All the literature I have found on determining whether female crayfish are Form I (reproductive) or Form II (non-reproductive) only mention glair, the presence of eggs, or the actual act of copulation. However, I was wondering if anyone knows of any other physical characteristics that might signal reproductive receptivity in females before the appearance of glair. For instance, I've noticed recently molted female O. rusticus have different coloration of the annulus ventralis/sperm receptacle compared to intermolt females. Any advice or suggestions appreciated!
HI Sarah,
No tried methods for crayfish from me but here's a few methods from other crustacean species that you may want to have a look at:
- in southern rock lobster Jasus edwardsii the abdomen changes shape and becomes wider. You could perhaps examine that with caliper measurements or 3D scanning also an option for more sophisticated measurements like volume.
- "mating scars" have been observed in a few crab species like Scylla serrata and Pseudocarcinus gigas. These are scratches or melanised marks around the gonopore. The mating process is different for crayfish but perhaps worth a look.
- non-lethal imaging methods for determining ovarian development may work. I've used CT scanning for Pseudocarcinus but other options like ultrasound, X-ray and MRI may work??
- in some species the haemolymph chemistry changes with lipid deposition - you may be able to see colour change on the underside of the abdomen, or else a sample taken by syringe.
- biochemical from a haemolymph sample eg for lipid levels or carotenoids.
Good luck!
Hello Sarah
Several Orconectes species are now widely invasive in Europe, and there has been a lot of work on their biology (to date, none have invaded Irish fresh waters, perhaps the last place in Europe!). . One active centre is the University of South Bohemia in Cesca Budejovice (Czech Republic), with researchers including Pavel Kozak, Antonin Kouba, Milos Buric etc. (I've omitted the accents on their names!). You might find the paper by Buric et al. useful, and do look at these authors on researchGate.
Best wishes
Julian Reynolds.
Thank you Caleb and Julian- I will definitely explore these options and new literature sources.
Dear Sarah,
if you are working with those crayfish, it is visible for you the wider abdomen.
This is only one character visible on the first look (except glair glands). There are some other marks as chelae size and robustness, but with a lesser importance (see my paper in Zoology: "Intrasex dimorphism in crayfish females").
Best regards
Milos
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