Chromosome behaviour upon fertilization in eggs of the giant freshwater prawn,Macrobrachium rosenbergii(de Man)

Abstract

Chronological changes of the chromosomes upon feritilization of the giant freshwater prawn, Macrobrachium rosenbergii (de Man), were followed. Egg chromosomes, within 2 min after spawning, were at the second meiotic metaphase whereas sperm nucleus retained a cupped shape of the base region. The egg chromosomes progressed to the second meiotic anaphase by 1&15 min and completed maturation by 20 min after spawning. Both female and male pronuclei were clearly differentiable at 1 hr after spawning. Female pronucleus was larger than the male pronucleus. But both pronuclei enlarged to an equal size when they were in proximity by 3 hr after spawning. Pronuclear fusion took place by 4 hr after spawning. The fused nucleus advanced into the first mitotic division rapidly so that the first mitotic metaphase or anaphase was observed by 5 hr after spawning. The first and the second nuclear divisions were completed by 6 and 8 hr after spawning, respectively. While the first and the second cytokineses occurred simultaneously at 9 hr after spawning resulting in a 4-cell embryo. Observations of chronology of the chromosomal events upon fertilization provide informations concerning the crucial times for further chromosome number manipulation.

The late events of fertilisation in the penaeoidean shrimpSicyonia ingentis

“…Pronuclear migration has been described in the caridian Macrobrachium (Damrongphol et al, 1991); however, the mechanism of pronuclear movement was not determined. Microtubules are likely to be involved in pronuclear migration in the brine shrimp Artemia (Anteunis et al, 1967;Criel, 1992) and the crab Eriocheir sinensis (Lee & Yamazaki, 1989), but neither study provided a description of the global microtubule patterns in crustacean eggs.…”

“…Although previous studies have described the initial events of fertilisation and subsequent development in penaeoidean shrimp (Hudinaga, 1942;Kajishima, 1951;Zilch, 1979;Pillai & Clark, 1987;Lindsay et al, 1992;, few studies have specifically addressed pronuclear migration and syngamy in these or other crustaceans. Pronuclear migration has been described in the caridian Macrobrachium (Damrongphol et al, 1991); however, the mechanism of pronuclear movement was not determined. Microtubules are likely to be involved in pronuclear migration in the brine shrimp Artemia (Anteunis et al, 1967;Criel, 1992) and the crab Eriocheir sinensis (Lee & Yamazaki, 1989), but neither study provided a description of the global microtubule patterns in crustacean eggs.…”