Abstract
Sexual maturation and reproduction influence the status of a number of physiological processes and consequently the ecology and behaviour of cephalopods. Using Octopus mimus as a study model, the present work was focused in the changes in biochemical compound and activity that take place during gonadal maturation of females and its consequences in embryo and hatchlings characteristics. To do that, a total of 31 adult females of O. mimus were sampled to follow metabolites (ovaries and digestive gland) and digestive enzyme activities (alkaline and acidic proteases) during physiological and functional maturation. Levels of protein (Prot), triacylglyceride (TG), cholesterol (Chol), glucose (Glu), and glycogen (Gly) were evaluated. Groups of eggs coming from mature females were also sampled along development and after hatching (paralarvae of 1 and 3 days old) to track metabolites (Prot, TG, Glu, Gly, TG, Chol), digestive enzymes activity (Lipase, alkaline proteases, and acidic proteases), and antioxidant/detoxification defence indicators with embryos development. Based on the data obtained, we hypothesized that immature females store Chol in their ovaries, probably from the food they ingested, but switch to TG reserves at the beginning of the maturation processes. At the same time, results suggest that these processes were energetically supported by Glu, obtained probably from Gly breakdown by gluconeogenic pathways. Also, was observed that embryos metabolites and enzyme activities (digestive and antioxidant/detoxification enzymes) where maintained without significant changes and in a low activity during the whole organogenesis, meaning that organogenesis is relatively not energetically costly. In contrast, after organogenesis, a mobilization of nutrients and activation of the metabolic and digestive enzymes was observed, together with increments in consumption of yolk and Gly, and reduction in lipid peroxidation. Derived from our results, we also have the hypothesis that reactive oxygen species (ROS) were produced during the metabolic processes that occurs in ovarian maturation. Those ROS may be in part transferred to the egg provoking a ROS charge to the embryos. The elimination of ROS in embryos started when the activity of the heart and the absorption of the yolk around stages XIV and XV were evident. Altogether, these processes allowed the paralarvae to hatch with buffered levels of ROS and with the antioxidant defence mechanisms ready to support further ROS production derived from paralarvae higher life stage requirements (feeding and metabolic demands).
Highlights
Sexual maturation and reproduction influence the status of a number of physiological processes and the animal’s ecology and behaviour (Zamora & Olivares, 2004)
Both eviscerated body weight (EBW) and BW, as well as the ovaries weight (OW) and reproductive system weight (RSW) were strongly correlated with PCoA1, suggesting they largely contributed to the separation of samples in the horizontal axis
Results obtained in the present study demonstrate that ovarium is a site for the reserve of some nutrients for reproduction
Summary
Sexual maturation and reproduction influence the status of a number of physiological processes and the animal’s ecology and behaviour (Zamora & Olivares, 2004). Earlier studies realized in four cephalopods species indicated energy acquisition for egg production directly from food rather than from stored products in digestive glands (DGs) or muscle (Farías et al, 2011; Rosa, Costa & Nunes, 2004). This finding highlighted the importance of trophic ecology for optimal reproduction of those species, awaking the need for laboratory studies assessing the influence of each type of food on the biochemical characteristics of octopus eggs, embryos and hatchlings (Márquez et al, 2013; Steer et al, 2004). The way nutrients are processed in females during maturation, stored in eggs and used afterward by embryos for their development still remain unknown
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