external fertilization


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external fertilization

the union of male and female gametes outside the bodies from which they originated, such as occurs in frogs and most fish.
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This process occurs due to differences in the acrosome and/or flagellum which produce prezygotic incompatibility (between sperms and eggs), because there are receptors located in these structures that are used for fertilization in some marine invertebrates, especially those with external fertilization (Pitnick et al.
These mechanisms are particularly important for broadcast-spawning marine invertebrates that release their gametes into the water for external fertilization, as gametes from a range of individuals will encounter each other.
Internal fertilization can therefore be related to a long middle piece and external fertilization to a short one (Mattei, 1991).
The best chance for organisms to increase external fertilization success in turbulent environments is to avoid releasing gametes during periods of high water motion.
Any precise prediction of the effectiveness of external fertilization would be problematic due to the complex nature of flow in the surf zone.
It is the first time that the phenomenon has been observed in a female with external fertilization.
Species with external fertilization had small sperm (usually <70-[micro]m long) with a simple morphology (head with sub-spherical nucleus and caplike acrosome, midpiece with a small number of unmodified mitochondria surrounding the two centrioles.
How can there be "pregnant females" in an animal with the external fertilization described in the article?
In this study, I compare the mating systems of sympatric congeneric sessile solitary ascidians in the genus Corella that share habitats, life-history attributes, and morphology, but that differ in a key morphological attribute leading to internal fertilization and embryonic development in one species and external fertilization and development in the other (Table 1; G.
The gametes were released into the environment through the apical aperture, indicating external fertilization.
On the basis of the four possible phylogenetic topologies linking the three species and on the known date of completion of the Central American Isthmus, we discussed the implications of this finding regarding the evolution of reproductive isolation in marine invertebrates with external fertilization.
Crassostrea virginica (Gmelin), the eastern oyster, is a broadcast spawner with external fertilization and a plank-tonic larval duration of 2 to 3 weeks before settlement (Galtsoff, 1964).