Abstract
The culture of the common octopus (Octopus vulgaris) is promising since the species has a relatively short lifecycle, rapid growth, and high food conversion ratios. However, recent attempts at successful paralarvae culture have failed due to slow growth and high mortality rates. Establishing an optimal nutritional regime for the paralarvae seems to be the impeding step in successful culture methods. Gaining a thorough knowledge of food regulation and assimilation is essential for paralarvae survival and longevity under culture conditions. The aim of this study, then, was to elucidate the characteristic metabolic organization of octopus paralarvae throughout an ontogenic period of 12 days post-hatching, as well as assess the effect of diet enrichment with live prey containing abundant marine phospholipids. Our results showed that throughout the ontogenic period studied, an increase in anaerobic metabolism took place largely due to an increased dependence of paralarvae on exogenous food. Our studies showed that this activity was supported by octopine dehydrogenase activity, with a less significant contribution of lactate dehydrogenase activity. Regarding aerobic metabolism, the use of amino acids was maintained for the duration of the experiment. Our studies also showed a significant increase in the rate of oxidation of fatty acids from 6 days after-hatching. A low, although sustained, capacity for de novo synthesis of glucose from amino acids and glycerol was also observed. Regardless of the composition of the food, glycerol kinase activity significantly increased a few days prior to a massive mortality event. This could be related to a metabolic imbalance in the redox state responsible for the high mortality. Thus, glycerol kinase might be used as an effective nutritional and welfare biomarker. The studies in this report also revealed the important finding that feeding larvae with phospholipid-enriched Artemia improved animal viability and welfare, significantly increasing the rate of survival and growth of paralarvae.
Highlights
Commercial octopus fishing has been exploited for several decades leading to strict regulations on fishing practices
Enzymes involved in protein metabolism, the activity of glutamate oxaloacetate transaminase (GOT), showed significant increase from day 3 post-hatching, remaining significantly higher until day 9
The results showed that dry weight (DW) was significantly higher in paralarvae from the LC group compared to the control group at 12 days old (P < 0.05)
Summary
Commercial octopus fishing has been exploited for several decades leading to strict regulations on fishing practices. Attempts have been made to culture Octopus vulgaris in captivity. These practices remain promising since the species has a relatively short lifecycle, fast growth, and high food conversion ratios. Nutritional deficiencies and food source imbalances are considered the primary causes for low paralarvae survival and growth, other factors related to zootechnical conditions (such as, tank volume, culture density, and light) cannot be ruled out (Iglesias and Fuentes, 2014). On the other hand, Navarro et al (2014) reported that a nutritional imbalance in both content and profile of the fatty acid in artificial food sources may be responsible for high mortalities since reared paralarvae differ from recently hatched individuals especially in these aspects. It is essential to have a thorough knowledge of the physiological processes regulating food assimilation and metabolism
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