Introduction
The pink shrimp, Palaemon serratus, is a commercially valuable species distributed along the European coast. It lives for 2-5 years and females can weigh up to 13 grams (Huxley, 2011). Although aquaculture trials were attempted in the 1970s and 1980s (Campillo , 1979; Rodriguez, 1981), this species is not commercially produced today. Due to its size and the temperature of the environment in which it naturally lives, P. serratus is an ideal candidate for extensive European marine shrimp farming.
Here we focus on the performance of the larval phase of P. serratus under controlled conditions. Temperature determines the duration of larval development by influencing the number of larval moults and the duration of intermoult (Gonzalez-Ortegon and Giménez, 2014). This temperature-mediated plasticity has consequences for juveniles, with size at metamorphosis decreasing with increasing temperature (Baudet et al., in press). Conversely, larval survival increases with temperature (Reeve, 1969).
The rate of metamorphosis of P. serratus larvae is very low at temperatures below 15°C (Reeve, 1969). However, the larvae of this species are released into the environment between April and July, in areas where the water can be between 10 and 15°C. We believe that the poor larval performance obtained in the laboratory in cold water is due to the poor diet used. Indeed, artemia nauplii contain little of the polyunsaturated fatty acids necessary for membrane fluidity in cold water (Sorgeloos et al., 2001).
In this study, we compared the larval performance of P. serratus at three temperatures (14, 18 and 22°C) by feeding the larvae three diets of more or less rich artemia. We hypothesise that larval survival increases with diet richness and temperature. The interaction of these two factors should have synergistic effects on larval survival. We also expect that diet richness will increase growth rate, regardless of temperature.
Materials and methods
We collected 5 ovigerous P. serratus females which we isolated in the laboratory. Upon hatching of each brood, 9 groups of 52 larvae were incubated in 9 conical vessels of 500 mL. These were then incubated in 3 waterbaths at 14, 18 and 22°C respectively (3 vessels of each brood per waterbath ).
To test the influence of the fatty acid richness of the diet on larval development, we prepared the following 3 diets (from the poorest to the richest): unenriched metanauplii I (24h after hatching), nauplii I (at hatching) and metanauplii I enriched for 24h with microalgae rich in polyunsaturated fatty acids. Each vessel was fed the same diet every day, i.e. 10 artemia per mL. We therefore had 45 containers each containing 52 larvae (5 females x 3 temperatures x 3 diets).
The larvae were observed during the water change 3 times a week. When they metamorphosed into juveniles (morphological and behavioural criteria), they were removed for weighing and stored individually at -80°C. Their lipid profile was then analysed.
We will test the effects of temperature and diets on larval metamorphosis rate, development time and weight of metamorphosed larvae. For this purpose, we will use mixed-effects models to consider that for each model, the larvae used at different temperatures were from the same females.
Results and Discussion
The experiment started in May 2022 and is currently not completed. The analysis of these and the discussion will be presented at the conference.
Bibliography
Campillo , A. (1979). Contribution à l’étude de la crevette rose Palaemon serratus (Pennant): Exploitation, Biologie, Elevage, Epidémiologie (Doctoral dissertation, Université des sciences et techniques du Languedoc).
Huxley, R. (2011). Population structure and morphology of the prawn Palaemon serratus (Pennant, 1777) in Welsh coastal waters with a consideration of two options for regulating the fishery (Doctoral dissertation, Aberystwyth University.).
Reeve, M. R. (1969). Growth, metamorphosis and energy conversion in the larvae of the prawn, Palaemon serratus. Journal of the Marine Biological Association of the United Kingdom, 49(1), 77-96.
Rodriguez, A. (1981). Growth and sexual maturation of Penaeus kerathurus (Forskäl , 1775) and Palaemon serratus (Pennant) in salt ponds. Aquaculture, 24, 257-266.
Sorgeloos , P., Dhert , P., & Candreva , P. (2001). Use of the brine shrimp, Artemia spp., in marine fish larviculture. Aquaculture, 200(1-2), 147-159.