The Hawaiian bobtail squid, Euprymna scolopes, has a female reproductive organ called the accessory nidamental gland that contains a symbiotic bacterial consortium. These bacteria are deposited from the accessory nidamental gland into the squid’s egg cases, where the consortium prevents microbial fouling. The symbiont community is environmentally transmitted and conserved across host populations, yet little is known about how the organ develops and is colonized by bacteria. In order to understand accessory nidamental gland development in E. scolopes, we characterized the gland during maturation by using histology and confocal and transmission electron microscopy. We found that an epithelial field formed first about four weeks after hatching, followed by the proliferation of numerous pores during what we hypothesize to be the initiation of bacterial recruitment (early development). Microscopy revealed that these pores were connected to ciliated invaginations that occasionally contained bacteria. During mid development, these epithelial fields expanded, and separate colonized tubules were observed below the epithelial layer that contained the pores and invaginations. During late development, the superficial epithelial fields appeared to regress as animals approached sexual maturity and were never observed in fully mature adults (about 2–3 months post-hatching), suggesting that they help facilitate bacterial colonization of the accessory nidamental gland. An analysis of 16S rRNA gene diversity in accessory nidamental glands from females of varying size showed that the bacterial community changed as the host approached sexual maturity, increasing in community evenness and shifting from a Verrucomicrobia-dominated to an Alphaproteobacteria-dominated consortium. Given the host’s relationship with the well-characterized light organ symbiont Vibrio fischeri, our work suggests that the accessory nidamental gland of E. scolopes may have similar mechanisms to recruit bacteria from the environment. Understanding the developmental and colonization processes of the accessory nidamental gland will expand the use of E. scolopes as a model organism for studying bacterial consortia in marine symbioses.

中文翻译：

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夏威夷短尾鱿鱼，虾up的附属线腺和相关细菌群落的发育

夏威夷短尾鱿鱼Euprymna scolopes有一个雌性生殖器官，称为副乳腺，其中含有一种共生细菌。这些细菌从附属的腺体沉积到鱿鱼的卵盒中，在那里财团阻止了微生物的结垢。共生体在环境上可以在宿主种群之间传播和保存，但是人们对器官的发育和细菌定殖知之甚少。为了了解大肠埃希氏菌的附件性新生腺发育，我们通过使用组织学，共聚焦和透射电子显微镜对成熟过程中的腺体进行了表征。我们发现，在孵化后约四周开始形成上皮区域，然后在我们假设是细菌募集的初期（早期发育）期间大量毛孔的扩散。显微镜检查显示，这些孔与纤毛状内陷相连，偶尔含有细菌。在中期发育中，这些上皮区域扩大，并且在包含孔和内陷的上皮层下方观察到单独的定植的小管。在后期发育过程中，随着动物接近性成熟，表皮上皮区域逐渐消退，在完全成熟的成年动物（孵化后约2至3个月）中从未观察到过，提示它们有助于促进副结膜腺的细菌定植。分析来自大小不一的雌性的附件性腺腺中的16S rRNA基因多样性表明，随着宿主接近性成熟，细菌群落发生了变化，群落均匀性增加，并从以疣状微生物为主导的组织转变为以丙酸杆菌为主导的财团。鉴于宿主与特征明确的轻器官共生弧菌弧菌之间的关系，我们的工作表明，美洲野的副结膜腺可能具有从环境中募集细菌的相似机制。了解副结膜腺的发育和定殖过程将扩大大肠杆菌的应用，使其成为研究海洋共生细菌菌群的典范生物。