Effects of mating order and male size on embryo survival in a pipefish

In species that provide parental care, individuals should invest adaptively in their offspring in relation to the pre- and post-zygotic care provided by their partners. In the broad-nosed pipefish, Syngnathus typhle L., females transfer large, nutrient-rich eggs into the male brood pouch during mating. The male broods and nourishes the embryos for several weeks before independent juveniles emerge at parturition. Given a choice, females clearly prefer large partners. Yet, females provide protein-richer eggs when the same individual mates with a smaller than a larger male. In the present study, we allowed each female to mate with one small and one large male, in alternated order. We found a strong effect of female mating order, with larger clutches and higher embryo mortality in first- than second-laid broods, which may suggest that eggs over-ripen in the ovaries or reflect the negative effects of high embryo density in the brood pouch. In either case, this effect should put constraints o...在存在亲本抚育（parental care）行为的物种中，个体应依据伴侣所提供的合子前、合子后抚育投入，适应性地调整对后代的投资。宽吻海龙（Syngnathus typhle L.）当属这类物种：雌性在交配过程中会将大型且富含营养的卵注入雄性的育幼囊（brood pouch）中，雄性将抚育并滋养胚胎数周，直至幼体在分娩时独立破囊而出。尽管雌性在择偶时明显偏好体型更大的雄性，但当同一雌性分别与体型更小和更大的雄性交配时，其产出的卵蛋白质含量更高。本研究让每只雌性依次与一只小型雄性和一只大型雄性进行交替交配。研究发现雌性的交配顺序对繁殖结果存在显著影响：首次产出的卵簇更大，但胚胎死亡率却高于第二次产卵的卵簇，这一现象可能提示卵巢内的卵出现过熟情况，或是反映了育幼囊内过高的胚胎密度所带来的负面影响。无论何种原因，该效应均会对……