AbstractsBiology & Animal Science

A common trait within many marine invertebrates is the ability to produce larvae of different fitness depending on environmental conditions. In unfavourable conditions, fewer but stronger larvae are produced than under favourable conditions. This project examines whether this trait applies to Capitella teleta, and what implication it has for the settling times of C. teleta larvae. C. teleta is a common test organism, and experiments have been carried out examining, among other things, larval settling preferences, adult fitness and response of adults to varying salinity, organic content and the presence of organic contaminants. However, very few experiments examine the time taken for larvae to settle. In the initial experimental design, which had to be abandoned, sediment was enriched with organic matter, which caused worms to die. This seemed to be due to bacterial blooms in the sediment, resulting in anoxic conditions. The revised experiment examined the effect of higher parent density on larval settling times. Experimental groups were control (~1800 m-2, 2.8% TOM) and triple density (~5400 m-2, 2.8% TOM). Worms produced much fewer brooding tubes than expected, only three tubes in total within one month. Due to this, coupled with time shortage, results were not conclusive. However, the control group appeared to produce more larvae per brooding tube than the triple density group, and the larvae settled faster than larvae from the high density replicates. Larvae appeared to prefer the richer sediment, but this preference was less obvious than expected. These observations provide some, albeit minor, evidence that fitter larvae can delay metamorphosis for longer time. This report also discusses unpublished results from a previous experiment by Annemette Palmqvist. This settling preference experiment on C. teleta examined the effects of two organic contaminants (acetyl cedrene, AC and fluoranthene, Flu) and organic content. Results showed that uncontaminated sediment was preferred to contaminated for both contaminants. However, larval preferences were for high organic content in the AC experiment, but for low organic content in the Flu experiment. This last result is highly surprising and warrants further experiments, to see if these results can be repeated.