113 — Bioluminescence and camouflage in the deep-sea

Once you get down to 1000m in the ocean sunlight is gone, absorbed by the water above.

One thing I noticed during my doctoral research was that many of the fishes at this depth were drab shades of brown, some darker than others. If you live in a world of complete darkness why be brown? For that matter why be any colour at all, what evolutionary advantage could being brown give you?

Well the thing is—it’s not completely dark at these depths—far from it. There may no longer be any sunlight, but there is light from other sources. The world at 1000m is full of point-source bioluminescence, created by the animals that live there. Watch this great TED talk by marine scientist Edith Widder for a more detailed look at deep-sea bioluminescence.

If you’ve watched that talk, you may have noticed that most of the bioluminescence was light-bluish. Now the interesting thing here is that if you invert light blue: you show the colour not being reflected by that object, and that is brown.

What does this mean: If you are a brown fish in a world where the only light is bluish, then you are camouflaged against it, since brown absorbs blue.

Big-scaled slickhead (Alepocephalus australis),
northestern Chatham Rise, 1196m.

Big-scaled slickhead - inverted colour.

Baxter's dogfish (Etmopterus baxteri),
Puysegur Seamount, 1050m.

Baxter's dogfish - inverted colour.

Warty oreo, (Allocyttus verrucosus),
northeastern Chatham Rise, 901m.
~30cm total length (TL).

Warty oreo - inverted colour

The photos show a few examples of brown-coloured fishes and what they look like when the colour is inverted; that is, the colour they absorb.

Apologies for my dodgy 2004 photography. Thanks again to NIWA for providing the fishes.

112 — Gruesome creatures live in the deep-sea…

I took a lot of pictures during my doctoral research, most of which I didn’t end up using for anything. Occasionally though, I would stumble upon something interesting, and by interesting I mean horrific.

A parasitic copepod attaching through the
body wall of a notable rattail.

Fish are often beset by parasites, not only internally, but also externally. Some of the external ones can be quite hideous. In this instance a notable rattail (Coelorinchus innotabilis, McCullock, 1907) has been attacked on its underside by a parasitic copepod. Copepods are crustaceans and these belong in the Order Siphonostomatoida and within that, probably the family Sphyriidae.

Sphyriid copepods attach through (yes, that’s through) the body wall of the fish by means of an anchored stalk and feed on the fish’s bodily fluids. The part you see on the outside is the body of the copepod and it’s reproductive parts ( ~1 cm). These particular copepod parasites are thought to only attack fishes that live close to the bottom and this feature can be used to ascertain details regarding the fish’s habits in lieu of other information. This was corroborated by the diet of this species, as notable rattails are bottom feeders (Jones 2008).

Notable rattail, NE Chatham Rise, 901m

Notable rattail, NE Chatham Rise, 901m.
Dorsal view.

Notable rattail, NE Chatham Rise, 901m.
Ventral view.

Don’t worry though, as these parasites don’t attack people (as far as I know). Plus, they tend to live in deep-water and if you happen to find yourself down at 1000m you probably have bigger problems.

As for the fish itself, rattails are ubiquitous in the deep-sea and about sixty species occur in New Zealand waters. Notable rattails live at an average depth of 985m (Anderson, et al. 1998), so most people won't have seen one. These came from a research trawl for orange roughy, which occurred on northeastern Chatham Rise, during July 2004 (Thanks go to NIWA).

Notable rattails feed on small invertebrates, which they pick from the sea bed (Jones, 2008). As such, they play an important role in the structuring of demersal (near the bottom) communities.























More info:

Anderson OF, Bagley NW, Hurst RJ, Francis MP, Clark MR, McMillan PJ 1998. Atlas of New Zealand fish and squid distributions from research bottom trawls. NIWA Technical Report 42.

Doonan IJ, Dunn MR, Dunford A, Hart AC, Tracey D 2006. Acoustic estimates of orange roughy abundance on the northeastern and eastern Chatham Rise, July 2004: wide-area and hill survey. New Zealand Fisheries Assessment Report 58.

Jones MRL 2008. Dietary analysis of Coryphaenoides serrulatus, C. subserrulatus and several other species of macrourid fish (Pisces: Macrouridae) from northeastern Chatham Rise, New Zealand. New Zealand Journal of Marine and Freshwater Research 42: 73–84.

111 — Wheel shell, Zethalia zelandica

Zethalia zelandica, north Piha Beach, 27/4/17.
These aren't that common here on the west coast. 

Zethalia zelandica, showing animal and
position in the sand. After Morton & Miller,
1968, p467.

The wheel shell, Zethalia zelandica, * is a small (~20 mm across), gastropod endemic to New Zealand and found throughout the three main islands. They are found off exposed sandy beaches and can wash up in great numbers after storms, particularly on the north eastern coast of North Island.

There are some morphological differences over their range, with examples from Stewart Island being higher in the spire and correspondingly narrower than those from the northeast of North Island. I can remember walking around the base of Mt. Maunganui as a boy and seeing banks of dead shells.

Wheel shells are thought to feed on diatoms and other organic matter; they do this through the ingestion of large amounts of sand, although their ecology isn't really all that well-known.

* (Hombron & Jacquinot, 1854)



More info:


Beu, A. G. & Maxwell, P. A. (1990). Revised descriptions of New Zealand Cenozoic Mollusca.

Morton, J. E. & Miller, M. (1968). The New Zealand seashore. Collins.