Snapping Shrimps and Sponges

Colonial Shrimps Shelter in Sponges

May 14, 2009 John Blatchford

The shrimps are safely housed inside the sponge and defend their host in return.

Within the phylum Porifera there are three types of sponge, grouped according to the way the ‘skeleton’ is made.

The Desmosponges use a material called ‘spongin’, Calcareous Sponges use calcium carbonate, and the Glass Sponges use silica.

Desmosponges are found in most marine and freshwater habitats, Calcareous Sponges are most common in shallow marine environments, and the Glass Sponges seem to prefer deep cold places in the sea.

Curious Relationship with Snapping Shrimps

Snapping Shrimp (of the genus Synalpheus) live inside sponges. They are colonial animals, and are similar to many insects in that there is a single queen and the rest of the 300 or so members are either workers or soldiers. Each species of shrimp appears to favour a particular type of sponge, and new forms are discovered as more sponges are investigated.

Just like their relatives (the ‘Pistol Shrimps’) snapping shrimps can generate enormous energy by ‘firing’ their pistol-like claw. (Watch YouTube video) This process can produce as much as 5,000 degrees Celsius, and is more than enough to stun other animals.

Their relationship with the sponge host is probably of benefit to both species – the sponge has a capable defender, and the shrimps a safe home.

Collar Cells and Molecular Studies

Sponges have very unusual cells called ‘choanocytes’ or ‘collar cells’ (see article image), that are able to whip water past a structure that captures plankton and other food. There are also free-living, single-celled organisms that have the same shape (the ‘choanoflagellates’), and the same type of cell is found in some flatworms. This kind of similarity suggests that some sort of sponge might well have been ancestral to all other animals, having evolved from a single-celled choanoflagellate.

DNA studies suggest that the desmosponges are closer to other animals than either the calcareous or glass sponges, and that the three types of sponge might not be very closely related. Despite this possibility all sponges are lumped together in the phylum Porifera, and thought of as the simplest form of multicellular animal.

Uses for Sponges

The skeleton of certain desmosponges have been used by humans since ancient times as padding and for carrying water and when bathing, and recently another species (dolphins) have been observed using sponges as ‘beak protectors’!

There is also the possibility that some of the peculiar abilities of sponges – for instance their ability to reform into a single large sponge after being thoroughly separated into a collection of single cells and passed through a sieve – might shed light on the way the cells of ‘higher’ animals communicate with one-another.

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