Callochiton septemvalvis (Montagu, 1803)

Avila, Sergio P. & Sigwart, Julia, 2013, New records for the shallow-water chiton fauna (Mollusca, Polyplacophora) of the Azores (NE Atlantic), ZooKeys 312, pp. 23-38 : 26

Callochiton septemvalvis (Montagu, 1803)

Chiton achatinus Brown, 1827 =

Chiton doriae Capellini, 1859 =

Chiton laevis var. navicula Jeffreys, 1865 =

Callochiton achatinus euboecus Kattoulas, Koukouras and Economidis, 1973 =

Chiton scytodesma Scacchi, 1836?

Chiton laevis Pennant, 1777 sensu Montagu 1803!

Records for the area.

Morton (1967), Kaas and Van Belle (1985a).

Distribution and biotope.

All Atlantic coasts of Europe, from Scandinavia, Britain and Ireland, south to the Mediterranean Sea, Morocco ( Kaas 1991), Azores and Canary Islands ( Kaas and Van Belle 1985b). From shallow subtidal to 500 m depth, usually on red algae and other hard substrates ( Poppe and Goto 1991). The animals can be extremely cryptic, grazing on the underside of stones and small boulders where their colours proved good camouflage.

Material examined.

No material seen.

Fossil record.

No fossil representatives are known from the Azores.

Description (abridged).

Moderate size (up to 22 × 14 mm), dorsal elevation ratio = 0.35 to 0.46, oval, valves beaked. Tegmentum very finely granulose, orange to brick red, often with white markings, or with shades of green, bright yellow, or bright orange. Intermediate valves rectangular. Sculpture smooth and glossy to the naked eye, diagonally set with black dots (the pigment cups of the ‘shell-eyes’); under magnification the valves are sculptured with small granules arranged in quincunx. Wide girdle, usually about 1/3 of the animal’s total width and covered in spicules, with a short marginal fringe of spicules. The girdle is coloured yellow or orange with red markings.

Remarks.

If this species does occur in the Azores, it must be very rare, as not a single specimen was found in the DBUA or DOP/ML collections. The species Callochiton septemvalvis was originally described from an abnormal specimen with seven valves. Montagu (1803) believed its missing valve to be a characteristic of an undescribed species of chiton. Although that specimen did represent an undescribed species, normal individuals of Callochiton septemvalvis have eight valves. Some authorities have criticised the name ' septemvalvis’ as being misleading, but as it was the first epithet used to describe a valid species, the name remains valid.