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Morphological adaptations of Aglaophenia harpago (Hydrozoa: Plumulariidae) to enhance feeding efficiency

Published online by Cambridge University Press:  11 May 2009

R. G. Hughes  and
D. H. J. Henderson
R. G. Hughes
Affiliation:
Centre for Research in Aquatic Biology, School of Biological Sciences, Queen Mary College, University of London, London, El 4NS
D. H. J. Henderson
Affiliation:
Centre for Research in Aquatic Biology, School of Biological Sciences, Queen Mary College, University of London, London, El 4NS
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Extract

The pinnate (feather-shaped) hydrocauli (stems) of Aglaophenia harpago are dish-shaped with the food catching hydranths borne on the convex side of the lateral branches, a morphology recognised as an adaptation to feeding from unidirectional currents. A. harpago experience unidirectional currents because the hydrocauli are able to rotate close to their bases on an articulation in the perisarc (the tubular exoskeleton) so that the concave surface always faces into the current and the hydranths face leeward. The structure of this articulation, revealed by light and electron microscopy, is described and its mechanism interpreted. The articulation consists of two oblique grooves of thin flexible perisarc which traverse around the hydrocaulus at an angle of 62–65°. The grooves terminate in areas of perisarc divided into longitudinal lamellae (probably of structural protein). The grooves and lamellae confer the flexibility which allows the hydrocaulus to ‘fold’ up to 90° clockwise or anticlockwise across each groove. The lamellae maintain the longitudinal support necessary to prevent the hydrocaulus collapsing.

Type
Research Article
Information
Journal of the Marine Biological Association of the United Kingdom , Volume 69 , Issue 1 , February 1989 , pp. 17 - 25
Copyright
Copyright © Marine Biological Association of the United Kingdom 1989

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