Age determination in crustaceans

美洲龙虾、雪蟹和北方虾等十足类甲壳类动物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6.331.81亿美元的收入，占加拿大所有野生捕捞渔业总上岸价值的34%。因此，对这一行业的健全管理至关重要。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，它被用来计算生长和死亡率、招聘和生产力。虽然野生动物的年龄通常可以通过检查钙化的结构(例如骨骼、鳞片、耳石、贝壳)来确定，但这种方法还没有用于十足类甲壳类动物，因为假设在每一次蜕皮时都会失去所有的珠被结构。我们提出的这项研究将探索一种新的方法来揭示个体十足类甲壳类动物的绝对年龄的可能性，该方法基于对眼柄横切面的生长带的观察。观察到的生长带似乎不同于以前在各种甲壳类贝壳中报道的微尺度特征。需要研究来确定我们初步工作中记录的条带是年龄、换羽事件的指示器，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带的准确位置、性质和个体发育，以及它们在身体其他部位(行走的腿、游泳圈、胃磨)和物种(总共8个)中的潜在存在。然后，我们将使用获得的知识对年龄决定假说进行更直接的测试，测试的基础是来自不同纬度的美国龙虾的I-身体大小-条带计数关系，已知年龄的十足类甲壳类动物的II-条带计数(通过饲养龙虾幼体以及对海洋实验室和水族馆设施的全球搜索获得)，以及III-使用化学标记技术的额外验证。如果这些带子被确认为年龄指标，将对加拿大和世界各地未来的龙虾、螃蟹和虾的种群评估和生物学研究产生重大影响。然而，即使是一个可靠的蜕皮数量指标，在监测甲壳类动物数量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.