Colour polymorphism and genetic structure in the cannonball jellyfish (Stomolophus meleagris, L. Agassiz, 1860) in the Gulf of California

Abstract

ABSTRACT The cannonball jellyfish Stomolophus meleagris display colour variations from blue to purple, and different pigmentation patterns on the umbrella surface. Although these colour phenotypes are common in this organism, surprisingly, little is known about the causes and the adaptive significance of these polymorphisms. In this study, we investigated the population genetic structure of S. meleagris distributed in the Gulf of California based on the partial regions of mitochondrial COI and 12S rRNA genes. Sample collections were carried out, and morphological data from organisms, as well as physicochemical parameters of the seawater at the collection sites, were recorded. White and blue phenotypes were found in April, and blue specimens were the more abundant. No specimens of the white phenotype were found in May, and the purple phenotype was present only in June. A correlation was found between the occurrences of white jellyfish and lower seawater temperatures (23.5 °C). Ten different COI gene haplotypes were detected, and 20 12S rRNA gene haplotypes. The clustering of haplotypes was not correlated with their geographical distributions. Moderate and low values of FST were obtained between samples collected in different locations. These results suggest that S. meleagris in the Gulf of California exist as a single genetic stock, and the different pigmentation patterns observed may result from specific environmental conditions.