A new Philippine ophiuroid symbiotic on a cassiduloid echinoid species

The small new brittle star Amphipholis conolampadis sp. nov. is reported from semi-infaunal cassiduloid echinoids Conolampas diomedeae collected at 75–300 m water depth at two sites in the Philippines. The ophiuroids show a preference to attach to the oral side of the echinoids, clustering in the region around the mouth. Orientation of the brittle stars, in contrast, seems to be random and ophiuroids appear to use echinoid spines for anchoring on the host. Neither detrimental effects could be observed in the sea urchins, nor do echinoid specimens bearing ophiuroids show differences in growth or size range. Clear evidence for a parasitic nature of the association is thus missing. Evidence for mutualism and commensalism is likewise weak, but seems more likely than parasitism. A review of echinoid–ophiuroid associations reported in the literature shows a strong dominance of amphiurids, associated mainly with irregular echinoids.