A sea slater (Sphaeroma serratum)

Distribution data supplied by the Ocean Biodiversity Information System (OBIS). To interrogate UK data visit the NBN Atlas.Map Help



Sphaeroma serratum is a mottled grey-brown isopod reaching 1 cm in length and found intertidally on rocky shores. The body is broadly oval and has a smooth dorsal surface. It will roll into a ball when disturbed. The outer rami of the uropods have a distinctly serrated edge and extend beyond the end of the pleotelson.

Recorded distribution in Britain and Ireland

Recorded from only the south and west coasts of the UK as far north as Angelsey and south and west coasts of Ireland.

Global distribution

Found south to the Azores, the Mediterranean and Black Seas.


Found intertidally on open or sheltered rocky coasts living in crevices or under rocks. Sphaeroma serratum may be found near areas influenced by freshwater but isn't found in truly estaurine areas, where it is replaced by other species.

Depth range


Identifying features

  • Broad oval body.
  • Dorsal surface of pleotelson smooth.
  • Pleotelson almost trapezoidal.
  • Uropod exopod has distinctly serrated outer edge.

Additional information

This marine species can be confused with the more estaurine species Lekanesphaera levii, Lekanesphaera rugicauda and Lekanesphaera hookeri. The former also has a smooth pleotelson, but Lekanesphaera levii has indistinct crenulations on the uropod exopod and a more triangular pleotleson which may extend beyod the tips of the uropods, While the pleotelson of the latter two is covered in small tubercles or two longitudinal rows of raised tubercles respectively.

Listed by

- none -



    1. Bristol Regional Environmental Records Centre, 2017. BRERC species records recorded over 15 years ago. Occurrence dataset: https://doi.org/10.15468/h1ln5p accessed via GBIF.org on 2018-09-25.

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

    3. Kent Wildlife Trust, 2018. Kent Wildlife Trust Shoresearch Intertidal Survey 2004 onwards. Occurrence dataset: https://www.kentwildlifetrust.org.uk/ accessed via NBNAtlas.org on 2018-10-01.

    4. Manx Biological Recording Partnership, 2018. Isle of Man historical wildlife records 1990 to 1994. Occurrence dataset: https://doi.org/10.15468/aru16v accessed via GBIF.org on 2018-10-01.

    5. National Trust, 2017. National Trust Species Records. Occurrence dataset: https://doi.org/10.15468/opc6g1 accessed via GBIF.org on 2018-10-01.

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

    7. OBIS (Ocean Biodiversity Information System),  2024. Global map of species distribution using gridded data. Available from: Ocean Biogeographic Information System. www.iobis.org. Accessed: 2024-05-18


    This review can be cited as:

    Hosie, A.M. 2009. Sphaeroma serratum A sea slater. 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 18-05-2024]. Available from: https://www.marlin.ac.uk/species/detail/2236

    Last Updated: 07/01/2009