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

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.

Pre-breeding Diets in the Seahorse Hippocampus reidi: How Do They Affect Fatty Acid Profiles, Energetic Status and Histological Features in Newborn?

“…Hence, the quantity of lipid of energy reserves would be particularly important for the newborns to withstand starvation or low-quality prey supply, especially in species lacking yolk sac at hatching (e.g., seahorses). However, the presence of ontogenetic shifting in the energy allocation strategy (growth vs storage) demonstrated in other fish larvae (Cunha et al, 2007;Olivotto et al, 2011a;Di Pane et al, 2019) is unknown in seahorses, deserving further investigation.…”

“…For that, newborn characteristics and initial viability must be properly addressed. Condition indices, energy allocation, and metabolic scope in early ontogeny aim to evaluate the physiological status of fish (Cunha et al, 2003(Cunha et al, , 2007Di Pane et al, 2019). Adenylic energy charge (AEC) was proposed as an indicator of the energy potentially available for cellular metabolism (Atkinson, 1977;Dickson and Franz, 1980;Harms, 1992).…”

Annually twice induced spawnings provide multiple benefits: Experimental evidence from an Indian major carp ( Catla catla , Hamilton 1822)

“…On the other hand, offspring themselves can modulate the energy budget mostly for the development of a specific trait rather than other traits (Di Pane et al, 2019;Huuskonen, Karjalainen, Medgyesy, & Wieser, 1998). In a review, Green (2008) explained with empirical examples in different fish populations about how maternal traits and environmental conditions may influence offspring fitness.…”

Morphological and biochemical effects of food deprivation during the early development of Pacific red snapper Lutjanus peru

“…The presence of larvae showing signs of starvation and on the PNR may result in erroneous estimates of larval abundance and survival since most larvae at the PNR die within 2 days (Park et al ., 2013; Wan et al ., 2007), affecting recruitment and year‐class strength. The effects of food deprivation on larval form and function have been widely studied and many criteria have been reported to identify starved larvae and to describe and evaluate their nutritional condition, including morphometry (Theilacker, 1980), tissue organization and appearance (Di Pane et al ., 2019), biochemical analysis, (Cousin et al ., 1987), digestive enzyme activities (Yúfera et al ., 1993), and swimming performance and behavioral changes (Blaxter & Ehrlich, 1974; Di Pane et al ., 2019; Laurence, 1972; Shan et al ., 2008).…”