The deep-sea finned Octopoda of New Zealand

The deep-sea finned Octopoda of 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 circularsaw-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 m (these are ‘typical’ or ‘common octopuses’).
Forty-two octopus species are now known from New Zealand waters; 10
cirrate species and 32 incirrate species. Despite this we probably have a limited
understanding of the real diversity of deep-sea octopus species, largely because of the
limited specimens known from such difficult-to-access environments. For example,
only 10 local octopus specimens are known from depths below 1400 m, despite the
fact that between coordinates 24.5–57.5’S, 157.0’E–167’W more than 50% of the
seafloor lies between 3000 and 8000 metres.
The location of all known deep-sea octopus captures around New Zealand is
shown in Figure 1. Species collected in areas not already sampled, or in areas marked
by arrows (a huge proportion of the seafloor), are quite likely to be new to science.
Not one deep-sea octopus has been collected from the Kermadec Island region since
1873; none was known from either the Louisville or Norfolk Ridges, and the Lord
Howe Rise until the NORFANZ expedition this month; very few are known from the
west coast of the North and South Islands, and few are known from local seamount
environments.
None of the following species is considered common (three are known from
single specimens only). Although each has a formal scientific name, each has been
given a common name also.
Order: Octopoda
Suborder: Cirrata (finned) octopuses
Opisthoteuthis spp. (umbrella octopuses)
Three new Opisthoteuthis species are recognised from New Zealand waters.
Generally species in this genus are squat-bodied, low in profile, lump-like and quite
gelatinous. Their colour usually ranges from pink to dark red, with rows of palecoloured blotches (areolar spots) running over their bodies.
Opisthoteuthis mero O’Shea, 1998 (Mero’s umbrella octopus; Figure 2).
This is our most common cirrate species, found between depths of 300 and 1000 m.
Currently it is known only from soft substrates, and was particularly common as a
bycatch species from the scampi fishery in the Bay of Plenty and around the
Auckland Islands (although it does not appear as common today as it was a decade or
so ago). This species has also proved abundant on the Wairarapa coast and Chatham
Rise. The animal attains a moderate size (to several kilograms), and is quite inedible
(although it is known from sperm whale gut contents). This species is presently
considered endangered, and in places locally extinct.
Opisthoteuthis chathamensis O’Shea, 1998 (roughy umbrella octopus; Figure 3)
A rare, deep-water species known from depths exceeding 1000 m off the Wairarapa
coast and Chatham Rise. It occasionally occurs in bycatch from the orange roughy
fishery. The animal is small bodied (fits into palm of hand), and the suckers along the
arms are comparatively few in number (less than 60), and quite enlarged (and
bulbous) in the oral region of the male’s mouth and also half-way along the arms.
The colour ranges from dark red to maroon, with a few pale white blotches. This
species is presently considered endangered.
Opisthoteuthis robsoni O’Shea, 1998 (deep-water umbrella octopus; Figure 4)
This very rare, large-bodied, deep-water species is known only from several male
specimens taken on the Chatham Rise at depths below 1300 m. In general
morphology it is similar to the two previous Opisthoteuthis species, but differs
notably from them in anatomy.
Cirroctopus hochbergi O’Shea, 1998 (4-blotched umbrella octopus; Figure 5)
This cirrate is recognised from the Wairarapa coast, East Cape, and from several
specimens recently collected off seamounts in the Bay of Plenty. Otherwise, the
distribution of this genus is restricted to Antarctic waters, where two other species are
known. It is known only from seamount and cold seep environments off New
Zealand, while the closely related Antarctic species are known from soft sediments. It
is distinguished from other cirrates by having two large, white blotches beneath the
eyes, and a second pair of smaller white blotches at the base of the fins, a muscular
body, and a dark-purple colouration. This species probably has a more extensive
distribution than now recognised; any specimens of this easily identifiable species
would be most valuable to science. Historically, this species was relatively common
off East Cape and Napier, although no specimen is known from either location for the
past 2 years. It is presently considered endangered, and locally extinct.
Grimpoteuthis abyssicola O’Shea, 1998 (red jellyhead; Figure 6)
Typical of the genus is the marked contrast in colour of the mantle and head from the
arms and web; in the New Zealand species the animal’s head and body are almost
transparent, while the arms and web are delightfully pigmented in a markedly
contrasting rich maroon (other species may be red, purple, or nearly black). Given the
abyssal depths this genus frequents it is unlikely that species are endangered (trawling
at this depth is rare in New Zealand waters). However, given their highly gelatinous
and delicate tissues, species in this genus are extremely susceptible to damage in trawl
nets.
Enigmatiteuthis innominata O’Shea, 1998 (small jellyhead; Figure 7)
This very rare species is represented in museum collections by two immature
specimens, collected together off the Chatham Rise at c. 2000 m. The animal when
mature is probably small (fitting in two outstretched palms), dark red to maroon over
all body surfaces, and elongated along its axis to give it a bell-shaped, longer-thanwide appearance; the fins are quite large.
Cirroteuthis sp. (big-finned jellyhead; Figure 8)
This extremely rare species is known only from a single specimen captured with
Enigmatiteuthis from c. 2000 m on the Chatham Rise. Three specimens of a similar
animal, possibly the same species, are known from Australian waters (Museum of
Victoria collections). This is the first Southern Hemisphere record of this very rare
genus (previously known only from the North Atlantic and North Pacific). The New
Zealand and Australian specimens probably belong to a separate species, although
additional specimens are required to fully resolve all the problems currently faced in
identifying it. The animal is probably small at maturity, and highly gelatinous, and
with its large fins, small eyes, and extremely long filament-like structures originating
from the between the suckers along the arms, is quite distinctive.
Luteuthis dentatus O’Shea, 1998 (Lu’s jellyhead; Figure 9)
This extremely rare animal is known only from 4 specimens, three from New Zealand
waters and one from off Macquarie Island (Australian waters). It is one of the most
interesting cirrate species known for it possesses a radula (teeth-like structures present
within the mouth of the animal, between the beaks — used for rasping prey into small
hunks); it is one of only three species known that possesses such a structure. This
species is extensively gelatinous, the fins are very large, their margins evidently
tinged with red to pink, and the arms are exceedingly long. A related species,
Luteuthis shuishi O’Shea & Lu, 2002, has recently been described from the South
China Sea.
?Cirrothauma sp. cf. Cirroteuthis magna Hoyle (big-eye jellyhead; Figure 10)
This species, which has an extremely long and confusing name, is known from New
Zealand waters by a single, large, damaged specimen. This animal probably grows to
over 1 m in total length; it is extremely gelatinous, delicate, and probably transparent
when fresh. It is not a particularly deep-dwelling species, and several specimens
known from Australian waters, like the New Zealand specimen, were collected at
about 1000 m depth. All specimens are damaged; hopefully with the capture of better
specimens we will be able to describe the species more fully, and perhaps allow us to
shorten its name.
Discussion
Scientists world-wide now recognise New Zealand marine cephalopod
collections to be amongst the most comprehensive of their kind for any EEZ. Our
fauna contains many interesting, bizarre, and previously unknown species. It is most
apparent, however, that almost daily species new to New Zealand or to science in
general are being discovered, particularly amongst bycatch retained from commercial
and research deep-sea trawling operations. Tragically, it is also apparent that some of
these deep-water finned-octopus species appear on the verge of extinction.
Although the New Zealand octopus fauna is relatively well known, our squid
fauna is not, although it currently is being revised. We’ll try and update the fauna on
a family-by-family basis in the months to come.
Kermadec Islands
Three Kings Islands
Opisthoteuthis spp.
Cirroctopus sp.
Grimpoteuthis sp.
CHALLENGER PLATEAU
new genus 1
new genus 2
CHATHAM RISE
Chatham Islands
Cirroteuthis sp.
Bounty Island
?Cirrothauma sp.
Stewart Island
BOUNTY PLATEAU
Auckland Islands
Antipodes Islands
CAMPBELL PLATEAU
Campbell Island
Figure 1. Recognised distribution of deep-sea octopods represented in New Zealand
museum collections. Arrows depict environments from which new species or new
distribution records are most likely. For ‘new genus 1’ read Enigmatiteuthis; for ‘new
genus 2’ read Luteuthis.
2
3
4
Figures 2–4, Opisthoteuthis spp., oral and aboral views: 2, O. mero; 3, O.
chathamensis; 4, O. robsoni.
5
7
8
6
Figures 5–8, dorsal and ventral views: 5, Cirroctopus hochbergi; 6, Grimpoteuthis
abyssicola; 7, Enigmatiteuthis innominata; 8, Cirroteuthis sp.
9
10
Figures 9, 10, dorsal views: 9, Luteuthis dentatus; 10, ?Cirrothauma sp. cf.
Cirroteuthis magna Hoyle.