Heart cockle (Glossus humanus)

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Summary

Description

A large heart-shaped shell up to 10 cm long. Its two shells are rounded and the beaks of the shell curve spirally, away from the hinge, giving it the characteristic heart-shape when viewed from the side. The two valves are similar in shape and structure (equivalve). The shell is globular with a slightly circular outline, deep and thick but light-weight. The outer layer of the shell (periostracum) is thick, dark brown, red-brown or very dark green in adults and light greenish-yellow in juveniles. The periostracum is often covered with firm short hairs radiating from the beaks, sometimes giving the shells a glossy appearance. Beneath the outer layer, the shell is off-white, yellowish or fawn, sometimes with red-brown streaks. Inside empty shells, the pallial line shows no indentation for the pallial sinus.

Recorded distribution in Britain and Ireland

Potentially found offshore around all of the British Isles, although most of the inshore records of this species in the UK are from scattered locations in western Scotland. It has also been collected from off the Ise of Man, in the Bristol Channel, the English Channel, and south-west Ireland.

Global distribution

Recorded from Norway and Greenland south to the Adriatic, Iberian Peninsula, into the Mediterranean Sea and along the Atlantic coast of Morocco.

Habitat

Glossus humanus buries itself beak down into the substratum, leaving the lower margin of the shell and the siphon exposed. The shell margin of very large specimens may sometimes support hydroids (Perigonimus sp.) and anemones. It is found in soft mud and sands (unlike the similar sized but heavier Arctica islandica, which is found in slightly coarser sediments) from depths of 7 m but more frequently below 50 m. It is thought that Glossus humanus inhabits areas with little disturbance to the sediment, and is a deep water species, sometimes associated with the mud around cold water coral reefs.

Depth range

ca 7 - 200 m

Identifying features

  • Shell is thick but light-weight.
  • Each valve is globular with a slightly circular outline.
  • Reaches up to 10 cm long.
  • Has a heart shaped appearance when both valves are viewed together from the side.
  • The beak of each valve curves spirally, away from the hinge.
  • Thick dark brown periostracum, covered with short hairs radiating from the beaks

Additional information

Glossus humanus is a rarely recorded species.

Listed by

Further information sources

Marine Bivalve Shells of the British Isles

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Bibliography

  1. Meikejohn, R.G., 1977. A note on the distribution of Glossus humanus (L., 1758) in British and Irish waters. Conchologists' Newsletter, 63, 46-47.

  2. Oliver, P.G., Holmes, A.M., Killeen, I.J. & Turner, J.A., 2016. Marine Bivalve Shells of the British Isles. Amgueddfa Cymru - National Museum Wales. Available from: http://naturalhistory.museumwales.ac.uk/britishbivalves [Cited:  3 July 2018].

  3. Owen, G., 1953. On the biology of Glossus humanus (L.) (Isocardia cor Lam.). Journal of the Marine Biological Association of the United Kingdom, 32 (1), 85-106.

  4. Tebble, N., 1976. British Bivalve Seashells. A Handbook for Identification, 2nd ed. Edinburgh: British Museum (Natural History), Her Majesty's Stationary Office.

Datasets

  1. Conchological Society of Great Britain & Ireland, 2018. Mollusc (marine) data for Great Britain and Ireland - restricted access. Occurrence dataset: https://doi.org/10.15468/4bsawx accessed via GBIF.org on 2018-09-25.

  2. Conchological Society of Great Britain & Ireland, 2023. Mollusc (marine) records for Great Britain and Ireland. Occurrence dataset: https://doi.org/10.15468/aurwcz accessed via GBIF.org on 2024-09-27.

  3. Fenwick, 2018. Aphotomarine. Occurrence dataset http://www.aphotomarine.com/index.html Accessed via NBNAtlas.org on 2018-10-01

  4. NBN (National Biodiversity Network) Atlas. Available from: https://www.nbnatlas.org.

  5. OBIS (Ocean Biodiversity Information System),  2025. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2025-05-21

Citation

This review can be cited as:

Wilding, C.M. 2009. Glossus humanus Heart cockle. In Tyler-Walters H. and Hiscock K. Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21-05-2025]. Available from: https://www.marlin.ac.uk/species/detail/2237

Last Updated: 13/10/2009