early life stages, in embryos, for example, which are more vulnerable to environmental fluctuations than adults. In this study, we subjected ovigerous female crabs of three crab species (Allopetrolisthes punctatus,Petrolisthes laevigatus, andPetrolisthes violaceus) to different periods of emersion (0, 1, 3, and 5 hr) to measure the weight and biochemical parameters (i.e., glucose and lactate) in their embryos after a period of stress induction through emersion. The results indicate that after five hours of emersion,P. laevigatus' embryos had the highest dry weight. This same trend was observed in the embryos ofP. violaceus.Allopetrolisthes punctatus' embryos had the lowest weight. The embryos' glucose content inP. laevigatusandP. violaceuswas consumed during the emersion time, while in embryos ofA. punctatusit remained relatively constant. The highest glucose content was reported inP. laevigatus, followed byP. violaceusandA. punctatus. The lactate content showed an opposite trend and was gradually accumulated with increasing emersion time.Petrolisthes laevigatushad the highest lactate content. This study reveals that the early ontogeny of these porcelain crabs is well adapted to long periods of emersion, showing biochemical adaptive responses linked to aerobic metabolism. These adaptations could reflect a distinctive physiological trait, explaining why porcelain crabs are able to survive in contrasting conditions.

Marine-derived nutrients (MDN) contained in gametes (mature eggs and sperm), carcasses and metabolic wastes from anadromous migratory salmon can transfer energy and materials to fresh water, thereby affecting the structure and function of stream ecosystems. This is crucial among ecosystems where humans have mediated biological invasions by propagating non-native species. Previous studies have demonstrated that consumption of MDN from salmon can benefit both native and invasive resident fishes. Yet, a more detailed understanding of the transfer of biomolecules with important physiological functions such as ω-3 highly unsaturated fatty acids (HUFAs) have received less attention among researchers. Here we demonstrate that consumption of MDN contained in invasive Chinook salmon eggs transfers ω-3 HUFAs (e.g., EPA and DHA) to resident invasive rainbow trout in a river food web. We conducted a field study in river sections previously identified as spawning areas for Chinook salmon in the Cisnes River, Patagonia. Rainbow trout were sampled around salmon spawning areas before, during, and after the salmon spawning season. Additionally, we collected tissue from different food web resources and components of different origin (e.g., primary producers, aquatic and terrestrial items) from the Cisnes River system. Analyses of stomach contents of trout were performed in conjunction with analyses of both lipid content and fatty acid profiles of trout tissue and food web components. Chinook salmon eggs showed higher content of ω-3 HUFAs, especially EPA (31.08 ± 23.08 mg g DW−1) and DHA (27.50 ± 14.11 mg g DW−1) than either freshwater or terrestrial components (0–6.10 mg g DW−1 both EPA and DHA). We detected marked shifts in the fatty acid profile (~six-fold increase in EPA and DHA) of trout following consumption of Chinook salmon eggs. Our findings suggest that MDN via consumption of salmon eggs by resident rainbow trout may positively influence resident trout and likely contribute to gauge synergistic interactions between invaders on receiving ecosystems of Patagonia.

Alexandrium catenella, one of the most common harmful microalgae observed in southern Chile, produces paralytic shellfish toxins, which can affect many organisms throughout the trophic chain. This research evaluated how paralytic shellfish toxins affected the principal bioenergetic constituents and fatty acids composition of the carnivorous snail Chorus giganteus. Snails were separated into a “toxic” group that was fed the toxic clam Mulinia edulis (which was previously fed A. catenella), and a “non-toxic” group, fed non-toxic clams. Both groups were kept under these conditions for 63 days. Our results indicated no difference in the ingestion rate of toxic versus non-toxic snails; however, a higher protein level was identified in toxic snails. The total lipid content proved to be no different in toxic versus non-toxic snails; although, an effect of the toxic diet on the fatty acid profile of C. giganteus was observed. High levels of essential polyunsaturated fatty acids, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) in toxic snails, were identified. Our results suggest that exposure to paralytic shellfish toxins, through diet, may cause changes in the biochemical composition of C. giganteus, which may have a subsequent impact on its energetic physiology.

Pleuroncodes monodon from the Chilean coast has seasonal reproduction. During the seasonal period, females and their eggs are exposed to seasonal variation in environmental conditions. In P. monodon populations inhabiting the Southern Pacific coast near Concepción, Chile, we quantified late summer (February–March 2014) and late winter (August–September 2014) seasonal variations in female reproductive parameters (carapace length, fecundity, reproductive output (RO), ash weight, organic content) as well as eggs parameters (length, volume, dry weight, organic content). There was conspicuous seasonal variation in the main reproductive parameters of this species. During the summer, the number of eggs and organic content of females were higher than winter, whereas RO was slightly higher in winter than in summer. Significant variation in the size and biomass of the eggs was also found between seasons. For example, eggs laid in summer were smaller, had a lower measured dry mass, and had a lower organic content than eggs laid in winter. Seasonal variations in the fecundity and size of the eggs have implications for fishery models, which can be used to estimate the relative contribution of different cohorts to recruitment and stability of adult benthic populations.

In coastal Antarctic environments, glacial meltwater changes the nutrients and physicochemical parameters in the water column. Consequently, top-down cascading effects are triggered throughout the food web, which can affect the bioenergetic condition of benthic invertebrates and their coupling processes between energy levels and flows throughout the marine food web. In this study, two benthic polychaetes (Maldane sarsi antarctica and Notomastus latericeus), exposed to the impact of glacial melting over a broad time scale, were used to evaluate the effect of glacial meltwater on their bioenergetic condition through the integrated analysis of: i) their biochemical composition; ii) fatty acid profiles and iii) total energy contents. The findings indicate that glacial meltwater has a direct effect on the bioenergetic condition of polychaetes. In areas where glacial meltwater has a significant impact, N. latericeus showed higher levels of proteins and glucose, but lower levels of lipids. On the other hand, M. sarsi antarctica exhibited decreased protein content with increasing glacial meltwater impact. M. sarsi antarctica presented varying levels of lipids across different sites, with the highest concentrations observed in areas with moderate impact. Both species showed a reduction in fatty acids with increasing glacial meltwater impact. Additionally, M. sarsi antarctica individuals from highly impacted areas had lower energy levels than those from less impacted areas, while N. latericeus had higher energy levels in the most impacted site. This information enables the development of a framework for assessing the impact of climate change using glacial meltwater and the integrated bioenergetics of key benthic polychaeta as a proxy. Therefore, identifying how glacial meltwater affects their bioenergetic condition helps us understand how climate change could affect trophic interactions, structure, and energy flows in the Antarctic marine food web.

The fishery resource Concholepas concholepas is a key species in the benthic marine ecosystems of the Southeastern Pacific Ocean. In the present study, the spatio-temporal changes in the biochemical parameters were evaluated for adult individuals of C. concholepas. They were sampled in summer and winter under upwelling and Non-upwelling conditions in two Management and Exploitation Areas for Benthic Resources of Valparaíso, Chile. The results indicated that the variation in the biochemical parameters is explained to a greater extent by the season. For example, in both upwelling and Nonupwelling conditions, we found a higher content of total lipids, proteins, glucose, and energy in winter than summer. Temporal variations can be explained by the reproductive process after summer season, in which the egg spawning require a greater energy reserves to be perform. Nonetheless, differences in the nutritional status of preys along seasons of the year, can also influence on these results. In fact, these variations in the biochemical parameters of C. concholepas may be indicative of an adaptive seasonal physiological response to the environment for maintaining an optimal energy budget year-round. Altogether, this knowledge will contribute to the Management and Exploitation Areas for Benthic Resources, improving regulatory measures during the annual period of captures and landings of C. concholepas, favoring a more sustainable fishery in the Southeastern Pacific Ocean within an ecosystem approach.

Pleuroncodes monodon is an important fishery resource and key species from the Southeastern Pacific. During its prolonged reproductive period (from February to December), ovigerous females are exposed to seasonal variation in environmental factors (e.g. temperature and food availability), with higher levels of these environmental parameters during summer and lower in winter, and must adjust their biochemistry to ensure their own survival and that of their embryos. The aim of this study was to analyse seasonal changes in the biochemical composition of ovigerous females and their eggs. The data show that the content of lipids, proteins and organic matter in the hepatopancreases of females was significantly higher in winter than in summer. Similarly, the lipid content of the eggs was significantly higher in winter than in summer, yet the protein content of the eggs had the opposite pattern with greater values found in summer. Consistent with the ‘reproductive energetic model’, the initial and final energy produced by the hepatopancreas showed significant seasonal variations, whereas female investment in egg production (in absolute values) did not show significant seasonal differences. The seasonal differences observed in the biochemistry, organic matter and energy content of the female hepatopancreases may be related to the storage of energy for growth and reproduction. Furthermore, the seasonal variation in the content of lipids, proteins and energy in eggs is likely related to embryogenesis and larval hatching in function with environmental conditions. Seasonal variation in the biochemical composition of P. monodon has direct effects on the marine food web and also upon fisheries.

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.