Siver Peter A
Department of Botany, Connecticut College, New London, CT, 06320, USA.
Sci Rep. 2025 Feb 12;15(1):5207. doi: 10.1038/s41598-025-88891-8.
Mallomonas is a species-rich genus within the chrysophycean order Synurales that originated in the lower Cretaceous, and today is a common constituent of planktic communities in a wide array of aquatic environments. Mallomonas cells are motile unicells with a cell covering consisting of siliceous scales and bristles, and the organisms also produce siliceous cysts as part of their life cycle. Because scales and cysts have species-specific designs, their remains in sediments and fossil localities are commonly used to infer past habitat conditions. Since mature cysts are rarely found with the diagnostic scales, the vast majority of cyst morphotypes have not been linked to specific species. Numerous scales with a morphology matching the modern species M. asmundiae were uncovered in an Eocene fossil locality near the Arctic Circle in northern Canada. Many of the scales were still attached to the cysts in their original arrangements. These unique specimens effectively linked the scales to a specific cyst type, and were further used to examine scale variability and the cell covering of this 48 Ma old synurophyte. Although scale structure was found to be variable compared to its modern congener, the arrangement of scales within the cell covering was highly conserved.
马洛莫纳藻属是金藻目合尾藻亚目内一个物种丰富的属，起源于白垩纪早期，如今是各种水生环境中浮游生物群落的常见组成部分。马洛莫纳藻细胞是可游动的单细胞，其细胞覆盖物由硅质鳞片和刚毛组成，并且这些生物体在其生命周期中还会产生硅质囊肿。由于鳞片和囊肿具有物种特异性的形态，它们在沉积物和化石地点的残骸通常被用于推断过去的栖息地条件。由于成熟囊肿很少与具有诊断性的鳞片一起被发现，绝大多数囊肿形态类型尚未与特定物种相关联。在加拿大北部北极圈附近的一个始新世化石地点发现了许多形态与现代物种阿斯蒙迪亚马洛莫纳藻相匹配的鳞片。许多鳞片仍以其原始排列附着在囊肿上。这些独特的标本有效地将鳞片与特定的囊肿类型联系起来，并进一步用于研究这种有4800万年历史的合尾藻的鳞片变异性和细胞覆盖物。尽管发现其鳞片结构与其现代同类相比存在差异，但细胞覆盖物内鳞片的排列高度保守。
