Colonial Sea Squirt

<em>Botrylloides violaceus</em>, a colonial sea squirt in the class Ascidiacea, is a tunicate in the family Styelidae found across European coastal waters and naturalised in North America and Australia. This species has not been evaluated by the IUCN. Colonial tunicates of the genus <em>Botrylloides</em> are sessile, filter-feeding invertebrates that form encrusting colonies on hard substrates including rocks, dock pilings, boat hulls, and kelp holdfasts. Each colony consists of numerous individual zooids embedded in a shared gelatinous tunic matrix, through which a common vascular system circulates. <em>Botrylloides violaceus</em> is considered an invasive species in many regions outside its presumed native range in the northwest Pacific, where it outcompetes native fouling communities and can smother shellfish aquaculture. The species reproduces both sexually, releasing lecithotrophic larvae, and asexually through budding, enabling rapid colony expansion. Its ability to tolerate a wide range of temperatures and salinities contributes to its success as an introduced organism in temperate coastal habitats. Biological traits of this species remain poorly documented in the scientific literature.