Age determination in crustaceans

十足类甲壳类动物，如美洲龙虾、雪蟹和北方虾，是加拿大社会和经济的重要组成部分; 2006年，仅龙虾一项就创造了6331.81亿美元，占加拿大所有野生捕捞渔业总上岸价值的34%。因此，对这一行业进行良好的管理至关重要。渔业科学家用来评估和管理种群的一个更重要的参数是个体的年龄，用于计算生长率和死亡率、补充量和生产力。而野生动物的年龄通常可以通过检查钙化结构来确定（例如，骨、鳞片、耳石、壳），但这种方法尚未用于十足类甲壳动物，因为推测在每次蜕皮时所有外皮结构都丧失了。我们提出的研究将探讨一种新方法的潜力，揭示绝对年龄的个别十足类甲壳动物，这是基于观察生长带的眼柄的横截面。所观察到的生长带似乎与以前报告的各种甲壳类动物壳中的微尺度特征不同。需要进行研究以确定在我们的初步工作中记录的条带是否是年龄、换羽事件或两者都不是的指标。 作为回答这个问题的第一步，我们将使用显微镜来确定这些条带的精确位置，性质和个体发育，以及它们在其他身体部位（步行腿，游泳池，胃磨）和物种（共8个）中的潜在存在。然后，我们将使用所获得的知识进行更直接的测试的年龄决定的假设，根据i-身体大小带计数的关系，在美国龙虾从不同的纬度，ii-带计数在已知年龄十足类甲壳动物（通过饲养的幼年龙虾以及海洋实验室和水族馆设施的世界搜索），和iii-额外的验证使用化学标记技术。如果这些条带被证实是年龄指标，对加拿大和世界各地龙虾、螃蟹和虾的未来种群评估和生物学研究将产生重大影响。然而，即使是一个可靠的蜕皮数量指标，在监测甲壳类动物种群方面也具有相当大的价值。

Decapod crustaceans, such as American lobster, snow crab and northern shrimp, are an important component of Canadian society and economy; in 2006, lobster alone generated $633,181 million, or 34% of the total landed value of all Canada's wild capture fisheries combined. Sound management of this industry is therefore crucial. One of the more important parameters fisheries scientists rely upon to assess and manage stocks is the age of individuals, which is used to calculate growth and mortality rates, recruitment and productivity. Whereas the age of wild animals can often be determined by examining calcified structures (e.g., bones, scales, otoliths, shells), this method has not been used in decapod crustaceans, due to the presumed loss of all integumental structures at each moult. The research we propose will investigate the potential of a new method for revealing absolute age of individual decapod crustaceans, which is based on observations of growth bands in transverse sections of the eyestalk. The observed growth bands appear different from the micro-scale features previously reported in the shells of various crustaceans. Research is needed to determine if the bands documented in our preliminary work are indicators of age, moult events, or neither. As a first step in answering this question we will use microscopy to determine the precise location, nature and ontogeny of these bands, as well as their potential presence in other body parts (walking legs, swimmerets, gastric mill) and species (8 total). We will then use the knowledge acquired to perform more direct tests of the age-determination hypothesis, based on i- body size - band count relationships in American lobsters from different latitudes, ii- band counts in known-age decapod crustaceans (obtained via rearing of juvenile lobsters as well as a world search of marine laboratories and aquarium facilities), and iii- additional validation using chemical marking techniques. If these bands are confirmed to be age indicators, the implications for future stock assessments and biological studies of lobsters, crabs, and shrimps, both in Canada and around the world, would be substantial. However, even a reliable indicator of moult number would have considerable value in monitoring crustacean populations.