LEPTOCHITON SCABRIDUS (JEFFREYS, 1880) - A LIVE RECORD FROM COUNTY DONEGAL, IRELAND

Submitted by admin on Sat, 02/08/2014 17:46
JANICE M. LIGHT
JOHN M. BAXTER
Volume
33
Part
5
Page from
318

During a Conchological Society field trip to Co. Donegal, 6 sites were visited by the main group between the 1st and 4th of June 1989. All sites yielded impressive lists of marine molluscs and one locality in particular, Broad Water was notable in its representation of the chitons, with 6 of the twelve species on the British Isles list being recorded alive. At this site, all three species of the genus Leptochiton were found alive. The site is an extremely sheltered, gently and the substratum of sand, gravel and shell debris with embedded rocks and boulder extends into the sub-littoral. At certain times during the tidal cycle the area experiences very fast flowing tidal currents creating a rapids effect.

Chitons were collected for later identification in the improvised laboratory at our rented accommodation. Of the Leptochiton specimens, the majority were found to be Leptochiton asellus (Gmelin, 1791), a smaller but significant proportion being Leptochiton cancellatus (Sowerby 11, 1840). A small number of specimens were identified by J.M.B. as Leptochiton scabridus. L.scabridus is a rather small chiton, elongate oval in shape with a narrow girdle and diagnostic valve sculpturing. In the live animal the foot is a characteristic bright red in colour; this is a particularly useful field identification character.

L.asellus is common from around low water mark extending to a depth of 250m , living on silty-stony bottoms often attached to shell debris. It has a wide distribution and is found commonly off the entire coast of the British Isles. L.cancellatus is not nearly as common and occurs from around extreme low water mark to depths of 900m., favouring attachm ent to small stones or shell debris on silty-stony bottoms. It is found around the British Isles. L.scabridus is rare with a very restricted distribution, previous records showing it confined to the south-west coast of England, the Channel Islands and the coast of Britanny. The south-west England records are pre 1951 only, but specimens have been found in the Channel Islands as recently as 1985 by J.M .B .

A feature of the preferred habitat of L.scabridus is that it is often found attached to stones and pebbles that are heavily embedded in clean sand to a depth of 15-20cm. Many of the rocks which were disturbed during the work at Broad Water were embedded in this manner. It is interesting to note that the substratum at the Broad W ater site was sufficiently diverse to accommodate all three species of Leptochiton - a hitherto unusual occurrence. The site does not have conservation status and it is a fragile ecosystem. There is always the possibility of disruption to the habitat with a consequent adverse effect on the chiton population. The lifting of deeply embedded rocks and boulders may result in animals being detached. In favourable conditions chitons may easily re-attach, but if the animals become buried in the turmoil of sand and gravel, re-attachm ent may not occur. It is proposed to revisit the site in 1990 when it is intended that a more detailed study of the Leptochiton populations will be carried out.

 

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Light & Baxter 1990.pdf