Control of mouth opening and pharynx protrusion during feeding in the sea anemone Calliactis parasitica

Area of Science:

• Neuroethology
• Marine Biology
• Physiology

Background:

• The sea anemone Calliactis possesses three identified nerve conducting systems: the nerve net, SS1, and SS2.
• Understanding the neural control of feeding behaviors is crucial for comprehending marine invertebrate physiology.

Purpose of the Study:

• To investigate the roles of the nerve net, SS1, and SS2 conducting systems in mediating feeding responses in Calliactis.
• To identify the specific stimuli and neural pathways involved in initiating feeding behaviors.

Main Methods:

• Observation of neural activity during feeding events.
• Electrical stimulation of the SS2 conducting system.
• Chemical stimulation using food extracts, amino acids, and reduced glutathione.

Main Results:

• Activity in all three conducting systems was observed during feeding.
• The SS2 (endodermal slow conducting system) exhibited the most significant increase in pulse frequency during mouth opening and pharynx protrusion.
• Electrical stimulation of SS2 mimicked feeding behaviors (mouth opening, pharynx protrusion).
• Food extracts, amino acids, and reduced glutathione elevated SS2 pulse frequency, with glutathione being particularly potent at 10(-5) M.
• Receptors for food stimuli appear to be ectodermal, despite the SS2 being an endodermal system.
• Pharyngeal epithelium conducts SS1 pulses, with evidence of conduction polarization.

Conclusions:

• The SS2 plays a key role in coordinating feeding responses in Calliactis.
• Feeding behavior is initiated by ectodermal receptors that signal to the endodermal SS2 system.
• The interplay between different conducting systems and receptor locations highlights the complexity of neural control in sea anemones.