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首页> 外文期刊>Estuarine Coastal and Shelf Science >Size at the onset of maturity (SOM) revealed in length-weight relationships of brackish amphipods and isopods: An information theory approach
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Size at the onset of maturity (SOM) revealed in length-weight relationships of brackish amphipods and isopods: An information theory approach

机译：咸淡水两栖类动物和等足类动物的长度-重量关系揭示了成熟时的大小（SOM）：一种信息论方法

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摘要

In amphipods and other small-sized crustaceans, allometnc relationships are conventionally analysed by fitting the standard model Y= a ·X~b (X and Yare, e.g., body length and weight, respectively) whose scaling exponent b is assumed to be constant However, breakpoints in allometric relationships have long been documented in large-sized crustaceans, ultimately determined by ontogenetic, abrupt variations in the value of b. Here, the existence of breakpoints in length-weight relationships was investigated in four amphipod (i.e., Gammarus aequicauda, Gammarus insensibilis, Microdeutopus gryllotalpa, and Dexamine spinosa) and three isopod species (i.e., Lekanesphaera hookeri, Sphaeroma serratum, and Cymodoce trun-cata) from three Mediterranean lagoons. The power of two candidate linear models fitted to log_(10)-transformed data - a simple model assuming a constant exponent b and a segmented model assuming b to vary after a breakpoint - was compared using a parsimonious selection strategy based on the Akaike information criterion. The segmented model with a breakpoint provided the most accurate fitting of length-weight data in the majority of the species analysed; non-conclusive results were obtained only for D. spinosa and C. truncata, of which a limited number of specimens was examined. Model parameters were consistent for amphipod and isopod species collected across the three different habitats; the generality of the results was further supported by a literature search confirming that the identified breakpoints corresponded with ontogenetic discontinuities related with sexual maturation in all the species investigated. In this study, segmented regression models were revealed to provide a statistically accurate and biologically meaningful description of length-weight relationships of common amphipod and isopod species. The methodological limitations of the approach are considered, while the practical implications for secondary production estimates are discussed.
机译：在两栖动物和其他小型甲壳类动物中，通常通过拟合标度指数b恒定的标准模型Y = a·X〜b（分别为X和Yare，例如，体长和体重）来分析异位关系。长期以来，异体关系中的断点已在大型甲壳类动物中得到了证明，最终由b值的个体发生，突然变化决定。在这里，研究了四种双足纲动物（即短尾线虫，伽玛氏小龙虾，Microdeutopus gryllotalpa和Dexamine spinosa）和三种等足类物种（即Lekanesphaera hookeri，Sphaeroma serratum和Cymodoce trun-cata）在长度-重量关系中存在断点的情况。 ）来自三个地中海泻湖。使用基于Akaike信息准则的简约选择策略比较了拟合到log_（10）转换数据的两个候选线性模型的功效-一个简单模型假设一个常数指数b和一个分段模型假设b在断点后发生变化- 。带有断点的分段模型在大多数分析物种中提供了最精确的长度-重量数据拟合。仅对棘孢梭状芽胞杆菌和特兰卡角梭状芽胞杆菌获得了非结论性结果，其中仅对有限数量的标本进行了检查。在三个不同生境中收集的两栖动物和等足动物的模型参数是一致的；结果的普遍性进一步得到文献检索的支持，这证实了在所有调查的物种中，确定的断点对应于与性成熟相关的个体发育不连续。在这项研究中，揭示了分段回归模型，以提供统计上准确的生物学意义上的常见两栖类和等足类动物的长度-重量关系描述。考虑了该方法的方法学局限性，同时讨论了对二次生产估算的实际意义。

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