Stalks, eyes and feet

Last time I wrote about life on Earth, we covered Cowries, and how they were used as currency.  We are staying within the molluscs still, as there are a couple more organisms I want to show you, to illustrate the different solutions that have been found to the same problems, namely feeding, and getting around.

Today, we are going to meet the cutely named Lambis lambis, or one of the Spider Conch molluscs, we may also meet some of its relatives.

Everyone knows what a conch shell looks like, it is the famous “Listen to the ocean in this” shell, and the ones you may have seen probably look like this:

A shell of Lobatas gigas, the Queen Conch. Image from wikipedia

This is the shell of Lambis lambis:

Lambis lambis shell. Image from gastropods.com

I have already covered how shells are formed, by secretions from the mantle, the fleshy part of the mollusc, so that is not what I am writing about today, although I am sure I will write a post about how the different shell shapes arise at some point!

The shell above has spikes all around it, and one long spike at the bottom.  The long spike at the bottom is where we will start today, because it is actually functional, it is called the Anterior siphon canal, and it provides support for an appendage called a siphon, which is an extension of the mantle.  This structure draws water into the cavity within the animal, and passes water over the gills, assisting in getting oxygen from the water, but also acting as a “nose” (Otherwise known as a chemoreceptor) to help the animal find food.

Lambis lambis is a herbivore, but this does not mean it is not guided towards food by what we would know as smells.

Here is what the external (outside the mantle cavity) body parts of Lambis lambis looks like:

Morphology of Lambis lambis. Image from University of Queensland

There are several features of this mollusc (and all conchs), which I want to elaborate a bit on, as I think they are fairly cool.

Firstly, the radula (the toothy tongue thing we met HERE), which is usually contained within the cavity, is actually on the end of the part labelled “proboscis”, so it has a stalk with its mouth on the end, and the radula too.

Here is a video of one chomping away happily on some algae, note the eyes which are also out on stalks, these are checking out the area for predators while it is eating, and if one is spotted, it pulls itself back inside its shell.  I personally like the eye stalks, as they look a little bit like cartoon alien eyes.

All true conchs are herbivores, (that is, ones which are members of the Strombidae family).  Other animals are known as conchs too, and not all these are herbivores, for example the crown conch (Melongena corona) feeds on oysters and clams by using its proboscis to pry open a bit of their shell and eat them from inside their shell.

The other very obvious structure in the morphology picture is the foot, and the part labelled “operculum”.  This is used to dig into the sediment to..well..propel the animal, or turn it over if it gets upside down.  I think this is easier to see than to explain, so here are two videos showing this in action:

Finally, here is a video showing this funky creature moving along a flat surface:

It is not just us humans who like these shells…hermit crabs also use them as mobile homes, as these two videos show:

I hope I have shown you some things so next time you see one of these pretty shells, you also think about the very cool animal which lives inside it.

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One thought on “Stalks, eyes and feet

  1. Pingback: Bivalves…Sucking and Sieving | Skeptical Squirrel

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