It’s almost another marbled clone.
There are parthenogenetic vertebrates (some of which have been featured on this blog), but the Mangrove killifish, Kryptolebias marmoratus, is the only vertebrate that regularly self-fertilizes. Most individuals have male and female reproductive organs. Obviously, this allows you to have individuals that are not quite clones, but certainly have much more limited variation than most sexual species.
But, because sex is rarely simple, some individuals in this species are just male.
And that little detail means that the hope that all these individuals will create nice, neat, clone lineages gets shot down. So Tatarenkov and colleagues decided to investigate how genetically similar these fish are to each other.
Some findings are depressingly familiar. Cell biologists have often found that what they thought was one type of cell cultures has been contaminated by nearby strains of other immortal cells. HeLa cells are particularly notorious in this regard. Similarly, Tatarenkov and company found about 20% of their marbled killifish did not have the expected genes. Incomplete record keeping meant that many sources of error, or sources of new variation they found, could not be traced back to its source.
They did find new genetic variation that appeared to have cropped up since the animals had been collected for the lab, which they attributed to new mutations. In fact, one gene seemed to be a mutational “hotspot,” mutating several times in different lines.
The major source of genetic variation, however, was the original source of the lab population. This fish has a wide distribution, and stocks collected from different locations did not resemble each other. Thus, this fish has a nice combination of being able to maintain genetic similarity within a lineage, but there remains some variation across lineages.
P.S. – If this fish’s specific name, “marmoratus,” looks a bit familiar, it’s because it is Latin for “marbled.” And that’s undoubtedly the same root for the word, “Marmorkrebs.”
Tatarenkov A, Ring B, Elder J, Bechler D, Avise J. 2010. Genetic Composition of Laboratory Stocks of the Self-Fertilizing Fish Kryptolebias marmoratus: A Valuable Resource for Experimental Research PLoS ONE 5(9): e12863. DOI: 10.1371/journal.pone.0012863
Picture from here.