Search results
Results From The WOW.Com Content Network
Among mammals, monotremes (four species of echidna, and the platypus) are uniquely oviparous. In all but special cases of both ovuliparity and oviparity, the overwhelming source of nourishment for the embryo is the nutrients stored in the yolk, pre-deposited in the egg by the reproductive system of the mother (the vitellogenesis ).
Among mammals, the monotremes are oviparous. Ovo-viviparity: or oviparity with retention of zygotes in either the female's or in the male's body, but there are no trophic interactions between zygote and parents. [1] This mode is found in the slowworm, Anguis fragilis. In the sea horse, zygotes are retained in the male's ventral "marsupium".
In oviparous fish, internal fertilisation requires the male to use some sort of intromittent organ to deliver sperm into the genital opening of the female. Examples include the oviparous sharks, such as the horn shark, and oviparous rays, such as skates. In these cases, the male is equipped with a pair of modified pelvic fins known as claspers.
Some monogeneans are oviparous (egg-laying) and some are viviparous (live-bearing). Oviparous varieties release eggs into the water. Viviparous varieties release larvae, which immediately attach to another host. The genus Gyrodactylus is an example of a viviparous variety, while the genus Dactylogyrus is an example of an oviparous variety. [1]
Development is usually oviparous (egg-laying) but can be ovoviviparous, or viviparous. Although there is usually no parental care after birth, before birth parents may scatter, hide, guard or brood eggs, with sea horses being notable in that the males undergo a form of "pregnancy", brooding eggs deposited in a ventral pouch by a female.
Oviparous fish are fish that reproduce by spawning fertilized eggs outside of the body that grow into hatchlings.This process is unlike live-bearing viviparous species, which develop and nourish embryos and inside the womb, or live-beaering ovovivipary species, which develop and nourish eggs with egg yolk.
Ovoviviparity, ovovivipary, ovivipary, or aplacental viviparity is a term used as a "bridging" form of reproduction between egg-laying oviparous and live-bearing viviparous reproduction. Ovoviviparous animals possess embryos that develop inside eggs that remain in the mother's body until they are ready to hatch.
All skates and some rays are oviparous (egg laying) while other rays are ovoviviparous, meaning that they give birth to young which develop in a womb but without involvement of a placenta. [ 7 ] The eggs of oviparous skates are laid in leathery egg cases that are commonly known as mermaid's purses and which often wash up empty on beaches in ...