Regular readers will know I photograph pond creatures on a fairly regular basis, but up until today I have never managed a shot I’m happy with of a Water louse Asellus aquaticus. I catch them on most pond dips, but because they are so common, combined with the fact they have the habit tucking themselves in to aquarium corners or under leaves and weed, I’ve rarely bothered to try photograph them, and failed when I have tried. Today however I got these shots.
Water lice are fascinating creatures. Also called water slaters or water hog-louse, their resemblance to woodlice is not a coincidence as they both types of isopod, a group of crustaceans. This means they are more closely related to crabs and lobsters than the insects like water boatman and dragonfly larvae with which they share the pond.
You can often find them in pairs, with the larger male over the top of a smaller female.
He is guarding her from other males and waiting for her to moult, as this the only time he can mate with her. Like woodlice they moult their exoskeleton in two halves, the posterior (rear) half first and the anterior (front) half second. He will continue guard her after mating until her exoskeleton hardens after the moult and no other male can mate with her.
Hi, an interesting collection of pictures. My pond filters are full of these lice, and I know that they are beneficial in that they consume the detritus, and the fish feed on them, however I have a concern about their waste products. My pond water has a higher level of nitrite than I would like, and phosphate was high but I have managed to reduce it. Do these lice produce these chemicals in their waste ?
Thanks in advance
Dave Webb.
I was wondering can they live in salt water?
I think they have some tolerance to salt/brackish water but not marine conditions. There are however an number of isopods that are found in brackish and marine waters