57 — Polyclad flatworm, Thysanozoon cruciatum

Thysanozoon cruciatum, under Ngapipi Bridge,
Tamaki Drive, Auckland, 19/10/16.

Thysanozoon cruciatum, Takapuna Reef,
Auckland, 2015. The head is on the left.

Thysanozoon cruciatum, under Ngapipi Bridge,
Tamaki Drive, Auckland, 19/10/16.

Thysanozoon cruciatum, under Ngapipi Bridge,
Tamaki Drive, Auckland, 19/10/16.

Thysanozoon cruciatum, under Ngapipi Bridge,
Tamaki Drive, Auckland, 19/10/16.

Thysanozoon crucatum, Takapuna Reef,
Auckland, 2015.

Polyclad flatworms are superficially similar to sea slugs, but belong in the order Polycladida; the name referring to the many branches of their gut. There are several species found in the Auckland region and this one is Thysanozoon cruciatum Schmarda, 1859. They get their name from the cross-like lighter area on their dorsal surface. I think that Thysanozoon might be my favourite genus name; it sounds like the name of an anime villain.

Anyway, it doesn't look these animals have been well studied in New Zealand waters and it's difficult to get information regarding their distributions. However, T. cruciatum is thought to be endemic to New Zealand (de Cook, 2010).

Polyclad flatworms are thought to be either predators or scavengers. They can be really bright colours or they can be camouflaged.

They are quite beautiful when they swim; even though these ones mostly crawl around like a small shag-pile rug. This species reminds me of a bathroom mat I used to own.






































More info:

An identification key:
http://pick4.pick.uga.edu/mp/20q?guide=Rhabditophora&flags=not_no:

https://www.rzuser.uni-heidelberg.de/~bu6/flatintr.htm

de Cook, S. (2010). New Zealand coastal marine invertebrates. Canterbury University Press, Christchurch.