The Life History of the Cirratulid Worm, Cirriformia Tentaculata, on an Intertidal Mudflat

Abstract

The seasonal fluctuation in numbers of C. tentaculata was investigated from December 1959 until February 1962. The lowest numbers were recorded in April followed by a rapid increase in numbers during May. The magnitude of the increase varied from year to year, as also did the number of peaks that occurred during the summer months.The worm was shown to have an extended breeding season from the end of March to September during which several spawning ‘bursts’ took place. Experiments suggest that some spawning may occur when the mudflat is inundated by the rising tide, although spawning was not observed in the field.The population of C. tentaculata exhibited an annual cycle of growth which was influenced by the seasonal variation in temperature. Laboratory observations suggest that a temperature of about 20° C is optimal for the growth of young worms. The growth rate (8 mm/year) is slow compared with that of other polychaetes.It is tentatively concluded from the field mortality data that between 10 and 16 % of animals survive to an age at which they are sexually mature; between 6 and 8 % of each generation reach an age of 15 months. Causes of mortality in the population are briefly discussed.