Ladder Ascidian

Overview

The ladder ascidian (Botrylloides leachii) is a colonial tunicate that forms soft, gelatinous, encrusting sheets on various marine substrates. It is a well-studied organism in biological research due to its remarkable ability to undergo whole-body regeneration from small tissue fragments.

Appearance

This species typically appears as a flat, fleshy, or gelatinous crust that can reach 15 cm or more in diameter. The individual zooids, which are about 4 mm in size, are often arranged in distinct, parallel, meander-like chains. Their coloration is highly variable, ranging from orange and yellow to brown, red, or violet, often with contrasting bands or spots.

Distribution & habitat

Widely distributed in temperate waters, the ladder ascidian is found from northern Norway to the Mediterranean and has been recorded in various regions across the globe, including parts of the Pacific and Atlantic. It commonly inhabits the lower shore and shallow sublittoral zones, where it encrusts rocks, shells, and large brown algae.

Biology & behavior

As a colonial invertebrate, it functions as a filter feeder. It possesses complex developmental strategies, including both sexual reproduction via free-swimming tadpole larvae and asexual reproduction through budding. Its capacity for whole-body regeneration allows it to restore a fully functional colony from isolated vascular tissue in as little as 10 days, making it a key model for studying stem cells and immunology.