On Cropping and Being Cropped: The Regeneration of Body Parts by Benthic Organisms

Abstract

To get food or oxygen, many benthic organisms expose body parts like siphons and tentacles near to, or above the sediment level. Others, like the deep-living worm Arenicola marina, defaecate at the surface of the sediment, thus exposing their tail tips. As a consequence of their opportunistic feeding strategy, cropping of such body parts can yield an important food source for flounder (Platichthys flesus) and juvenile plaice (Pleuronectes platessa) (de Vlas, 1979a). In the westernmost part of the Wadden Sea, called Balgzand, about one third of the total food intake of these fish consisted of siphon tips, tentacles, tail ends and heads of molluscs and polychaetes. Figure 1 shows a number of organisms from which body parts (arrows) were found in flatfish stomachs. This paper briefly considers this cropping from the points of view of the food source they represent, secondary production and as losses which the invertebrates have to cope with.