Balanus balanoides (L.) (Cirripedia). Life cycle and growth in Greenland

Abstract

A material of Balanus balanoides, regularly collected during the course of one season in different stations in Greenland, has established the seasonal-cycle and the lifecycle of the species. The hatching period, settling period and mating period indicate the sexual cycle. The pelagic stage is given as the period from maximum hatching to maximum settling. Fig. 33 shows a comparison between the sexual-cycle in the different localities. The dependence of this cycle on external factors is discussed and demonstrated, e. g., by curves on temperature and primary production. From the author's own observations and from the literature, it is shown that the cypris larvae prefer marine conditions at the northern limit and estuarine conditions at the southern limit. The influence of the West Greenland Current on the distribution taking place towards the north is shown by the settling periods and by the size distribution of the first winter ring.

The growth of the O.-gr. animals and adult animals is demonstrated by measurement and age determinations of the scutae. Figs. 45, 65 and 66 give comparisons between the different localities. Growth parameters, calculated preferably according to methods used for fish populations, are compared in Table 9. A comparison between the results obtained here and those of other scientists from the North Atlantic area are attempted in Table 10. However, the value of the comparison is reduced by the fact that no previous material has been treated in a similar manner. It is emphasized that the climatic differences inside Greenland are of importance-varying from the 11-month ice cover in Angmagssalik, to Sukkertoppen, which has no ice cover. The distribution of the species towards the north is discussed in the light of the results, and the possibilities are considered of forming a picture of the fluctuations in hydrographic and climatic conditions from the changes from year to year in the northern limit.