Haemolymph biochemistry of the giant clam, Tridacna gigas L.

The primary aim of this study was to evaluate the suitability of routine uterinary tests in the detection of stress in Tridachna gigas L. These tests were designed for assessing electrolytes and enzymes in the mammalian plasma. This study also aimed to determine changes in the haemolymph composition of T. gigas after exposure to selected environmental stress (28 day light exclusion, re-exposure to light after light stress, elevated temperatures and exposure to varying salinities) and the infection with Vibrio spp. Although these plasma analyses have been optimized for human biochemistry, these kits have been adapted for domestic mammals and birds. However when applied to T. gigas haemolymph, only the values obtained for calcium, magnesium, chlorine and total protein were consistent. Results from enzyme analyses and other compounds were highly variable. Of all the haemolymph components measured, total protein appears to be a promising indicator for environmental stresses such as exposure to darkness and salinity variations. Mean value for the total protein content of T. gigas haemolymph exposed to complete darkness was 6.3 g/L while the controls ranged from 5.2-5.6 g/L. In the salinity experiment, the mean values were 5.36 g/L at 25 ppt, 78.28 g/L at 35 ppt and 9.49 g/L for 45 ppt. The variable results for enzymes and other compounds were due to several factors. Firstly, the tests were operated in a matrix to which they were not designed for. The native `enzymes' may have had vastly different requirements (in terms of pH, ionic cofactors and ionic strength) equivalent to the mammalian enzymes of the same name. Secondly, the absence of either physical similarity in requirements between enzymes from different sources. Thus, the results of enzyme assays should be considered unreactive in the systems used. Like the variable results for creatinine, the Trace method used contained alkaline picric acid, which may have been affected by non-specific reactions with other tridacnid substances