Saturday, July 29, 2006

The Deep Blue

Excitement here as a couple of new arrivals have been added to the household. I spent a bit of time cleaning up a fishtank of mine, pulling up algae, adding some logs and doing a water change. I originally planned to put a handful of feeder yabbies in the tank (these are small Cherax destructor) and are very entertaining, but in making enquiries about them I was told of some cheap Marrons so snatched them up.

The Marron is Cherax tenuimanus ('slender hands'), a species of freshwater crayfish from the rivers of south-western Western Australia (that hotspot of biodiversity). Marrons are generally dark brown to black, but apparently this brilliant blue form occasionally occurs and has been bred for aquaria. The species is farmed for the table too, supposedly nicer than yabbies or redclaws.

Crayfish make very good aquarium animals. They do interesting things, like climb around, fight, attempt to escape, bulldoze the gravel, moult their exoskeletons and eat snails. A slightly more annoying trait is their tendency to tear up any plants and eat them, causing quite a mess.

The pair turned out to be both males, so I'll probably be in the market for a female at some stage. I'm a bit worried about the damage to the telson/uropods that one of them has experienced, as I've lost redclaws in the past to tail infections. Did you know that you can sex crayfish by examining the bases of their legs? On the base of the rear-most pair, each leg has a little projection in males (just visible on the photo to the right). Females lack this but have a couple of pores on the next pair of legs to the front). Upon mating, the male deposits a spermatophore between the female's last pair of legs, and she subsequently releases eggs and has them pass through the sperm on their way to the underside of the tail where they are held during development.

Hope these guys enjoy their new home and do well in it. Maybe one day I'll try to get hold of some Euastacus australasiensis for a bit of a contrast. Posted by Picasa


Snail said...

If you made a video, you could call it a blue movie. Or not.

Have you spotted any temnocephalans on your animals? They're pretty cute. (The temnos and the crusties.)

David Nelson said...


Yeah, there are what I believe to be Temnocephalans (a type of flatworm except they look superficially more like Hydra).

The tail is still looking a bit dodgy, I wonder if there's anything I can do?

Snail said...

I wonder if there's anything I can do?

Lemon juice? A nice bit of garlic butter?