Friday, August 13, 2010

Chitons are Safe as Houses

The chiton Lepidochitona cinerea attached to the bottom of an intertidal rockpool

The chitons (class Polyplacophora) are exclusively marine molluscs that are characterised by eight calcium carbonate shell playes that cover the animals muscular foot and mouth (Okusu et al., 2003 Organisms Diversity and Ecology 3 pp. 281-302). These plates are articulated and can be curved to fit closely a range of surfaces. This gives chitons a great deal of protection and allows the chiton to roll into a ball if dislodged from the surface. Chitons possess laterial or posterior gills that run either side of their foot that are quite striking in some species.

Lepidochitona cinerea curled in a ball on removal from surface

They are a very ancient class of molluscs with fossil records from the Upper Cambrian (510-480 million years ago) (Slieker, 2000 Chitons of the World p. 154). Eleven species in Ireland have been described, from the families Lepidochitonidae, Hanleyidae, Ischnochitonidae and Acanthochitonidae and range from 8 - 33 mm in length. They can be found on hard bottoms and rocky coasts where they graze on algae (Ferriss et al., 2009 Irish Biodiversity: a taxonomic inventory of fauna p. 57).

Underside of Lepidochitona cinerea

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