Pagurus hemphilli

Pagurus. hemphilli is a rich maroon color with small blue dots, yellow-tipped dactyls, gold-ringed corneae, and red to orange-red antennae^[2] that lack spots or rings.^[3] Juveniles sometimes have white bands on their ambulatory legs. The chelipeds ("claws") are dramatically different in size, with the major cheliped being much larger than the minor cheliped.^[1] It is almost totally hairless over its entire body and has a smooth, shiny shield.^[1] It has a distinct rostrum that is produced well beyond the carapace lateral frontal lobes.^[1] The chela palms are rough with visible bumps.^[1] The uropods are asymmetrical, and the carapace can measure up to 15 mm (0.6 in).^[1]

Its congener Pagurus granosimanus is similar in appearance,^[2] with both being dark in color with light dots,^[3] but true to its name, P. hemphilli is more maroon than the olive P. granosimanus.^[3] and can also be separated from P. granosimanus based on the comparatively longer length of the outer portion of the carapace, even at the juvenile stage.^[2] The legs of the two species are also quite different, with P. hemphilli having legs that are dark red with tiny yellow to blue spots and a white dot at the end, whereas P. granosimanus has olive legs with light blue spots.^[3]

Pagurus hemphilli ranges along the North American coast from Alaska^[4] to the Central Coast of California.^[5][1] It is more common towards the southernmost extent of its range in Central California.^[1]

Pagurus hemphilli is found on rocks in shallow water.^[6] It mostly occupies the upper subtidal region to a depth of 50 m (160 ft), but can occur in low intertidal pools.^[5] P. hemphilli occupies a deeper zone of the shoreline compared to its congeners, Pagurus samuelis, Pagurus granosimanus, and Pagurus hirsutiusculus.^[5] It therefore has a comparatively lower tolerance of warm water, experiencing increased mortality from high water temperature, reportedly 50% mortality at 30.1 °C (86.2 °F).^[5] In the wild, it prefers waters that do not exceed 20 °C (68 °F).^[5]

Most commonly, P. hemphilli dwells in the shells of Tegula species,^[6] such as Tegula brunnea, Lithopoma species,^[6] and Astraea species.^[1] To acquire a better shell, P. hemphilli engages in shell fights,^[7] with the loser conceding their shell. These shell fights may be intraspecific or with other Pagurus species.^[7] In these fights, the larger hermit crab has the advantage.^[7]

The shells that this species inhabits are often heavily encrusted with coralline algae and with hitchhikers like the slipper snail Crepidula adunca and the limpet Acmaea mitra.^[1] A species of Amphipod in the genus Liljeborgia has been observed residing with this species of hermit crab inside the shell;^[8] this commensal occupant remains undescribed.^[9]

Pagurus hemphilli is named after Henry Hemphill, an amateur American shell collector, malacologist, and member of the San Diego Society of Natural History.^[10]