Palolo

Palola viridis, commonly known as the palolo worm, Samoan palolo worm, balolo, wawo, or nyale, is a Polychaeta species from the waters of some of the Pacific islands, including Samoa, Tonga, Fiji, Vanuatu, the Solomon Islands, Papua New Guinea, and the islands of the maritime Southeast Asia (which are part of Indonesia, Timor-Leste and the Philippines ). Reproduction involves mass spawning at night in spring or early summer (October – November in the Southern Hemisphere). The terminal parts of their bodies drop off and float over the surface of the water, releasing sperm and eggs. The mechanisms or triggers which induce spawning such that it occurs during nights of a waning moon, continuing for several nights, are not completely known. Exposure to sunlight destroys this "tail" part of the worm's body afterwards. In Fiji, the palolo worms' rising is preceded by the descent of a local red land crab to the sea the same night. In Samoa a crab known as mali'o also descends to the sea around the time when palolo rises. Other sea creatures such as sharks and fishes come to spawn during the event.

Source: Wikipedia