The Bythograeidae are a small family of blind crabs which live around hydrothermal vents. The family contains 16 species in six genera. Their relationships to other crabs are unclear. They are believed to eat bacteria and other vent organisms. Bythograeidae are a monophyletic, sister taxon of the superfamily Xanthoidea which split to inhabit hydrothermal vents around the Eocene.

Origins

Due to the lack of fossils found in this group the exact date of origin of Bythograeidae remains unknown. It has been suggested that bythograeidae do not originate from an ancient hydrothermal bathyal groups but instead arose from brachyuran stock that was adapted to shallow hydrothermal vents and then transitioned to deep sea hydrothermal vents around the Eocene.

A consortium of Cyanagraea praedator crabs in an area of hydrothermal activity

Distribution

Bythograeidae are almost exclusively found in the East Pacific Rise. Some exceptions include Austinograea alayseae, Austinograea williamsi and the genus Gandalfus which are found in the western Pacific and Austinograea rodriguezensis which is found only in the Central Indian Ridge.

Ecology

The hydrothermal vents where these crabs live are typically short lived, lasting from 10 to 100 years. These are extreme environments, with high temperatures, high concentrations of sulphides, heavy metals, carbon dioxide and an acidic environment. At this depth there is also limited access to light, making photosynthesis nearly impossible. Instead, organisms rely on Chemosynthetic bacteria to sustain the vast amounts of life in Chemotrophic ecosystems.

Bythograeidae are omnivorous scavengers, they are believed to eat bacteria and other vent organisms however they can also be found far from active sites.

Species

Austinograea rodriguezensis
Austinograea alayseae
  • Genus Allograea Guinot, Hurtado & Vrijenhoek, 2002 Allograea tomentosa Guinot, Hurtado & Vrijenhoek, 2002
  • Genus Austinograea Hessler & Martin, 1989 Austinograea alayseae Guinot, 1990 Austinograea hourdezi Guinot & Segonzac, 2018 Austinograea jolliveti Guinot & Segonzac, 2018 Austinograea rodriguezensis Tsuchida & Hashimoto, 2002 Austinograea williamsi Hessler & Martin, 1989
  • Genus Bythograea Williams, 1980 Bythograea galapagensis Guinot & Hurtado, 2003 Bythograea intermedia Saint Laurent, 1988 Bythograea laubieri Guinot & Segonzac, 1997 Bythograea microps Saint Laurent, 1984 Bythograea thermydron Williams, 1980 Bythograea vrijenhoeki Guinot & Hurtado, 2003
  • Genus Cyanagraea Saint Laurent, 1984 Cyanagraea praedator Saint Laurent, 1984
  • Genus Gandalfus McLay, 2007 Gandalfus puia McLay, 2007 Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000)
  • Genus Segonzacia Guinot, 1989 Segonzacia mesatlantica (Williams, 1988)