Telford Malcolm, Harold Antony S, Mooi Rich
Biol Bull. 1983 Dec;165(3):745-757. doi: 10.2307/1541476.
In the Firth of Lorne, Scotland, Echinocyamus pusillus was found most abundantly in highly variable, poorly sorted substrates at depths of 10-20 m. It was common in areas exposed to extensive wave and tidal current activity, but absent in fine sediments in sheltered areas. In size, feeding mechanism, and behavior, the species is highly adapted for nestling in the interstices between relatively large pebbles. The feeding mechanism is atypical for clypeasteroids: substrate particles with attached organisms are selected and transported by the suckered podia. At the mouth, particles are held in place and slowly rotated by the free margin of the peristomial membrane, while the teeth strip away diatoms and organic debris. The peristomial membrane and ciliation of spines and podia are shown in scanning electron micrographs of critical point dried material. The histology of these structures is described with special reference to mucus secretion. High resolution SEM micrographs show mucus secreting pores among the epithelial microvilli of suckered and buccal podia but not in the epithelium of miliary spines. The suggestion that E. pusillus might represent a sand dollar ancestor is discussed. The evidence presented supports the view that it is specialized rather than primitive.
在苏格兰的洛恩湾，微小海胆在深度为10至20米、高度可变且分选差的基质中数量最为丰富。它在受到广泛波浪和潮流活动影响的区域很常见，但在避风区域的细沉积物中不存在。在大小、摄食机制和行为方面，该物种非常适合在相对较大的卵石之间的空隙中栖息。其摄食机制在楯海胆类中是非典型的：带有附着生物的基质颗粒被有吸盘的管足选择并运输。在口部，颗粒被围口膜的自由边缘固定在原位并缓慢旋转，同时牙齿剥离硅藻和有机碎屑。临界点干燥材料的扫描电子显微镜图像显示了围口膜以及棘和管足的纤毛。这些结构的组织学特别参考了黏液分泌进行了描述。高分辨率扫描电子显微镜图像显示，有吸盘和口部管足的上皮微绒毛中有黏液分泌孔，但在粟粒状棘的上皮中没有。文中讨论了微小海胆可能代表沙钱祖先的观点。所提供的证据支持了它是特化而非原始的观点。
