Table 1.

Estimated rates of Na+ and Cl- accumulation and loss attributed to the anal papillae in comparison with the timing of observed increases and decreases in hemolymph Na+ and Cl- levels upon transfer between freshwater and 30% seawater

Na+Cl-
Transfer from FW to 30%SW
    Observed initial rate of increase in hemolymph (pmol s-1)2.202.86
    Estimated rate of uptake attributed to all four papillae (pmol s-1)4.518.14
    Observed time required to achieve increase (h)53
    Estimated time required to achieve observed increase (h)2.41.4
Transfer from 30% SW to FW
    Observed initial rate of decrease in hemolymph (pmol s-1)1.914.13
    Estimated rate of loss attributed to all four papillae (pmol s-1)0.211.07
    Observed time to achieve decrease (h)66
    Estimated time required to achieve observed decrease (h)55.623.1
  • FW, freshwater; SW, seawater

    The Jmax values from freshwater-held larvae were used to estimate rates of ion uptake upon transfer from FW to 30%SW. The mean effluxes measured from papillae of individual larvae held in 30%SW for between 15 and 24 h (Na+ N=8; Cl- N=6) were used to estimate rates of ion loss attributed to the anal papillae upon transfer from 30%SW to FW. Total ion fluxes across all four papillae were estimated by multiplying the calculated fluxes by the surface area of the papillae (see Donini and O'Donnell, 2005). The time required for ion fluxes at the anal papillae to achieve the observed changes in hemolymph ion levels was estimated by first determining the magnitude of the ion change in mmol 1-1 and multiplying by 1.65 μl (total hemolymph volume). The magnitude of the ion change in moles was divided by the total ion flux to obtain an estimate of the time required for changes to occur. Observed rates of increase and decrease in hemolymph ion levels were calculated from the results presented in Figs 1 and 2 using the time at which changes were first found to be significant.