APHOTOMARINE

An educational resource dedicated mainly to the photography
and diversity of marine life that can be found in coastal waters
and intertidal areas of Great Britain and Ireland by David Fenwick.

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Four-horned spider crab
Pisa tetraodon ?
- ventral view / abdomen 1

Four-horned spider crab
Pisa tetraodon ?
- ventral view / abdomen 2

Four-horned spider crab
Pisa tetraodon ?
- dorsal view / carapace 1

Four-horned spider crab
Pisa tetraodon ?
- dorsal view / carapace 2

Four-horned spider crab
Pisa tetraodon ?
- lateral view 1

Specimen found under a rock on the lowershore at Hannafore, near Looe, Cornwall. 12.03.09. The tide that day was an extra low spring tide and many people were able to cross to St. George's or Looe Island.

? - The identification to Pisa sp. here is certain and thanks go to Dr. Pierre Noël of the Muséum national d'Histoire naturelle, Paris, France; for pointing out the genus and suggested the species is likely to be P. tetraodon. County records for Cornwall also suggest the specimen is likely to be this species. However, the crab is covered by too much algae for the images to be of use to identify the species.

Spider crabs can be quite tricky to identify with any certainty because of a covering of algae. This means verification from images may be impossible. It may be necessary to remove some of the algae with fine tweezers in order to identify weed covered specimens using a stereomicroscope and key. It is too easy to assume specimens are the common Macropodia rostrata, when they may not be, and detailed examination is important if under-recorded species are to be found and identified.

The main objective of this website is in furthering environmental awareness and education through the medium of photography. To increase awareness and access to the wildlife of the region and help

people find and identify it. Sometimes the difference between species is obvious but many species can only be determined by observing microscopic characteristics that are specific to any one species.