THE GILLS OF THE COELACANTH, LATIMERIA-CHALUMNAE, A STUDY IN RELATION TO BODY-SIZE

Measurements of the surface area of the gill lamellae of specimens of the coelacanth, Latimeria chalumnae have been made. This involved measurement of total filament length, frequency of lamellae along the filaments and the weighted average bilateral area of a single lamella. Regression analyses of these parameters which combine to give total area were made for the mass range 434 g-80 kg. Results show that the slope is close to 0.81 which is similar to that of many other fishes. However, the intercept value is exceptionally low and confirms the low mass-specific measurements made on two 10 kg specimens in 1972. Material from a recently caught specimen has been used to extend previous transmission electron microscopy by the use of scanning electron microscopy. The surface of epithelial cells on lamellae and filaments is covered in microvilli and microridges with transitional zones. The appearance of microridges suggests that they may have arisen by coalescence of microvilli. Ventilatory movements of the mouth and operculum (three to four per minute) have been observed using videorecordings of resting specimens in caves. Specimens of the larval stage of a gnathiid isopod parasite were found but only on one of the nine sets of gills that were examined. It is concluded that this more extended study of gill morphometrics of Latimeria confirms predictions made from earlier comparative studies regarding the life habits of this fish which have also been confirmed by direct observation using submersibles.