Not a dot, not a bullseye...?

[DonyaQuick]

So I know that a dot or otherwise amorphous solid blob means unfertilized, and a clear bullseye means fertilized. I've seen many examples of both from my flock. But, for lack of a better way to put it, what does the appearance of the Greek letter Theta mean? I've seen it more than once from the same hen recently. I have never seen a clear bullseye from her eggs though. I've also turned the yolks over when I've found these theta shapes in case it was an anomaly other than "the" dot but no, that's the only thing present that could be it.

 

[sourland]

New one for me.

 

[FunClucks]

Have you tried incubating this hen's eggs? I'd guess it meant fertile, but it would be interesting to see how many of her eggs made it through to hatching and whether they had any abnormalities in the chicks. I've never seen this before, and am curious.

 

[BigBlueHen53]

Twins?

 

[DonyaQuick]

Have you tried incubating this hen's eggs?

Earlier this year yes, all duds sadly. Never saw any hint of embrio and did check post-incubation by cracking them open; just runny yellow yolk. However, those dud eggs pre-dated the appearance of these theta shapes. I really, really want to hatch from this hen, but she's 9lbs with an 8lbs roo who is having a somewhat hard time getting the important parts lined up because of how big she is. The theta shapes did show up after I saw what looked like more successful mating attempts.

When I tried incubating her eggs before, I wasn't seeing a clear bullseye but was seeing more like an O with a dot touching the edge of the ring. I've got other eggs incubating right now so will have to wait a while to test hers again if it's worth doing. I am worried though whether I've stumbled into some kind of early development lethal trait with this pair's eggs though. I know there are some that hit very early in development, I just don't know what they look like when cracked open.

 

[my21chickens]

thats interesting! i almost wonder if its "twins"

 

[DonyaQuick]

An egg from today from the theta-shape hen is now back to more what I'd been seeing from her before the thetas started. You can see some of the theta shape is still there but it's more wonky than that. I had been interpreting this as infertile but it is quite strange. I don't know if it makes any difference, but this hen is a giant cochin cross (I don't know the other half of the cross). The rooster is also a cochin cross with an unknown.

Meanwhile for comparison, these other 3 eggs from different hens who are with the same rooster.

Infertile from a purebred cochin hen who does not mate with the roo.

Fertile from another pure cochin hen; I am incubating two of these eggs right now. Both eggs in the incubator are showing good development with one week left to go.

And then I got a pacman today from 4th pure cochin hen that has been giving me a roughly 50/50 mix of clear fertile and infertile (tried to incubate 2 of hers and they were duds...). That's the first occurrence of a weird shape from someone other than my cochin cross hen. Maybe it's something to do with the roo???

It seems like I have two main possibilities:

• Something about the blastodisc is just mucked up, rendering it unable to develop even if fertilized. This would be an issue from the hen.
• I have one of the fast-acting lethal traits lurking in one or more individuals. This could be from either parent or both...

 

[DonyaQuick]

Forgot to mention something in my last post: I did look into the twin possibility after it was mentioned here. Seems like that is only likely in the event of a double-yolk. While I have seen a couple double-yolkers from other hens, none in this flock have done it. There is also apparently an extremely rare documented situation of two chicks developing from the same yolk, but it seems they do develop to a greater degree when that occurs even if they don't survive to hatch. But getting a sequence of several of those thetas in a row goes against the extreme rarity for that case. So I don't think twins is what's going on with the weird blastodiscs or blastoderms.

 

[DonyaQuick]

To follow up on this, I have five of the original hen-in-question's eggs in the incubator right now. I had seen shapes that were definitely trending towards the bullseye category prior to setting. No more thetas, but the edges of the bullseyes I started seeing still had irregularities to the shape, mostly around the outer rim. Anyway, after a week I believe I have 5 duds. I will give them full benefit of the doubt and let the incubator run for another week since this hens' eggs are extremely hard to candle; I can't even see the air cell boundary on 4 of the eggs so I doubt I'd ever be able to see a vein if there was one. But, they all seem too glowy with too uniform of a dark blob where the yolk is for me to be optimistic after 7 days.

This combined with two other pairs of her eggs being duds earlier this year leads me to think there is some kind of lethal trait in the mix that is causing development to fail very, very early at the blastodisc/blastoderm phase. The only part that doesn't fit is that lethal traits are usually only possible to carry in a heterozygous state, so it's weird to have 100% failure from a pairing of mature healthy birds even if both are carriers - I would only expect more like a 25% failure rate with that model (25% aa lethal, 50% Aa carrier, 25% AA normal). Unfortunately trying her with a different rooster isn't really an option at this point; she's 3 years old now and never got along in any other arrangement, and she is so big and strong that she can and will beat the snot out of my other roosters...so it's a depressing outcome but that's life I guess.

 

[DonyaQuick]

Ok, I have an extremely weird idea to float here. It relates a bit to the twins idea but with a twist.

What if this particular rooster's sperm is somehow unusually prone to multi-fertilization? In other words, what if he is somehow making chimeras?

I haven't gone totally insane, I promise lol just bear with me a moment.

The rooster's one offspring is looking like a possible chimera right now at 10 weeks. She (I think it's a she anyway...) is showing splashes of brown feathers only on one side of the body, and the asymmetry is getting rather noticable at this point. She's also showing what might be a weird form of heterochromia. I will try to get pictures. Up until today I was just thinking "huh what an interesting pattern" but then I got thinking about the thetas and actually looked up whether chimerism from the father was possible in chickens, and I gather it is.

This chimera idea would also possibly explain the theta shapes as an attempt to develop two conjoined bullseyes and failing. And it would make sense with the high rate of failure looking like an early lethal trait when the adult birds are totally fine.

Ok I said I wasn't totally insane, but I will admit it's along the lines of that meme of the guy linking pictures together with string all over the wall. And the one offspring is probably just waiting for me to make this post and then molt to a more uniform color just to make a fool of me. But I though it was an interesting possibility to keep in the back of my mind at least while I watch and see how that one chick develops.

The part of the idea that's problematic is I can't find anything on sperm traits that make chimerism more likely, since typically it's just a one-off-oops not a recurring phenomenon.