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 Заголовок сообщения: Какие виды ахатин могут скрещиваться между собой?
СообщениеДобавлено: 28 мар 2010, 09:45 
Конкретно интересуют фулика, иредалии, иммакулата вар. пантера и глютиноза. Читала, что скрещивание происходит внутри вида, а между видами быть не может. Но многие говорят, что происходит иногда, или это просто спаривание?

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 Заголовок сообщения: Re: Какие виды ахатин могут скрещиваться между собой?
СообщениеДобавлено: 28 мар 2010, 11:09 
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By crossbreeding I do not mean breeding between two subspecies/variants such as Archachatina marginata var. ovum and Archachatina marginata var. suturalis. Not only do we know this is possible, we have seen many examples of it. By crossbreeding I mean two distinct species, mating and/or having offspring.

This is a tricky topic to deal with, because it is so incredibly complicated. After a number of conflicting opinions on the subject I have come to the following conclusions.

Originally I thought that a species was a definite compatibility boundary in the sense that species that are sexually dissimilar would have infertile offspring, if they managed to have offspring at all, like in the case of Mules and Ligers. If the offspring were fertile then in fact the specimens were either misidentified, or the two species were in fact subspecies of the same species.

However, a recent article on the hybridisation of fish has led me to a different conclusion. Whilst I was looking into hybridisation I came upon the following paper investigating the potential fertility of hybrids between two native British fish, the Roach (Rutilus rutilus) and the Bream (Abramis brama):

"Adult roach, bream and their presumed F1 hybrid from an Anglian Water reservoir were identified on the basis of morphological and meristic characteristics. The hybrid was clearly intermediate. Four hybrid breeding crosses were induced to spawn by hypophysis. A bream x roach cross (female named first) failed to produce fertile eggs, whereas F1 hybrid x roach, roach x F1 hybrid and F1 hybrid x F1 hybrid all produced fry. Fertility (defined as survival of eggs to hatching) was high for the F1 hybrid x roach back-cross (56%) but low for the others (<2%), in comparison to the pure species controls (roach 69%, bream 76%). Progeny from these crosses were reared until anal fin rays could be counted. These counts indicated intermediacy between the parents and back-crossed individuals, and similarity between F1 hybrids and their F2 progeny. 3

Whilst this isn't directly related to snails I think it does tell us that snails are likely to be able to hybridise and produce fertile offspring. Perhaps not in all cases, but in at least some and quite likely a lot. What is different is the delivery method of sperm. In fish, eggs are laid and then sperm is squirted on and over them. It is inevitable then, that sperm from one species can quite easily come into contact with eggs from a different one during spawning. With snails this isn't the case so the question of whether a snail will a) choose to mate in the first place with a member of a different species and b) ultimately choose that particular sperm donor to fertilise the eggs is not yet clear or documented.

Until more documentation on what the current species list stands at and why, it is unlikely any progress will be made into the field of snail hybridisation any time soon. With species and indeed variants of Achatinids living mainly isolated from other species and variants, there doesn't seem to be many natural precedents or examples to refer to or gain knowledge from.

We have certainly seen two different species mating in captivity and I think it is likely we have seen crossbreeds in captivity. The problem is verifying it conclusively. Often the ancestry of the snails isn't clearly known, and conditions are such that it is rarely clear which coupling resulted in fertile eggs. At least self-fertilisation can be ruled out for any offspring that differ noticeably from the parent; whilst self-fertilisation wouldn't produce identical clones I think it is fair to say it would at least be an example of particularly restrictive inbreeding, and should result in offspring very similar to the parent.

Achatina fulica and Achatina iredalei mating.
Picture Courtesy of a member of the Italian Yahoo Group: achatina_gasteropodi


Snails certainly do inbreed, and a lot of snails in captivity are the result of inbreeding, particularly well established species such as Achatina fulica. A lot of the time, this doesn't seem to cause any problems, but recently there has been discussion on the possibility that various problems such as bad shell growth and deep retraction disorder may be the result of inbreeding. I'd prefer to keep an open mind on that until there is sufficient evidence to make a judgement. It is certainly less desirable to have inbred offspring because studies in other animals show conclusively that it does inevitably lead to weakened populations. I do think that invertebrates in general are less prone to weakness than other animals, but it's not something to aim for. There are a growing number of people in the hobby community who want to encourage people to swap snails to reduce this. There have also been calls to keep a record of this somehow, so the progeny of snails can be researched; a family tree if you like. This would also fit in with the need to provide locale info to ID snails. If it was recorded from snails first being imported right through to successive generations of offspring, we'd have a much more accurate map of species in captivity. There are of course problems with knowing who are the parents but we could certainly record the line of "mothers".


fulica_iredalei_mating.jpg [ 62.42 KiB | Просмотров: 4374 ]
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 Заголовок сообщения: Re: Какие виды ахатин могут скрещиваться между собой?
СообщениеДобавлено: 28 мар 2010, 14:22 
А по-русски и своими словами никак???
В моем общем знании английского нет терминов по биологии. Поняла, только что это может случиться.

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 Заголовок сообщения: Re: Какие виды ахатин могут скрещиваться между собой?
СообщениеДобавлено: 28 мар 2010, 16:22 
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Если коротко, то данных на этот счет мало. Предположительно явление межвидового скрещивания имеет место, но весьма редко. Потомство в данном случае бесплодно.

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