. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. B R harrisii Stage IV. D N say/ Stage N 04 06 08 02 04 Amount of Salinity Increase (ppt) 06 08 Figure 6. The percentage of Rhithropanopeus harrisii (A, B) and Neopanope sari (C, D) larvae aggre- gating in the upper section upon exposure to the threshold rate of salinity increase (A, B = X ICT'ppt s ': C = x 10~4 ppt s~': D = \ 10 4 ppt s~'). Responses were measured after different absolute amounts of salinity change. R harrisii larvae were acclimated to 20 ppt and A' tavi to 28 ppt. Five determi- nations were
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. B R harrisii Stage IV. D N say/ Stage N 04 06 08 02 04 Amount of Salinity Increase (ppt) 06 08 Figure 6. The percentage of Rhithropanopeus harrisii (A, B) and Neopanope sari (C, D) larvae aggre- gating in the upper section upon exposure to the threshold rate of salinity increase (A, B = X ICT'ppt s ': C = x 10~4 ppt s~': D = \ 10 4 ppt s~'). Responses were measured after different absolute amounts of salinity change. R harrisii larvae were acclimated to 20 ppt and A' tavi to 28 ppt. Five determi- nations were made for each zoeal stage except R. harrisii Stage IV zoeae where four determinations were made. Means and standard errors are plotted. An asterisk indicates the smallest salinity increase to induce a response significantly greater (P < ) than the control (C) plotted at zero salinity change. respond by ascending or descending, they are not ex- posed to a change in salinity during vertical movement. Similarly, when testing in sharp haloclines lower salinity water rests on top of higher salinity water. In this system larvae are either in one salinity or the other because the distance separating the salinities is small. For the present experiments, there was a gradient of low to high salinity extending from the top of the experi- mental chamber to the bottom. In this situation larvae experience a continual increase in salinity upon descend- ing and a continual decrease upon ascending. Thus if lar- vae respond to a salinity decrease and begin to descend, they will experience a salinity increase which evokes the opposite response. If there are differences in the thresh- old rates for responses to a salinity increase and decrease and the absolute amount of salinity change that must oc- cur before a response, then only one directional response can occur in a gradient. For example, the threshold rates for responses to a sa- linity increase are probably well below those to a sal
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
