Key Characteristics of Ovoviviparity:
Embryonic Development within Egg: Ovoviviparous animals initially produce fertilized eggs, similar to oviparous species. However, instead of laying these eggs outside of the body, they retain them internally.
Nutrient Provision: Developing embryos inside the retained eggs rely on the yolk sac as the primary source of nutrients. The yolk sac contains stored nutrients essential for embryonic growth and development.
Lack of Placental Connection: Unlike viviparous species, ovoviviparous animals do not establish a direct placental connection between the mother and the embryo. Therefore, oxygen and waste exchange occur mainly through the egg's permeable shell or membrane.
Examples of Ovoviviparous Species:
1. Certain Reptiles: Many species of snakes, such as boa constrictors and rattlesnakes, as well as some lizards, including skinks and certain geckos, are ovoviviparous. They retain fertilized eggs within the body until they hatch, but without establishing a placental connection.
2. Sea Snakes: Most sea snakes belong to the ovoviviparous group. For example, species like the yellow-bellied sea snake (Pelamis platura) retain their eggs internally and give birth to live young without providing direct nourishment through a placenta.
3. Certain Shark Species: A few species of sharks, such as the dogfish shark (Squalus acanthias) and some species of hammerhead sharks, exhibit ovoviviparity. Fertilized eggs are retained in the females' oviducts, and nourishment is solely derived from the egg's yolk sac.
4. Anglerfish (Deep-Sea Species): In certain anglerfish species found in the deep sea, the reproductive strategy varies. Typically, females attach fertilized eggs to specialized skin glands or structures on their own body or body parts of mating males. They are referred to as "parasitized males" in this case.
In summary, ovoviviparity is a reproductive method where fertilized eggs develop inside the female's body, drawing nourishment from the egg's yolk sac rather than via a placental connection. Several reptile, sea snake, shark, and deep-sea fish species employ this reproductive strategy.