Banning Jenifer L, Weddle Anna L, Wahl George W, Simon Mary Alice, Lauer Antje, Walters Robert L, Harris Reid N
Department of Biology, James Madison University, MSC 7801, Harrisonburg, VA 22807, USA.
Oecologia. 2008 May;156(2):423-9. doi: 10.1007/s00442-008-1002-5.
We examined a novel hypothesis for the maintenance of communal nesting in the salamander, Hemidactylium scutatum, namely that communal nests are more likely than solitary nests to be associated with cutaneous antifungal bacteria, which can inhibit fungal infections of embryos. A communal nest contains eggs of two or more females of the same species. The nesting behavior of H. scutatum females and survival of embryos were determined by frequent nest surveys at three ponds. For communal nests, embryonic survival tended to be higher and catastrophic nest failure was lower. Pure bacterial cultures of resident species were obtained from the salamanders' skins by swabbing and tested against a fungal pathogen of embryos (Mariannaea sp.) in laboratory assays. We found that 27% of females had skin bacteria inhibitory to Mariannaea sp. Communal nests were more likely to have at least one female with antifungal bacteria than were solitary nests. Using a culture-independent assay (denaturing gradient gel electrophoresis of 16S rRNA gene fragments), we found that bacterial species on females and embryos were more similar to each other than they were to bacterial species found in soil within the nest, suggesting that females transmitted skin bacteria to embryos. The presence of anti-Mariannaea skin bacteria identified from the laboratory assays did not prevent fungal presence in field nests. However, once a nest was visibly infected with fungi, presence of anti-Mariannaea bacteria was positively correlated with survival of embryos. Microbe transmission is usually thought to be a cost of group living, but communal nesting in H. scutatum may facilitate the transmission of antifungal bacteria to embryos.
我们研究了一个关于蝾螈（Scutalina属）维持群居筑巢行为的新假说，即群居巢穴比独居巢穴更有可能与皮肤抗真菌细菌相关联，这些细菌可以抑制胚胎的真菌感染。群居巢穴包含同一物种的两只或更多雌性的卵。通过对三个池塘的巢穴进行频繁调查，确定了Scutalina属雌性的筑巢行为和胚胎的存活率。对于群居巢穴，胚胎存活率往往更高，灾难性的巢穴失败率更低。通过擦拭从蝾螈皮肤中获得常驻物种的纯细菌培养物，并在实验室检测中针对胚胎的真菌病原体（Mariannaea属）进行测试。我们发现27%的雌性具有抑制Mariannaea属的皮肤细菌。群居巢穴比独居巢穴更有可能至少有一只带有抗真菌细菌的雌性。使用一种不依赖培养的检测方法（16S rRNA基因片段的变性梯度凝胶电泳），我们发现雌性和胚胎身上的细菌物种彼此之间比与巢穴内土壤中发现的细菌物种更相似，这表明雌性将皮肤细菌传递给了胚胎。实验室检测中鉴定出的抗Mariannaea皮肤细菌的存在并不能阻止野外巢穴中真菌的存在。然而，一旦巢穴明显被真菌感染，抗Mariannaea细菌的存在与胚胎的存活率呈正相关。微生物传播通常被认为是群居生活的一种代价，但Scutalina属的群居筑巢可能有助于将抗真菌细菌传递给胚胎。
