Internal hydrostatic pressure of the fundulus egg II. Permeability of the chorion

STUDIES ON CORTICAL ALVEOLI IN SOME TELEOSTEAN EGGS1)

“…I n Cyprinus egg, OJIMA (1943) held that the alveoli consist of fatty material. T h e similar view has been maintained by KAO and CHAMBERS (1954) with Fundulus egg, in which t h e "platelets," probably identical with the cortical alveoli, a r e stained with Sudan 111. In these eggs, it seems to be highly probable that lipoid substance, if present, is contained in the coating membrane of alveoli, a s i n the Oryzias eggs (T. YAhfAMOTO, 1951a, b ;AKETA, 1954).…”

“…AOKI, 1939). But in either cases, there is no room for doubt that development of colloid osmotic force in the perivitelline fluid makes the whole egg rather turgid, and this in turn exerts a strong hydrostatic pressure on the egg proper, as is recently shown in Fundulus egg by KAO and CHAMBERS (1954).…”

“…But in the presence of the above mentioned irrefutable evidence, this postulate by AOKI is now quite untenable. However, in some fish eggs, the separation of egg membrane is accomplished by the corresponding shrinkage of the egg proper, as shown in the eggs of Fundulus ( KAGAN, 1935;KAO and CHAMBERS, 1954) and Clupea (KANOH, 1953). In fact, t h e stickleback eggs, when activated, slightly shrink all over the surface, accordingly, the egg membrane being separated chiefly by extending the membrane itself, b u t in part by shrinking t h e egg proper.…”

Pressure-Volume Relationship of the Fundulus Egg in Sea Water and in Sucrose

“…Because of the absence of D~O exchange under conditions of osmotic filtration and diffusion, Ussing (15> suggested that the plasma membrane of the trout egg was composed of a continuous lipide phase containing no pores, and allowing no solution of water molecules. Experiments in which pressure and volume were measured simultaneously and continuously have shown that the impermeable quality of the plasma membrane of Fundu/u,~ egg occurs only in activated or fertilized eggs, and that it is acquired during the activation process (5). This has been confirmed for the salmon egg b y studies of D20 exchange (12).…”

“…The fact that the eggs of some teleosts, Fundugus (4,5), trout (1,6,13), and salmon (12) possess a plasma membrane which is impermeable to water remains an enigmatic problem. Because of the absence of D~O exchange under conditions of osmotic filtration and diffusion, Ussing (15> suggested that the plasma membrane of the trout egg was composed of a continuous lipide phase containing no pores, and allowing no solution of water molecules.…”