Crayfish Mating

[Colin McLay]

How do you tell when a female crayfish is reay to mate?
How does she attract a male?

[Luis]

How do you tell when a female crayfish is reay to mate?
How does she attract a male?

I used to have 1 male- 2 female crayfish when I lived in NY , I had them for several years .They lived way past the few yrs they were supposed to live . They were a blue strain of a northern crayfish which is illegal in Florida , can't recall the name, either way after good size water changes (dechlorinated and room temp ) they would mate.

The females never showed any sign but the male was more than ready only after good size water changes.

What type of crayfish do you have ?

I ask as suspect not all crays are the same when it comes to mating and someone here might have the type you have.

[Mustafa]

In my experience you can't really tell. It just happens. The female does not try to attract the male, either. He just looks for her and grabs her and tries to mate...against her protests. With many crayfish species that forceful action may cost the female a claw or two, or even a few legs.

How do you tell when a female crayfish is reay to mate?
How does she attract a male?

[Colin McLay]

It seems that mate attraction and advertizing receptivity is enigmatic in crayfish! I do not have any crayfish myself, but I have looked at videos on YOUTUBE and these do not provide any answer - although these are admittedly edited sequences rather than included the pre-mating and post-mating bits.
It seems to me that males would only copulate and/or females would only solicit mates when they had a mature ovary that was ready to lay eggs. Some female crays can store sperm, but others cannot so you would think that they would need to mate close to the time of ovulation, otherwise the external spermatophores would be lost.
Why should a male waste sperm on females who are not likely to lay eggs very soon.
So I have two questions:
1) is mating linked to moulting?
2) can you see that state of the female's ovary before mating - or at any time for that matter?
Thanks for the replies.
Colin

[Mustafa]

In my experience mating does not seem to be linked to molting, although you can see males trying to mate with females right after molting, too (just not exclusively after molting). No, you can't see any eggs developing in crayfish ovaries as you can with most shrimp...their carapace is too opaque for that. Obviously hormones are released into the water so that males are attracted, but when exactly that happens is not immediately obvious in an aquarium environment. When you see crayfish mate, you know that females are going to be running around (or more likely hiding somewhere) with eggs sooner or later.

[Colin McLay]

Mustafa: thanks for your observations about crayfish mate attraction. Do you know anyone who might have recorded how long after observing a mating episode that eggs were laid by the female? Have you ever seen a male try and mate with a female who is already carrying eggs? As you might have guessed I am not a crayfish expert, but I do have some knowledge of crab mating behaviour and I'd like to be able to compare them.
I mentioned before that I had viewed YOUTUBE videos obtained by using the search terms "Crayfish Mating". Do you think that these give a representative portrayal of crayfish reproductive behaviour as a whole?

[Mustafa]

Yes, the videos do represent their reproductive behavior quite well as they describe what I wrote above: the male just grabs the female and forces mating. You can also see that the female hasn't freshly molted as the females in the videos are walking around looking for food as opposed to hiding and waiting for their shells to harden. No, I have not observed a male try to mate with an ovigerous female.

[Colin McLay]

Yes I thought that there were enough repeated examples for different species that one could get a good idea of the mating behaviour.
One other thing puzzles me: there are several published studies which say that, for example, in the red claw crayfish the copulation position is female over male, and yet all the YOUTUBE videos clearly show male over female. Is there some variation in copulation position and that the published studies are wrong or perhaps they have a different strain/variety of Cherax quadricarinatus? The Japanese crayfish Cambaroides japonicus has female over male mating and also differs in that the male does not grasp the female chelae in order to restrain her.

[Mustafa]

In my experience *all* crayfish mate with the male turning the female on her back while holding her claws. The female tries to resist by rolling up her abdomen to prevent mating, while the male tries to do the reverse. During that struggle it can happen that the crayfish end up in various different positions. I have seen mating crayfish side by side and also with the female temporarily on top. Even Cambaroides japonicus is likely to mate that way (although I obviously don't have personal experience with that species). That one mating video on youtube (of Cambaroides) just shows a pair on a smooth surface in the middle of mating. Since there is no substrate it's likely that the male could not get a good footing and just ended up in the lower position after starting up on top. As you can see it could not even get a hold of her claws (although) her abdomen is curled under still to prevent mating).

As for published studies...the fewer peer reviewers are out there, the more likely it is that there are plenty of errors in published studies (it already starts with methodologies and experimental setups). The freshwater invertebrate field has not attracted too many researchers thus far, so peers to review and point out mistakes are hard to come by. I read plenty of nonsense in published papers all the time... Having said that, published papers are, of course, *usually* much more reliable still than some random people reporting observations from their living rooms in online forums or blogs. Nothing is perfect, not even close to it.