Sigwart Julia D, Wong Nur Leena W S, González Vanessa Liz, Machado Fabrizio Marcondes, Greve Carola, Schell Tilman, Chen Zeyuan
Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt, Germany.
Institute of Ecology, Evolution & Diversity, Goethe University, Frankfurt, Germany.
BMC Genomics. 2025 May 9;26(1):460. doi: 10.1186/s12864-025-11622-w.
In this study, we present the first chromosome-scale genome of Verpa penis (Linnaeus, 1758), and the first for the bivalve clade Anomalodesmata. The present study has two separate foci. Primarily, we provide the genetic resource to bridge further studies from genome to phenome and propose hypotheses to guide future empirical investigations. Secondarily, based on morphology, we outline a conceptual exploration to address their adaptation. Watering-pot shells have been called "the weirdest bivalves" for their fused tubular shell resembling the spout of a watering can. This adventitious tube arose twice convergently in clavagelloidean bivalves. However, previous literature has never provided a convincing adaptive pathway.
The genome assembly of V. penis was about 507 Mb, with contig N50 of 5.33 Mb, and has 96.5% of sequences anchored onto 19 pseudochromosomes. Phylogenomic analyses of this new genome in context of other bivalves confirms the placement for Anomalodesmata as sister to the clade Imparidentia. Contrary to expectations from its highly modified body plan, there is no evidence of chromosome reduction compared to the ancestral karyotype of heterodont bivalves (1 N = 19). Drawing on established principles from engineering as well as morphology, the thought experiment about the adventitious tube seeks to extend current understanding by exploring parallels with other built structures. A new hypothesis explains one possible interpretation of the adaptive significance of this body form: it is potentially structurally optimised for vertical stability in relatively soft sediments, with parallels to the engineering principles of a suction anchor.
While the conclusions presented here on morphological interpretations are theoretical, this serves as a foundation for further empirical validation and refinement. Our study offers new insights to a long-standing mystery in molluscan body forms and provides genomic resources that are relevant to understanding molluscan evolution, biomineralisation, and biomimetic design.
在本研究中，我们展示了阴茎钟螺（林奈，1758年）的首个染色体水平基因组，这也是双壳贝类异韧带类的首个此类基因组。本研究有两个独立的重点。首先，我们提供遗传资源，以衔接从基因组到表型组的进一步研究，并提出假设以指导未来的实证研究。其次，基于形态学，我们概述了一项概念性探索，以探讨它们的适应性。喷水壶贝壳因其融合的管状贝壳类似喷壶的壶嘴而被称为“最奇特的双壳贝类”。这种不定管在棒蛎蛤类双壳贝类中曾两次趋同出现。然而，以往文献从未提供令人信服的适应性途径。
阴茎钟螺的基因组组装大小约为507 Mb，重叠群N50为5.33 Mb，96.5%的序列被锚定到19条假染色体上。结合其他双壳贝类对这个新基因组进行的系统基因组分析证实，异韧带类是不对称齿类进化枝的姐妹群。与其高度特化的身体结构预期相反，与异齿双壳贝类的祖先核型（1N = 19）相比，没有证据表明其染色体数目减少。借鉴工程学和形态学的既定原理，关于不定管的思想实验旨在通过探索与其他建筑结构的相似之处来扩展当前的理解。一个新的假设解释了这种身体形态适应性意义的一种可能解读：它可能在结构上针对相对松软沉积物中的垂直稳定性进行了优化，类似于吸力锚的工程原理。
虽然这里提出的关于形态学解释的结论是理论性的，但这为进一步的实证验证和完善奠定了基础。我们的研究为软体动物身体形态这一长期存在的谜团提供了新的见解，并提供了与理解软体动物进化、生物矿化和仿生设计相关的基因组资源。
