[Reason to split the genus Aurelia. Mesoglein from two populations differ].

The medusa, Aurelia aurita (Scyphozoa, Cnidaria), is considered to be a cosmopolitan species with a worldwide distribution in most seas from the poles to the tropics. Cnidarian is thought to possess two tissue layers: endoderm (gastroderm) and ectoderm, which are separated by huge mesoglea in medusa. The basic morphology of medusa is similar in different populations. Previously we have determined a new protein "mesoglein" as one of the main components of mesoglea. Deduced amino acid sequence of mesoglein contains Zona Pellucida (ZP) domain. In this paper, we have comparied of mesoglein and its gene in medusa from three habitats (White Sea (WsA), Black Sea (BsA), Japonic Sea (JsA)). The set of the mesoglea protein bands after SDS-PAGE is similar in all samples. Nevertheless, JsA mesogleins' M(r) is 53-55 kDa, while WsA and BsA mesogleins have M(r) of 47 kDa. Antibodies raised against WsA mesoglein recognize only mesogleins with M(r) of 47 kDa, but not 53-55 kDa, both on immunoblot and immunocytochemistry. Mesogleal cells and elastic fibrils are stained intensively in the mesoglea both from WsA and BsA but not from JsA. The possibility of gene divergency was checked by PCR with primers specific for WsA mesoglein gene. PCR products of expected length obtained on polyA-cDNA template from mesogleal cells of WsA and BsA medusa but not on cDNA of JsA medusa. Our results evidence that there are two different species in genus Aurelia: Aurelia aurita inhabits White and Black Seas while Aurelia sp. inhabits Japonic Sea. This is consistent with findings of other recept molecular biological studies.

[Morphodynamics of the contract plate in the course of oocyte maturation in the scyphozoan Aurelia aurita (Cnidaria: Semaeostomae)].

The structure forming in the area of contact between the oocyte and the germinal epithelium in the course of oocyte maturation of the scyphozoan Aurelia aurita is termed the contact plate. This study traces the successive stages of contact plate formation in the course of oocyte maturation at the light microscopic and ultrastructural levels. At early stages ofoocyte development, the appearance of granules is observed in the peripheral cytoplasm of the oocyte; these granules accumulate at the pole, which retains its connection with the germinal epithelium of the gonads. Two types of these granules are recognized: (1) granules with homogeneous content and (2) granules containing loose shapeless material in the form of thick cords. The transformation of type two granules into larger structures, as well as the consolidation of type one and type two granules at later stages of oocyte development, are probably the processes that lead to the formation of the characteristic structure and contact plate, visible in paraffin and semithin sections. It remains unclear where exactly the contact plate is localized at the moment of fertilization: inside or outside the oocyte. The content of granules and components of the plate specifically bind the antibodies (RA47) against mesoglein, the ZP domain-containing protein of the mesoglea of A. aurita. The contact plate, covering only the anomalous pole of the oocyte but detected by the presence of ZP domain-containing proteins, may prove to be the simplest egg membrane of the zona pellucida type.

[The plate in the zone of oocyte and germinal epithelium contact in scyphomedusa Aurelia aurita binds antibodies to ZP-domain-containing protein mesoglein].

Cnidaria are lower multicellular animals with the body consisting of two epithelial layers. An extracellular substance--mesoglea--is situated between epidermal and gastrodermal layers of these animals. Mesoglein is one of the major mesogleal proteins of adult medusa of Scyphozoan jellyfish Aurelia aurita. Search for the known domains in mesoglein amino acid sequence reveals prominent zona pellucida (ZP) domain (which was found at first in the mammal oocyte zona pellucida proteins), so the protein belongs to ZP family of extracellular matrix proteins and it is an early metazoan member of ZP-domain-containing protein family. However, nothing is known about oogenesis related ZP-domain proteins in the lower multicellular animals. Oogenesis in Scyphozoa is described poorly. In this work morphological features of the zone in contact area between the oocyte and the germinal epithelium were investigated in semi-fine sections: To make it more convenient we identified seven stages according to the oocyte size and the structure found in this area was named the plate. It was shown that the components of the plate bound specifically the antibodies against mesoglein. So it seems the plate material contains ZP-domain proteins. Electrophoresis and immunoblot results give evidence that the proteins immunologically related to mesoglein have a higher molecular mass. It might be due to either the posttranslational modifications of the precursors or that they represent other proteins of ZP-domain family in Cnidaria.