Paczolt Kimberly A, Jones Adam G
Department of Biology, 3258 TAMU, Texas A&M University, College Station, Texas, 77843, United States of America.
PLoS One. 2015 May 13;10(5):e0124147. doi: 10.1371/journal.pone.0124147. eCollection 2015.
Syngnathid fishes (pipefishes, seahorses and seadragons) are characterized by a unique mode of paternal care in which embryos develop on or in the male's body, often within a structure known as a brood pouch. Evidence suggests that this pouch plays a role in mediating postcopulatory sexual selection and that males have some control over the events occurring within the pouch during the pregnancy. These observations lead to the prediction that males should invest differently in broods depending on the availability of food. Here, we use the Gulf pipefish to test this prediction by monitoring growth rate and offspring survivorship during the pregnancies of males under low- or high-food conditions. Our results show that pregnant males grow less rapidly on average than non-pregnant males, and pregnant males under low-food conditions grow less than pregnant males under high-food conditions. Offspring survivorship, on the other hand, does not differ between food treatments, suggesting that male Gulf pipefish sacrifice investment in somatic growth, and thus indirectly sacrifice future reproduction, in favor of current reproduction. However, a positive relationship between number of failed eggs and male growth rate in our low-food treatments suggests that undeveloped eggs reduce the pregnancy's overall cost to the male compared to broods containing only viable offspring.
海龙科鱼类（管口鱼、海马和叶海龙）的特点是具有独特的雄性育幼模式，即胚胎在雄性的体表或体内发育，通常是在一个被称为育儿袋的结构内。有证据表明，这个育儿袋在交配后的性选择中发挥作用，而且雄性对孕期育儿袋内发生的事件有一定的控制权。这些观察结果预示，雄性应该根据食物的可获得性对不同的一窝幼体投入不同。在此，我们利用海湾管口鱼，通过监测处于低食物或高食物条件下的雄性孕期的生长速率和后代存活率来检验这一预测。我们的结果显示，怀孕的雄性平均生长速度比未怀孕的雄性慢，并且处于低食物条件下的怀孕雄性比处于高食物条件下的怀孕雄性生长得更慢。另一方面，食物处理之间的后代存活率并无差异，这表明海湾管口鱼雄性为了当前的繁殖，牺牲了在体细胞生长方面的投入，从而间接牺牲了未来的繁殖。然而，在我们的低食物处理中，未发育的卵的数量与雄性生长速率之间呈正相关，这表明与只包含存活后代的一窝幼体相比，未发育的卵降低了雄性孕期的总体成本。
