Saturday, 18 February 2012

Chitons on the rocks ~

My first acquaintance with a chiton (pronounced 'kite-on') was unexpected and I had no idea what it was.  Rewi had been gathering mussels, and once back home he found this large lump on one of them which neither of us could identify.  Here it is:
 

It was cool and hard to the touch, so that we weren't even sure if it was a live creature, yet it had an astonishing row of eight shell-like shapes down the centre of its back which seemed to suggest that it must be.  Further enquiry revealed it to be a chiton, probably of the species Eudoxochiton nobilis, otherwise known as the 'Noble' Chiton, no doubt so named on account of its size: it can reach 10cm!  This one was about this length. 
Chitons are characterised by having eight shell-like plates (valves) down their backs which are surrounded by leathery flesh which is described as a girdle.  The whole creature is highly flexible but once it decides to set up camp in one particular spot it is almost impossible to dislodge.  When dislodged it rolls into a ball to protect itself, rather like a slater / woodlouse.

Our household rule is that any live creatures that are inadvertently brought home with the mussels are returned to the sea as soon as possible.  In the interim they are housed in a makeshift aquarium, which is a bowl on the table filled with seawater.  This has also proved to be an ideal place in which to observe and photograph them!   
Note: seawater needs to be replaced at least every day, and preferably more often.

The next time we came across one it was one of the variety most common in New Zealand, a 'snakeskin' chiton, so named because of its banded girdle: once again Rewi had been shelling mussels and I spotted it on the kitchen floor!  Fortunately it hadn't had time to fasten itself to the vinyl and I managed to scoop it up without difficulty and put it in the temporary aquarium.  Here it is in the company of two lively crabs, which had been found inside mussel shells, and a small 'ribbed' mussel.  The little crabs are probably 'pea' crabs.


You can see what a completely different scale it is compared to the one at the top of the page!  Also the detail of colouration is different, and really beautiful.  If you look carefully you can see the rows of hair around the edge of its girdle.


When returned to the beach and placed into this rocky pool it blended in with its surroundings to the extent that it was barely noticeable:


Once I became familiar with chitons I started to see them everywhere:


They blend wonderfully with their own particular places:


I wouldn't mind a bit of wallpaper of this:


Many snakeskin chitons can be found on the surrounding rocks, as can be seen in these images which were taken within close range of each other.

There is certainly an enclave of Noble chitons there as well but their favoured sites seem to be more exposed to the water and waves and are often close to the waterline.  

Chitons can be very mobile, moving about to feed.  Some have an ability to locate back to their exact 'home' spot!  I've looked for this one again, but not seen it there so it may have been out to feed at the time.


This chiton looked like a a young 'Noble' to me: it might have been about 4cm long.  It was highly mobile and seemed keen to explore its temporary home: it glided about busily:





By the time I was ready to return it to the beach it had fastened itself onto the side of the ceramic bowl and I had a hard time prizing it off - it felt like set cement!  Finally it gave up and came away.  Here you can see its underside: it moves about on the central portion which is termed its foot:


I put it into a plastic container with some seaweed and shells, and when I came to take it out it had fastened onto a small shell.  Here it is - from underneath again:


The tide was coming in, and since I didn't want it to get washed away in the waves I carefully pried it off so that it would fasten onto the rock face.  There it would be at leisure to find its way back home:


These seemingly barren rocks are the home of many!  Two Variable Oystercatchers survey the view:


At least twice are day the rocks are inundated by the sea:


I have more to share about these another time...

You can find my other articles about exploring the beach and its rock pools via the link below: 

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