Vertebrates that incubate embryos on or within the body cavity exhibit diverse strategies to provide nutrients to developing embryos, ranging from lecithotrophy (solely yolk-provided nutrition) to substantial matrotrophy (supplemental nutrients from the mother before birth). Syngnathid fishes (seahorses, pipefishes and sea dragons) are the only vertebrates to exhibit male pregnancy. Therefore, they provide a unique opportunity for comparative evolutionary research, in examining pregnancy independent of the female reproductive tract. Here, we tested the hypothesis that the most complex form of syngnathid pregnancy involves nutrient transport from father to offspring. We compared the dry masses of newly fertilised Hippocampus abdominalis eggs with those of fully developed neonates to derive a patrotrophy index. The patrotrophy index of H. abdominalis was 1, indicating paternal nutrient supplementation to embryos during gestation. We also measured the lipid content of newly fertilised eggs and neonates and found that there was no significant decrease in lipid mass during embryonic development. Since lipids are likely to be the main source of energy during embryonic development, our results suggest that lipid yolk reserves being depleted by embryonic metabolism are replaced by the brooding father. The results of our study support the hypothesis that nutrient transport occurs in the most advanced form of male pregnancy in vertebrates.

中文翻译：

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海马腹海马在雄性怀孕期间的父系营养供应

在体腔上或体腔内孵化胚胎的脊椎动物表现出多种策略来为发育中的胚胎提供营养，从卵磷脂（仅由蛋黄提供的营养）到大量的母体营养（在出生前从母亲那里补充营养）。Syngnathid 鱼类（海马、尖嘴鱼和海龙）是唯一表现出雄性怀孕的脊椎动物。因此，它们为比较进化研究提供了独特的机会，在独立于女性生殖道的情况下检查怀孕。在这里，我们检验了最复杂的合颌妊娠形式涉及从父亲到后代的营养运输的假设。我们将新受精的腹海马卵的干质量与完全发育的新生儿的干质量进行了比较，以得出一个营养指数。H. patrotrophy 指数 腹肌为1，表明父亲在妊娠期间对胚胎进行了营养补充。我们还测量了新受精卵和新生儿的脂质含量，发现在胚胎发育过程中脂质含量没有显着降低。由于脂质可能是胚胎发育过程中的主要能量来源，我们的研究结果表明，被胚胎代谢耗尽的脂质蛋黄储备被育雏的父亲所取代。我们的研究结果支持这样的假设，即营养物质运输发生在脊椎动物最先进的雄性妊娠形式中。由于脂质可能是胚胎发育过程中的主要能量来源，我们的研究结果表明，被胚胎代谢耗尽的脂质蛋黄储备被育雏的父亲所取代。我们的研究结果支持这样的假设，即营养物质运输发生在脊椎动物最先进的雄性妊娠形式中。由于脂质可能是胚胎发育过程中的主要能量来源，我们的研究结果表明，被胚胎代谢耗尽的脂质蛋黄储备被育雏的父亲所取代。我们的研究结果支持这样的假设，即营养物质运输发生在脊椎动物最先进的雄性妊娠形式中。