Ooplasmic Segregation in the Medaka (Oryzias latipes) Egg

Abstract

Using time-lapse video microscopy, we found that ooplasmic inclusions in the fertilized medaka egg displayed two types of movement during ooplasmic segregation. The first manifested itself as the movement of many inclusions (diameter = 1.5-11 μm) toward the animal pole at about 2.2 μm min-1; this type of movement appeared to be streaming. The second type of movement was faster (about 44 μm min-1) and saltatory; inclusions displaying this type of movement were smaller (diameter ≤1.0 μm) and moved toward the vegetal pole. The movement of oil droplets toward the vegetal pole of the egg may represent a third type of motion. All these movements began only after a strong contraction of the ooplasm toward the animal pole, which at 25°C began 10-12 min after fertilization and <3 min after formation of the second polar body. In eggs treated with microtubule poisons--colchicine, colcemid, or nocodazole--oil droplets did not move toward the vegetal pole, saltatory motion toward the vegetal pole was absent, and the growth of the blastodisc was slowed. Eggs treated with β-lumicolchicine, an inactive derivative of colchicine, showed normal movements. Colchicine, while not inhibiting formation of the second polar body, did inhibit pronuclear migration. These results suggest that microtubules are involved in the movement of some ooplasmic inclusions, including oil droplets, toward the vegetal pole; the movement of ooplasmic inclusions toward the animal pole; and pronuclear migration.

Discrimination of fish egg quality and viability by Raman spectroscopy

“…21 Therefore, our result can be interpreted as showing that the cytoplasm is rich in glycogen and the materials in the cytoplasm are collected from all around the egg yolk aer fertilization. This was conrmed using Raman spectra, which showed that the averaged concentration of glycogen in the yolk during Stages I-IV was lower than that in Stage 0.…”

Stages of normal development in the medaka Oryzias latipes

“…A transient 'contractile wave' of cortical cytoplasmic layer follows the wave of exocytosis (Iwamatsu, 1973;Iwamatsu and Hirata, 1984). Due to the oscillatory contractions following this distinct contractile wave, the cortical cytoplasm progressively accumulates toward the animal pole to form a thick cytoplasmic layer (Abraham et al, 1993;Sakai, 1964). At 7 -8 min after sperm entry, the second polar body is extruded onto the surface of the cytoplasm at the center of the area where the germinal vesicle broke down during oocyte maturation.…”

As the fat flies: The dynamic lipid droplets of Drosophila embryos

“…Like in Drosophila , embryonic droplets in many species are highly motile: for example, lipid droplets in both mouse and fish embryos display active motion dependent on the cytoskeleton [92, 94], and for fish, annelids, and moths, massive redistribution of the droplet population accompanies early development [95, 97, 98]. Very little is known about mechanism and function of droplet motility in these species.…”