THE ROLE OF THE SPLEEN DURING EXERCISE IN THE ANTARCTIC TELEOST, PAGOTHENIA BORCHGREVINKI

Abstract

Physiological changes in fish associated with swimming are highly dependent on the intensity of exercise performed (Wood, 1991). Swimming at high speed requires large increases in the delivery of oxygen to the tissues and the circulatory system must be able to meet this demand. Exercise at a speed great enough to cause exhaustion results in an elevation in haematocrit (Hct), which can increase the oxygen content of the blood. The magnitude of the Hct increase varies among different species of fish, although generally the increase is about 50 % (Milligan and Wood, 1987; Wells and Weber, 1990; Yamamoto et al. 1980; Yamamoto and Itazawa, 1989). The antarctic cryopelagic teleost Pagothenia borchgrevinki (Boulenger, 1902, see also Notothenia hodgsoni) appears to be an exception as exercise produces an increase in Hct of more than 110 % (Davison et al. 1988), an increase approximately 2–4 times greater than that in other species of fish studied.