Anyone do genetic analysis with apple snails?

[snailspace]

Has anyone on this forum ever tried investigated the genetics of shell color (or body color) in P. difusa? I know there is a demo in the Genetics forum that give some hypothetical possibilities for the genetics of color traits. Has anyone ever tried to do crosses to validate that model? Are there any mutations in apple snails that have been characterized as recessive or dominant?

[pbgroupie]

Most of the charts and results are from observation of generations of apple snails. Some crosses were bred to bring about specific results with consistant findings and those findings were confirmed with the community at large. There was a topic about genetic abnormalities that tended to be inherited. It states:


Heritable Traits - these conditions show a strong heritability trend. This means that if a parent snail exhibits the condition, some of the offspring in the vast majority of or all same-trait crossing display that trait.

Thin Shell Disorder. This is a condition in bridgesii that affects the thickness of the calcium-based layer of the shell that gives the shell it's strength. The shell is perpetually very thin, extremely fragile, and breaks easily. It tends to display the following pattern across generations:

Parents: one or both parents may show some tendency towards shell breaks, but not significantly enough that they cannot breed.
Offspring: many offspring may show the same trends as the parents, but some (and in rare cases most) will display severe shell problems and will crush easily. These ultra-fragile snails usually die before they reach reproductive age, die from mating damage, or die shortly after reproduction. There is a strong correlation between these two levels of severity, and often little occurance of snail groups that show a continuous gradient of the condition; there are primarily only two levels at which the condition is expressed.

This pattern suggests that the trait may be a simple Mendelian trait, where the number of copies of the recessive gene determines the severity of the condition:
TT = normal (hypothetically)
Tt = parent condition
tt = severe condition that is usually fatal

Snails that crush easily do not have offspring with thick shells, further indicating that the trait is heritable.

Other shell deformities

There are other, rarer types of deformities in bridgesii that affect the shell and may be heritable. The heritability pattern of these is less certain since mortality rates tend to be high and therefore it is difficult to study such conditions across generations. These conditions often cause the mantle to be improperly shaped and therefore the shell grows strangely. Generally these snails suffer growth complication and do not survive to adulthood, and the parent snails may not show the condition obviously. The mantle may be unevenly shaped, causing the shell to bluge or twist oddly. It has been observed to affect entire clutches of snails raised under different conditions, and the parents may consistently produce clutches of offspring that show the problem, indicating that it is likely not an environmentally induced problem.


Potentially Heritable Conditions - these traits need further study to determine if they may be heritable or constitute a true genetic trait.

Forked Siphon
There have been some reports that snails posessing forked siphons have offspring that later go on to develope a "fork" in the same place on the siphon.

Dysfunctional Siphon
Some snails have siphons that are kinked and do not extend properly. It is questionable whether this is an environmentally induced problem, but offspring of a snail with a dysfunctional siphon may suffer from the same problem (although not always).

[snailspace]

Thanks for the info. I have wondered whether the shell defects I've seen in my insularum snails is genetic, but I've not done any crosses to find out. It is striking though when you see some snails with many severe cracks together in the same tank with snails that have no defects at all, and they are all sibs.

[Soothing Snails]

I am hoping to *start* my breeding program breeding within a month or two to set the purple as a morph. I've had experience with mouse genetics and corn genetics, but apple snails will be totally new to me. Right now my learning is consisting of cycling and environment. Next is studying what is involved for the phenotype. Get the basics down and then I can be successful in my breeding methinks.

Someone just suggested that perhaps setting a wild strain would be more beneficial, so simple recessives could be figured out easier, so who knows what direction I'll go...

[Fancyfish]

Have you made any progres with snail color genetics? It is something I was wondering about specifically regarding the striped snails. I am familar with cat color genetics and I was wondering if the only 2 snail shell colors are gold and ivory or if other colors such as solid purple, pink or green exist. Or are those the result of enviroment or other causes.