The Life Cycle of Ciona intestinalis (L.) f. typica in Relation to the Environmental Temperature
- 1 January 1965
- Vol. 16 (1/2) , 109-+
- https://doi.org/10.2307/3564870
Abstract
Investigations of Scandinavian populations of Ciona Intestinalls f. tygica and a survey of the literature concerning other areas evidences a clear relation between age, growth, spawning and embryonic development, on the one hand, and the environmental temperature on the other. Growth is more rapid at high temperatures than at low and the number of yearly generations which succeed each other in the warmer seas seems to be at least 3 and possibly 4. In boreal regions there are 2 generations per year in restricted and sheltered water, while populations in more open waters and at somewhat greater depths, about 15-30 m, have one generation per year. In deeper waters (below 50-60 m), In which temperatures of 6-9[degree] C prevail all the year round, each generation lives for at least 2 years and in the colder, sub-arctic waters even longer. The greater the difference between the summer and winter temperatures, the more distinct the spawning periods. In areas with an even temperature all the year round, it seems that reproduction may take place, broadly speaking, throughout the year. Experiments show that on the coasts of Europe embryonic development from the fertilized egg usually takes place between 8 and 23[degree] C. Some populations seem to deviate from this pattern and have other tolerance limits. Later stages exhibit wider tolerance ranges than earlier ones. There Is so far no evidence of whether the adaptatio of the form to different temperatures Is due to a division into hereditary races or to the formation of environmental modifications.This publication has 0 references indexed in Scilit: