Feeding biology of intertidal sea anemones in the south-western Cape

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University of Cape Town

The species composition, abundance and distribution of intertidal sea anemone assemblages were investigated by means of line-transects at two sites on the Cape Peninsula - Wooley's Pool in False Bay and Blouberg in Table Bay. A single species, Bunodactis reynaudi dominated at Blouberg (average density 901 running m⁻¹). Juveniles < 35mm basal diameter) were particularly abundant in mussel beds. Seven species exhibiting clear vertical zonation were found at Wooley's Pool (average density 658 m⁻¹). High-shore species were Actinia equina and Anthothoe stimpsoni. A. stimpsoni was the smallest (9.1mm mean basal diameter) and most abundant (maximum density 1450. m⁻² ) anemone at Wooley's Pool. Three species were found at mid-shore: of these Anthopleura michaelseni and Bunodosoma capensis had the same vertical distribution and extended to higher tidal levels than Bunodactis reynaudi. Two species of Pseudactinia favoured the sheltered low-shore. P. flagellifera was confined to the subtidal zone and was the largest (60.2mm mean basal diameter) and least abundant of all the species (10. m⁻² ), while P. varia extended into the low intertidal. Although different anemone species exhibit distinct zonation on the shore, they show considerable overlap. Different morphological and behavioural characteristics facilitating this zonation are discussed. Bibliography: pages 86-98.