Genomics in shellfish and crustacean disease control

Invertebrates do not possess acquired/adaptive immunity and therefore their defence mechanisms rely solely upon the innate immune system. 

The first libraries to be reported were on the eastern oyster, C. virginica, from hemocytes and embryos with the aim of identifying transcripts involved in the stress response for use as bioindicators of exposure to environmental pollutants and to toxic and infectious agents (Jenny et al., 2002). This was 

The recent production of these tools has led to a time lag in respect to studies using microarray in fish that over the past decade represent 1% of the total number of publications in fish biology. Clearly resources are significantly more developed for the oyster however, as with fish this situation is likely to change rapidly over the next few years as several NGS projects come to fruition. It can be expected that the availability of genomic tools for studies in bivalves will increase as resources expand and further insights into the biology of bivalve disease resistance will be revealed. 

The crustaceans, a very diverse and ancient group of arthropods, have been largely studied in order to understand animal evolution and physiology, and for use as models in environmental studies. Advances in sequencing methodologies have resulted in a significant volume of information related to genomics. For an in-depth and comprehensive review see Stillman et al. (2008). 

In terms of relevance to disease resistance little information is available for the crustaceans. The exceptions to the rule are two studies published for P. monodon. A cDNA microarray composed of 2028 different ESTs from two shrimp species, P. monodon and Masupenaeus japonicus, was employed to identify YHV-responsive genes in hemocytes of P. monodon. A total of 105 differentially expressed transcripts were identified and grouped into five different clusters according to their expression patterns (up, down, up-down, down-up, etc). One of these clusters, which comprised of five transcripts including cathepsin L-like cysteine peptidase, hypothetical proteins and unknowns, was of particular interest because the transcript abundance rapidly increased ( 0.25 hours) and reached high expression levels in response to YHV injection (Pongsomboon et al., 2008). A second version 

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