''Radsia nigrovirescens'', the brooding chiton, is a small

polyplacophoran Chitons () are marine (ocean), marine molluscs of varying size in the class (biology), class Polyplacophora (), formerly known as Amphineura. About 940 Extant taxon, extant and 430 fossil species are recognized. They are also sometimes known ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

in the

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Chitonidae Chitonidae is a family of chitons or polyplacophorans, marine mollusks whose shell is composed of eight articulating plates or valves. There are fifteen extant genera in three subfamilies. Subfamilies and genera Subfamilies and genera within the ...

, found on the west coast of southern Africa.

Description

The

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...

s of the shell are dark brown to black and bear indistinct radiating ridges. The

girdle A belt, especially if a cord or rope, is called a girdle if it is worn as part of Christian liturgical vestments, or in certain historical, literary or sports contexts. Girdles are used to close a cassock in Christian denominations, including th ...

is of a rufous color and has a black band; it is covered with large, smooth scales that may have a coppery sheen. Individuals are 10–25 mm in length.

Distribution and habitat

''Radsia nigrovirescens'' occurs along the western portion of the south coast of Africa, from

Cape Columbine Cape Columbine is well known for its lighthouse, the last staffed lighthouse built on the South African coast The Cape Columbine Lighthouse was commissioned on October 1, 1936. Both the headland and lighthouse derive their name from the barque C ...

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

Cape Agulhas Cape Agulhas (; pt, Cabo das Agulhas , "Cape of the Needles") is a rocky headland in Western Cape, South Africa. It is the geographic southern tip of the African continent and the beginning of the dividing line between the Atlantic and Indian ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

. The species forms tightly packed groups that can be found under stones below the inter-tidal zone.

Ecology

left, Underside view of brooding specimen. The juvenile chitons are visible clustered beneath the parent's girdle. The species derives its common name from the unusual adaptation of brooding its eggs under its girdle, protecting them until they develop into fully formed baby chitons.

References

Chitonidae Molluscs of Africa {{chiton-stub