Snail parasite resistant

In a B. glabrata resistant snail line (LAC) that was derived from a previously susceptible snail stock NMRI (Cooper et ai, 1994), histological studies indicated that they possessed abnormal albumen glands compared to their susceptible counterparts. Concurrent with these results was the observation that the LAC snail displayed a reduced fecundity, manifested by the presence of abnormal egg clutches. There is as yet, no evidence that the reduced reproductive capacity seen in these snails is directly related to their parasite refractory phenotype. 

Suppression-subtractive hybridization (SSH) is another hybridization strategy that is being pursued to examine differential gene expression following parasite infection in the snail host. At least two major laboratories are currently engaged in using this approach towards the isolation of genes that are specifically expressed in either resistant or susceptible snails in response to infection. Initial results from these studies showed differential expression of several transcripts in a resistant (BS-90) and susceptible snail (M-line) in response to... 

Moreover, the observation of an interesting antibiotic activity for some Lactarius extracts (3) stimulated the search of new biologically active compounds among those isolated from these mushrooms. In fact, simple bioassays (4) led to the identification of new products with antimicrobial, cytotoxic, antifeedant and other interesting activities. No less important was the observation that some species seem to withstand attack from parasites such as snails and insects better than others. In fact, it has been shown that resistant species are armed with a chemical defence system which protects the mushrooms from predators and invaders. 

Many evolutionary biologists believe that parasitism has had an important influence on the evolution of species. In a 2009 study of a species of snail from New Zealand, researchers found that in populations with high levels of parasites, the snails will switch from asexual reproduction (producing clones) to sexual reproduction, which produces genetically diverse offspring that are more resistant to infection. This discovery led the researchers to speculate that parasites may have been instrumental in the evolution of sexual reproduction. 

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