Laboratorio de Oceanografía Biológica, Centro para el Estudio de Sistemas Marinos - Consejo Nacional de Investigaciones Científicas y Técnicas (LOBio-CESIMAR-CONICET), Bvd. Brown 2915, U9120ACD, Puerto Madryn, Chubut, Argentina; Instituto Patagónico del Mar, Universidad Nacional de la Patagonia San Juan Bosco (IPam-UNPSJB), Bv. Almte Brown 3051, U9120, Puerto Madryn, Chubut, Argentina.
Universidad de Buenos Aires, CONICET, Instituto de Biodiversidad y Biología Experimental y Aplicada (IBBEA) -Facultad de Ciencias Exactas y Naturales, Departamento de Biodiversidad y Biología Experimental, Laboratorio de Biología de la Reproducción, Crecimiento y Nutrición de Crustáceos Decápodos, Intendente Güiraldes 2160, Ciudad Universitaria, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina.
Zoology (Jena). 2020 Dec;143:125847. doi: 10.1016/j.zool.2020.125847. Epub 2020 Sep 25.
Reproductive strategies vary according to season length, individual reproductive traits, and factors associated with the social context such as density and sex ratio of the individuals. The social context predicts the intensity of sexual selection due to its effect on mate choice and intra-sexual competition. Moreover, it exacerbates the costs derived from sexual conflict and allows for the existence of alternative reproductive tactics to counteract such costs. However, these mechanisms are still underexplored in many animal taxa. Majoidea "spider crabs" show a diversity of life history, and behavioral and morphological adaptations for reproduction, which have evolved as an outcome of competition to maximize reproductive success. We aimed to analyze in this study, male reproductive strategies through mating behavior under different social contexts, density of individuals, and males size differences in two species of "spider crabs", Leurocyclus tuberculosus and Libinia spinosa. The experiments were as follows: one female and one male per aquarium (Experiment 1); a female and three males of similar sizes per aquarium (Experiment 2); and a female and three males of distinct sizes per aquarium (Experiment 3). The experiments showed that mating behavior and duration of mate guarding differ between species and among different social contexts. The presence of males with similar or different sizes showed a relevant different behavior, the female copulated with more than one male when males were similar in size (E2), and copulated only with the largest male when males were different in size (E3). In mate guarding, the shape and the use of the chelipeds had an important role: the male of Leurocyclus tuberculosus grasped the female with the chelipeds and did not fight with other males, but the male of Libinia spinosa surrounded the female with the chelipeds and fought with other males. The longest duration of mate guarding was during precopulatory guarding. Precopulatory guarding was present in all the experiments and its duration did not present significant differences among the experiments. However, in both species, the experiments differ in the duration of postcopulatory guarding until spawning. Gonopod morphology revealed important differences between species and are probably associated with sperm competition. The experiments under distinct social contexts linked to the use and shape of the chelipeds and the morphology of the gonopods, could allow to understand the functional significance of the different reproductive strategies.
生殖策略因季节长度、个体生殖特征以及与社会环境相关的因素（如个体密度和性别比例）而异。社会环境通过对配偶选择和种内竞争的影响，预测性选择的强度。此外，它加剧了性冲突带来的成本，并允许存在替代的生殖策略来抵消这些成本。然而，这些机制在许多动物类群中仍未得到充分探索。Majoida“蜘蛛蟹”表现出多种生活史、行为和形态适应生殖的特征，这些特征是竞争的结果，旨在最大限度地提高生殖成功率。我们旨在通过交配行为分析两种蜘蛛蟹（Leurocyclus tuberculosus 和 Libinia spinosa）在不同社会环境、个体密度和雄性体型差异下的雄性生殖策略。实验如下：一个鱼缸一只雌蟹和一只雄蟹（实验 1）；一个鱼缸一只雌蟹和三只体型相似的雄蟹（实验 2）；一个鱼缸一只雌蟹和三只体型不同的雄蟹（实验 3）。实验表明，交配行为和配偶守护持续时间在种间和不同社会环境中存在差异。相似或不同体型的雄性存在着明显不同的行为，当雄性体型相同时，雌蟹会与多个雄蟹交配（E2），而当雄性体型不同时，雌蟹只与体型最大的雄蟹交配（E3）。在配偶守护中，螯肢的形状和使用起着重要作用：Leurocyclus tuberculosus 雄蟹用螯肢抓住雌蟹，不与其他雄蟹战斗，但 Libinia spinosa 雄蟹用螯肢围住雌蟹，并与其他雄蟹战斗。最长的配偶守护持续时间是在交配前守护期间。所有实验都存在交配前守护，而且其持续时间在实验之间没有显著差异。然而，在这两个物种中，实验在交配后守护直到产卵的持续时间上有所不同。雄蟹附肢的形态揭示了种间的重要差异，并且可能与精子竞争有关。不同社会环境下的实验与螯肢的使用和形状以及雄蟹附肢的形态有关，可以帮助理解不同生殖策略的功能意义。
