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Dernière mise à jour : Mai 2018

Menu Logo Principal AgroParisTech Université Paris-Saclay

INRA GABI Unit

GABI : Génétique Animale et Biologie IntégrativeUnité Mixte de Recherche INRA - AgroParisTech

Malagasy carps and their scales

 Malagasy carps and their scales
Partially scaleless (“mirror”) or completely scaleless (“leather”) genotypes of domesticated common carps were introduced in Madagascar in 1912 for aquaculture purposes. We showed a very rapid evolution of the animals that colonized the natural environment to a complete scaled “wild” type whereas they remain carriers of a mutation normally producing the “mirror” phenotype. We also showed that the breeding performances of the “leather” carps, which are highly appreciated in Madagascar, were lower than those of the “mirror” carps, contrary to what local breeders claim.

Context and stakes

Since 2007, in partnership with the ONG APDRA Pisciculture Paysanne, Inra has been studying population genetics of the common carp, a species that was introduced into Madagascar in 1912 to develop aquaculture, and which spread rapidly to the natural environment. The introduction of domestic genotypes of a new species, without any complementary introduction before 1979, and with two distinct compartments (wild and farmed) allows the study of the evolution of animal traits over the last century in two environments. On an applied point of view, studying  farmed carp also provides important information to farmers, helping them choose the right genotypes and to manage genetic variability , without having to introduce new animals, which is risky for health reasons due to the worldwide spread carp virus, the Koi Herpes Virus.

Results

We showed that the majority of wild carps of Madagascar come from the initial strain introduced in 1912, but that most of them have scales all over their bodies even though they carry the “mirror” mutation associated with reduced scales. This shows the rapid evolution of this species (approximately 40 generations) that allowed restoring the protective scale covering, by using different genes than the originally mutated gene. This shows the efficacy of natural selection in providing alternative solutions to organisms therefore helping them to adapt to their environment (Hubert et al., 2016).
In farms, most carps  come from this initial introduction even though we also find traces of carp introduced in1979 via Hungary. However, in this environment, carp that carry the “mirror” mostly conformed to the original “mirror” phenotype, that is with few scales.
Concerning the animals that carry the “leather” mutation that are almost completely scaleless and well-appreciated by consumers since they are easy to prepare, we showed that on the contrary to what breeders affirm, they do not survive as well as the “mirror” carp and have poorer growth. In addition, the ones that we tested do not have a reduced number of intermuscular bones (Andria-Mananjara et al., 2016). Their use is therefore not recommended.
Finally, and more generally, we showed that the genetic variability present in the Madagascan carp population is sufficient for farming and that the introduction of new individuals is not necessary.

Perspectives

We showed that new scaling pattern of Malagasy carps was not due to a reversion of the original mutation nor to the appearance of new mutations to compensate. The identification of new zones of the genome implicated in this new phenotype may be possible using high throughput sequencing approaches.
In fact, we have offered to look more actively through a larger sampling on the field, for “leather” carps that possess either few or no intermuscular bones, which would confirm the claims of breeders, since recent results on another carp species suggest that such an association of scaled traits with bone number is possible.

Valorization

The results on the evolution of scale phenotype have been the object of many citations by the press, for example:

The more applied results of the study, on the breeding performances and genetic variability, were presented to the authorities and managers during a seminar in Antanavarivo on 30 June, 2014 and were popularized by the APDRA for farmers.

References

Hubert J.N., Allal F., Hervet C., Ravakarivelo M., Jeney Z., Vergnet A., Guyomard R., Vandeputte M., 2016. How could fully-scaled carps appear in natural waters in Madagascar ? Proceedings of the Royal Society B 283: 20160945

Andria-Mananjara D.E., Rasamoelina H., Vandeputte M., 2016. Comparison of rearing performances and intramuscular bone number in the mirror and nude genotypes of common carp (Cyprinus carpio L.) in a controlled field test in Madagascar. Aquaculture Reports 3: 77-81

A book with all results from “PARRUR” project (French Ministry of Foreign Affairs - which financed part of the experiments) is available online