FEEDING STRUCTURES, BEHAVIOR, AND MICROHABITAT OF ECHINOCYAMUS PUSILLUS (ECHINOIDEA: CLYPEASTEROIDA)

Abstract

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.

The Origin and Paleoecology of Clypeasteroid Assemblages From Different Shelf Settings of the Miocene of Sardinia, Italy

“…Occurrence in deep-water environments has been reported for the minute clypeasteroid Echinocyamus. This echinoid shows a wide geographical and ecological distribution ranging from tropical to temperate regions, where it lives from shallow water to a depth of 1250 m (Tortonese 1965;Telford et al 1983;Nebelsick and Kowalewski 1999;Zavodnik 2003;Degraer et al 2006;Grun et al 2014). Further, the sand dollar Echinarachnius parma, which occurs in the north Atlantic and Pacific, extends from the intertidal zone to depths of about 1600 m (Mortensen 1948b;Ellers and Telford 1984).…”

Biostratigraphy and palaeoecology of the marine Pleistocene of Rhodes, Greece: Scleractinia, Serpulidae, Mollusca and Brachiopoda

“…Telford et al (1983) showed that it most commonly occurs in substrates exposed to intensive wave and tidal activity, and exposure to strong currents seems an essential requirement. The common occurrence of E. pusillus in facies D and E therefore seems to indicate that these sediments were derived from shallow water above the fair-weather base.…”

Function of eponymous structures in echinoderms: a review

“…Märkel et al (1977) distinguished the grinding lantern of the Clypeasteroida from the gripping lantern of the regular echinoids. The teeth of the tiny fibulariid Echinocyamus pusillus chew ingested food (Telford et al 1983). Lovén (1892) noted the distinctive changes that occur in the highly modified Aristotle's lantern of sand dollars, which include compression and a pentagonal star shape with unequal sides and lantern structures.…”