Cyclograpsus henshawi is a marine crab of the familyVarunidae.[2] Zoologist Mary J. Rathbun named the species in 1902 after Mr. H. W. Henshaw, who collected the first specimens from Hilo, Hawaii.[2] This species is also referred to as Henshaw’s Shore Crab[3] and is endemic to the Hawaiian Islands.[3]
Carapace
The largest male specimen recorded measures 16mm long by 19.5mm wide[2] while an average male specimen measures 13.5 mm long by 17mm wide.[2]
The carapace of the Henshaw’s Shore Crab measures 3/4" wide[3] and is noticeably broad as opposed to long.[3] Their carapace is 4/5th as long as they are wide[3] and has a smooth texture with microscopic holes.[3] The front of the carapace is turned down, creating a sharp, straight edge.[4] There are six white spots located on the front half.[2] Its fronto-orbital width is 11.7mm, and its front width is 6.2mm.[2]The front and anterolateral regions are covered in spikes,[4] faint sutures, and small granules.[2] The carapace's sides are smooth and parallel.[4] Male specimens also have abdomens that curve inwards.[4]
Top view of the Henshaw's Shore Crab provided by the Smithsonian Institution: National Museum of Natural History(1902)[5]
Cheliped
Its chelipeds are nearly equal in size [4] with granules on the margins and slightly gaping fingers.[2] Its fingers are slightly opened and contain miniature teeth, with more prominent teeth on their pollex.[4] Both its chelipeds and fingers are smooth.[4] Male specimens have significantly larger chelipeds compared to female specimens.[4]
Leg
Its legs have short black bristles and rough surfaces.[2] Their merus has a grainy texture on its upper and outer surface.[4] Opposed to their carpus, which has a smooth texture, with only their inner side possessing a grainy texture.[4]
Studies
Henshaw’s Shore Crabs were part of a case study that measured Na⁺/K⁺-ATPas gill activity in five crab species exposed to different seawater concentrations.[6] The highest enzyme activity occurred in the Metopograpsus thukuhar and Cyclograpsus henshawi specimens.[6] When placed in 50% seawater, it showed no change.[6] The results suggest that gill Na⁺/K⁺-ATPase plays a key role in helping crabs both absorb salts in dilute conditions and release them in concentrated environments.[6]
Distribution and habitat
The Henshaw’s Shore Crab is endemic to Hawai’i and can be found on the islands of Oahu, Maui, and the Big Island.[2] It resides in the intertidal zone[2] under stones along the water's edge of sheltered bays[2] and along the breakwater.[4]
