High genetic homogeneity of the moon jelly Aurelia aurita (Scyphozoa, Semaeostomeae) along the Mediterranean coast of Tunisia

Abstract

The moon jelly Aurelia aurita is one of the most common and widespread species of scyphomedusa in the Mediterranean Sea. In all, 18 allozyme loci were studied to investigate the genetic variation and population structure of 11 A. aurita populations from the Tunisian coast. Polymorphism was detected at 14 loci across the sampling localities. Gene frequency differences rather than alternative fixation of alleles characterised the collecting sites. The mean number of alleles per locus ranged from 1.89 to 2.17 (average 2.02), and the mean values of observed (H o) and expected (H e) heterozygosities ranged from 0.20 to 0.36 and from 0.32 to 0.37 respectively. Five out of 14 polymorphic loci were out of Hardy-Weinberg equilibrium (H-WE). Likewise, the multilocus tests showed deviation from H-WE in six populations. These populations apparently showed heterozygote deficiency, whereas the average heterozygosity for the remaining ones is quite similar to the expected values. Despite extensive sampling across a microgeographical scale and genotyping efforts, the populations of A. aurita under study showed an absence of genetic differentiation under the background of high gene flow (mean F ST = 0.01, p < 0.05) and higher value of N e m, suggesting that A. aurita is genetically homogeneous throughout the study area. The absence of population genetic structuring may be associated with environmental conditions and life-history parameters.