And the first time we found it, we missed the best part!

If you spot a shark when it’s halfway gone, does that mean your limbs will be too? With the taillight shark (and most sharks, to be honest), no. Despite the traditional use of a tail-light, it doesn’t want you to know it’s there. And not for nefarious reasons.

You can’t really blame it given its size and home. It barely comes off the end of a ruler, and veers between the sunlight (epipelagic) and twilight (mesopelagic) zones of the Atlantic and Pacific Ocean,

Image by K. Aainsqatsi, via Wikimedia Commons.

which, as we know, are teeming with friendly creatures and short on places to hide. So what can it do to defend itself?

Simple: with the bioluminescent pouch under its tail, it can use counter-illumination to disguise itself as “the surface” when its enemies look up. At least, that’s what we think it does.

Since it hangs out in places hostile to humans, only feeds at night, and is of zero interest to fisheries, we neither come across it very often nor know that much about it. Case in point: the first time we examined it properly, we didn’t even realise it had the aforementioned pouch of blue bioluminescent liquid.

I say “properly”, because before Hulley and Penrith took at look at it, the taillight shark had already been dredged up and donated to the South African Museum as a longnose pygmy shark (Heteroscymnoides marleyi).

You can see the resemblance, despite the century(ies) between drawings!
Image from Bulletin – United States National Museum (1877).

Although Hulley and Penrith noticed it was an entirely new species, they managed to miss the large gland under its tail, thinking it was a pair of claspers (the shark version of a penis), and the fact that it was female. To be fair, the specimen they examined had been bashed around on deck a bit, and various authors have mixed up its depth and location at least once since. Its “tail-light” is also unique among sharks, so it’s not the kind of thing you’d expect to find.

The jury’s out on its diet too, but the needle-like teeth in its top jaw and blade-like teeth in its bottom jaw point to bony fish. An x-ray also found some round structures in its intestinal tract, which may have been squid eye lenses. Yummy!

So it’s not completely defenceless. As for its social life, it’s not clear if it really has one. The taillight shark doesn’t seem to form schools, and like some other sharks, there’s an aura of mystery surrounding its life cycle. Based on the specimens we’ve seen so far, we think the pups only have a yolk sac to snack on and are born live, rather than having a protective egg or umbilical attachment to Mum. In more formal circles this is known as “lecithotropic viviparity”.

Informally, that’s pretty much all we have on this rare little shark, so you probably read this in a flash. (Sorry.)

Taillight Shark Fact File

Imagery ©2022 NASA, TerraMetrics, Map data ©2022 INEGI United Kingdom

What? A small, blunt-nosed shark with a light-emitting gland under its tail.

Scientific Name: Euprotomicroides zantedeschia

Euprotomicroides basically means “similar to the pygmy shark” (Euprotomicrus, from the Greek for “good”, “first”, and “small”, and with “oides” stuck on the end for “similar to”).

Zantedeschia is after the South African trawler that caught it, Zantedeschia aethopica, which is itself named after the Callum lily.

Where? So far we’ve found it off South Africa and Brazil in the Atlantic, and off the coast of Chile in the Pacific. But it’s probably more widespread.

In terms of depth, it hovers between 195 and 641 metres/639 and 2,103 feet down, in both the sunlight (epipelagic) and twilight (mesopelagic) zones.

How big? It’s pretty dinky. About 41cm / 16 inches long.

First recorded? In 1966 by Hulley & Penrith, who infuriatingly (for them) managed to miss its amazing bioluminescent gland!

Diet? We’re not sure, but probably squid and bony fishes.

Behaviour? Given the vaguely terrifying neighbourhood it lives in, it probably uses its bioluminescence for camouflage. It doesn’t seem to live in schools, and the young develop inside a yolk sac but are born live.

Endangered? We hardly ever see it, but it’s not used commercially and doesn’t exactly hang out in areas desirable to humans. Let’s hope that keeps it safe and undisturbed!

Featured Image Credit:Euprotomicroides zantedeschia“, Food and Agricultural Organization of the United Nations (F.A.O.), CC A-N 3.0.

Just to prove I’m not fibbing:

Carpenter, Kent E. No date. “Euprotomicroides zantedeschia Hulley & Penrith, 1966, Taillight shark“. Fishbase.se.

Claes, Julien & Mallefet, Jérôme. 2009. “Bioluminescence of sharks: First synthesis“. In Bioluminescence in focus – A collection of illuminating essays (pp.51-65).

Curious about what shark species occur in South Africa?” 2021. IUCN SSC, Shark Specialist Group.

Hulley, P. & Penrith, M.J. 1966. “Euprotomicroides zantedeschia, a New Genus and Species of Pigmy Dalatiid Shark from South Africa“. Bulletin of Marine Science, 16: 222-229.

Pollom, R., Ebert, D.A. & Leslie, R. 2019. “Euprotomicroides zantedeschia. The IUCN Red List of Threatened Species” 2019: e.T44603A2998283.

Saborido-Rey, F. 2016. “Fish reproduction“. Encyclopaedia of Ocean Sciences (Third Edition).

Stehmann M., van Oijen M., Kamminga P. 2016. “Re-description of the rare taillight shark Euprotomicroides zantedeschia (Squaliformes, Dalatiidae), based on third and fourth record from off Chile“, Société Française d’Ichtyologie (Cybium), 40(3):187-197.