Halisarca caerulea

Halisarca caerulea is a sponge species native to the Caribbean Sea. It is characterized by its thinly encrusting form, typically forming patches about 1.5 mm thick. The sponge has a smooth, slightly slimy surface with a reticulated pattern due to bundles of collagen fibers. It features long tubular choanocyte chambers and lacks spicules. The oscula are about 3 mm in diameter and are centered in a star-shaped group of superficial canals. The sponge is bright blue when alive, making it distinctive in its habitat. Halisarca caerulea inhabits shallow to moderately deep waters, ranging from 2 to 15 meters in depth. It is commonly found on dead coral in reef environments, as well as in mangroves. The sponge prefers the undersides of coral, overhangs, and crevices in both shallow and deep reefs. As a filter feeder, it draws in water through small pores, filtering out bacteria and organic particles, and expels the water through the oscula. Despite the nutrient-poor waters of the Caribbean, this sponge pumps large volumes of water to meet its nutritional needs. In terms of reproduction, Halisarca caerulea belongs to the class Demospongiae, which are hermaphroditic. The life cycle involves the development of a zygote into a free-swimming parenchymella larva, which eventually settles on a substrate to grow into a new sponge. The species has not been evaluated for conservation status by the IUCN, and it poses no threat to humans.