Biotechnology of Marine Invertebrates —Recent Advances in Shrimp and Shellfish

Marine invertebrates possess a variety of interesting functions and some of them have been well studied from the standpoint of biotechnology. Shrimp and shellfish are useful animals among marine invertebrates. In this section, we describe the recent advances in biological defense system of shrimp and the biomineralization system of shellfish as examples of which molecular mechanisms have been well elucidated. First, we focus on shrimp antimicrobial peptide (AMPs) which are considered to play a major role in the innate immunity against invading microbes. A total of 767 ESTs encoding putative AMPs were identified in the Penaeus monodon EST database (http://pmonodon.biotec.or.th), which were comprised of homologues of the three AMP families; penaeidins, crustins and antilipopolysaccharide factors. Sequence analysis revealed that each AMP family had sequence diversity and constituted multiple isoforms or subgroups. The relevance of this sequence variability to the potential antimicrobial function was investigated. These shrimp AMPs with high selectivity to severe pathogens are potential candidates as an alternative to antibiotics in aquaculture. As a second example, we present the recent advances in the molecular mechanism of shell formation. A variety of animals and plants have the ability to make hard biological structure called biominerals made of calcium, silicon and other minerals. Molluscan shell is a typical biomineral composed of CaCO3, but a small amount of organic matrix proteins included in the shell direct the crystal growth that is specific for the shell species. Ca adsorbed through specific transporters and HCO3 synthesized from CO2 are mixed under well regulated conditions, thereby forming shell.