P. clarkii breeding

[savaia]

Hi All,
this is my first visit to the Forum.
i have been trying to breed clarkii's in my RAS system (also growing Cherax quadricarinatus, Perfect conditions), but every time i recognize a clarkii female with eggs, after a few days she throw's them away.
i tried to isolate her from the broodstock (i keep 3 females and 1 male in a 100 liter aquarim with a lot of shelters) to a separate aquarium but she threw away the eggs.
the second time i saw eggs, i kept her in the tank with all the others, but it also didn't work..
any idea's what i might be doing worng ?
Thanks a lot,
Savaia

[Craw Chief]

Hi Savaia,

I've bred clarkiis a few times (both blue and white varieties) and haven't seen this problem. However, I have seen a female with some eggs fertilized and others not in the same brood. I would think if she's throwing them away, that may indicate that they're not fertilized. This could mean the male is not in breeding "form". Male crayfish from the family "Cambaridae" (of which P. clarkii are members) alternate between breeding (Form 1) and non-breeding (Form 2) forms. Perhaps the male in your tank is in Form 2 and the eggs are not fertilized? The only way to tell would be for you to get a highly detailed picture of the male's underside, focusing on his reproductive organs like so:



Hopefully someone else can chime in on this issue.

[savaia]

Thanks a lot for the quick answer !
Craw Chief, i don't fully understand the figure you uploaded. do you have the legend of that figure ? are those different species (A&B vs C&D vs E&F)?

i have taken some pics of the males Clarkii i have.
from what i understand, they seem to be reproductive, but i have another speculation about the failure of the breeding :
According to your knowledge, is it necessary to supply the females with gravel ?!

many thanks,
Savaia

[Craw Chief]

Thanks a lot for the quick answer !
Craw Chief, i don't fully understand the figure you uploaded. do you have the legend of that figure ? are those different species (A&B vs C&D vs E&F)?

That picture was just to illustrate what part of the crayfish needed to be examined in order to determine breeding form.

According to your knowledge, is it necessary to supply the females with gravel ?!

I've not heard that before, but here's a good read on P. clarkii biology: http://www.issg.org/database/species/ecology.asp?si=608. Here's a quote from the "Reproduction" section:

"Procambarus clarkii employs an r-strategy, exhibiting a short life cycle and high fecundity. It matures when it reaches a size of between 6 and 12.5 cm. A 10 cm female may produce up to 500 eggs, while smaller females may produce around a 100 eggs. The eggs are 0.4 mm, notably smaller than those produced by European native members of the family Astacidae. Newly hatched crayfish remain with their mother in the burrow for up to eight weeks and undergo two moults before they can fend for themselves (Ackefors, 1999). Unlike the European native Astacus and Austropotamobius species, populations of P. clarkii contain individuals that are incubating eggs or carrying young throughout the year (Huner and Barr, 1994, in Lindqvist and Huner, 1999). This allows P. clarkii to reproduce at the first available opportunity, which contributes to its colonization success (Huner, 1992, 1995, in Gutierrez-Yurrita and Montes, 1999). In places with a long flooding period, greater than 6 months, there may be at least two reproductive periods in autumn and spring. The spring period is longer and more prolific and persists until the drying of the marsh. For large females to reproduce it is necessary to have hormonal induction induced by the photoperiod, a hydroperiod longer than four months, a temperature above 18 °C, and a pH between 7 and 8 (Gutierrez-Yurrita, 1997). If females have only a short period to prepare themselves for reproduction they must prematurely their burrow to feed; in such circumstances many females will die of dehydration, bringing about a depression in the population (Huner, 1995; Gutierrez- Yurrita, 1997, in Gutierrez-Yurrita and Montes, 1999)."

I'm going to try to go to the library this weekend and check out a book by Hobbs, Jr. entitled "An Illustrated Checklist of the American Crayfishes" so I can try to answer your question better.