Gill Morphometry of the Mudskipper,Boleophthalmus Boddarti

Abstract

Measurements of gill dimensions in relation to body weight have been carried out in a mudskipper,Boleophthalmus boddarti. The data was analysed with respect to body weight using logarithmic transformations (logY= loga + blogW). The slope(b)of the log/log regression lines for the gill area, total filament length, average number of secondary lamellae/mm, bilateral area of an average secondary lamella, and total gill area/g were 1·0496, 0·427, -0·229, 0·851 and 00496 respectively.These results indicate variations in growth patterns for the different dimensions of the gills. The analysis shows that the increase in gill surface area with the body size is mainly due to an increase in the area of individual secondary lamellae and, to a lesser extent, an increase in filament length and total number of lamellae.The average weight-specific area for 14 specimens measured (3·6–35·4 g) was 108–15 mm2/g. This value is consistent with results obtained with some other intertidal species.Marked differences were found in the thickness of the water/blood barrier, which is thinner around the marginal channels. Morphometric diffusing capacity taking this heterogeneity into account was estimated as 0·0208 ml O2min1mmHg−1kg−1.INTRODUCTIONMorphological studies on the gills of many fish have shown adaptations of the basic structure which can be related to the particular mode of life. Among these adaptations, air-breathing species show many remarkable structural modifications (Munshi, 1976), which extend to the gills forming air sacs in species such asHeteropneustes fossilis(Hughes & Munshi, 1979). Fish which inhabit the intertidal zone, like other seashore animals, are subjected to periodic exposure to air, which may produce problems of water loss and reduction in support for the gills, with consequent collapse and restriction of gas exchange surfaces.