Holland, L.Z., Gorsky, G. & Fenaux, R.

Zoomorphology 108, 229–243 (1988). doi:10.1007/BF00312223

Fertilization in Oikopleura dioica (Tunicata, Appendicularia): Acrosome reaction, cortical reaction and sperm-egg fusion.

“Males [...] were placed in cold (4° C) seawater to induce testicular rupture.” “Each egg is about 80-100 µm in diameter and is surrounded by a thin vitelline layer 80-100 nm thick [...] There is an asymmetrical perivitelline space ranging from 2 to 7 µm in width”. “The maximal diameter of the chromosomes in our section is about 150 nm”. “By 60 s after insemination, when the egg is regaining its spherical shape, the sperm nucleus, centriole, axoneme and mitochondrion have moved into the egg cortex”. “Fertilization [...] occurs almost simultaneously throughout an egg population after the addition of sperm”. “The central cytoplasm of the unfertilized appendicularian egg contains a preponderance of multivesicular bodies and the periphery has alternating areas rich in mitochondria and rich in endoplasmic reticulum”. “the anterior portion of the nuclear envelope evaginates together with the acrosomal membrane and may help to stiffen the resulting acrosomal tubule. The lumen of the tubule, which is consequently lined by the nuclear envelope, contains some fine fibrils that extend back into the nucleus.”