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  BBC 31 Jan 06
Smallest fish compete for honours

National Geographic 30 Jan 06
It may be tiny, but this fish has sparked a debate that's big--
though nowhere near as ugly
Blake de Pastino

EurekAlert 30 Jan 06
Flap over fishes: Who's the smallest of them all?

The authors of a paper in last week's Proceedings of the Royal Society of London Section B, who say their 7.9 mm-long fish from a peat swamp in Southeast Asia is the smallest fish and vertebrate known, have failed to make note of work published last fall that describes sexually mature, male anglerfishes measuring 6.2 mm to 7.4 mm in length.

The 6.2 mm specimen is by far the smallest of any vertebrate, beating the recent claim by a full 1.7 mm, according to Ted Pietsch, a University of Washington professor of aquatic and fisheries sciences, who has described the specimen.

Pietsch includes information about the tiny specimen, collected in the Philippines, in a review of what's known about reproduction in anglerfishes, so called because they have bioluminescent lures growing from their heads that they wave or cause to blink in order to attract prey to their mouths.

The work appeared in the September issue of Ichthyological Research, published by the Ichthyological Society of Japan. In the "Summary and Conclusions" section of that paper,

Pietsch wrote of specimens of Photocorynus spiniceps, the smallest of which was 6.2 mm. Pietsch has the histological evidence that it is a mature male. The male is attached to the middle of the back of a 46 mm long female Photocorynus spiniceps because that is how they mate.

It's called sexual parasitism and in five of the 11 families of anglerfishes, the males are tiny compared to the females and fuse for life to their mates by biting onto the sides, backs or bellies of a female.

An attached male – even two, three or up to eight, depending on the family – essentially turns the female into a hermaphrodite, providing her body with everything she needs to reproduce.

For the task, the 6.2 mm male, for instance, has testes so huge they nearly fill his entire body cavity, crowding his other internal organs. The female takes care of swimming, eating – everything.

Anglerfishes live in deep water off both U.S. coasts and across the world's oceans. Home includes some of the most desolate stretches of the seafloor on Earth.

Scientists estimate that 80 percent of the females, many of which live 25 or 30 years, never encounter a male. So it makes sense that anglerfish have evolved this strategy for reproducing, Pietsch says.

The sexually parasitic males don't have the lures typical of males of non-parasitic anglerfishes, instead their tiny bodies are dominated by nostrils – to detect females – and large eyes to scrutinize the female's lure. The male makes certain the female is of his family before biting onto her.

The specimen Pietsch describes is borrowed from the vertebrate collection of the Scripps Institution of Oceanography. Along with including information in his published work, Pietsch's findings about the specimen were presented and illustrated at the Seventh Indo-Pacific Fish Conference in Taiwan last May.

"There are always difficulties in talking about the smallest – would that be length, volume or weight – the debate goes round and round," Pietsch says.

The co-authors of the paper in the Proceedings of the Royal Society of London Section B, two of whom Pietsch knows, call the fish they found "the world's smallest vertebrate" and compare lengths. They also compare numbers of vertebrae.

On that count, Pietsch's Photocorynus spiniceps scores an 18 and Paedocypris progenetica, the subject of this week's paper, scores 33 to 35.

National Geographic 30 Jan 06
It may be tiny, but this fish has sparked a debate that's big--
though nowhere near as ugly
Blake de Pastino

A U.S. scientist says a male anglerfish found in the Philippines is the smallest fish in the world. Ted Pietsch, a fisheries professor at the University of Washington in Seattle, discovered the fish in the collection of the Scripps Institution of Oceanography in San Diego, California.

He first announced his find last May. A mere 0.24 inch (6.2 millimeters) long, the fish known as Photocorynus spiniceps may take the prize as the world's smallest catch.

But it has some wee competition. Last week an international team of researchers announced that they, too, had discovered Earth's littlest fish. Their find, a member of the carp family found in the peat swamps of Indonesia, is 0.31 inch (7.9 millimeters) long and so slim that it's transparent.

What's more, scientists at the Australian Museum in Sydney in 2004 unveiled a tiny fish found in the Great Barrier Reef that measures from 0.28 to 0.31 inch (7 to 8 millimeters) in length.

In the end, the real winner in this fish tale depends on how you size things up, Pietsch says. "The debate centers on how you define 'smallest,'" Pietsch writes by email. "The [Australian Museum] folks want to use volume as the measure, but [other scientists] use length.

"If length is an acceptable criterion, then surely my Photocorynus is the smallest known sexually mature vertebrate by a full 1.7 millimeters [0.06 inch]."

Pietsch re-released his study late last week as a kindly reminder to his colleagues, who have been taking part in this "friendly rivalry" for years, he says. "The other researchers know my work and I theirs," he says. "But somehow in the latest story that broke early last week, my publication on Photocorynus was left out. So I thought I'd jump into the fray."

BBC 31 Jan 06
Smallest fish compete for honours
By Rebecca Morelle BBC News science reporter

When is the smallest really the smallest? It seems that when it comes to fish, the answer is just not clear-cut.

Last week saw the announcement that the world's tiniest fish and vertebrate had been found, measuring a mere 7.9mm. The little creature, a female of the Paedocypris genus, was discovered in the peat swamps of Sumatra, Indonesia.

But miniscule though this may seem, two other fish reported in the past couple of years claim to be smaller still.

Sexual parasite

In 2004, the Records of the Australian Museum described a male stout infantfish (Schindleria brevipinguis) measuring a diminutive 7mm. It was found living around Australia's Great Barrier Reef.

And then there was the male anglerfish (Photocorynus spiniceps) discovered in the Philippines. Snout to tail it was just 6.2mm. The fish was reported in the journal of Ichthyological Research last September.

It spends its life fused to its much larger female counterpart, which in some species are up to half a million times greater in weight. While the female takes care of swimming and eating, the male fish, with its enormous (relatively speaking) testes, is charged with the task of aiding reproduction.

In scientific terms, the male P. spiniceps is labelled a sexual parasite. Professor Ted Pietsch, from the University of Washington, US, who described the 6.2mm anglerfish, believes this specimen to be the true champion of the small.

Difficult measurements

Dr Ralf Britz, a fish expert at the Natural History Museum in London, UK, was an author on the paper last week that described the 7.9mm Paedocypris vertebrate. He said the anglerfish was not mentioned in his team's paper because they had simply not seen the P. spiniceps work at the time that it went to press. "We just had no idea of this publication; none of us knew about it," Dr Britz explained.

He told the BBC News website that the whole affair raised some interesting questions about how the sizes of such small fish were established. It was not always clear, he said, when a specimen had reached adulthood and was therefore fully grown. "It is easier to see how sexually mature a female fish is compared with a male fish. For a male fish, you have to carry out a histological [tissue] section to see if the gonads are ripe," he added. "Even if you just do a dissection and look at the testes, you can't really tell if they are mature or not, so you need histological studies to prove that."

While the stout infantfish's maturity was not proven using such methods, the anglerfish did have histological evidence that it had reached sexual maturity.

Professor Pietsch, a fish researcher (or ichthyologist), agreed there was some difficulty in describing a creature's size. "You can use weight, volume or length to describe the smallness of an animal," he told the BBC News website.

"Mine probably isn't the smallest in volume or weight, say compared to the Schindleria [stout infantfish]; but in terms of length it probably is."

Study needed

When asked about the difficulty of measuring a fish that is attached to the back of another, he commented: "You can see exactly where the tip of the snout ends in these tiny males - they are so small they are almost translucent. "I can't tell you how many times I measured that thing - and if anything 6.2mm is conservative. "Although this fish lives an unusual existence, it is still a fish; it is still a vertebrate.

"The smallest vertebrate [search] has been going on for a really long time. The three that have been mentioned recently are just the tip of a really long discussion."

And while the quest to find the smallest vertebrate looks certain to continue, Dr Britz is in no doubt about the value to science in investigating such miniature animals. "At the end of the day, these are all very interesting, very unusual fish that need to be studied in more detail," Dr Britz told the BBC.

"The question over whether they are the smallest or not is not so much a scientific issue but more a popular one."
links
Miniature Asian fish sets a whale of a record Channel NewsAsia 25 Jan 06
Smaller parasitic male anglerfish and more about really small fishes on the Raffles Museum blog
Related articles on global biodiversity
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