Deep-sea finned Octopoda of New Zealand

By Dr. Steve O'Shea

Note: Steve welcomes discussion in TONMO.com's Opisthoteuthidae forum.

S. O'SHEA
Earth and Oceanic Sciences Research Institute
Auckland University of Technology
Private Bag 92 006
Auckland, New Zealand

The most often-cited distinction between a squid and an octopus is in the number of arms and tentacles – squid usually have eight arms and two tentacles, while octopus have only eight arms. It also has been said that squid possess fins, whereas octopus do not, but neither generalisation is entirely true. Some squid have only eight arms in the adult form, and some specimens of octopus are known with more or less than eight arms (although they never have tentacles). Furthermore, many deepwater octopus species possess well-developed fins. In fact, one of the most fundamental differences between octopus and squid is that squid possess circular-saw-like rings or talon-like hooks on the suckers, whereas octopuses do not (their suckers are simple suction cups).

Squid and octopus are amongst the most conspicuous and interesting components of fisheries bycatch. Although little is known of the New Zealand squid fauna, a revision of the local octopus fauna is complete; as a consequence, the number of species known from local waters nearly tripled.

There are two basic types of octopus, those with fins (cirrates) and those without (incirrates). Cirrate octopuses are extremely primitive, generally rare, and usually found on the seafloor at depths in excess of 300 m (world wide, they are known to depths of 7500 m). Incirrate octopuses are more common, and are found from rock pools to depths of 3500...
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About the Author
Steve O'Shea
Steve is an expert in the systematics and biogeography of cephalopods, and joined the TONMO.com staff in June 2002. He can be seen on the Discovery Channel documentary, Chasing Giants: On the Trail of the Giant Squid. For more information, see his Autobiography and Select Bibliography (2003). Dr. O'Shea lives in New Zealand.

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