Polybranchia (gastropod)

Polybranchia is a genus of sea slugs, specifically aeolid nudibranchs, marine gastropod mollusks in the family Hermaeidae. These small, often vibrantly colored, sea slugs are characterized by their numerous cerata, or dorsal appendages, which are arranged in clusters or branches along the body. These cerata serve a dual purpose, functioning both for respiration and for the storage of nematocysts obtained from their cnidarian prey.

The genus Polybranchia is found in various tropical and subtropical marine environments. They are typically found grazing on algae and hydroids, from which they obtain their nematocysts. The nematocysts are then stored undischarged in specialized sacs, called cnidosacs, at the tips of their cerata, providing a defensive mechanism against predators.

Species within the Polybranchia genus are distinguished by subtle variations in color, cerata arrangement, and other morphological features. Identification can often be challenging and requires careful examination.

The classification of species within Polybranchia has been subject to revision and ongoing research. New species are occasionally discovered, and the phylogenetic relationships between existing species are continually refined through molecular and morphological studies.