Observations on the population of Scoloplos armiger at Whitstable
Gibbs, P.E. (1968) Observations on the population of Scoloplos armiger at Whitstable. Journal of the Marine Biological Association of the United Kingdom, 48 (1). pp. 225-254.
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The population of Scoloplos armiger O. F. Muller at Whitstable was investigated from January 1964 to April 1965. Initially the population density was high, being over 600/m2, but the numbers sharply declined during the summer of 1964 and by the following winter the density had dropped to under l00/m2. In addition to this decline, the population structure changed, and the overall effect was a marked reduction in the fecundity of the population. The cause of the high mortality in the summer of 1964 is unknown. During the breeding season of 1964, four separate spawnings were detected but only a single spawning occurred in 1965. At Whitstable the spawning of Scoloplos usually takes place at the time of the spring tides in the period late February to April when the sea temperature is above 5 degrees C. Scoloplos appears to breed for the first time in its second year. Evidence was gained to show that females produce one egg cocoon during the breeding season, the size of which and the number of eggs it contains being dependent on the age of the female since fecundity increases with age. The cocoon-forming habit in polychaetes is discussed; it is concluded that the chief function of the cocoon in Scoloplos is to retain the larvae within the adult habitat.
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