Ontogenetic shift in the energy allocation strategy and physiological condition of larval plaice (Pleuronectes platessa)

PLoS One. 2019 Sep 16;14(9):e0222261. doi: 10.1371/journal.pone.0222261. eCollection 2019.

Abstract

Condition indices aim to evaluate the physiological status of fish larvae by estimating both the level of starvation and potential of survival. Histological indices reveal direct effects of starvation whereas biochemical indices such as lipid classes or RNA:DNA ratios are used as proxies of condition, giving information on the amount of energy reserves and growth rate, respectively. We combined these three indices to evaluate ontogenetic variations of growth performance, lipid dynamics and nutritional condition of plaice larvae caught in the field during winter 2017 in the eastern English Channel and the Southern Bight of the North Sea. RNA:DNA ratios showed that larvae at the beginning of metamorphosis (stage 4) had a lower growth rate than younger individuals (stages 2 and 3). A significant increase in the proportion of triglycerides also occurred at stage 4, indicating energy storage. Histological indices indicated that most of the larvae were in good condition, even younger ones with low lipid reserves. There was, however, an increase in the proportion of healthy individuals over ontogeny, especially with respect to liver vacuoles which were larger and more numerous for stage 4 larvae. Combined together, these condition indices revealed the ontogenetic shift in the energy allocation strategy of plaice larvae. Young larvae (stages 2 and 3) primarily allocate energy towards somatic growth. The decrease in growth performance for stage 4 was not related to poor condition, but linked to a higher proportion of energy stored as lipids. Since the quantity of lipid reserves is particularly important for plaice larvae to withstand starvation during metamorphosis, this could be considered as a second critical period after the one of exogenous feeding for larval survival and recruitment success.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • DNA / genetics
  • Energy Metabolism / genetics
  • Energy Metabolism / physiology*
  • Flounder / genetics
  • Flounder / physiology*
  • Genetic Variation / genetics
  • Larva / genetics
  • Larva / physiology*
  • Lipids / genetics
  • Liver / physiology
  • Metamorphosis, Biological / genetics
  • North Sea
  • RNA / genetics
  • Starvation / genetics
  • Starvation / physiopathology

Substances

  • Lipids
  • RNA
  • DNA

Associated data

  • figshare/10.6084/m9.figshare.9742496.v2

Grants and funding

This work was supported by IFREMER and the Pôle Métropolitain de la Côte d'Opale through the PhD of Julien Di Pane. This work was also supported by Recherche marine et littorale en Côte d’Opale, des milieux aux ressources, aux usages et à la qualité des produits de la mer https://marco.univ-littoral.fr/. This study was partly funded by the SFR Campus de la mer (grant 2019 ULCO). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.