The chemosymbiotic gastropod Alviniconcha (Provannidae), first described in 1988, is one of the most emblematic hydrothermal-vent taxa described from the Central Indian Ridge and the Southwest (SW) Pacific. Symbiotic bacteria found in the gill of Alviniconcha are thought to be their principal source of nutrition. In the SW Pacific, species distributions for A. kojimai, A. boucheti - and to a lesser extent A. strummeri - overlap. While Alviniconcha species do not appear to truly co-exist in these highly energetic but spatially limited habitats, certain species regularly co-occur within a single vent field and in rare instances, the same edifice. Past research suggests that SW-Pacific Alviniconcha species might aggregate around fluids with distinct geothermal profiles. These small-scale distribution patterns have been attributed to differences in their symbiont assemblages or host physiologies. However, little is known about the anatomy of most Alviniconcha species, beyond that detailed for the type species Alviniconcha hessleri, whose geographic range does not overlap with other congeners. In fact, species within this genus are currently described as cryptic, despite the absence of any comparative morphological studies to assess this. To test whether the genus is genuinely cryptic and identify any functional differences in host anatomy that might also mediate habitat partitioning in SW Pacific species, the current study examined the morphoanatomy of A. kojimai, A. boucheti and A. strummeri from the Fatu Kapa vent field, an area of hydrothermal activity recently discovered north of the Lau Basin near the Wallis and Futuna Islands and the only known example where all three species occur within adjacent vent fields. A combination of detailed dissections, histology and X-ray computed tomography demonstrate that A. kojimai, A. strummeri and A. boucheti are readily identifiable based on shell morphology and ornamentation alone, and therefore not truly cryptic. These traits provide a rapid and reliable means for species identification. However, aside from some subtle differences in radular morphology, these species of Alviniconcha exhibit conserved anatomical features, providing no evidence that functional host anatomy is implicated in habitat partitioning. This provides support for the current belief that host-species distributions are probably governed by symbiont-mediated physiological factors.

中文翻译：

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来自西南太平洋热液喷口的不太神秘的Alviniconcha物种复合体的经典和计算机断层摄影解剖学分析。

最早于1988年描述的化学共生腹足动物Alviniconcha（Provannidae）是中部印第安海岭和西南太平洋地区描述的最具标志性的热液排放类群之一。Alviniconcha ill中发现的共生细菌被认为是其主要营养来源。在西南太平洋，曲霉曲霉，boucheti曲霉和稀疏的A. strummeri的物种分布重叠。虽然Alviniconcha物种似乎并没有真正并存于这些高度活跃但空间有限的栖息地中，但某些物种通常会在一个通风孔内经常共生，而在极少数情况下，它们是同一建筑物。过去的研究表明，西南太平洋Alviniconcha物种可能聚集在具有不同地热剖面的流体周围。这些小规模分布模式归因于其共生体组合或宿主生理的差异。但是，除了对Alviniconcha hessleri类型物种的详细解剖之外，对大多数Alviniconcha物种的解剖知之甚少，该物种的地理范围与其他同类动物没有重叠。实际上，尽管没有任何比较的形态学研究对此进行评估，但该属中的物种目前被描述为隐性的。为了测试该属是否真正隐秘并鉴定宿主解剖结构中的任何功能差异，这些差异也可能介导西南太平洋物种的栖息地分区，当前研究检查了来自法图卡帕喷口的A. kojimai，A。boucheti和A. strummeri的形态。领域，最近在劳斯盆地以北的瓦利斯群岛和富图纳群岛附近发现了一个热液活动区，这是唯一已知的例子，其中所有三种物种都发生在相邻的通气区内。详细的解剖，组织学和X射线计算机断层扫描的结合表明，仅基于壳的形态和装饰就可以容易地识别A. kojimai，A。strummeri和A. boucheti，因此并不是真正的隐秘。这些特征为物种识别提供了一种快速而可靠的手段。但是，除了胚根形态上的细微差异外，这些Alviniconcha物种还表现出保守的解剖特征，没有提供证据表明功能宿主解剖结构与栖息地的划分有关。