Xenophora

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Assemblage artists of the deep!

Marine snails of the genus Xenophora collect shells, rocks, and other debris from their environment. They attach these objects to their shells at intervals during the shell's growth. Sometimes it creates a neat radiating pattern; sometimes the effect is more that of a jumble of debris. The result for us in any case is that their collections become little samplings of a variety of faraway underwater realms.

Top row: X. flindersi X. solarioides X. conchyliophora X. robusta
Middle row: X. pallidula X. pallidula X. pallidula X. japonica X. pallidula (underside)
Bottom row: X. cerea X. cerea X. konoi X. corrugata

Natural History

It is not known to what extent an artistic sensibility plays a part in this behavior. The snails who live in shallower water (where there is enough light for them to be seen) probably use their collections for camouflage. The ones that live in the deeper, dark waters, such as X. pallidula, are believed to be motivated more by a desire to not to be sucked into the viscous muck in which they live. Attaching extensions to their shells spreads out the shell's surface area and helps prevent the animal from sinking. The additions may also strengthen the snail's relatively thin shell.

"Characteristically, the shell is covered with other shells, shell fragments, coral pieces, or stones that are attached or cemented with secretions from the animal. The shells are attached dead, although there is one account of a live kitten's paw being attached in an aquarium. All bivalves and bivalve pieces are attached inner side up and gastropods are usually attached with the aperture up. Once an object is selected, it is cleaned (as is the site of intended attachment), and then the object is rotated and fitted to the attachment site. This may take up to 1 1/2 hours. The piece is then held in place with the animal's foot, snout, and tentacle bases and glued into place. The Xenophora may then lay motionless for up to 10 hours, only rocking in place now and then, seemingly a check on the strength of its new attachment."

From the Xenophoridae home page (retrieved Aug 30, 2009). The "kitten's paw" referred to is actually a bivalve and the source of the tale is here

Not all of the items on a Xenophora's shell are put there by the creature itself. As a solid substrate in a mucky environment, the shell is an enticing landing spot for tube worms, oysters, and, most spectacularly, glass sponges. Their new home even has the advantage of being mobile, transporting a rooted animal to new feeding grounds.

Cultural significance

During the Rust Age, Xenophora were valued for their mystical connections as "messengers from the deep." During the Age of Wonder, their collections were seen as little samplings of a variety of faraway underwater realms, a sort of natural curiosity cabinet. It was in the Modern Age that they acquired the nickname "assemblage artists of the deep."

The Zymoglyphic Postal Sevice has recently issued a commemorative stamp to honor these beloved mollusks.

Outsiders have doubted the existence of these animals for many years. Visitors to the region often imagined that the shell assemblages were created by bare-breasted native women working in happy little groups on the beaches, who then sold their creations to unwitting tourists.

This collection was on display at the Peninsula Art Museum as part of their "Obsessions" show (on collectors and their collections) as a collection of collectors. It was also featured in the Proceedings of the Athanasius Kircher Society on May 17th, 2006

Further reading

Xenophoridae of the World: A Revision of the Recent Xenophoridae of the World and of the Australian Fossil Species (1983) W.F. Ponder, The Australian Museum. This obscure volume is, as its author states, "the only comprehensive review of the family in 100 years."

Recent Xenophoridae (1999) Kurl Kreipl and Axel Alf, ConchBooks. A somewhat less technically oriented publication for the serious shell collector

Other "assemblage artist" animals:

Gallery


X. flindersi - Probably the most highly camouflaged species. On the underside of this specimen, you can see a smaller Xenophora attached to the larger one. This view also proves that there is in fact a shell in the rock pile.

X. solariodes - A small X. solarioides, completely covered in flat rocks.

X. conchyliophora - An interesting collection of bivalves, with a large coral.

X. robusta - A specialist in clam shells, each positioned concave side up (more or less).

X. pallidula - An X. pallidula with a "one of each" philosophy: a coral, then a shell fragment, a snail, a rock...

X. pallidula - An X. pallidula whose prizes are a nice pelican shell and a very long piece of coral.

X. pallidula - The classic big X. pallidula, with elegant long shells in a radiating pattern

X. joapinica - A small X. japonica with a big snail, a big clam, and lots or corals of various sizes

X. pallidula - A wildly eclectic collection on this X. pallidula, including sea urchin spines, clams, snails, and pieces of sea urchin bodies. The round snails are best seen from the underside.

X. cerea - An X. cerea with an elegant display of clean black stones and white clam shells.

X. cerea - An X. cerea with a more eclectic collection than its cousin above

X. konoi - An X. konoi with an interesting collection of corals and encrusted pebbles.

X. corrugata - An X. corrugata displaying its neat rows of stones