66 — Red warratah anemone - Actinia tenebrosa

Actinia tenebrosa, Tamaki Drive,
Auckland, 12/15.

Actinia tenebrosa, Tamaki Drive,
Auckland, 12/15. The small snail just above the
anemone is Risellopsis varia (Hutton, 1873).

Actinia tenebrosa, Tamaki Drive,
Auckland, 12/15.

The red warratah anemone (Actinia tenebrosa Farquhar, 1898) is the anemone most people see around New Zealand as a small dark reddish blob at mid-tidal level. It's found throughout New Zealand and the southern parts of Australia. This is a very hardy species and has been known to tolerate temperatures of up to 49°C in western Australia.

It is thought that its distribution is controlled by predators on the lower shore: it could live lower, but there are animals there which can eat it if it tries to, so it survives higher up where they can't reach it.

In New Zealand waters red warratah anemones can be eaten by the sea-slug Pleurobranchaea maculata if they get too low on the shore and juveniles can be mowed down and squashed by chitons. This is a good example of how an intertidal animal's distribution can be controlled by biological and not physical factors (e.g., desiccation, wave exposure).