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Journal of Experimental Biology 57,161-171 (1972)
Published by Company of Biologists 1972

Pulsatile Pressures in the Cranial Fluids of Heterodontus Portusjacksoni

G. H. SATCHELL ¹ and G. T. ROSSITER ²

¹ Department of Zoology, Otago University New Zealand
² St Pius X College, Sydney, Australia

1. The mean pressure of the extrabrain fluid (EBF) of nine Port Jackson sharks (Heterodontus portusjacksoni) following 12 h rest was 1.9±1.4 cm H₂O.

2. Low to normal EBF pressures favoured the appearance of respiratory pressure pulsations in the EBF; higher pressures favoured the appearance of blood pressure pulsations.

3. Two routes of communication of pressure pulses from the orobranchial cavity were investigated by regression analysis of pulse pressure records;

(a) a direct route from the olfactory capsule to the cranial cavity

(b) an indirect route via the branchial blood vessels and the craniospinal vessels.

4. The hypothesis is advanced that a protective mechanism exists, paralleling that in mammals, whereby dilation of craniospinal vessels during coughing is offset by the directly communicated pressure pulse in the extrabrain fluid.