Morphological diversities in envelope surface and micropyle of marine teleosts eggs with different ecological types in the Bohai Sea and the Yellow Sea

Marine teleosts eggs distributed in the Yellow Sea and the Bohai Sea cover almost all the egg ecological types. Scanning electron microscope (SEM) observation was conducted to examine the ultrastructure of external egg membrane and micropyle of the 15 species with different egg ecological types which have been collected during the fisheries resource surveys in recent years. Taxonomic diagnostic ultrastructures have been accumulated, also habitat suitability of some related ultrastructures have been discussed. Current SEM studies have demonstrated that ultrastructure of the external egg membrane varies among egg ecological types or even among species. The external egg membrane of the floating eggs and mouth-breeding eggs was thin, but was thick in the demersal eggs and the eggs with adhesive egg filaments. The pores distribution density, sculptured patterns and peculiar elaborations of the external egg membrane and type of the micropyle in the floating eggs; fine structure of the external egg membrane and type of the micropyle in the demersal eggs; number and location of membrane thread or filament of the external egg membrane and type of the micropyle in the adhensive eggs; number and arrangement of the filaments and surface ridges in the micropyle region in the mouth-breeding eggs could be used as the diagnostic characters in taxonomy of fish eggs. Untrastructural differences in envelope surface and micropyle between species were associated with its systematic groups, spawning environment and geographic differences. Envelope surface ultrastructures were considered to be taxonomically useful features for identifying fish eggs to the family or genus level, with the pores distribution density, sculptured patterns and peculiar elaborations of the external egg membrane may be possible to assign the eggs to a species. While morphology of the micropyle was usually species-specific. Egg envelope structure and thickness of various teleosts often reflect the ecological challenges a species is faced with during its embryonic life stages. The sculptured patterns and peculiar elaborations on the outer egg membrane were considered as biological response to different habitat environments. The present study would accumulate basic data on ontogeny and morphological classification features during its embryonic life stages of the teleost fishes distributed in the Yellow Sea and the Bohai Sea.