EVIDENCE OF A COUNTERCURRENT HEAT-EXCHANGER IN THE RAY, MOBULA-TARAPACANA (CHONDRICHTHYES, ELASMOBRANCHII, BATOIDEA, MYLIOBATIFORMES)

A vascular network, or rete, has been found in the pectoral fin of the mobulid ray, Mobula tarapacana. This role appears to be a counter-cur rent heat exchanger which, in conjunction with a high level of red mus cle, indicates that this ray is warm-bodied. Preliminary results on ot her closely related rays indicate that retia may be more common amongs t the rays than previously thought.