Fine structure of gills and skins of the amphibious mudskipper, Periophthalmus chrysospilos Bleeker, 1852, and a non-amphibious goby, Favonigobius reichei (Bleeker, 1853)

Background. Periophthalmus chrysospilos and Favonigobius reichei are most abundant gobies species (Family: Gobiidae) inhabiting estuaries in the west coast of Peninsular Malaysia. Thirty-six goby species are amphibious: the rest remain in water, like other teleosts. However, information on the fine structure of gills and skins of these gobies species that may help to understand their functions in air breathing is still lacking. This study was aimed at describing fine structure of the gills and skins of these two co-existing species of gobies living in the terrestrial and aquatic environment. Materials and methods. Fifty-six specimens of amphibious (Periophthalmus chrysospilos) and 67 specimens of nonamphibious gobies (Favonigobius reichei) were collected from estuary. Gills and skins were dissected out and samples were treated following the standard electron microscopy sample preparation. Samples were affixed onto specimen stubs with silver paint and then coated with a thin layer of gold using a BIO-RAD-SC500 ion sputter. All samples were viewed using SEM Series XL 30, Philips. Results. P. chrysospilos possesses short, thick, bent and twisted gill filaments whereas the F. reichei has long, thin, and straight filaments. There were differences in shapes and numbers of the secondary lamellae attached to the filaments in P. chrysospilos and F. reichei. The skin of F. reichei also has a significant difference in architectural build-up compared to P. chrysospilos. The functional adaptation on the use of gills and skins in P. chrysospilos and F. reichei in natural environment are discussed. Conclusion. The gills of P. chrysospilos show some unique features (i.e. low density of secondary lamellae and smaller gill rakers) that can be used to explain the animal′s ability to successfully live out of water in comparison to F. reichei that are more adapted to aquatic life like other teleosts. Special architectural plan of gills and skins of both goby species may have contributed to their existence in the estuary area.