Growth and Differentiation of Daphnia Mana Es in vitro.

Abstract

In the course of some ultra-centrifuging experiments there arose the need of rearing the parthenogenetic eggs of Cladocera in vitro. A review of the literature revealed no record of the successful growth of eggs of this group of animals outside the brood-chamber of the mother. We have succeeded in rearing the eggs of Daphnia magna in tissue culture slides and inasmuch as the embryos are transparent, this enabled us to make observations on some of the sequence of events in the course of the development of the embryos without the necessity of staining and sectioning.

A number of different media were used in an endeavor to grow Daphnia magna eggs in vitro. A modified Ringer's solution utilized successfully for physiological work on isolated organs of Cladocera by Levy, 1 proved injurious to the eggs. The growth of eggs in a medium consisting of the fluid obtained from the brood-chamber of animals in which there were developing eggs showed no advantage over a simpler medium consisting of sterile pond water. This is of considerable interest in view of the fact that it has been held (Dearborn, 2 Birge 3 ) that the brood-chamber of Cladocera secretes a fluid which serves as nourishment in the course of the development of the embryos. Careful controlled experiments revealed that the parthenogenetic eggs in the brood-chamber of Daphnia magna completed their development in about 46 hours at 25 °C. When the parthenogenetic eggs of this animal were reared in sterile pond water on tissue culture slides, they too completed their embryonic history from eggs to free swimming independent organisms in the same period of time. This demonstrates very clearly that the eggs of this animal are self-sufficient with regard to the nutritive material already stored in them at the time of their deposition.