brachiolaria

Brachiolaria is a larval form in certain echinoderms, most commonly associated with starfishes (Asteroidea). It follows the bipinnaria stage in species that produce brachiolar larvae and represents a developmental transition toward the juvenile coral reef or rocky shore starfish. The defining feature of brachiolaria larvae is the appearance of one or more slender brachiolar arms and a stalk-like base that can anchor the larva to a substrate.

Morphology and feeding in brachiolaria larvae include ciliated bands for locomotion and feeding, with the brachiolar arms helping capture food and interact with the surrounding water. The stalk and adhesive structures allow temporary attachment to the substrate, facilitating metamorphosis in some species. The digestive system and other organ systems continue to develop during this stage.

Development and life cycle in this context involve progression from the brachiolaria to the juvenile starfish. After attachment and reorganization, the larva undergoes metamorphosis, during which the stalk is reduced or discarded and the typical radial symmetry and juvenile body plan emerge.

Ecology and diversity: brachiolaria larvae can influence dispersal and population connectivity by extending the free-swimming phase, though developmental pathways vary among species. Not all starfish lineages produce brachiolaria; some may exhibit alternative larval forms or skip this stage entirely. The term highlights one key larval morphology within the broader array of echinoderm developmental strategies.