Instinctive mate choice with genetically different partners assists sustaining genetic diversity in giant freshwater prawn (Macrobrachium rosenbergii)

The giant freshwater prawn, Macrobrachium rosenbergii, is a very economically important species cultured in tropical and sub-tropical countries. Previous studies on the prawn reported a similar level of genetic diversity in both hatchery and wild populations, although it is believed that a small number of brooders are generally carried out in hatcheries. Here, thirteen microsatellite loci were used to observe and characterize the genetic diversity in hatchery and wild populations of the prawn. These microsatellite loci were also used to investigate the prawn mate choice. Two experiments of mate choice were done in 1000-liter tanks containing 48 mating partners from four different broodstocks. Newly hatched larvae were daily observed and used for parental analysis to reveal their parents as successful mating pairs. The instinctive mate choice that occurred in the mating tanks was thus disclosed for the first time. The level of genetic diversity, including the allelic richness and observed and ex-pected heterozygosities, was shown not to significantly differ among hatchery and wild populations (P > 0.05). Based on the analysis of pairwise relatedness among mating partners and internal relatedness of larvae, the prawn prefers to mate with partners from different broodstock. Evidently, the internal relatedness of larvae according to the successful mating pairs was significantly lower than in the random mating scenario (P < 0.01). This mating instinct is hypothesized to be important for sustaining genetic diversity in populations of the prawn. This is the first report on inbreeding avoidance of giant freshwater prawn. Future studies on how prawn can recognize partners from different broodstocks are awaiting.

Automated summary

This study investigated the genetic diversity of giant freshwater prawn populations in hatcheries and the wild using microsatellite loci. The results showed no significant difference in genetic diversity between hatchery and wild populations. Moreover, the prawns exhibited a preference for mating with partners from different broodstocks, which is important for maintaining genetic diversity in the populations. This is the first report on inbreeding avoidance in giant freshwater prawns, and future studies should further explore how prawns recognize partners from different broodstocks.