MOULT FINAL ABDOMINAL SEGMENT WIDTH: A NON-INVASIVE APPROACH TO ASSESS SHRIMP LARVAL GROWTH IN LIVE PREY FEEDING TRIALS

Introduction

Aquaculture is an industry providing animal protein to meet the needs of a growing world population (FAO, 2022). In marine shrimp production, nutrition remains a major limiting factor in hatcheries sustainability by affecting growth, quality, survival rate and post-larvae production (Campillo, 1979; Sorgeloos et al., 1998). The common shrimp, Palaemon serratus is widely distributed along European and North African coasts (Huxley, 2013). Despite early aquaculture trials (Campillo, 1979; Rodriguez, 1981), it is not currently farmed. However, it remains a promising candidate for European aquaculture. This study investigates larval performance of P. serratus under controlled conditions using different feeding regimes including a local rotifer species (Hexarthra sp.). The low larval density in our experimental tanks constrained direct sampling, leading us to investigate a non-invasive growth monitoring approach based on the daily collection of moults at the water surface.

Materials and methods

One ovigerous female P. serratus was isolated from our broodstock. Upon hatching, larvae were reared in 10 L Zug bottles under three feeding treatments, each in triplicate. To assess the effect of diet on development, growth and survival, we tested the following three diets: Artemia nauplii (A), a mixed diet (50% Hexarthra, 50% Artemia) (RA), and a final diet in which larvae were first fed Hexarthra sp. during the first five days post-hatching, followed by a mixed diet (50% Artemia, 50% Hexarthra) for 2 days, and finally fed on Artemia nauplii exclusively until the end of the experiment (RTA).

Moults were collected daily, the total number of one morphologically recognizable part (tail-fan) were counted. Developmental stages were assigned to each moult. Tail fans from each tank were photographed (Figure 1) on a "Cellule de Nageotte" with 0.25mm grid lines used as the size reference and measurements were performed using ImageJ software.

Results

Feeding regimes had a highly significant effect on final abdominal segment width at different developmental stages (Figure 2), where the Artemia (A) treatment resulted in a wider last abdominal part than the RTA treatment until stage 4 (P < 0.001). The mixed diet (RA) ranked second place with significantly greater values than RTA treatment at stage 4 and 6 (P < 0.01).

These results highlight additional metrics, including daily moult counts and biometric measurements performed at the end of the experiment, after metamorphosis into post-larvae, using the conventional invasive method, which involves measuring and weighing sacrificed post-larvae. Final length and weight showed the same pattern as the non-invasive approach, with significantly higher values in treatment A than in treatment RA (P < 0.05). Larvae in treatment A also had a faster development up to stage 4 and exhibited higher moult counts per stage.

Discussion

Zootechnical performance results are consistent with those obtained from measurements of the final abdominal segment width, confirming that the larvae fed exclusively on Artemia nauplii exhibited overall higher performance than the other treatments. These findings suggest that rotifers of the genus Hexarthra are not suitable for shrimp larval rearing. This may be explained by their evasive behavior (Kak and Rao, 1998), which has also been reported in fish larvae, where Hexarthra sp. are actively avoided when alternative prey are available (Mookerji and Rao, 1993).

This study also demonstrates the feasibility of monitoring growth through the daily collection of moults. This non-invasive approach avoids the stress induced by larval capture, which can increase energy demand and negatively affect biological performance (Martínez-Antonio et al., 2019). At an industrial scale, automated image-based measurement of these moults could provide an efficient tool to monitor growth and zootechnical performance in shrimp hatcheries.

Figures

Figure 1: Last abdominal segment width measurement method a: abdomen width b: Reference size 250µm

Figure 1: Last abdominal segment width measurement method a: abdomen width b: Reference size 250µm

Figure 2: Last abdominal segment width measurement (mm) per treatment and stages. *** = P < 0.001, ** = P < 0.01

Figure 2: Last abdominal segment width measurement (mm) per treatment and stages. *** = P < 0.001, ** = P < 0.01

References

Campillo, 1979. Contribution à l'étude de l'élevage de la crevette rose Palaemon serratus (Pennant) en captivité.

Huxley, 2013. 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.

Kak, A., Rao, T.R., 1998. Does the evasive behavior of Hexarthra influence its competition with cladocerans? Hydrobiologia 387, 409–419. https://doi.org/10.1023/A:1017055013639

La situation mondiale des pêches et de l'aquaculture 2022, 2022. . FAO. https://doi.org/10.4060/cc0461fr

Martínez-Antonio, E.M., Racotta, I.S., Ruvalcaba-Márquez, J.C., Magallón-Barajas, F., 2019. Modulation of stress response and productive performance of Litopenaeus vannamei through diet. PeerJ 7, e6850. https://doi.org/10.7717/peerj.6850

Mookerji, N., Rao, T.R., 1993. Patterns of prey selection in rohu (Labeo rohita) and singhi (Heteropneustes fossilis) larvae under light and dark conditions. Aquaculture 118, 85–104. https://doi.org/10.1016/0044-8486(93)90283-5

Rodriguez, A., 1981. Growth and sexual maturation of Penaeus kerathurus (Forskäl, 1775) and Palaemon serratus (Pennant) in salt ponds. Aquaculture 24, 257–266. https://doi.org/10.1016/0044-8486(81)90061-2

Sorgeloos, P., Coutteau, P., Dhert, P., Merchie, G., Et., A., 1998. Use of Brine Shrimp, Artemia spp., in Larval Crustacean Nutrition: A Review. Reviews in Fisheries Science. https://doi.org/10.1080/10641269891314195

Campillo, 1979. Contribution à l'étude de l'élevage de la crevette rose Palaemon serratus (Pennant) en captivité.

Huxley, 2013. 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.

Kak, A., Rao, T.R., 1998. Does the evasive behavior of Hexarthra influence its competition with cladocerans? Hydrobiologia 387, 409–419. https://doi.org/10.1023/A:1017055013639

La situation mondiale des pêches et de l'aquaculture 2022, 2022. . FAO. https://doi.org/10.4060/cc0461fr

Martínez-Antonio, E.M., Racotta, I.S., Ruvalcaba-Márquez, J.C., Magallón-Barajas, F., 2019. Modulation of stress response and productive performance of Litopenaeus vannamei through diet. PeerJ 7, e6850. https://doi.org/10.7717/peerj.6850

Mookerji, N., Rao, T.R., 1993. Patterns of prey selection in rohu (Labeo rohita) and singhi (Heteropneustes fossilis) larvae under light and dark conditions. Aquaculture 118, 85–104. https://doi.org/10.1016/0044-8486(93)90283-5

Rodriguez, A., 1981. Growth and sexual maturation of Penaeus kerathurus (Forskäl, 1775) and Palaemon serratus (Pennant) in salt ponds. Aquaculture 24, 257–266. https://doi.org/10.1016/0044-8486(81)90061-2

Sorgeloos, P., Coutteau, P., Dhert, P., Merchie, G., Et., A., 1998. Use of Brine Shrimp, Artemia spp., in Larval Crustacean Nutrition: A Review. Reviews in Fisheries Science. https://doi.org/10.1080/10641269891314195