Ryan Photographic - Gecarcinidae - Land crabs
Family Gecarcinidae
There are currently 22 species of gecarcinids distributed in 5 genera. These land crabs have been highly successful, particularly in places like Christmas Island where there are endemic species. The family is in much need of additional research and it is highly likely that new species will be described with more widespread DNA testing.
In 2012, a new species of gecarcinid, Discoplax celeste, long believed to be D. hirtipes, was described from Christmas Island.
The gecarcinids live out of the ocean, often quite far from the sea. They are able to survive out of water because of evolutionary changes to their gills which may be stiffened more than in their marine relatives. In addition, there is a proliferation of blood vesels in the wall of their branchial cavity which carry out gas exchange. This "lung" must be kept moist, so gecarcinids typically spend their day inside their burrow (where humidity is high) and only venture out at night, unless it is raining.
While the gecarcinids may do some damage to human crops, their burrowing and tunneling activities bring oxygen into the soil and may fill a role similar to that of earthworms. In these harsh environments, land crabs are essentially "ecosystem engineers".
As with nearly all "terrestrial" crabs they must return to the ocean to release their eggs, where their larvae undergo a series of metamorphoses until they reach the megalopae stage, at which point they leave the sea and head inland.
Many thanks to Professor Peter Ng and Bee Yan Lee for helping me with identifications.
Cardisoma carnifex Land crab
Cardisoma carnifex Female land crab with eggs, Fiji
Cardisoma guanhumi Land crab
Cardisoma guanhumi Land crab Belize City
Gecarcinus quadratus Halloween or moon crab
, captive-0521 med res.jpg)
Gecarcinus quadratus Halloween or moon crab, captive IMG_0521
, captive-0532 med res.jpg)
Gecarcinus quadratus Halloween or moon crab (Gecarcinidae), captive-0532
, captive-0534 med res.jpg)
Gecarcinus quadratus Halloween or moon crab (Gecarcinidae), captive-0534
Gecarcoidea lalandii
Gecarcoidea lalandii Rao Island, Morotai, Indonesia
Gecarcoidea lalandii, Rao Island, Morotai, Indonesia IMG_7516
Gecarcoidea lalandii Gecarcinid land crab, Magic Bay, Rao,
Tuerkayana hirtipes Pacific land crab
 Land crab, Waisalima, Kadavu, Fiji-7326 med res.jpg)
Tuerkayana hirtipes (ex Discoplax hirtipes) Land crab, Waisalima, Kadavu, Fiji-7326
 Land crab, Lavena, Taveuni Fiji-0631 med res.jpg)
Tuerkayana hirtipes (ex Discoplax hirtipes) Land crab, Waisalima, Kadavu, Fiji-0631
 Large unidentified Taveuni land crab-0632 med res.jpg)
Tuerkayana hirtipes (ex Discoplax hirtipes) Land crab, Waisalima, Kadavu, Fiji-7326
, Fiji med res.jpg)
Tuerkayana hirtipes (ex Discoplax hirtipes) Land crab, Fiji