What does it look like?
The Eudistoma sea squirt, also known as the Australian droplet tunicate, is a type of sea squirt. It forms large colonies that attach to hard surfaces and look like clusters of white or cream-coloured cylindrical tubes . Each colony contains numerous small individuals and they can appear orange flecked due to the colour of the larvae within them. The species is firm and gelatinous to the touch and the cylindrical colonies are generally 5-30 cm long, but can occasionally reach 1.5 m in length. Colonies are generally 5-20 mm in diameter and regress and over-winter as small (c.10 mm) cream buds, re-growing the following spring to larger colonies.
This species is generally found in soft-bottomed tidal habitats and on hard structures such as wharf piles, aquaculture equipment and mangrove roots. It prefers submerged habitats just below the waterline, but can be found out of the water for periods during low tide.
Why is it a problem?
The Eudistoma sea squirt competes with native species for both space and food. It has a rapid growth rate, can inhabit a wide range of habitats, and can reach high abundances. It is also possible that it can ingest and kill the eggs and larvae of native species. When present in high densities the Australian droplet tunicate has the potential to have significant impacts on habitats and species. However some of the competitive ability of this species is minimised by the fact it is only present in large numbers during summer months and dies down during rain events and winter months.
This species is also a prolific breeder, reproducing for at least nine months of the year, from October through to June (Spring to late Autumn). The larvae are free-swimming for approximately six hours before they begin to settle on surfaces. Reproductive output decreases after high rainfall and in the early winter months due to the colony size also decreasing.
You can help prevent the spread of marine pests by:
• Regularly cleaning your boat’s hull – ideally keep fouling growth to no more than a light slime layer.
• Applying good thorough coatings of antifouling paint and keep it in good condition
• Ensuring your hull is clean and free of fouling before you go travel to a new region
• Cleaning and drying any marine equipment (e.g. ropes, lines, pots) before using in a new location.
• Inspecting areas on your boat that retain water in case they’re harbouring marine life.
• Checking anchors, trailers and other equipment for tangled weeds.