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• Sphaerium nucleus (S. Studer, 1820)

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© Dr Roy Anderson

Very similar to the widespread Sphaerium corneum but with a shell which is more distinctly inflated, and possessing dense accumulations of glassy pores around the umbo. Probably widespread but much under-recorded and so far known mainly from shallow, calcareous and sometimes temporary water bodies in Ireland.

Key characteristics

• A small, very broadly oval and very tumid bivalve
• Surface silky with fine, concentric growth ridges
• Coloured shades of brown to greyish
• Umbos rounded, more or less central
• With high concentrations of very fine glassy pores near the umbos (!microscope, x40)

Size

9-11 mm.

Irish Distribution

With only a few confirmed records in Ireland. Locally common in turloughs in Clare/south-west Galway (Williams et al., 2010)

Ecology

• Little known but suggesting a preference for base-rich lentic water bodies
• Prefers shallow but richly vegetated places, sometimes temporary habitats
• Often found with a rich molluscan fauna

Taxonomy

Not recognised in the British Isles before about 2001 so little known to British and Irish conchologists.

Red List status

• Vulnerable (VU).

Wikipedia link

Wikipedia page for Sphaerium nucleus