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.

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.