Two Nembrotha chamberlaini in the mating act. Komodo. Indonesia
Nudibranchs, a common group of shell-less snails collectively know as sea slugs, are simultaneous hermaphroditic with reproductive organs of both sexes. After reaching sexual maturity, the short-lived mollusks have only a few days to a few months to find a mate, copulate and lay eggs. Courtship involves little more than two animals, attracted by pheromones, moving into a side-by-side, head-to-tail position, which place their reproductive organs ( always located on their right sides ) in close proximity. Frequently, lingering pheromones attract the attention of third parties that attempt to break into the action.
One genital papillae thouch, the penis of each extends into the female duct of the other simultaneously fertilizing both partners. the internally impregnated eggs first acquire a nutrient layer, then a capsule before they are bound together by mucus into ribbons, which are characteristically laid in counterclockwise spirals that emerge from the same reproductive opening. The typically brightly colored masses indicate the eggs' caustic or toxic nature intended to repel predators.
Hypselodoris tryoni (up) and Hypselodoris pulchella (down) mating. Komodo
Chromodoris villani mating.
Mating sequences of two Flabellinopsis iodina.
Phases of approach.
One genital papillae thouch, the penis of each extends into the female duct of the other simultaneously fertilizing both partners.
After mating the Nudibranchs will stick eggmass ribbons to rocks or algae.
Halgerda batangas laying its yellow eggs. Bunaken N.P. Indonesia
Doriprismatica astromarginata laying its eggs on corals. Lembeh Strait. Indonesia.