SECONDARY PRODUCTION BY TAIL REGENERATION IN A TIDAL FLAT POPULATION OF LUGWORMS (ARENICOLA MARINA), CROPPED BY FLATFISH

The effects of partial tail amputation, as exerted particularly by flatfish, on growth and tail regeneration in a population of lugworms, Arenicola marina, was studied in a tidal flat area of the Dutch Wadden Sea and in the laboratory. Per attack, flatfish removed only one or a few tailtip segments. The losses were not compensated for by neoformation of new segments. Consequently, numbers of segments declined in the course of the life of individual worms, from about 100 to some tens or even less. The annual losses observed in the tidal flat populations were 40 to 50% of the available tail segments per worm. Tail size was kept in balance with trunk size by enlengthening the remaining segments. Compensation of tail weight went at the expense of growth, and could lead to weight loss of the trunk. Expressed as ash-free dry weights, the mean annual flatfish consumption of lugworm segments amounted to about 120 mg per lugworm, an amount almost equal to the mean weight of a tail of an adult lugworm, or about 20% of its total weight. Nevertheless, the lugworms were able to keep the weights of their tails almost constant. For the period from March to December, estimates of tail segment consumption by flatfish (de Vlas, 1979), in numbers and in weights, were close to independent estimates of the rates of loss of tail segments in the field populations of lugworms at 2 locations. At a third location loss rates were about double the flatfish consumption. In that area, at least one other predator (Nereis) will also have cropped notable numbers of tailtips of lugworms. Including losses to such other predators, biomass elimination by cropping tail ends almost equalled lugworm biomass elimination in the form of complete worms. Therefore, at least in lugworms, production of regenerating parts after cropping should be taken into account in studies of food chain transfer. © 1979.