Research on Clibanarius taeniatus and Clibanarius virescens in Australia

C. taeniatus and C. virescens are common inhabitants of the rocky intertidal areas of tropical Queensland, Australia. From 1997 to 2001, my work focused on the physiological responses of these related species to conditions of environmental stress, such as high temperature, rapid changes in salinity and prolonged exposure to dilute seawater. Each of these, along with biotic interactions, are important factors in the survival and distribution of intertidal organisms.

C. taeniatus                  C. virescens
Photos: S.G.Dunbar

My studies included comparing measurements of oxygen consumption for both species in combinations of temperature and salinity stress, as well as measurements of osmoregulatory and ionoregulatory ability. 

Testing hermit crab osmoregulatory ability in salinities from 8 - 45ppK.
Photo: S.G.Dunbar

Although measurements of oxygen consumption, osmoregulation and ionic regulation demonstrated no differences between species, tolerances of prolonged exposure to dilute salinity did. This is an important factor, since many intertidal organisms are exposed to both small-scale, seasonal flooding and occasional catchment-scale flooding. Both situations may reduce the salinity of inshore water for many days to weeks (Coates, unpublished data). A prediction that followed the physiological and survival work was that the two species should differ in relative abundance on a geographical scale. 

In early 2000 I began a large scale survey for the relative abundances of C. taeniatus and C. virescens over much of the coast of Queensland. I covered over 2600 km of beautiful, tropical coastline and found the two species distributed throughout the many types of habitats encountered. 

Surveying  for C. taeniatus and C. virescens at Turkey Beach, Queensland.
Photo: S.S.Dunbar

Deep Water National Park
Sabine surveying at Deep Water National Park, Central Queensland.
Photo: S.G.Dunbar

Results of the survey showed that wherever the intertidal zone was uninfluenced by freshwater, there was a very high relative abundance of C. virescens while that of C. taeniatus was very low. However, where freshwater did influence inshore waters, the relative abundance of C. taeniatus was high and that of C. virescens was very low. 

I concluded that the geographical distribution of the two species was highly influenced by the presence of freshwater.

We (Dunbar, Coates and Kay, 2003 PDF here) have proposed that that these species can be used as a simple, cost-effective indicator system by which changes to coastal ecosystems can be monitored due to the influence of freshwater inundation, especially in areas where freshwater has previously been absent (i.e. new coastal developments).

Other publications from this research are:

Dunbar, S. G. and Coates, M. 2004. Differential tolerance of body fluid dilution in two species of tropical hermit crabs: not due to osmotic/ionic regulation. Comparative Biochemistry and Physiology (A), Vol. 137(2): 321 - 337. Link to PDF

Dunbar, S. G. 2002: “Determinants of distribution of tropical marine hermit crabs.” Australia Marine Science Association Bulletin, 158: 25

Dunbar, S. G., 2001. Respiratory, Osmoregulatory and Behavioural Determinants of Distribution of Two Tropical Marine Hermit Crabs. PhD Thesis. Central Queensland University, Rockhampton, QLD. 322 p. Link to PDF

Dunbar, S. G. and Coates, M. 2000. Range extension and new host records of the ectoparasite Pseudostegias setoensis Shiino, 1933 (Crustacea: Isopoda: Bopyridae). Transactions of the Royal Society of South Australia. 124(1): 49. Link to PDF