Dr. Urzua-Osorio, Angel

In marine invertebrates, the bioenergetic fuel available for fundamental physiological processes (growth, reproduction) may present intra-individual variability depending on the storage organ, sex and state of sexual maturity. This variability is considered relevant information for fishery management. In the squid Dosidicus gigas, an important fishery resource, we analyzed adult males (immature vs. mature) and females (immature I vs. immature II) off the coast of Chile. Their bioenergetic fuel (protein, glucose, lipid and fatty acid content-FAs) was quantified in different organs of the body (digestive gland, gonad and mantle). When comparing the organs of males at both stages of maturity, a greater amount of glucose and lipids were observed in the digestive gland than in the gonad and mantle, while a higher protein content was recorded in the gonad. In turn, the same tendency of biochemical variations among the organs was observed for the female at both stages. Regarding the FA profiles of the analyzed organs, the digestive gland had the highest mean proportion of FAs. However, no significant differences were observed related to sex and sexual maturity. According to the multivariate analyses for both sexes and maturity stages, the FA profiles of the mantle and gonad showed overlap and a high similarity, while the profile of the digestive gland was completely dissimilar. Our findings indicate that D. gigas from Chilean coastal waters showed, mainly in the digestive gland, high levels of all biochemical constituents, which are obtained through food and stored in their organs as bioenergetic fuel, and may then be used for the subsequent process of migration and reproduction in oceanic waters.

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.

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.

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.

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.

Swordfish (Xiphias gladius), a highly migratory fishery resource of great importance in the Southeastern Pacific Ocean (SEPO), is a species with late sexual maturation, high longevity, and a large body size that spawns and reproduces several times throughout its adulthood. In the present study, we hypothesized that the Biochemical-Ecological Composition (BEC) of the gonad (measured as the lipid, protein, glucose, and energy contents) and its bio-stoichiometric ratios (lipid/protein: L/P; lipid/ glucose: L/G) would be influenced by both female body size (lower jaw fork length in cm, LJFL: <180, 180–260, >260) and time (trimesters: 1,2,3; years: 2017, 2019). Our results revealed that in relation to their body size, female swordfish gonads varied significantly in their BEC, but not in their L/P and L/G ratios during their quarterly development within an annual cycle. These variations in the BEC were noticeable in females of medium (180–260) and larger (>260) sizes. Particularly, as the year progressed, females stored significant amounts of energy during their trophic migration, made evident by the increase in the lipid and protein contents of the gonads, which reached maximum levels towards the end of the year, during the second and third trimesters. These high energy reserves can be used for the reproduction during the last trimester of the year (i.e. austral spring–summer), when the warm temperature and high productivity in the SEPO are optimal for the successful development of oocytes. Future studies considering an ecosystem approach should analyze the classes of lipids and types of fatty acids that are involved in the reproduction of this species, and how they are acquired through the consumption of lipid-rich prey, and subsequently metabolized to be used in reproduction and during early ontogeny.

One of the key factors affecting larval survival is food availability. This study investigated the influence of starvation on the nutritional condition of zoea I larvae of Pleuroncodes monodon. Experimental treatments with differential periods of starvation and subsequent feeding (point of no return: PNR) in addition to treatments with differential periods of feeding and subsequent starvation (point of reserve saturation: PRS) were used to quantify larval survival and the occurrence of lipid droplets in the hepatopancreas. Larval survival differed significantly depending on the starvation and feeding treatment administered. A high percentage of survival was found for the starvation treatment until day 1 (S1-PNR), for the feeding treatment until day 4 (F4-PRS), and for the continuously fed control groups (FC). Survival was minimal for the starvation treatment lasting until day 7 (S7-PNR) and for the continuously starved control groups (SC). In turn, similar tendencies were observed in the utilization of energy reserves; the lipid droplets significantly decreased throughout the PNR treatment, while the presence of lipid droplets gradually increased during the PRS treatment. All these larval condition parameters can be used in fishery models of population dynamics, which estimate the nutritional status of the offspring and their effects on survival.

Petrolisthes crabs inhabit a wide range of coastal environments, from the upper intertidal to the subtidal, experiencing regular changes in pH, salinity, and temperature. Hence, such subtidal and intertidal invertebrates are likely to show physiological and biochemical adaptive responses in order to successfully develop during early ontogenetic stages and thus reach reproduction. We herein evaluated the biochemical responses to contrasting environmental conditions of the early ontogenetic stages of two coastal crabs from the Southeast Pacific coast: Petrolisthes laevigatus and Allopetrolisthes punctatus. For this purpose, stage I embryos of both species were subjected to two treatments: (1) emersion (i.e., a daily 3 h aerial exposure until the zoeas hatched) and (2) immersion (i.e., uninterrupted underwater submersion until the zoeas hatched); the total contents of glucose, proteins, lipids, and fatty acids of the organisms were measured in stage I embryos and recently hatched zoeas in order to assess the biochemical constitution of the two species. Both species showed changes in their energetic reserves when treatments within species were compared. Our results found that A. punctatus was negatively affected by stressful periods of emersion, while P. laevigatus showed the opposite tendency and was affected by periods of immersion. The sensitivity of the response and the contrasting outcomes for these two crabs underpin the fact that changes in environmental conditions along the Chilean coast due to climate change (e.g., increased anoxic coastal waters) may have significantly negative consequences on the populations of these ecologically important species and the associated taxa within their ecosystems.

Upwelling systems deliver nutrient-rich water into coastal ecosystems, influencing primary productivity and potentially altering seaweed-herbivore interactions. Upwelling bottom-up effects on distinct trophic levels are wellknown. However, their influence on seaweed biomolecules and on algae-herbivore interactions and growth are less known. The aim of this study was threefold: i) to compare physical-chemical characteristics and nutrient levels in the water of upwelling (U) and downwelling (DU) zones, ii) to quantify their influence on the content of protein and carbohydrates in seaweed tissues of representative U and DU locations, and iii) to experimentally assess their effect on the feeding behavior and growth of a prominent intertidal herbivore, the sea urchin Loxechinus albus. Waters from U zones showed lower temperatures and pH, and higher phosphate concentrations than those from downwelling zones. Similarly, the tissue of seaweeds from a U location had significantly more proteins and carbohydrates than those from a DU location. The origin location of the sea urchins had a significant influence on consumption and growth rates: in general, those coming from a site with U conditions consumed and grew more than those coming from DU conditions. The quality of the algae was a significant factor on consumption rates, although in the case of preference trials, this factor interacted with sea urchin origin location. Our results show that the availability and quality of the food in upwelling zones has an influence on herbivore-seaweed direct interactions. However, these interactions and the growth of the sea urchins were also related to the coastal site and conditions from which the sea urchins came from. These results are relevant considering the expected impact of climate change on the world's oceans, and the importance of U zones as thermal (cold water) refuges for marine ectotherms.

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.