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Ecology and Ecotoxicology

Academics in the group are specialists in two core areas: the ecotoxicology of lead and the sexual selection in simultaneous hermaphrodites

Ecotoxicology of lead

All plants and animals bind toxic metals to specific proteins to minimise their impact. Unlike cadmium and mercury, lead has no such protein and so its toxicity in the animal kingdom is currently poorly understood. Snails are the animal where it is commonly found to be the least toxic and some claim it to be the most closely regulated of the major toxic metals.

The group's research has been examining the evidence for a regulatory mechanism for lead. Garden snails (Cantareus aspersus) have a long-term store of lead in their shell, rather like the bone of vertebrates. With these invertebrates we can easily separate this storage site from the sensitive soft tissues to analyse its movement through the animal.

Recent work in the group shows that lead uptake may be determined by growth or cell turnover in the soft tissues. Interestingly, this differs between populations: snails from the Mediterranean Basin have very different dynamics to those of southern England. Most significantly, the work has found there is little indication of a specific and evolved regulatory mechanism for lead in Cantareus.

Sexual selection in simultaneous hermaphrodites

Charles Darwin noted the significant role that sexual selection might play in defining a species and it is now clear that this has contributed to the speciation of several major groups. Sexual selection theory is best developed and most easily tested for species where the sexes are separate and the genders vie with each other to promote the survival of their genes. This becomes problematical when male and female gametes are produced in the same individual and when they are swapped during copulation.

The garden snail Cantareus aspersus is such a simultaneous hermaphrodite, where a large individual may have an advantage over competing partners. A larger partner is obviously successful, indicating a fit genotype but it may also be favoured because of its capacity to provision the fertilised eggs. The group's research has attempted to link size to resource availability, and in particular, the need for calcium to support egg production.

Unlike slugs, snails are iteroparous – they will breed several times during their life – and the large, highly mineralised, external shell may be an important part of this strategy. Beyond its protective function, the Ecology and Ecotoxicology Group have suggested the shell may serve to facilitate repeated reproductive events ie for every clutch of eggs, as much as half of the calcium in the soft tissues may be donated to the brood. The shell may thus represent an important reserve that facilitates the production of large broods and allow for short intervals between copulations.


Dr Larry Richmond
Tel: 020 7815 6229