# Lugworm Case Study

2521 Words
11 Pages

*Register to read the introduction…*The conclusion that can be drawn from this is that Arenicola is a clear osmoconformer, lacking the ability to maintain its internal cell volume, adjusting the cell’s conditions passively by diffusion to match that of its environment. The weight increase is roughly proportional to the change in salinity. At 25% salinity there is a rapid uptake of water by the lugworm until 75 minutes at which point the cells lose their ability to intake any more water and, as figure 4 shows, stops increasing in weight. Reports indicate that Arenicola marina cannot tolerate much less than 35% salinity for any reasonable length of time (Shumway & Davenport, 1977) and this is backed up by the lack of Arenicola found in estuarine environments where freshwater runoff influences the salinity (Hayward, 1994). Research has shown that between the ranges of 29% to 97% seawater the lugworm is an osmoconformer (Oglesby, 1973), below this the lugworm struggles as there is a net movement of water by diffusion into the cell cytoplasm causing the cells to swell and eventually burst. It is beneficial for the lugworm to be an osmoconformer because the difference between the osmolarity of the worm’s internal fluid and that of its surroundings is

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Deviation | Std. Error Mean | Weights | 1 | 7 | 4.122857 | 1.2518082 | .4731390 | | 4 | 7 | 4.648571 | 2.0067588 | .7584835 |

Independent Samples Test | | Levene's Test for Equality of Variances | t-test for Equality of Means | | F | Sig. | t | df | Sig. (2-tailed) | Mean Difference | Std. Error Difference | 95% Confidence Interval of the Difference | | | | | | | | | Lower | Upper | Weights | Equal variances assumed | 1.543 | .238 | -.588 | 12 | .567 | -.5257143 | .8939563 | -2.4734777 | 1.4220491 | | Equal variances not assumed | | | -.588 | 10.055 | .569 | -.5257143 | .8939563 | -2.5160863 | 1.4646577 |

T-Test

Group Statistics | | Groups | N | Mean | Std. Deviation | Std. Error Mean | Weights | 2 | 6 | 4.525000 | 2.5266401 | 1.0314965 | | 3 | 7 | 3.528571 | 1.6352312 | .6180593 |

Independent Samples Test | | Levene's Test for Equality of Variances | t-test for Equality of Means | | F | Sig. | t | df | Sig. (2-tailed) | Mean Difference | Std. Error Difference | 95% Confidence Interval of the Difference