The spider crab Petramithrax pygmaeus (Bell, 1836), a phyletic dwarf, was used to test predictions regarding reproductive performance in small marine invertebrates. Considering the disproportional increase in brooding costs and the allometry of egg production with increasing body size, it was expected that this minute-size species would produce large broods compared to closely related species that attain much larger body sizes. Fecundity in P. pygmaeus females carrying early and late eggs varied, respectively, between 17 and 172 eggs crab^–1 (mean ± SD = 87.97 ± 48.39) and between 13 and 159 eggs crab^–1 (55.04 ± 40.29). Females did not experience brood loss during egg development. Egg volume in females carrying early and late eggs varied, respectively, between 0.13 and 0.40 mm³ (0.22 ± 0.07) and between 0.15 and 0.42 mm³ (0.26 ± 0.06 mm³). Reproductive output (RO) varied between 0.91 and 8.73% (3.81 ± 2.17%) of female dry body weight. The RO of P. pygmaeus was lower than that reported for closely related species with larger body sizes. The slope (b = 0.95 ± 0.15) of the line describing the relationship between brood and parental female dry weight was not statistically significant from unity. Overall, our results disagree with the notion that the allometry of gamete production and increased physiological costs with increased brood size explain the association between brooding and small body size in marine invertebrates. Comparative studies on the reproductive investment of brooding species belonging to monophyletic clades with extensive differences in body size are warranted to further our understanding about disparity in egg production in brooding marine invertebrates.

中文翻译：

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蜘蛛蟹Petramithrax pygmaeus（系统发育性侏儒）的生殖性能（Bell，1836年）（十足目：Brachyura：Mithracidae）

蜘蛛蟹Petramithrax pygmaeus（Bell，1836）是种系矮小，用于测试有关小型海洋无脊椎动物生殖性能的预测。考虑到育成成本的不成比例的增加以及随着体型的增大产蛋的异形性，与拥有更大体型的密切相关物种相比，这种微小的物种预计会产生较大的亲体。携带早卵和晚卵的P. pygmaeus雌性的生殖力分别在17和172个卵蟹^–1之间（平均值±SD = 87.97±48.39）和13和159个卵蟹^{–1之间变化。}（55.04±40.29）。雌性在卵发育过程中没有产卵量下降。携带早卵和晚卵的雌性的卵量分别在0.13和0.40 mm ³（0.22±0.07）之间和0.15和0.42 mm ³（0.26±0.06 mm ³）之间变化。女性干体重的生殖产出（RO）在0.91至8.73％（3.81±2.17％）之间。pygmaeus的RO低于体型较大的密切相关物种的RO 。斜率（b= 0.95±0.15）描述亲代与母本女性干重之间关系的直线从统一上看没有统计学意义。总体而言，我们的结果与以下观点不同：配子生产的异速生长和育雏尺寸增加导致的生理成本增加，这说明了海洋无脊椎动物育雏与小体型之间的关联。对属于单生代进化枝，体型差异很大的育雏物种进行生殖投资的比较研究有必要进一步加深我们对育雏海洋无脊椎动物产蛋差异的理解。