Long‐term mild hypoxia does not reduce thermal tolerance or performance of the freshwater prawn Macrobrachium tenellum

Abstract

The present study was designed to assess the performance of the freshwater prawn Macrobrachium tenellum in optimal and sub-optimal dissolved oxygen conditions, considering increasing environmental pressures. Thermal tolerance and thermal metabolic scope (TMS) with related integrated biomarker response (IBR) were measured in prawns exposed to normoxia (80% air saturation), mild (40% air saturation) and severe hypoxia (25% air saturation) at three exposure time points (10, 20 and 30 days). Effects of hypoxia on thermal tolerance were not detectable over time; they were perhaps masked by hyperventilation, or by an increase or diversion of haemolymph processes.After 30 days, TMS was 11% higher in mild hypoxia compared with normoxia, while it was 64% lower in severe hypoxia, indicating the loss of aerobic metabolism capacity during the latter. Mild-hypoxia prawns maintained a high IBR over time, supported by antioxidant enzyme activities (mainly superoxide dismutase), which helped avoid the serious oxidative damage (proteins and lipids) seen in severe hypoxia animals, as well as lower acetylcholinesterase activity that indicated failure of communication between the nervous and locomotor systems. Our results documented a high tolerance by M. tenellum to mild-hypoxia events, which should be further tested under seasonal and extreme habitat/tank temperatures.

Variations of digestive enzymatic activity of the longarm river prawn, Macrobrachium tenellum (Smith 1871) adapted from the wild to culture with prepared meals

“…Those capabilities are because of its adaptations to live in rivers, coastal lagoons, and estuaries, which are places varying in its water physicochemistry. The species is adapted to survive in wide intervals of salinity (0-14 ppt; Vargas-Ceballos et al, 2018), temperature (17-29.5 C; Hernández-Sandoval et al, 2018), and dissolved O 2 (from 3 mg L À1 to saturation; Tremblay et al, 2021). However, this exposes them to different food kinds, seasonally and spatially (De Los Santos et al, 2020).…”