Grounds for genus Aurelia subdivision: Two jellyfish populations differ in mesoglein amino acid sequences

Abstract

The jellyfish Aurelia aurita (Scyphozoa, Cnidaria) is regarded as a cosmopolitan species with a worldwide distribution in most seas, from the poles to tropics. Cnidaria possess two tissue layers: endoderm (gastroderm) and ectoderm separated by mesoglea, which are typically thick for jellyfish. A main component of mesoglea is the novel protein “mesoglein” that we have already described earlier. The protein has a conservative ZP (Zona Pellucida) domain. In the current work, we compare mesoglein and its gene from three jellyfish habitats (the White Sea (WS), Black Sea (BS), and Sea of Japan (SJ)). The pattern of mesoglea protein bands after SDS-PAGE is similar in all samples. Nevertheless, SJ mesoglein Mr is 53–55 kDa, while WS and BS mesoglein Mr is 47 kDa. Antibodies raised against WSA mesoglein recognize only mesogleins with Mr 47 kDa, but not 53–55 kDa, in both immunoblot and immunocytochemistry. Mesogleal cells and elastic fibrils are intensely stained in the mesoglea from both WSA and BSA, but not from SJA.The possibility of gene divergence was tested by PCR with primers specific for the WS mesoglein gene. PCR products of expected length were obtained on a polyA-cDNA template from mesogleal cells of WS and BS jellyfish, but not with cDNA of SJ jellyfish. Our results evidence that there are two different species in the genus Aurelia: aurita inhabits the White and Black Seas, while Aurelia sp. inhabits the Sea of Japan. This is in agreement with the results of comparisons previously done using other methods of molecular biology.