10 — Colonial ascidians

Compound ascidians,
Tamaki Drive, Auckland, 1/9/16.

Another colony of compound ascidians.
These are a different species to the ones above.
Tamaki Drive, 1/9/16.

This little animation shows the opening and
closing of siphons in a colony of ascidians.

Colonial ascidians are sea squirts. However, they differ from solitary sea squirts in that they are a colony of separate animals (solitary sea squirts are one animal and have an inhalant and exhalent opening). They also differ from solitary sea squirts in that each individual animal is smaller, but the colony is larger, and several individual animals will share an exhalent opening. Water goes in through the small openings, gets filtered for food, and is expelled out through the large, communal openings. Apart from a few carnivorous deep-sea species, sea squirts are filter feeders.

Being filter feeders, coolonial ascidians like to live in habitat with lots of current flow (so they get more opportunities to feed), so you tend to find them on wharf piles or on bridge supports. These particular colonies were from under bridges along Auckland’s Tamaki Drive.

From my observations over the last couple of years, I've noticed that these colonies are largest in winter and seem to break down over the summer months. These colonies were missing from these localities in the winter of 2018, which suggests that they have good and bad years.

They can be a range of quite bright colours from yellows to vivid oranges, reds, and purples.





More info:

This is NIWA's guide to common NZ ascidians (both solitary and compound):

https://www.niwa.co.nz/coasts-and-oceans/marine-identification-guides-and-fact-sheets/seasquirt-id-guide