external fertilization


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external fertilization

[ek¦stərn·əl ‚fərd·əl·ə′zā·shən]
(physiology)
Those processes involved in the union of male and female sex cells outside the body of the female.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
In most aquatic species with external fertilization, spermatozoa are immotile in the testis and become motile at release into the external medium (Perchec et al., 1995).
Our results suggest that fucoid algae possess a "physiological sensor" of hydrodynamic conditions that is coupled to the control of gamete release, a key event in the life history of organisms with external fertilization. The depletion of inorganic carbon, in the unstirred boundary layer next to the thallus in the light when water motion is low, may then provide a signal involved in triggering the release of gametes.
First, it brings to biologists' attention the likelihood that external fertilization is a very inefficient process, at least under turbulent flow conditions.
inflata is genetically based, other mechanisms such as a partial incompatibility system or external fertilization may so effectively prevent or lower the incidence of selfing in C.
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.
All shallow-water (with the exception of species of Erginus) and intertidal Patellogastropoda are regarded as broadcast spawners with external fertilization. It is therefore not surprising that those species examined to date have ectaquasperm (Azevedo, 1981; Koike, 1985; Hodgson and Bernard, 1988, 1989; Hodgson and Chia, 1993; Hodgson, 1995; Hodgson el al., 1996; Buckland-Nicks and Howley, 1997; Hodgson and Morton, 1998; Ridgway el al., 2000).
Mitochondria are usually spherical in shape and their array as spherical masses on the proximal end of the spermatozoon head is also typical of species with external fertilization. Suwanrajat and Parnrong (1999) say the number of mitochondria may be species specific.
Here we present another example of assortative fertilization in external fertilization species of marine bivalves.
However, reproductive isolation and speciation are less well understood in marine animals with external fertilization than in terrestrial species, and very little is known about the mechanisms responsible for maintaining species identity when two species make secondary contact in the ocean (Knowlton, 1993; Palumbi, 1994; Gardner, 1997).
This reproductive strategy is similar to that of many marine bivalves that also exhibit external fertilization (Longwell and Stiles, 1968; Longo and Anderson, 1969a, b; Stiles and Longwell, 1973; Ackerman et al., 1994).
Thus the only means by which mothers with external fertilization can reduce the planktonic period of their offspring is by reducing the size of the offspring that they produce.
1989, Consequences of surf-zone turbulence for settlement and external fertilization. Am.