EPOW - Ecology Picture of the Week

Variable Chiton (Ischnochiton maorianus)
Foveaux Strait, New Zealand

Explanation:  This week we find ourselves on a remote rocky beach along Stewart Island, south of South Island, New Zealand, in the turquoise waters of Foveaux Strait that links the South Pacific Ocean to the east with the Tasman Sea to the west.  Clinging to an intertidal rock face made smooth by countless waves are these two fingernail-sized shellfish called variable chitons.

Chitons are one of 5 groups of shellfish.  The shells of chitons consist of curved bony plates that overlap and that are bound by a leathery ring.  Chitons adhere to rock surfaces where they usually move about slowly, consuming algae and other plants that grow there.  However, they move more quickly when struck with direct light, seeking shelter under stones.   

This species, the variable chiton, is found only in New Zealand, but is a locally common resident of these southern ocean shorelines, existing in tidal zones where rocks become exposed to the air for half the time or less.  Variable chitons are so-named because they can occur in many colors.