Australian droplet tunicate

The Australian droplet tunicate is a type of sea squirt that forms large colonies attached to hard surfaces. These colonies look like clusters of white or cream‑coloured tubes, often hanging together in groups. Each colony is made up of many tiny individual animals, and they can sometimes appear orange‑flecked because of the larvae inside them.

The colonies feel firm and slightly gelatinous to the touch. Individual tube clusters are usually between 5 and 30 centimetres long, but in some cases, they can grow much larger - up to 1.5 metres. Over winter, colonies shrink back to small cream‑coloured buds, before growing again into larger colonies in spring.

The Australian droplet tunicate competes with native species for both space and food. It grows quickly, can live in a wide range of habitats, and can build up in large numbers. There is also evidence it may ingest and kill the eggs and larvae of native species, which can further affect marine life.

When droplet tunicates occur at high densities, they can have significant impacts on habitats and the species that rely on them. That said, their impact is somewhat reduced by their seasonal pattern. They tend to be most abundant over summer and usually die back during periods of heavy rain and through the winter months.

This species is also a prolific breeder. It can reproduce for much of the year, from around October through to June. The larvae are free‑swimming for several hours before settling on surfaces, which helps the species spread. Reproductive output drops after heavy rainfall and in early winter, when colony sizes naturally shrink.