I’m having a break before starting my PhD next week, so I thought I’d have a brief non-microbial post with a few adventures from my fish-tank. The other day, my husband decided to try sticking a whole prawn (dead and cooked) into the fish tank to see the reaction of our underwater lodgers.

Most of the fish weren’t too interested, but as well as the fish we also have five assassin snails in the tank and they loved it. Within seconds of dropping in the prawn, one of the snails extended its little feeding tube and headed straight towards it.

You can see the feeding tube extending from the snail as it looks for a way in. All pictures (c) me, linkback if you use them!

Assassin snails eat by pushing the feeding tube into their prey, releasing enzymes, and then sucking up the dissolved food. Which is fine for eating other, smaller snails (their normal prey) but isn’t very good against things with an exoskeleton, as the snail needs to find a way to the soft flesh within the hard outer covering.

While the first snail was looking for a way to get at this intriguing new food, a few more of our snails came over to take a look:

Some of the fish swam by as well; it was the talk of the fishtank!

By the end of the evening, all of the snails had managed to get a go at the poor little prawn. Only two of them actually managed to find a way to eat anything from it though. One snail got in through the head (I have a horrible feeing it was via the eye area, although the eye itself was undamaged) and another found a gap through the belly and latched on there:

The two snails feeding. The fish behind is a sucking loach, which kept disrupting matters by latching onto the prawn and dragging it around.

Eventually the prawn was stolen by a large black pleck called Dyson, who dragged it behind the plant at the back of the tank and wouldn’t let any of the other fish near it. Neither Dyson nor the sucking loach (the yellow fish above – Dyson is the only fish in our tank with a name) actually ate any of the prawn, but they certainly enjoyed sucking at it. It’s hard to get a picture of Dyson when he’s trying to hide, but I did try.

You can just about see Dyson sulking behind the prawn. The strange pointy thing above is the water-filter.

At the end of the evening we rescued the poor unfortunate prawn to see what had happened to it. It looked pretty much identical on the outside, but the head and a small middle-section of the body were empty – containing water rather than prawn. Without disturbing the outside of the prawn the snails had managed to devour the insides, including all of its brain.

I’ll be back with more bacteria next week!