OSMOREGULATION, IONIC EXCHANGE, BLOOD CHEMISTRY, AND NITROGENOUS WASTE EXCRETION IN THE LAND CRABCARDISOMA CARNIFEX:A FIELD AND LABORATORY STUDY

Abstract

Cardisoma carnifex in Moorea, French Polynesia, were sampled in the field and after exposure in the laboratory to either fresh-or seawater under conditions which allowed the crabs to flush their branchial chambers with the medium but not to ventilate it. Relative to field data, ionic and osmotic status of the hemolymph was virtually unchanged by exposure to freshwater, but markedly disturbed by seawater. The crabs were capable of net Na + and Cl uptake from freshwater. Water sampled from natural crab burrows was essentially freshwater. It is concluded that the population was "in equilibrium" with freshwater in the wild.Net H + uptake (= base excretion) occurred in both fresh-and seawater; in freshwater there was a 1:1 relationship between net H + flux and strong cation minus anion flux (i.e., Na + + Mg ++ + Ca ++ + K + -Cl"). Unidirectional Na + and Cl" exchanges, measured radioisotopically, were typical of euryhaline crabs in freshwater, but influxes were unusual in showing no increase in seawater. Mild dehydration caused complex alterations in these exchanges in both media, associated with small and quickly reversed changes in hemolymph composition in freshwater, but larger effects in seawater which were not reversed. High levels of ammonia in hemolymph occurred in the field but declined in the laboratory, while the level of urea was low in both situations. Both wastes were excreted into the water. Neither uric acid nor gaseous ammonia excretion were detected, and uric acid was generally not found in hemolymph. The results are discussed in relation to the ecology of this unusual animal.

Hemolymph ammonia and urea and nitrogenous excretions of Scylla serrata at different temperature and salinity levels

“…Hemolymph urea-N levels between 8.4 and 56 mg I-' have been reported in Carcinus maenas (Binns 1969), and a level of 3.18 mg 1-' in Cardisoma carnifex (Wood & Boutilier 1985). In the present study, hemolymph ammonia-N levels between 4.66 and 9.27 mg 1-' and hemolymph urea-N levels between 13.41 and 82.82 mg 1-' were found for Scylla serrata and were dependent on salinity level…”

“…The higher ammonia-N excretion at low salinity (10%) suggests that catabolism of amino acid is required to reduce Hrabak et al 1992). For the final step of ornithine-urea, arginine is hydrolyzed by arginase and produces urea and ornithine (Regnault 1987 (Wood & Boutilier 1985).…”

To the Land and Beyond: Crab Microbiomes as a Paradigm for the Evolution of Terrestrialization

“…The differences between aquatic and terrestrial habitats are enormous and nearly every aspect of a crab life needs to cope with such a transition ( Little, 2009 ). During this process, remarkable morphological and physiological changes were required to tackle challenges relevant to locomotion ( Burggren and McMahon, 1988 ), gaseous exchange ( Farrelly and Greenaway, 1993 , 1994 ; Paoli et al, 2015 ), excretion ( Wood and Boutilier, 1985 ; Greenaway, 1988 ), reproduction ( Cannicci et al, 2011 ; Simoni et al, 2013 ), foraging ( Lindquist et al, 2009 ), and salt availability ( Anger, 1995 ; Faria et al, 2017 ), given the huge difference in physical properties of air and water ( Little, 1990 ; Figure 2 ).…”

Physiological responses of two ecologically important Kenyan mangrove crabs exposed to altered salinity regimes

“…In the laboratory, hemolymph ammonia concentrations ranged from 195±164 to 970±561 µmol l -1 in N. meinerti and from 1137±429 to 1753±54 µmol l -1 in N. smithi; the upper values being rare (Calybrook, 1983), but not unheard of, especially in more terrestrial crabs (cf. Wood and Boutilier, 1985). The higher hemolymph ammonia concentrations observed in N. smithi held in the laboratory for one month as compared to those in the field clearly indicate the poor condition of these animals.…”