Biodiversity & Conservation

A cumacean - Diastylis rathkei

Diastylis rathkei

Image Crown copyright - Close up of Diastylis rathkei. Image width ca XX cm.
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Distribution map

Diastylis rathkei recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

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Diastylis rathkei is not listed under any importance categories.

Taxonomy icon Taxonomy Taxon English term
Phylum Arthropoda Arthropods, joint-legged animals, e.g. insects, crustaceans & spiders
Class Malacostraca Crabs, lobsters, sand hoppers and sea slaters
Authority Kröyer, 1841
Recent synonyms None
Map icon Recorded Distribution in Britain and Ireland Recorded from the Firth of Forth, south to Flamborough Head, the Wash, Harwich, Whitstable, the Severn estuary, Menai Straits, Cumberland, the Solway Firth and Belfast in Northern Ireland.
Habitat information icon Habitat information Found burrowing in fine muddy sand on the continental shelf down to depths of 200 m. Fairly common.
Text page icon Description A small tadpole shaped cumacean, up to 22 mm long but usually smaller. The carapace is a large, broad, shield-like structure covering the head and part of the thorax. The carapace is produced into lateral folds that enclose the anterior appendages of the animal. On the most forward part of the carapace is a projection called a pseudorostrum formed by two adjioning points (the pseudorastal lobes). The pseudorostrum is horizontal. The females carapace has a double row of forward pointing denticles on the sides. A males carapace does not have denticles except near the carinae. There is a single small eye present behind the pseudorostrum. Behind the carapace there are five thoracic segments. There are three pairs of leg like structures on the rear of the thoracic region. The abdomen consists of six cylindrical segments (pleonites). Attached to the last pleonite is a long pointed strucutre called a telson, with 10-15 or sometimes more pairs of lateral spines. The telson is longer than the two structures on each side. These three long structures attatched to the last segment forming a fork like tail.
Identifying features
  • Small, tadpole shaped cumacean.
  • Length of up to 22 mm but usually smaller.
  • Carapace has a pointed tip at the anterior end.
  • Antennae small.
  • Front appendages covered by carapace.
  • Female has rows of denticles along carapace.
  • Three pairs of leg like structures at posterior end of carapace.
  • Tail made up of six segments.
  • Three long, thin structures attached to last segment, forming a fork like tail.
Additional information icon Additional information Feeds on micro-organisms and organic matter from the bottom deposit. Represented in north west Europe by subspecies typica.

This review can be cited as follows:

Tracy Heath 2005. Diastylis rathkei. A cumacean. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 21/05/2013]. Available from: <http://www.marlin.ac.uk/speciesinformation.php?speciesID=3155>