SECONDARY CIRCULATION OF THE VASCULAR HEAT-EXCHANGERS IN SKIPJACK TUNA, KATSUWONUS-PELAMIS

Vascular corrosion replicas of the counter current heat exchanger micr ocirculation in skipjack tuna, Katsuwonus pelamis, were examined by sc anning electron microscopy. Small-bore (7-10 mu m diameter) vessels, w ith characteristics typical of those associated with the secondary cir culation, were abundant in the central and lateral heat exchangers. Th ese vessels arise from the large-bore (70 mu m diameter) retial arteri oles and, after a tortuous path, anastomose repeatedly to form 50-200 mu m diameter secondary collecting vessels which ultimately exit from either pole of the rete. (C) 1994 Wiley-Liss, Inc.