#laurelnosetxt
ALTthis is the funniest reaction i’ve gotten to my drowner babies like bro are u ok they are just litle creachers
three people sent me articles on parthenogenesis in California condors today. you talk about accidental parthenogen baby acquisition through oviposition kink one time and you’re The Parthenogenesis Guy forever!! (I love you all.)
anyways this is a neat new fact and a pretty interesting wrinkle to condor propagation. most likely a problematic one, given that avian parthenogenesis is on the whole somewhat less viable than reptile and fish parthenogenesis, but we’ll see! that said, I’m not really surprised that in such a small and extensively genetically monitored population we would end up finding evidence of parthenogenesis; most of the rarity of parthenogenesis seems to be because except in the extreme cases where females are kept in captivity without contact with males their entire lives, you can’t confirm it without a frankly ridiculous amount of genetic testing. i’m not overly familiar with the situation with avians, but for instance while it’s still (iirc) less than a dozen chondrichthyan species confirmed as parthenogenetic, I expect parthenogenesis is actually extremely widespread amongst chondrichthyans and we just can’t detect it. (it’s never been confirmed in chimaeriforms but I would be absolutely shocked if it turned out that none of an almost entirely deep-water clade were parthenogenetic. ...it would also have super weird phylogenetic implications if that were the case but that’s all hypothetical. anyways.) it’s likely similarly much more widespread than we know of in avians and even non-avian reptiles.
(honestly how many new species have to be confirmed as parthenogenetic before journalists stop breathlessly going “is parthenogenesis far more common than we used to think it was!?” every single time. the answer at this point is conclusively yes, LMFAO.)
however I’m really fascinated by a bit in the Atlantic’s coverage of the condor news—they offhandedly mention that parthenogenesis occurs at different rates in different species (I was aware of this) and it also apparently occurs at different rates between different domestic lines (I was not aware of this):
3 percent in commercial turkeys, to 16.9 percent in Beltsville small white turkeys.
16.9% in Beltsville small whites! almost six times the rate of parthenogenesis in a different line of the same fucking species!what!what!!what is parthenogenesis in turkeys linked to? how the fuck did we accidentally select for that?!
reading Ramachandran & McDaniel 2018, the paper linked by the Atlantic, it seems that not only do Beltsville small white (BSW) turkeys exhibit a vastly higher rate of parthenogenetic eggs (i.e. any unfertilized egg that undergoes some degree of embryonic development, even if ultimately nonviable), their parthenogens are also more viable than other lineages’. while commercial turkey parthenogens have not been observed to hatch, BSW parthenogens do hatch, though rarely (slightly less than 1%).
there’s also this: it is apparently very easy to select for even higher and more effective rates of parthenogenesis.
In BSW turkeys, selective breeding increased the incidence of parthenogenesis almost threefold in five generations, from 16.7% to 41.5%. Interestingly, there was an increase in parthenogen size as generation of selection increased. In fact, there was also an increase in the relative number of advanced parthenogenetic embryos from 0.2% to 11.7% (Olsen 1965b).
this is just fucking wild. could I make a fully parthenogenetic turkey strain if I tried hard enough. such a breed would be of absolutely no use to anyone but it sure would be fascinating.
the article doesn’t really offer a proposed reason for why BSWs are so inclined to parthenogenesis over other lineages, though. it’s pretty clear that avian parthenogenesis is at least partially heritable somehow. however, what other traits it might be linked or correlated to and why is unclear. they do mention this:
On the other hand, Savage and Harper (1986) demonstrated that in turkeys, the selection for low semen volume increased the incidence of parthenogenesis, probably as a means of genome survival.
the way they phrase this doesn’t really make sense (the thing they were talking about before was different types of inbreeding affecting parthenogenesis rates, so, still heritability, but I am not sure how that is the “other hand” of this). I’m also not sure that I follow how the gene(s) for low semen volume would be linked with the gene(s) for make-babby-sans-semen. parthenogenesis allows only the female to pass on genes. female partners being inclined to produce parthenogens makes a low-semen-volume male even less likely to pass on his genes. unless the idea is that the male’s daughters pass on his genes parthenogenetically, since his sons are unlikely to do so sexually? (provided he can, actually, produce daughters. which given his apparent relative fertility seems unlikely. and would still be a dodgy strategy given low viability of avian parthenogens.) hmm. I tracked down Savage & Harper 1986 and their experiment involved selecting turkeys over ten generations, and ngl, that seems like a pretty complex adaptive mechanism to arise in only ten generations.
of course, the actual Savage & Harper paper is a page and a half long and there are no citations in the discussion whatsoever. lolol science in the 1900s was a fucking trip. anyways it also offers NO actual interpretation of why low semen volume would be correlated with parthenogenesis, but the abstract says “stimulation” which suggests a relationship to a non-heritable mechanism:
The study suggests that selection for low semen volume may result in the stimulation of parthenogenesis as a means of genome survival.
not that they say what kind of “stimulating” mechanism they might be talking about. Ramachandran & McDaniel being perhaps slightly disingenuous including this study in a discussion of the heritability of parthenogenesis, methinks.
to me this really sounds more like a potentially hormonal or environmental phenomenon, possibly similar to how many of the parthenogenetic lizards engage in sexual acts in order to trigger ovulation but don’t actually exchange genetic material. something about hens trying to reproduce and failing to get their eggs fertilized increasing parthenogenesis, maybe. this isn’t a fully coherent thought, but it’s not like anyone else here appears to know what to do with this correlation, what even the fuck.
(also the semen correlation may be interesting but the creators of BSWs were not selecting for that when they developed the breed so I am still wondering what traits desirable to humans that parthenogenesis might be correlated with!)
I will say that BSWs are currently an endangered heritage breed—according to Wikipedia they had nearly disappeared by the 70s—and while the studies cited in Ramachandran & McDaniel are older, if Wikipedia is accurate they would still be roughly coincidental with the decline of the BSW. I have a suspicion that one of the factors that increases parthenogenesis rates is genetic bottlenecks, which can fix all sorts of usually rare traits at relatively high rates in a population. (not to mention that, while this applies in somewhat complex ways to domestic animals, whose breeding is managed carefully, reproductive strategies that don’t require partners become highly adaptive if partners are difficult to find on account of the overall rarity of your species.) that combined with the nature of selective breeding to begin with can get you some pretty weird subpopulations. yeah! i don’t actually have a conclusion to all of this. birds are weird. what are birds? we just don’t know.
ALTman I know Norris isn’t any good for actual historical reference at this point, but my god, the aesthetic. PEAK poet looks right here
i respect gerveth shippers but i simply do not think Iorveth fucks centrists
