Diogenes pugilator (Roux, 1828)

Diogenes pugilator imageSynonyms: Diogenes varians Makarov, 1938.

Common names: Engl: hermit crab; Russ: Rak otshel'nik diogen; Ukr: Rak-diogen samitnik.

Order (Scientific): DECAPODA.

Family (Scientific): PAGURIDAE.

Taxonomic descriptions: One of two species of the Paguridae family in the Black Sea. The first left leg with claw is much bigger than the right leg. Dactylus moves on vertical plane. The coloration of its body is yellow. The anterior edge of the carapace has acute triangular lateral projections. The internal sides of the dactyli have unequal tooths. Length up to 30 mm.

Diogenes pugilator arealIUCN Status:
    World level:
    Black Sea Regional level:
    Subregion level: EN (Ukrainian sector)

Distribution: Black Sea coastal waters and southern Sea of Azov, Mediterranean Sea, East Atlantic coast from the North Sea untill the coasts of Angola.

Habitats type, Critical habitats, Limiting factors: Inhabiting shallow water sandy bottom shelf areas. The critical habitats are the hypoxic shelf zones. The main limiting factors are oxygen deficiency and a decline in populations of the gastropod mollusc Tritia reticulata.

Biology: A psammophilic hermit crab, inhabiting shallow water biotopes including low salinity areas. Prefers sandy and shelly grounds, usually at depths of 1-10 m , but sometimes can be found up to a depth 40-42 m . It is easily recognized by its habit of carrying a snail shell of Tritia reticulata, Ceritium vulgatum, or sometimes, young Rapana thomasiana, in which the unarmored Diogenes abdomen is concealed.

Population trends: Decline in population numbers since the late 1970s. A reduction of 60-70% over the last 10 years according to direct visual observations.

Threats: Bottom hypoxia provoked by eutrophication.

Conservation measures taken: None.

Conservation measures proposed: Enter in the Black Sea Red Data Book. Reduction in Black Sea coastal zone pollution.


  1. Povchun, A.S., 1992. Izmenenie donnykh soobschestv Karkinitskogo zaliva (Changes in the bottom communities of Karkinitsky Bay). In: Mnogoletnye izmenenya zoobentosa Chernogo morya (Multiannual changes in the Black Sea zoobenthos), Kiev, Naukova dumka, p. 105-138 (in Russian).
  2. Kiseleva, M.I., 1992. Smena donnykh soobschestv biotopa peska u yugo-zapadnogo poberezhya Kryma (Changes in bottom communities on the sand biotope near the south-western Crimean coast). In: Mnogoletnye izmenenya zoobentosa Chernogo morya (Multiannual changes in the Black Sea zoobenthos), Kiev, Naukova dumka, p. 62-69, (in Russian).

Compiled by: Yu.Zaitsev.