A preliminary investigation into the potential value of gastric mills for ageing crustaceans
A preliminary study was conducted to assess the usefulness of calcified ossicles from the gastric mills of decapod crustaceans for ageing, based on the application of a traditional fisheries biology method for the analysis of concentric growth marks in scales, bones and otoliths. Transverse cross sections of prepyloric, zygocardiac and pyloric ossicles of gastric mills from Cherax quadricarinatus, Euastacus valentulus, Ranina ranina, Scylla serrata and Thenus orientalis showed the presence of alternating translucent and opaque growth rings. Growth ring analysis indicated a growth record in two series, each likely representing different periodicities. Comparisons of growth ring counts showed close agreement between all gastric ossicles examined. Progressive sectioning of zygocardiac ossicles from C. quadricarinatus and S. serrata showed that growth ring counts varied along the length of these structures and demonstrated the need for species-specific assessment of gastric mill components. In conclusion, further empirical research is warranted to validate the periodicity of the gastric ossicle growth record to further elucidate its potential for ageing crustaceans.