Oxidative Stress and Digestive Enzyme Activity of Flatfish Larvae in a Changing Ocean

Abstract

Until now, it is not known how the antioxidant and digestive enzymatic machinery of fish early life stages will change with the combined effects of future ocean acidification and warming. Here we show that high pCO2 (~1600 μatm) significantly decreased metabolic rates (up to 27.4 %) of flatfish larvae, Solea senegalensis, at both present (18 °C) and warmer temperatures (+4 °C). Moreover, both warming and hypercapnia increased the heat shock response and the activity of antioxidant enzymes, namely catalase (CAT) and glutathione S-transferase (GST), mainly in post-metamorphic larvae (30 dph). The lack of changes in the activity of CAT and GST of pre-metamorphic larvae (10 dph) seems to indicate that earlier stages lack a fully-developed antioxidant defense system. Nevertheless, the heat shock and antioxidant responses of post-metamorphic larvae were not enough to avoid the peroxidative damage, which was greatly increased under future environmental conditions. Digestive enzymatic activity of S. senegalensis larvae was also affected by future predictions. Hypercapnic conditions led to a decrease in the activity of digestive enzymes, both pancreatic (up to 26.1 % for trypsin and 74.5 % for amylase) and intestinal enzymes (up to 36.1 % for alkaline phosphatase) in post-metamorphic larvae. Moreover, the impact of ocean acidification and warming on some of these physiological and biochemical variables (namely, lower OCR and higher HSP and MDA levels) were translated into larvae performance, being significantly correlated with decreased larval growth and survival or increased incidence of skeletal deformities. The increased vulnerability of flatfish early life stages under future ocean conditions is expected to potentially determine recruitment and population dynamics in marine ecosystems.

The development of contemporary European sea bass larvae (Dicentrarchus labrax) is not affected by projected ocean acidification scenarios

“…Studies that examined larval development through the maturation of this specific function are still scarce and only one used similar proxies to ours (Pimentel et al 2015). These authors reported normal ontogenetic development under acidification conditions (: 1600 µatm, pH 7.5), even if a general decrease in enzymatic activities was observed.…”

Investigations of temperature and pH variations on metal trophic transfer in turbot (Scophthalmus maximus)

“…In contrast to temperature, fewer studies investigated the influence of pH on the assimilation of metals by marine biota (Lacoue-Labarthe et al 2011;Götze et al 2014;Ivanina et al 2015), and to the best of our knowledge, even none has investigating the influence of pH on metal trophic transfer in fish. However, in the context of the current ocean acidification, some authors have recently highlighted the effects of the partial pressure of CO2 (pCO2) on the digestion of fish (Pimentel et al 2015;Rosa et al 2016). Indeed, these authors have shown that the activity of the digestive enzymes in marine fish is dependent of the pCO2.…”

“…However, few studies indicated that pH can alter the structure and functioning of the digestive tract (e.g. Frommel et al 2014), and even the digestive enzyme activities (Pimentel et al 2015;Rosa et al 2016) of early stages of marine fish.". The variation of temperature and pH may occur simultaneously, and organisms can be affected differently by them.…”

Repellent action and contact toxicity mechanisms of the essential oil extracted from Chinese chive against Plutella xylostella larvae

“…A pool of 10 larvae was homogenized in 4 ml of saline buffer (pH 7) and centrifuged at 13,000 g for 15 min. The supernatant was used as the enzyme source (Pimentel et al, ). Six replicates were used for each treatment.…”