mollusc | An Bollenessor

The Pheasant Shell is one of my favourite little critters in the rockpools in Falmouth. It is a bit weird to refer to these organisms as ‘shells’ actually, as they are living things and the nonliving shell is ofcourse only a part of them. The confusion extends to its scientific name: this species was previously known as Tricolia pullus, but has recently been split into a Southern European T. pullus species and a Northern European T. picta species. Perhaps the dust needs to still settle on that one.

I have taken these photos, on different occasions, with the mzuiko 60mm macrolens and the nauticam cmc-1 wetlens. The extra magnification the latter lens (screwed onto the housing) offers is great; although somehow I always want to get even CLOSER! I have not nailed the Pheasant Shell shot either. Reflecting on these pics I think I need to use a shallower depth of field to get rid of cluttered backgrounds. Next time.

The calcified operculum (the little door to close the shell) is clearly visible in the first photo above, as are the tentacles. On the second photo above you can even see that the left ‘neck lobe’ is more deeply digitated (fingerlike) than the right one. For more detailed (studio)shots of this and other molluscs please see Morddyn’s flickr account. I will post more macroshots of other mollusc species soon!

I usually head down straight to the lowest reaches of the shore when rock pooling, but when there is a neap tide and a lot of inshore wind as there was this weekend, you have to make do with turning rocks higher up the shore. Although biodiversity is lower, there are some species that are only found there (see for instance this recent post) and so it is actually nice to have a look there for a change. The very first rock turned over actually had a couple of interesting inhabitants underneath it. Another lifer, the tiny gastropod mollusc Onoba semicostata (surrounded by a couple of even tinier Rissoa parva), very quickly identified by members from the British Marine Mollusca facebook group:

The same rock had a number of the tiny (< 1 cm) Cushion star species Asterina phylactica on it as well. It is prettier than the common Cushion star Asterina gibbosa (one of my favourite aquarium species), but perhaps a bit too small to be an option for the tank.