Scanning electron microscopy of the operculum of Garra lamta (Hamilton) (Cyprinidae:Cypriniformes), an Indian hill stream fish

Abstract

The surface architecture of the epidermis on the outer surface of the operculum (OE) and the epithelium on the inner surface of the operculum (EISO) of Garra lamta was examined by scanning electron microscopy. The surface appeared smooth on the OE and wavy on the EISO. A wavy epithelium is considered to facilitate an increase in its stretchability, during the expansion of the branchial chamber. The OE and the EISO were covered by a mosaic pavement of epithelial cells with characteristic patterns of microridges and microbridges. Interspersed between the epithelial cells were mucous goblet cell pores, which were not significantly different in number in the OE and the EISO. Nevertheless, their surface area in the EISO was significantly higher than in the OE. This could be an adaptation to secrete higher amounts of mucus on the EISO for keeping the branchial chamber lining clean, avoiding clogging, the increased slipperiness reducing friction from water flow and increased efficiency in protecting against microbial attachments. Rounded bulges on the OE and the EISO were associated with mucous goblet cells. The absence of the taste buds in the EISO, in contrast to the OE, suggests that their function in the branchial chamber may not be of much significance in this fish. Breeding tubercles on the OE are believed to facilitate better contact between the male and female during breeding.