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    An Octopuses garden


    An Octopuses garden

    By Darren Stevens

    First published in Aquarium World August 2013

    We have about 40 octopus species in our waters, including representatives of all twelve octopus families.

    Octopus are among the most intelligent of all invertebrates (animals without a backbone) and many shallow water species are masters at camouflage being able to change their colour and texture to suit their surroundings using chromatophores (pigment filled sacs under individual nervous control). This is despite the fact that they are colour blind. Most octopus species live on or close to the bottom, however there are several pelagic (live in the water column over deep water) species, many of which are found in New Zealand waters. Pelagic octopuses tend to have a gelatinous body and are often small. An exception is the rare pelagic species Haliphron atlanticus, which may be the largest of all Octopuses. The single incomplete specimen collected in New Zealand waters is the largest specimen known and is estimated to have weighed 75 kg’s and to have been about 4 metres long. The other contender for the world’s largest octopus is the giant Pacific octopus (Enteroctopus dofleini) which reaches at least 71kg. In stark contrast, the world’s smallest known octopus is the tiny star-sucker pygmy octopus (Octopus wolfi) which grows to only 1.5 cm in length and weighs less than 1 gram.

    Octopus are dived into two main groups: the incirrate octopus (Suborder Incirrata) which resemble our large common inshore octopus, and the cirrate or ‘dumbo’ octopus (Suborder Cirrata) which are much more bizarre. In this article we will look at a selection of the octopus species we have in New Zealand waters.

    Incirrate octopus

    Our large common inshore octopus, Pinnoctopus cordiformis (also sometimes called Octopus maorum) is a typical incirrate octopus with a sac-like, often lumpy body, two eyes, and four pairs of arms. There are a number of New Zealand cirrates with this general body plan. Here’s a selection.

    Common octopus

    Pinnoctopus_cordiformis_copy.thumb.jpg.9

    Pinnoctopus cordiformis  (Photo credit: Darren Stevens, NIWA)

    This large long-armed light to dark brown or red octopus needs little introduction. The common octopus grows to about 1.5 metres in total length (end of head-like body to tip of longest leg) and about 10 kg’s. Its inquisitive nature and coastal distribution mean it is frequently seen by divers and is a common display animal in large public aquariums. As juveniles common octopus are often found in tidal rock pools but as they mature they move out to deeper water. It is found around North, South, Stewart, and Chatham Islands, and Southern Australia from the intertidal zone to about 300 metres depth.

    Yellow octopus

    Enteroctopus_zealandicus_copy.thumb.jpg.

    Enteroctopus zealandicus (Photo credit: Darren Stevens, NIWA)

    The yellow octopus (Enteroctopus zealandicus) is striking large (to 1.4 metres total length) yellow to orange smooth-bodied octopus. It is found on the East Coast of the South Island from the Chatham Rise (an undersea ridge between the South Island and the Chatham Islands) to the sub-Antarctic Auckland and Antipodes Islands. It is generally found in deep water (300–522 metres), but in southern waters juveniles are found in the intertidal zone. The yellow Octopus is closely related to the giant Pacific octopus (E. dofleini), one of the world’s largest octopus species.

    The real Octopus

    Along with the large common and yellow octopuses there are also about 7 true Octopus species in New Zealand waters. Most New Zealand Octopus species are small ranging in size from about 13 to 40 cm in total length. Some of the smaller species would make great subjects for a saltwater aquarium and can be found in shallow water. Octopus huttoni grows to about 24 cm in total length and is found around New Zealand from the intertidal zone to 386 metres depth. Octopus kaharoa (pictured) grows to about 40 cm in length and is found from 7–540 metres depth on the east coast of the North and South Islands from the Poor Knights Islands to Kaikoura. Octopus gibbsi grows a little larger reaching 68 cm in length and is found on the northeastern coast of the North Island from the intertidal zone to about 40 metres depth. 

    Octopus_kaharoa_copy.thumb.jpg.9bb0ffc05Octopus kaharoa (Photo credit: Darren Stevens, NIWA)

    Along with these more ‘typical’ looking octopus there are few deeper water incirrate octopus that are a little more unusual. Here are a couple.

    Deepwater warty octopus

    Granelodone_taniwha_copy.thumb.jpg.74b63    

    Graneledone taniwha (Photo credit: Darren Stevens, NIWA)

    These unusual stocky octopus have clusters of cartilage-like warts on the head, mantle, and arms giving rise to their common name of deepwater warty octopus. There are 2 species of deepwater warty octopus (Graneledone species) in New Zealand waters found in 450 to 1500 metres depth.

    Thaumeledone zeissThaumeledone_zeiss_copy.thumb.jpg.cd0bd0Thaumeledone zeiss (Photo credit: Darren Stevens, NIWA)

    This endearing little octopus (to 12 cm total length) with short arms and big eyes doesn’t have a common name and is only known from a handful of specimens captured in very deep water (1000–1400 metres) off the east coast of the South Island. A related species is found in even deeper water.

    Cirrate octopus

    These spectacular deep-sea octopus are anything but typical and come in a variety of bizarre forms. All species have a semi-gelatinous body, a pair of fleshy ‘fins’ on the mantle (head-like body), strong webbing between the arms, and a row of cirri (minute fleshy finger-like projections) along each side of the suckers on a leg. Most species are an orange/red/purple colour and all species lack chromatophores, so they are incapable of changing colour. Most species live close to or on the sea floor and generally feed on small, slow moving prey, such as small crustaceans (amphipods - like the sand-hoppers found at the beach, and shrimps) and polychaetes (sea worms). Unlike the more typical-looking inshore octopus which can move rapidly by jet propulsion, dumbos generally move at a sedate, energy efficient pace; crawling along the bottom, drifting with the current, swimming using their large fins, or by pumping their webbed arms. There are about 9 species of dumbo octopus in New Zealand waters. Here are a couple of types:

    Umbrella Octopus

    Opisthoteuthis_robsoni_copy.thumb.jpg.58

    Opisthoteuthis robsoni (Photo credit: Darren Stevens, NIWA) 

    The bizzare gelatinous umbrella octopus (Opisthoteuthis spp.) look a little like a flattened jellyfish. However as with all cirrate octopus they have a pair of ear-like fins and eight strongly webbed arms, each with a single row of suckers. There are 3 species of umbrella octopus in New Zealand waters, which grow up to about 30 cm in length and depending on the species they can be found from 360 to 1700 metres depth.

    Dumbo octopus

    Cirroctopus_hochbergi_copy.thumb.jpg.610

    Cirroctopus spp. from the Ross Sea, Antarctica (Photo credit: Peter Marriott, NIWA) 

    With its large muscular fins resembling ears and plain coloration it’s not hard to see why these octopus are sometimes called dumbo octopus. The New Zealand species Cirroctopus hochbergi is found off the east coast of the North Island in 700 to 1350 metres depths. The remaining 3 species are found in Antarctic waters (including the one pictured above).

    So there we have it. An introduction to New Zealand’s cephalopods. So next time when see a common octopus or a broad squid during a dive in the sea, or dive into a feed of squid rings at your local takeaway just think of the many other cephalopods that make up New Zealand’s marine fauna.

    There are lots of other cool invertebrate critters on the NIWA Invertebrate Collection Facebook page (www.facebook.com/NIWAInvertebrateCollection).

    References

    Wikipedia (http://en.wikipedia.org)

    Tolweb (http://tolweb.org)

    Cook, S. de C.  (ed.) (2010). New Coastal Marine Invertebrates 1. Canterbury University Press. 640 pp.

    O'Shea, S. 1999. The Marine Fauna of New Zealand: Octopoda (Mollusca: Cephalopoda). NIWA Biodiversity Memoir 112: 280pp.

     

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