[b said:
Quote[/b] (dlybrand @ Feb. 21 2006,9:28)]Octoploid?! That's ridiculous! How do you get a polyploid frog?
It is not ridiculous it is absolute fact. If you don't believe me then google it I am sure all the info you need is there. Try it for both the frogs I mentioned, you'll see.
I'll even do the first step for you. If you perform a google search for "
Ceratophrys ornata, octoploid" the first 2 hits you get are these 2 articles which I have copied straight off of the PubMed database:
Rahn IM, Martinez A.
Chromosome pairing in female and male diploid and polyploid anurans (Amphibia) from South America.
Can J Genet Cytol. 1983 Oct;25(5):487-94.
Abstract:
Chromosome pairing in females and males of diploid (2n = 22) and tetraploid (2n = 44) Odontophrynus americanus and diploid Ceratophrys cranwelli (2n = 26) and tetraploid C. ornata (2n = 104) showed that diploid females formed more chiasmata per paired arm than diploid males and polyploids of both sexes. There was a reduction in the level of recombination in female polyploids by forming multivalents with terminal chiasmata. The reduction reflected a change in the genetic control of pairing in females after polyploidization
(note that even though they say "tetraploid" in the abstract if you do the actual math it is octoploid.)
And this one as well:
Leipoldt M, Kellner M.
Ribosomal RNA structure in the diploid and phylogenetically polyploid amphibian species Hyla and Odontophrynus.
Comp Biochem Physiol B. 1984;79(2):181-5.
Abstract:
Ribosomal RNA of the diploid amphibian species Hyla chrysoscelis and Odontophrynus americanus is structurally modified by hidden breaks. Phylogenetically polyploid related species like the tetraploid Hyla versicolor, the tetraploid Odontophrynus americanus and the octoploid Ceratophrys ornata do not show hidden breaks in ribosomal RNA. Structural modifications of rRNA molecules in diploid amphibians has no detectable effect on the ribosomal activity in vitro.
To get an octoploid I would guess would require a 2 step evolutionary process. First you would get a tetraploid animal, either from a failed first stage mitotic division of the embryo or from 2 diploid gametes combining. These tetraploids would then have to mate against themselves or against a normal diploid animal. In the first case you could go through the same processes above. In the second case only a diploid gamete from the diploid parent would work. At a guess, since a tetraploid intermediate has not been found I am guessing that it was not evolutionarily stable and died off leaving only the diploid and the octoploid.
Of course that is just my radical theory since amphibian genetics is not my absolute field of study (I am bacterial geneticist
)