Pseudoviviparity is an interesting offshoot of oviparity, or egg-laying. Embryos are secondarily internalized by females after they are externally fertilized by males.
The female reproductive system is therefore not directly involved in the gestation or the fertilization of the embryos in pseudoviviparous species. It sounds somewhat ridiculous to describe it this way. Perhaps a few examples will do a better job of communicating the meaning of pseudoviviparity.
Gastric Brooding Frogs
Gastric brooding frogs live in the tropical aquatic environments of Australia. Females swallow early-stage larvae and brood them in their stomachs for the duration of their development.
Essentially, the stomach becomes a makeshift uterus. The actual reproductive system is not involved. The offspring eventually make up almost 70% of mom’s entire mass.
When it’s time to “give birth,” some females lie passively and allow the infants to crawl up their digestive tracts and out through their mouths.
The more active moms expel the fully developed froglets through a process called propulsive vomiting.
Yes, they actually vomit out their own babies.
Surinam and Pipa Pipa Toads
The male sexual partners of pseudoviviparous Surinam and Pipa pipa toads place fertilized eggs on the mother’s back. The eggs are embedded in a matrix of skin and epithelium that completely covers them up.
When the toadlets are ready to hatch, they break out of their mother’s back.
Here is a lovely video by National Geographic Wild that shows what this process looks like.[embedyt] https://www.youtube.com/watch?v=SgROaJY6Xnk[/embedyt]
This is not technically the same as viviparous (live) birth, but it most definitely merits substantial maternal investment.
This post is an adapted excerpt from my book “Wild Moms: Motherhood in the Animal Kingdom“