RESEARCH ACCOUNT CURRENT SCIENCE, VOL. 83, NO. 9, 10 NOVEMBER 2002 1112 Studies on the behavioural ecology and physiology of a hypogean loach, Nemacheilus evezardi, from the Kotumsar Cave, India Atanu Kumar Pati* and Arvind Agrawal School of Life Sciences, Pandit Ravishankar Shukla University, Raipur 492 010, India The Kotumsar Cave, one of the largest known caves of India, has been successfully colonized by a species of loach, Nemacheilus evezardi. This species is found in both hypogean and epigean form. This paper summa- rizes the current knowledge on the behavioural eco- logy and physiology of the hypogean form as a result of 15 years of field and laboratory studies. Most stu- dies have concentrated on metabolism, biological rhythms, general behaviour, ecophysiology and the biochemical composition of its metabolically impor- tant tissues. Yet, little is known on the evolutionary history of this species. HYPOGEAN fishes that have yet to show complete troglo- morphy are becoming the focus of studies aimed to understand the evolution of cave organisms. One of these species is the hill-stream loach, Nemacheilus evezardi. Studies with special reference to this species were carried out only 27 years after its discovery 1 . Since then, our group at the Pt. Ravishankar Shukla University, Raipur has been actively engaged in studying various aspects of the ecology of the cave, as well as the behavioural eco- logy and physiology of the hypogean loach. This paper provides an updated account of these studies. The results obtained were compared with those obtained on its epigean counterpart, whenever it was possible. Kotumsar Cave The Kotumsar Cave is located along the bank of the River Kanger, flowing in the Kanger Valley National Park (KVNP) (18°52′09″N; 81°56′05″E), at an altitude of 560 m, in Jagdalpur, Bastar, India (Figure 1). It is one of the largest caves in India, and one among several explored and unexplored natural limestone caves of KVNP that is open to tourists. The cave was discovered in 1958. The entrance to the cave is a vertical fissure in the wall of a hill. It is a narrow but twisted opening measuring about 15 m in length. The cave in general contains irregular chambers that make it appear honeycombed in structure (Figure 2). The main tunnel of the cave extends for nearly half a kilometre and there are many sideward and downward passages that have been partially ex- plored. The roofs and walls of the different chambers are lined with colourful dripstone formations as result of pre- cipitation of calcite-dissolved carbonate of lime. The chambers of this cave are floored with either rocks or pebbles of varying dimensions or surface-derived soil/ clay deposits. The air temperature and several other abiotic para- meters of Kotumsar Cave were monitored during six dif- ferent months between May 1987 and March 1988. The air and water temperatures of the cave remain relatively stable at an annual average of 28.25 ± 1.23°C and 26.33 ± 0.96°C respectively (range = 25.0–32.7°C for air; 22.9– 29.3°C for water). The water pools are distinctly alkaline. The annual average of pH values is 8.04 ± 0.36. Further, a statistically significant annual variation in the conduc- *For correspondence. (e-mail: akpati19@hotmail.com) Figure 1. Location map of the Kotumsar Cave located in the Kanger Valley National Park, Jagdalpur, Bastar, India.