11 — Tubulariid athecate hydroids, Ectopleura sp.

A colony of Ectopleura sp.
from under Ngapipi Bridge,
Tamaki Drive, July 2018.

A colony of athecate hydroids (Ectopleura sp.)
from under Ngapipi Bridge, Tamaki Drive,
Auckland. In the top right corner is the
medusa of another hydroid: Turritopsis.
July 2018.

Hydroids are animals related to jellies and corals and are found within the class Hydrozoa. Athecate hydroids are found in the order Anthoathecata. Theca means case in Greek, so athecate means ‘without case’. For hydroids this means that the polyp (the flowery-looking bit) is not surrounded in a protective sheath.

A colony of Ectopleura sp.
low tide, Tamaki Drive, 1/9/16.

These particular hydroids are from the family Tubulariidae and are in the genus Ectopleura. There are a few similar-looking species and to identify them you need to look at their stinging cells under a microscope (de Cook 2010).

They like to live in habitat with lots of water flow, so you often find them on wharf piles and bridge supports. Ectopleura forms colonies in clumps, which can be made up of dozens of individuals. The colonies seem to be transient, although their longevity seems unclear.

















More info:

De Cook S., (ed) 2010. New Zealand Coastal Invertebrates 1. Canterbury University Press.

Morton, J. E., & Miller, M. M. 1968. The New Zealand Sea Shore. Collins.

https://www.britannica.com/animal/hydroid-hydrozoan