The neural control of feeding in elasmobranchs: A review and working model

A working model of the neural control of feeding in elasmobranchs is presented and summarized in graphic form. The model is based on a review of studies in sharks and batoids augmented by suggestions and comparisons from research in mammals and teleosts. The focal point of the model is a proposed Hypothalamic Feeding Area (HFA) that encompasses the medial periventricular zone in the inferior lobe and a small area immediately dorsal to it. Electrical stimulation in the HFA has evoked feeding in nurse sharks and neuropeptides and neurotransmitters known to influence feeding in mammals and teleosts have been localized immunocytochemically in the region in several elasmobranchs. The HFA of elasmobranchs appears to be analogous to and possibly homologous with ??hypothalamic feeding centers?? in bony fishes and tetrapods. Such ??centers?? are thought to integrate external and internal stimuli and control feeding in relation to available energy stores. The HFA??s strong olfactory connections in elasmobranchs are consistent with smell-induced feeding activities. In elasmobranchs, the HFA has reciprocal connections with the central pallium of the telencephalon, a region that processes visual, acoustic, mechanoreceptive and electroreceptive lateral line and possibly somatosensory information. These pathways may provide multisensory control in feeding. HFA connections with the cerebellum, brainstem and spinal cord most likely mediate hypothalamic co-ordination of the sensorimotor components of elasmobranch feeding. The review and model help to identify areas for suggested research.