Differential survivorship of congeneric ornamental fishes under forecasted climate changes are related to anaerobic potential

Abstract

Two Amazonian closely related tetras – cardinal Paracheirodon axelrodi and green neon P. simulans – were artificially acclimatized to environmental chambers mimicking future climate change scenarios (mild, moderate and extreme), using a microcosm facility. P. simulans survived (100%) to all scenarios after 30 days exposure, while P. axelrodi presented decreasing survival percentages according to environmental severity. These differences may be the reflection of distinct natural acclimatization to microhabitats between the species, which differ in thermal conditions. Survival responses might be related to differences in relative gene expression of lactate dehydrogenase (Ldh), suggesting that P. axelrodi anaerobic potential is lower or non-existent compared to P. simulans, not tolerating long-term thermal challenges. Accordingly, increases in temperature and in CO2 levels caused increases in energy demand and resulted in activation of the anaerobic pathway, as demonstrated by the higher enzyme levels measured in head and tail portions of both species. Sustained anaerobic glycolysis is possible when fish live in challenging environments (low oxygen or high temperature). Our results clearly show that P. simulans has a larger scope for survival to higher energy demands due to its increased anaerobic potential compared to P. axelrodi.

Capítulo 20: Impulsores e impactos de los cambios en los ecosistemas acuáticos

“…Cardinal tetras are sensitive to increased temperatures (Fé- Gonçalves et al 2018). The two congeneric species of cardinal tetras are distributed in inter-fluvial areas in the upper part of the Rio Negro Basin and inhabit two distinct environments with different vegetation covers and temperatures (Marshall et al 2011).…”

“…Increased temperatures and reduced oxygen concentrations resulting from reduced water volumes are expected to be detrimental for many aquatic organisms, including fish (Lake 2003;Ficke et al 2007;Frederico et al 2016;Nelson and Val 2016;Gonçalves et al 2018;Lapointe et al 2018;Campos et al 2019). In adult organisms, energy is allocated to growth, reproduction, and maintenance metabolism (Val and Almeida-Val 1995;Almeida-Val et al 2006;Wootton 1998).…”

Transcriptomic evidences of local thermal adaptation for the native fish Colossoma macropomum (Cuvier, 1818)

“…In general, fish are highly able to respond plastically to a myriad of environmental changes, but whether their plastic responses are beneficial seems to depend on the environmental variable that they are being subjected to ( Schulte, 2001 ). Climate changes may negatively affect fish populations living close to their thermal comfort zone ( Pörtner and Peck, 2010 ), and fish, particularly in the Amazon region, will be those most threatened ( Fé-Gonçalves et al , 2018 ; Campos et al , 2019 ).…”