Age determination in crustaceans

美国龙虾、雪蟹、北方虾等十足甲壳类动物是加拿大社会经济的重要组成部分；2006年，仅龙虾就创造了6331.81亿美元的收入，占加拿大所有野生捕捞渔业总价值的34%。因此，对该行业的健全管理至关重要。渔业科学家用来评估和管理鱼群的一个更重要的参数是个体的年龄，它被用来计算生长和死亡率、招募和生产力。虽然野生动物的年龄通常可以通过检查钙化结构（例如骨骼、鳞片、耳石、贝壳）来确定，但这种方法尚未用于十足甲壳类动物，因为每次换毛时所有的被皮结构都会丢失。我们提出的研究将探讨一种揭示个体十足甲壳类动物绝对年龄的新方法的潜力，这种方法基于对眼柄横切面生长带的观察。观察到的生长带与以前报道的各种甲壳类动物的微尺度特征不同。需要进行研究，以确定我们初步工作中记录的条带是年龄、换羽事件的指标，还是两者都不是。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（走路的腿、游泳的腿、胃磨）和物种（总共8个）中的潜在存在。然后，我们将利用所获得的知识对年龄测定假设进行更直接的测试，基于不同纬度的美国龙虾的体型-波段计数关系，ii-已知年龄的十足甲壳类动物的波段计数（通过饲养幼年龙虾以及海洋实验室和水族馆设施的世界搜索获得），以及iii-使用化学标记技术进行额外验证。如果这些波段被证实是年龄指标，对加拿大和世界各地的龙虾、螃蟹和虾的未来种群评估和生物学研究的影响将是巨大的。然而，即使是一个可靠的换毛数量指标，在监测甲壳类动物种群方面也有相当大的价值。

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.