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Table 7.

The effect of tested pharmacological compounds on the rates of water efflux, P production and drinking of Gecarcoidea natalis during the 1998 wet season

Water efflux (ml kg−1 day−1)
Drinking (ml kg−1 day−1)
P production rate (ml kg−1 day−1)
Wet seasonFWSWFWSWFWSW
Saline (control) 29.5±9.30 41.4±9.90  6.00±2.45 6.09±2.49 17.6±3.94 1.8±2.03  
Dopamine 21.3±12.92 66.7±15.98  7.02±2.87 14.17±5.78 4.5±0.70 * NP  
db-cAMP 22.5±11.91 64.0±15.28  10.52±4.29 8.19±3.34 11.0±2.27 NP  
Serotonin 21.7±8.59 30.4±13.10  7.69±3.14 11.14±4.55 4.4±2.99 * 2.7±1.93 
Water efflux (ml kg−1 day−1)
Drinking (ml kg−1 day−1)
P production rate (ml kg−1 day−1)
Wet seasonFWSWFWSWFWSW
Saline (control) 29.5±9.30 41.4±9.90  6.00±2.45 6.09±2.49 17.6±3.94 1.8±2.03  
Dopamine 21.3±12.92 66.7±15.98  7.02±2.87 14.17±5.78 4.5±0.70 * NP  
db-cAMP 22.5±11.91 64.0±15.28  10.52±4.29 8.19±3.34 11.0±2.27 NP  
Serotonin 21.7±8.59 30.4±13.10  7.69±3.14 11.14±4.55 4.4±2.99 * 2.7±1.93 

The rate determinations were made over a 24 h period inside P-chambers (see Materials and methods). The crabs were either acclimated to drinking 50%seawater (SW) or assigned to a control group provided with normally available freshwater (FW), as for the branchial perfusion determinations. Crabs from each of the SW and FW groups were treated by infusion of either saline,dopamine, serotonin (both at 10−10 mol g−1)or db-cAMP (10−9 mol g−1). Infusions, in saline carrier at 1 μ1 g−1, were performed at 8 h intervals for 3 days. Crabs were held prior to determinations within enclosures that were open at the top and allowed crabs contact with the forest floor. Values are means ± s.e.m. (N=8 in each group).

*

effect of drug infusion;

effect of drinking saline water; NP, none produced (in the case of NP values, the significance of the SW values was derived by testing the FW values in a one-tailed t-test against a value of zero - i.e. none produced).

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