Brittle stars

Most brittle stars reproduce sexually.

An excerpt from the article 26 facts about Brittle stars
Gametes are being produced inside the central disc and released to the external environment when fully developed. There, fertilization takes place. From the zygote, a larva develops which, contrary to adult individuals has bicubic symmetry. There is a high probability of different larvae forms among other brittle star species, but as only 2% were examined, discoveries are yet to come.