Brown venus, fish parasite and jewelbox sighted

March 18th, 2008

Photo: Dave Jarvis

The bivalve Callista chione, also known as the brown venus, was found stranded on a beach in Hayle, Cornwall. Callista chione is an uncommon species in Britain although it is found in South-West England and the Channel Islands. It is a large oval shell that can grow up ton 9cm in length. The outer shell is a reddish-brown colour with darker streaks and the inner shell is an off white colour.

Photo: Steve Trewhella

This isopod, Gnathia maxillaris was also found this month. Gnathia maxillaris is a small isopod; up to 5mm in length and male, female and juvenile Gnathia maxillaris are significantly different in their appearance. The one pictured is a Juvenile. They can usually be found in crevices, empty barnacle shells and Laminaria holdfasts. Around 100 embryos develop inside the body of the female before being released as larvae or Zupheae where they become fish parasites. The usually attach to the bodies of; the Shanny (Lipophrys pholis), the Long-spined Sea Scorpion (Taurulus bubalis) and the Corkwing Wrasse (Symphodus melops). They leave the fish host after a blood meal, their thoracic region expanded and become Pranizae larvae. Not much is known about the adult Gnathia maxillaris but it is believed that they do not feed.

Photo: Steve Trewhella

Found in a fish box in Chesil was the shell Pseudochama gryphina, known as a jewelbox. The first of this species recorded in the UK.

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