THESIS APPROVAL
THESIS APPROVAL
THESIS APPROVAL
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Table 10 Description of endpoints for short-term sediment toxicity test using<br />
L. hoffmeisteri.<br />
Mortality<br />
Autotomy<br />
Endpoint Description<br />
Sediment avoidance<br />
Reworking activity<br />
Source: Meller et al. (1998)<br />
4.5 Data Analysis<br />
Animals were recorded as dead when they did not respond to a<br />
gentle mechanical stimulus to the front end<br />
Autotomy starts with a local constriction of the circular muscles,<br />
which can be seen macroscopically. The segments behind the<br />
constriction are completely autotomized (Kaster, 1979). Autotomy<br />
was defined as all animals showing either constriction and/ or loss<br />
of segments.<br />
According to Keilty et al. (1988) a worm was considered<br />
unburrowed if more than an estimated 75% of its body was visible<br />
on the sediment surface.<br />
The animals leave traces while digging through the sediment (socalled<br />
galleries). To estimate the reworking activity, a qualitative<br />
comparison on replicate level was performed. The reworking<br />
activity of all animals in one test chamber was defined reduced<br />
when the visible number of galleries was distinctly lower than in<br />
the control chamber (Figure 12)<br />
The effect rates in percentages of mortality, autotomy and sediment<br />
avoidance for each concentration (i) and each test duration (j) were calculated<br />
according to the following equations;<br />
Mortality in ij = (Σ dead animals in ij) × 100 (1)<br />
(Σ exposed animals in ij)<br />
Autotomy in ij = (Σ dead animals in ij + Σ animals showing autotomy in ij) × 100 (2)<br />
(Σ exposed animals in ij)<br />
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