. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BEHAVIORAL ECOLOGY OF CRAB LARVAE 407 shown at the bottom of Figure 4. In the tests at 30%c S, there was considerable variability in responses shown in experimental replicates. h it appears that negative geotaxis is exhibited by a portion of the sanipl u:h replicate, there is also an indication in all replicates thai a portion of ti. may be responding with a positive geotaxis. A reduction in salinity from , 25%o S decreases ihe proportion of the sample responding with a negative- while an increase from 30 to 35#c S increases
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. BEHAVIORAL ECOLOGY OF CRAB LARVAE 407 shown at the bottom of Figure 4. In the tests at 30%c S, there was considerable variability in responses shown in experimental replicates. h it appears that negative geotaxis is exhibited by a portion of the sanipl u:h replicate, there is also an indication in all replicates thai a portion of ti. may be responding with a positive geotaxis. A reduction in salinity from , 25%o S decreases ihe proportion of the sample responding with a negative- while an increase from 30 to 35#c S increases the proportion exhibiting negative The fourth stage may be in a transition period during which the sign of geotaxis is variable and is sensitive to salinity change. The data in Table II show thai al 25'/<t S, mean position values of controls exceeded experimental values in every case, although a AIann-\Yhitney U test indicates no significant difference. At 30/{f S, however, experimental mean posi- lion values exceeded conlrols in 9 of 10 replicales, although again the differences were not stalistically significant. At 3Sr/n, S, experimental values significantly exceeded controls for all replicates. Figure 5 shows the distribution at 30 min for all replicates conducted on stage VII larvae at the three salinities. The mean distribution at each salinity is shown at the bottom of Figure 5. Dispersal from a point source (bottom quadrant) in ihe verlical chamber is clearly lower than thai attributable to random move- ment alone. We interpret these results as indicating positive geotaxis in the vast majority of individuals. A 5''« S increase or decrease from 30'/c S appears to have little effect. TEST SALINITY (PPT) 25 30 35 TEST SALINITY ( PPTJ 25 30 35. -100%- L E G E N D Experi mental Co n t r ol -100%- LEGEND E xper i ment al Cont rol FIGURE 3. (Left.) Geotaxis in Callinectes sapidus zoeal stage I. Proportional distribu- tions of larvae among the four sections of experimental
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
