Tuesday, February 16, 2010
Stuck on You
I've just come back from a marine zoology camp, where I've spent a week working on a group project about competition between two species of limpet. This didn't mean we were racing the limpets. We were looking at competition for a common food source - in this case, delicious microscopic algae that grows on rocks.
Below is a picture of a boulder covered in limpets. You can see why I didn't end up taking many photos on camp.
Our project involved lifting limpets off the rocks with a bread knife and relocating them to produce areas of higher than natural population densities. Then we waited to see if they would exhibit a behavioural response to being in a high density area. Having a shell is a bit like wearing a burqa - it makes it difficult for others to read one's non verbal cues - but I'm sure that the limpets' little faces were contorted with effort as some of them practically galloped away from the higher density areas at speeds of more than 4 cm per hour.
You can think of the intertidal rock pools as being like a great savannah full of grazing beasts. The herbivorous limpets are the gazelles and antelope. The predatory whelks, who drill through the limpets' shells and suck their flesh out, are like the big cats. Check out this vicious killer, Dicathais orbita:
And this glorious creature would be the elephant:
Elephant Snails (Scutus antipodes) are the giants of the intertidal rock pools. Their distinctively shaped shell is usually hidden under thin flaps of skin. When they feel threatened, the skin retracts and the shell is revealed. Having so much juicy flesh can be a liability, so these snails are typically found under ledges at the edge of pools. They come out to graze at night, when there are fewer predators around.
This Elephant Snail was part of a group which we were responsible for relocating at the end of the camp. They had been used in another group's project, in which they were tested for their responses to both a native and an invasive predatory starfish. It was a bit like the witness relocation program. Maybe, in time, these Elephant Snails will be able to come to terms with horrors they witnessed in our laboratory tanks.