Dr. Urzua-Osorio, Angel

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.

Environmental variables are pivotal factors for the condition of marine invertebrate species with a complex life cycle, influencing larval biochemical composition, and therefore, indirectly affecting later benthic stages. We herein explore the physiological responses of the fishery resource the red squat lobster (Pleuroncodes monodon) under contrasting environmental conditions of seawater surface temperature and planktonic food availability in the Humboldt Current System (HCS), through the analysis of larval condition and its consequences in the HCS. Larval condition was measured as dry weight, biochemical composition and fatty acids profile at hatching during ‘late summer’ (i.e. March) and ‘early winter’ (i.e. June). Larvae hatching from larger eggs produced in winter months showed a higher size, dry weight and a higher content of bioenergetic fuel (i.e. lipids and essential fatty acids) compared to those from larvae hatching in summer months. Temperature and food availability can to be key driving factors favouring an evolution of temporal variability in larval condition of the red squat lobster. These physiological adaptations provide an extension of the reproductive period of P. monodon, specifically planktonic larval development during ‘early winter’, characterized by a period with restricted food availability and lower temperatures than ‘late summer’.

Decapods have successfully colonized changing coastal habitats throughout the world by adapting their behavior, physiology, and biochemistry. Biochemical reserves, such as lipids and fatty acids (FAs), play fundamental roles in this adaptation process. These energy reserves are key for the development of decapods and their composition mainly depends on the type and quality of food available in their habitats. This study evaluated the lipid content and FA composition of three tissues (hepatopancreas, gills, and muscle) in two widely distributed, semi-terrestrial coastal crab species in Chile, Cyclograpsus cinereus from the upper intertidal and Hemigrapsus crenulatus from estuaries. This evaluation aimed to assess the physiological role of the bioenergetic reserves of these crabs, which tolerate fluctuating environmental conditions. Our results showed that both species had a higher lipid content in the hepatopancreas and a lower lipid content in its gills and muscle. All three of the evaluated tissues in C. cinereus showed high contents of saturated fatty acids (SFAs), and its hepatopancreas displayed the highest contents of monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs). In turn, H. crenulatus had the highest contents of MUFAs and PUFAs in its gills and muscle tissues, including an important amount of eicosapentaenoic acid (EPA). The FA content of C. cinereus may indicate an adaptive physiological response aimed at maintaining its cellular fluid balance during periods of desiccation in the upper intertidal zone. In contrast, the FAs found in H. crenulatus may be linked to the high activity of the sodium‑potassium pump in its gills, in order to maintain osmoregulation in estuaries.

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.

The estuarine crab Hemigrapsus crenulatus is a key benthic species of estuarine and intertidal ecosystems of the South Pacific, habitats that experience wide fluctuations in salinity. The physiological strategies that allow this crab to thrive under variable salinities, and how they change during the benthic stages of their life cycle, were evaluated under laboratory conditions. Oxygen consumption, ammonia excretion and the regulatory capacity of Na+ through the normal range of environmental salinities (i.e. 5, 10, 15, 20, 25, 30) were evaluated in three size classes, ranging from juveniles to adults. In all sizes, the oxygen consumption, ammonia excretion and regulatory capacity of Na+ decreased as salinity increased, with the highest values at 5 and the lowest values at 30 salinity. Bigger crabs showed a higher capacity to regulate Na+, as well as higher respiration and excretion rates compared to smaller crabs, suggesting that they are better equipped to exploit areas of the estuary with low salinity. Regardless of its size, H. crenulatus is a strong hyper regulator in diluted media (i.e. 5–20) while a conformer at salinities higher than 20. The regulatory capacity of Na+ was positively related with oxygen consumption and ammonia excretion rates. These relationships between sodium regulation, respiration and excretion are interpreted as adaptive physiological mechanisms that allow H. crenulatus to maintain the osmotic and bioenergetic balance over a wide range of environmental salinities.