Wednesday 8 October 2014

In An Octopus’s Garden

“I'd like to be under the sea
In an octopus's garden in the shade”

So sang Ringo Starr back in 1969 and that’s where we’re off to today. So grab your snorkels and we’ll head off down the beach and enter the underwater realm. I can’t promise you octopus (although there is a good chance) but plenty of other strange and fascinating inhabitants that occupy the octopus’s garden.

Sea Squill
 Here we are at the top of the 139 steps where we’ll pause a while to admire this dramatic flower spike. You’ve probably noticed these growing all over the island in late summer and into the autumn; they are Sea squills. Clever plants, they produce their leaves in winter and spring which are packed full of toxins to stop them being eaten. The leaves produce energy by photosynthesis which they then store as sugars in a massive underground bulb like a huge onion which is also packed with toxins. These include a skin irritant and cardiac glycosides  so don’t go digging them up and for heaven’s sake don’t try eating them unless you want to die very suddenly of a heart attack. There aren’t so many insects about now but the sea squill, by virtue of being in a minority of flowering plants at this time of year, attracts whatever is about, particularly members of the hymenoptera such as bees and paper wasps and if they fail to do the business it can also be wind pollinated.

Our route: 1 fish; 2 crabs; 3 algae
But I digress: once more onto the beach, dear friends. Here we are and here’s where we’re going: It’s not a long swim and you’re never far from a convenient rock so don’t worry about getting out of your depth. One of the beauties of swimming in October is that the sea is still very warm after the long, hot summer and when you come out it’s pleasant enough to dry off on the beach without being burnt to a crisp. So, masks on – here we go. We start off over a coarse sandy substrate which shelves quite quickly (out beyond the horizon is a 4,000 metre trench marking the subduction zone at the edge of the Aegean tectonic plate – but don’t worry, we won’t be going that far) and there’s not much on the bottom so look up to the surface. These shallow waters are the domain of the small fry; shoals of tiny fish with neon bright red or blue stripes.

Ornate Wrasse
Now we’re into deeper water and the bottom is littered with rocks as big as cars and we’re swimming along through a shoal of bream.  Here come a shoal of damselfish looking almost black with deeply forked tail fins like scissors. Float gently and the fish will come close, curious to see what you’re about. Look down there hugging the rock. Here’s a fish I want to introduce you to – the Ornate wrasse. Isn’t she beautiful? I say she because she’s quite small. Wrasse are what is known as  protogynous hermaphrodites, that is, they start their lives as females and then grow up to be males thus getting the best of both worlds as it were. Some animals have all the luck!

Sally Lightfoot Crab
These rocks are totally submerged so we’ll make our way now to a different habitat where the rocks poke their heads above the water. Take care not to scraze yourself as we thread our way, eel-like among the sharp projections. Here we can look at the animals of the inter-tidal zone (tides are very small in the Med, only about a metre or so, as it’s virtually an inland sea). In particular I want you to meet the delightfully named Sally Lightfoot crab. A beautiful chestnut brown carapace and yellow bands around the leg joints but sadly, it shouldn’t be here. It is an invasive species having been first recorded in the Mediterranean (off Italy) in 1999. Unusually in the crab world it is herbivorous, its diet being primarily algae which it scrapes off the rocks. Talking of algae lets go and have a look at some among the rocks closer to shore and I’ll tell you a bit about the wonderful world of phycology.

Red Algae
Phycology is the study of algae which can be distinguished from the higher plants by a lack of true roots, stems or leaves. This is a somewhat simple definition and for our purposes phycology includes the study of seaweeds. Seaweeds fall into three groups simply called red algae (Rhodophyta), brown algae (Phaeophycae) and green algae (Chlorophyta and Charophyta). The trouble is you can’t always tell which is which from the colour. Take these two for instance: to me, one looks greenish brown and the other looks reddish brown. Under the microscope I’d say the top one is green and the bottom one red. I’d be wrong – apparently they are both red algae. Well I did say that phycology was a wonderful world and it’s in a bit of a state of flux at the moment with some major taxonomic revisions going on. Whenever a subject goes up in the air like this it produces openings for the amateur naturalist as there are plenty of observations and connections to be made so if you’re looking for an area to delve into then try phycology.

Hooded Crow
We’ll make our way back to the beach and dry off. Did you notice that streak of electric blue just skimming over the water behind us? That was King, not a very inventive name for a kingfisher I know but that’s what I call him. He often accompanies me on my snorkelling expeditions. I see we’ve also got a group of rowdy hoodies further along the beach. No, not British lager louts but hooded crows. They do, however, exhibit the same sort of raucous behaviour, chasing each other up and down the beach oblivious of everyone else and generally making a lot of noise. Hooded Crows aside it’s very peaceful down here today. There’s a fig tree at the back of the beach, I wonder if we can find any figs?


Special thanks this week to Joc Avila of the Phycology Group on facebook for help with the seaweeds.

Naturalists (the facebook page that accompanies this blog)

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