EMBRYONIC DEVELOPMENT IN POECILIID FISHES

¹ Biological Laboratories, Harvard University, Cambridge, Mass.

In poeciliid fishes the embryos are retained within the ovarian follicles until parturition. When the dry weight of the intact follicle is determined at various stages of development, no significant weight change can be demonstrated in the 18 species studied. This is in marked contrast to the situation in a truly ovoviviparous fish where one-third of the initial weight of the egg is used for maintenance during development. Accordingly, it is concluded that all of the species studied receive nourishment from the mother and hence are not ovoviviparous in the strict sense of the word. Furthermore, they apparently receive only as much nutriment, quantitatively at least, as they require for their maintenance metabolism. Some limiting mechanism must be operating, but its nature is not known. This situation is contrasted with that in Heterandria formosa and Aulophallus elongatus, members of the family which have developed nearly complete dependence on the mother for nourishment during development.

This article has been cited by other articles:

				J. F. Downhower and E. L. Charnov A resource range invariance rule for optimal offspring size predicts patterns of variability in parental phenotypes PNAS, May 26, 1998; 95(11): 6208 - 6211. [Abstract] [Full Text] [PDF]