Orchid Island, Taiwan -- The nudibranch Hypselodoris apolegma laying an egg ribbon containing thousands of eggs on coral branches.
Nudibranchs lay their eggs in every size, color and shape imaginable from an oviduct located on the right side of their body. In some instances a single ribbon can contain up to 25 million eggs!
Most often the egg ribbon takes the shape of coils or spirals, but sometimes they appear as tangled masses of strings, chains of beads, or cylinders.
The egg ribbon is usually laid counterclockwise, which allows the nudibranch to achieve a better spiral shape and also to anchor the egg mass with its foot.
Some species produce eggs that are caustic or even toxic. These egg masses are usually brightly colored as a warning to potential predators.
Hypselodoris apolegma is considered a part of the Hypselodoris bullocki complex, but has recently been described as a distinct species.
Its brilliant pinkish-purple body color, yellow-orange gills and rhinophores, and the diffuse white mantle make it easy to recognize. At the edge of the mantle the border is solid white, but inside this is a region of varying width in which the white forms a reticulated pattern gradually merging into the pinkish purple.