Female pronucleus migrations and polyspermy female pronucleus can choose amongst several male pronuclei !

In Beroe Ovata, the female pronucleus generated under the polar body at the animal pole migrates for long distances (more than a mm) under the surface and fuses with one of the sperm nucleus. The female nucleus does not generally migrate towards the closest sperm and moves in a relatively straight line in a forrest of microtubules emanating from the different sperm asters.We have observed that after fertilization by multiple sperm the egg nucleus either: (see films)
-1) goes directly to one sperm nucleus
-2) hesitates between two sperm situated close to each other before migrating to one
-3) moves first to one sperm nucleus and then to other ones
We do not know what is the basis of the "choice" . We suspect it has to do with situations where sperm from different animals have entered the egg Fertilization is hard to control in ctenophores and we have note solved this question yet.
When the egg has not been fertilized the nucleus migrates randomly under the surface.

-Carré D. & Sardet C. (1984) Fertilization and early development in Beroe ovata. Dev. Biol. 105, 188-195.
-Carré D, Rouvière C. & Sardet C. (1991). In vitro fertilization in Ctenophores : sperm entry, mitosis and the establishment of bilateral symmetry in Beroe Ovata. Dev. Biol. 147, 381-391.
-Rouvière, C., Houliston, E., Carré, D., Chang, P. and Sardet, C. (1994). Characteristics of pronuclear migration in Beroe ovata. Cell Mot. & Cytoskel. 29, 301-311
-Houliston, E., Carré, D., Chang, P. and Sardet, C. (1995). Cytoskeleton and Ctenophore Development. Curr. Top. in Dev. Biol. 31, 41-63