NEURAL MECHANISMS GOVERNING DISTRIBUTION OF CARDIAC-OUTPUT IN AN ISOPOD CRUSTACEAN, BATHYNOMUS-DOEDERLEINI - REFLEXES CONTROLLING THE CARDIOARTERIAL VALVES

In Bathynomus doederleini all of the cardioarterial valves located at the origin of the lateral arteries are dilated by impulses of lateral cardiac nerves. Tactile stimuli applied to sensillar setae depress imp ulse activities of the 1st and 5th lateral cardiac nerves. The 1st lat eral cardiac nerve controls the valve of the lateral artery which runs to the walking-legs and viscera. The 5th lateral cardiac nerve contro ls the valve of the lateral artery which runs to the swimmeret muscles . The response indicates that tactile receptor reflexes bring about de creased haemolymph flow to the organs. Augmented swimmeret movements w ere always accompanied by an increased firing rate in the 5th lateral cardiac nerve. Artificial full protraction of swimmerets simultaneousl y induced excitation of the 5th lateral cardiac nerve and inhibition o f the 1st lateral cardiac nerve. The excitation corresponds to an incr ease in haemolymph flow to the swimmerets, and the inhibition a decrea se in haemolymph flow to walking-legs and viscera. Three kinds of mech anoproprioceptors which were activated by swimmeret movements were fou nd. Two of the mechanoproprioceptors are located at the base of the ba sipodite. The other mechanoproprioceptor supplies processes to a nerve to the retractor muscles. Activation of three kinds of mechanoproprio ceptors, induced by artificial swimmeret protraction, triggered latera l cardiac nerve reflex responses.