Age determination in echinoderms: first evidence of annual growth rings in holothuroids

While age is fundamental in animal biology, forming the basis of critical concepts such as life-history strategies, longevity and population structures, measuring this variable in some taxa remains problematic. Such is the case of holothuroid echinoderms, which play key roles in marine benthic communities from the shore to the abyss, and are extensively fished in many regions across the globe. Here we present and validate a promising aging technique using the cold-water species Psolus fabricii. The method involves the extraction of the oldest dermal plates (largest dorsal ossicles) to preserve their original pigments and structure. While plates initially appear to have a uniform texture, polishing and dying them reveals layered ring patterns. A study of laboratory-reared juveniles, from settlement to 40 months of age, confirmed that one layer is added annually, making plates both larger and thicker, and generating successive light and dark rings, the latter representing the transition (...年龄是动物生物学的核心基础变量，为生活史策略、寿命及种群结构等关键学术概念提供了核心支撑，但在部分生物类群中，该变量的测定仍存在诸多难题。海参纲棘皮动物便是此类存在年龄测定难题的类群：它们从潮间带至深渊均在海洋底栖群落中发挥关键生态作用，且在全球诸多区域被广泛捕捞。在此，我们提出并验证了一项颇具应用前景的年龄测定技术，研究对象为冷水性物种法氏海参（Psolus fabricii）。该技术的操作流程为：提取最老龄个体的真皮板（最大的背侧骨片），以保留其原始色素与结构。尽管这类真皮板初始外观质地均一，但经过抛光与染色处理后，即可显现出分层的环状纹路。我们对实验室人工繁育的幼体——从附着定居至40月龄——开展研究，结果证实：该类真皮板每年新增一层纹路，伴随板体体积与厚度同步增长，同时形成依次排列的明暗相间环带，其中深色环带代表生长过渡（……