Studies on the cranial osteology of the blind catfish Horoglanis krishnai Menon (Pisces, Clariidae).

Abstract

Horaglanis krishnai Menon is a blind catfish inhabiting the dug- out wells at Kottayam, Kerala, South India. Studies on the cranial osteology of the fish show that the bones on the skull are firmly articulated. The frontoparietal fontanella is very large so that the cranium virtually lacks a roof. The sphenotics and alisphenoids are hardly recognizable and the orbital bones are entirely lacking. In osteological features H. krishnai closely resembles Uegitglanis zammaroni. But in H. krishnai the orbital bones are further reduced or even absent. The fontanella is larger than that of any other known catfish. These two species must have evolved from the same ancester and have taken up nearly identical ways of life. The difference between the skeletons of these two appears to be largely dependent on the relative size of the frontoparietal fontanella. Its greater development in H. krishnai brought about a suppression or reduction of some of the bones clearly visible in Uegitglanis. It would appear that the modification initiated in Uegitglanis gatered momentum in Horaglanis. These two fishes form a group distinct from clariids and bagrids but form a connecting link between the two.

Keywords

• Horaglanis krishnai
• cave fishes
• osteology