ABSTRACT
In echinoderms, the fertilisation envelope is typically smooth, but ornate fertilisation envelopes (with ridges) have been reported for 9 crinoid species (reviewed in Holland 1991, Nakano et al. 2003, Kohtsuka and Nakano 2005). In addition, 3 Ophiocoma species in the Ophiuroidea are known to have thorny fertilisation envelopes (Mortensen 1937). Several roles for these ridged structures in crinoid eggs have been suggested; to enhance buoyancy thereby facilitating dispersal of embryonic stages and to provide protection against filter feeding predators (Mortensen 1920, Holland and Jespersen 1973, Mladenov and Chia 1983). Here, we document the presence of ornate fertilisation envelopes in two additional Ophiocoma species (Ophiocomidae, Ljungman 1867), and describe the structure of the ridges in Ophiocoma eggs using confocal scanning electron microscopy.
