Are some species of animals born pregnant?

Question

I've heard of claims that aphids can be born pregnant, like tribbles in ''Star Trek''.

However, doing a web search didn't provide very convincing evidence.

The Straight Dope refers to being pregnant before birth as paedogenesis. The Wikipedia article on paedogenesis has no citations on pregnancy before birth (it does, however, have a citation on male offspring eating its mother!). It also states that the term also refers to animals that get pregnant before they're fully sexually mature.

Wikipedia's article on Aphids refers to the phenomenon as Telescoping generations, which is a single paragraph stub article that has no citations.

Searching for paedogenesis in pubmed only got 8 hits. (Is pubmed an appropriate tool for such a search?)

Are animals being born pregnant well-established but little discussed, or is is yet to be well-established?

(Note: I'm referring to organisms being pregnant to their own offspring, rather than accidentally being pregnant with their own siblings)

Answer 1

A good tool to use for this is Google Scholar. The first hit revealed this article which claims

Most aphids are born pregnant and beget females without wastrel males. ... Embryos complete development within the mother’s ovary one after another, in assembly line fashion. These developing embryos contain developing embryos of the third generation within them, like Russian dolls.

The second hit is an interesting set of slides on the subject.

Answer 2

In some gall midges, the larvae develop inside the mother even before she is mature (pupal paedogenesis). Stephen Jay Gould wrote about them in 'Ever Since Darwin,' which you can find from google books at this large link:

http://books.google.com/books?id=_VCnI02FwHAC&pg=PA91&lpg=PA91&dq=gall+midges+stephen+jay+gould&source=bl&ots=KOHnKuFWFt&sig=irJkYgdR23KARbO8MGXh-8Qe_f0&hl=en&ei=eySyTdi-Eojh0QHH_-SbBg&sa=X&oi=book_result&ct=result&resnum=1&sqi=2&ved=0CBgQ6AEwAA#v=onepage&q&f=false

Answer 3

sexual reproduction would exclude the possibility (as there'd be no way to impregnate them prenatally, obviously, unless you want to have offspring impregnated by their own fathers by encapsulting some of their semen into their bodies during gestation), so you should limit your search to those creatures reproducing a-sexually.

The closest I could find quickly was the budding of jellyfish, but that's not really the same. Here a single polyp splits into multiple young jellyfish over time. This is asexual reproduction of a polyp which is itself the result of sexual reproduction.

Nice description (with a diagram) on wikipedia: http://en.wikipedia.org/wiki/Jellyfish More info confirming this on http://www.wildsingapore.com/wildfacts/cnidaria/others/jellyfish/jellyfish.htm http://www.nature.com/scitable/blog/creature-cast/more_budding_jelly_babies http://fusionanomaly.net/jellyfish.html