雄性懷孕僅限于海馬,、海龍和它們的近親——海龍科動物（在這個(gè)科的動物中，幼仔是在雄性的育仔囊中撫育的）,。
正如Kimberly Paczolt 和Adam Jones在一項(xiàng)新的研究中所發(fā)現(xiàn)的那樣,，這些撫育幼仔的雄性所做的事情并不只是充當(dāng)一個(gè)被動的孵化者。人們已經(jīng)知道,，育仔囊是一個(gè)撫育發(fā)育中幼仔的復(fù)雜結(jié)構(gòu),。但在撫育的同時(shí)，它還會除雜,。
在“海灣海龍”（Syngnathus scovelli）中,，雄性能夠選擇性地使來自雌性的、被認(rèn)為缺乏吸引力的胚胎夭折,，以便將資源留給以后會碰到的更有希望的胚胎,。這是在一個(gè)性逆轉(zhuǎn)物種中有關(guān)交配后性沖突的惟一已知例子。(生物谷Bioon.com)
生物谷推薦原文出處：
Natue doi:10.1038/nature08861
Post-copulatory sexual selection and sexual conflict in the evolution of male pregnancy
Kimberly A. Paczolt1 & Adam G. Jones1
Department of Biology, 3258 TAMU, Texas A&M University, College Station, Texas 77845, USA
Male pregnancy in seahorses, pipefishes and sea dragons (family Syngnathidae) represents a striking reproductive adaptation that has shaped the evolution of behaviour and morphology in this group of fishes1, 2, 3, 4. In many syngnathid species, males brood their offspring in a specialized pouch, which presumably evolved to facilitate male parental care5, 6. However, an unexplored possibility is that brood pouch evolution was partly shaped by parent–offspring or sexual conflict, processes that would result in trade-offs between current and future pregnancies. Here we report a controlled breeding experiment using the sexually dimorphic Gulf pipefish, Syngnathus scovelli, to test for post-copulatory sexual selection within broods and for trade-offs between successive male pregnancies as functions of female attractiveness. Offspring survivorship within a pregnancy was affected by the size of a male’s mate, the number of eggs transferred and the male’s sexual responsiveness. Significantly, we also found that embryo survivorship in a current pregnancy was negatively related to survivorship in the prior pregnancy, clearly demonstrating fitness trade-offs between broods. Overall, our data indicate that post-copulatory sexual selection and sexual conflict occur in Gulf pipefishes. The conflict seems to be mediated by a strategy of cryptic choice in which males increase rates of offspring abortion in pregnancies from unattractive mothers to retain resources for future reproductive opportunities. Hence, the male brood pouch of syngnathid fishes, which nurtures offspring7, 8, 9, also seems to have an important role as an arbiter of conflict between the sexes
