Cardio-regulatory neurons

The central mechanism of crustacean cardio-regulation has been studied by many investigators. In most crustaceans, the heartbeat is regulated by a pair of cardio-inhibitory and two pairs of cardio-acceleratory nerves from the CNS.

It had long been thought in decapods that the cardio-regulatory neurons are somewhere in the thoracic ganglion mass. These neurons were first identified by K. Tanaka & K. Kuwasawa @ Tokyo Metropolitan Univ. in 1991 in a marine giant isopod, Bathynomus doederleini. Their colleagues also identified a whole bunch of motoneurons for the cardio-arterial valves using the same animal.
In 1996-'97, we (A. Sakurai, A. Mori & H. Yamagishi @ Univ. of Tsukuba) identified all the three cardio-regulatory neurons in the CNS of Ligia.

Left: 3 cardio-regulatory neurones in the CNS of Ligia exotica.
Top: peripheral pathways of the cardio-regulatory axons.
(CI, cardio-inhibitory neuron; CA1, 1st Cardio-acceleratory neuron; CA2, 2nd cardio-acceleratory neuron).

Morphological investigation by intracellular injection of neurobiotin revealed that the cardio-regulatory nerves innervate both the CG and the cardiac muscle.

Right: Peripheral processes of the cardio-acceleratory neurones (CA1, CA2) inside the heart stained by intracellular injection of neurobiotin into the cell bodies in the CNS.

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