Temperature and feeding frequency impact the survival, growth, and metamorphosis success of Solea solea larvae

Abstract

Human-induced climate change impacts the oceans, increasing their temperature, changing their circulation and chemical properties, and affecting marine ecosystems. Like most marine species, sole has a biphasic life cycle, where one planktonic larval stage and juvenile/adult stages occur in a different ecological niche. The year-class strength, usually quantified by the end of the larvae stage, is crucial for explaining the species' recruitment. We implemented an experimental system for rearing larvae under laboratory conditions and experimentally investigated the effects of temperature and feeding frequencies on survival, development (growth), and metamorphosis success of S. solea larvae. Specific questions addressed in this work include: what are the effects of feeding regimes on larvae development? How does temperature impact larvae development? Our results highlight that survival depends on the first feeding, that the onset of metamorphosis varies according to rearing temperature and that poorly fed larvae take significantly longer to start (if they do) metamorphosing. Moreover, larvae reared at the higher temperature (a +4°C scenario) showed a higher incidence in metamorphosis defects. We discuss the implications of our results in an ecological context, notably in terms of recruitment and settlement. Understanding the processes that regulate the abundance of wild populations is of primary importance, especially if these populations are living resources exploited by humans.

Fig 1. Fully metamorphosed Solea solea larva.

A fully metamorphosed larva showing full asymmetrical body, rounded head and complete left eye migration.

Fig 2. Experimental design.

Number of plates used per treatment at both experiment 1 and 2 (a) and timeline protocol followed during experiment 2, for larvae reared at 16°C (control temperature treatment) and at 20°C (RCP 8.5 temperature treatment), that included a temperature acclimation for larvae.

Fig 3. Larvae survival during the experiment.

Percentage of survival with fitted four parameter logistic regressions in S. solea according to the feeding frequency at two different temperatures. a: whole experiment duration (33 days larvae aged 35 dph). b: Solid lines represent linear models fitted to the to the second’s week percentage of survival with 95% confidence level intervals (shadow area).

Fig 4. Length of sole (mm) larvae reared at different temperatures and different feeding frequencies in experiment 2.

Left panels: larvae reared at 16°C. Right panels: larvae reared at 20°C at high (blue), medium (yellow) and low (grey) feeding frequencies.

Fig 5. Dry weight of sole (mm) larvae reared at different temperatures and different feeding frequencies in experiment 2.

Left panels: larvae reared at 16°C. Right panels: larvae reared at 20°C at high (blue), medium (yellow) and low (grey) feeding frequencies.

Fig 6. Metamorphic index in Solea solea larvae.

Differences in the metamorphosis onset and development of larvae reared at two temperatures and 3 different feeding frequencies (high, medium and low food).