Due to their sensitivity and dramatic declines, freshwater mussels are prime targets for conservation and environmental monitoring. For this, however, information is needed on life history and ecological traits, which is lacking in many taxa, including threatened species. Species recently described or recognized as valid are of particular concern, due to the shortage of even basic knowledge. A case in point is the recently recognized and Near Threatened dolphin freshwater mussel Unio delphinus Spengler, 1793, which is endemic to the western Iberian Peninsula and has suffered marked population declines. To overcome information gaps for U. delphinus, we carried out a holistic biological study across the species range, aiming to: i) estimate the area of occupancy (AOO) and extent of occurrence (EOO) based on updated distribution data taken from the literature and recent surveys; ii) estimate growth patterns from biometrical (shell dimensions and growth annuli) measurements taken on specimens from seven populations; iii) estimate sex ratios from gonad tissue biopsies collected on specimens from eight populations; iv) estimate gametogenesis and sex ratio through histological examination of gonad and gill tissues collected monthly for a year, from a single population; and v) determine host species from infestation trials of glochidia with co-occurring fish species. We estimated an EOO of 706 km² and an AOO of 61 km², which together with data on declines assigns the species to the Endangered category using IUCN criteria. Unio delphinus was found to grow faster and to be shorter-lived (up to 11 years, maturity at around 2 years old) than other European freshwater mussels. Growth and life span are similar across the range in lotic habitats, but different from that in lentic habitats. The larvae of U. delphinus may attach to most co-occurring fish species, but only native species were effective hosts. Native cyprinids, especially those from the genus Squalius, seem to be the primary hosts. Overall, the information provided contributes to a better conservation status assessment, selection of conservation and rehabilitation areas, guidance for the establishment of propagation programs and better timing for specimens’ manipulation including monitoring and possible translocations. The framework presented here highlights the importance of basic biological studies to define good ecological and physiological status.

由于它们的敏感性和急剧下降，淡水贻贝是保护和环境监测的主要目标。但是，为此，需要有关生活史和生态特征的信息，这在包括濒危物种在内的许多生物分类中都缺乏。由于缺乏基本知识，最近被描述或被认为是有效的物种尤其令人关注。一个典型的例子是最近认识到的濒临灭绝的海豚淡水贻贝Unio delphinus Spengler，1793年，它是伊比利亚西部半岛的特有种，人口显着减少。克服U. delphinus的信息鸿沟，我们在整个物种范围内进行了全面的生物学研究，旨在：i）根据从文献和最新调查中获得的最新分布数据，估计居住面积（AOO）和发生程度（EOO）；ii）根据对七个种群的标本进行的生物特征（壳尺寸和生长环）测量来估计生长方式；iii）从八类人群的标本中收集的性腺组织活检样本估计性别比；iv）通过组织学检查一年一次每月从单个人群收集的性腺和g组织，估计配子发生和性别比；v）从球虫和共生鱼类物种的侵染试验中确定寄主物种。我们估计EOO为706 km ²，AOO为61 km ²，再结合下降数据，使用IUCN标准将该物种归为“濒危”类别。发现Unio delphinus比其他欧洲淡水贻贝生长更快，寿命更短（长达11年，成熟时约2岁）。在整个抽水栖息地中，其生长和寿命均相似，但与长镜头栖息地不同。U. delphinus的幼虫可能会附着在大多数同时出现的鱼类上，但是只有本地物种才是有效宿主。本地塞浦路斯人，特别是来自Squalius属的人，似乎是主要的主机。总体而言，所提供的信息有助于更好地进行保护状况评估，选择保护区和修复区，为制定传播计划提供指导，以及为标本处理提供更好的时机，包括监测和可能的易位。这里介绍的框架突出了基础生物学研究对定义良好的生态和生理状态的重要性。