The cough or expulsion reflex in the port jackson shark, Heterodontus portusjacksoni

Abstract

1. l. Two types of cough occurred in the Port Jackson shark, Heterodontus portusjacksoni. 2. 2. The parabranchial cough back-flushed the secondary gill lamellae by a vigorous contraction of the pharyngeal constrictor muscles against the gill bars braced by the contraction of the interarcualis dorsalis muscles. 3. 3. The orobranchial cough emptied the orobranchial cavity, but electro-myography showed that the contraction of the constrictor muscles was inhibited. 4. 4. It is suggested that the parabranchial cough may serve to clear the respiratory channels of debris and parasites and the orobranchial cough denies access of noxious substances to the secondary gill lamellae.