Category: Biology

Japan’s Deadliest Delicacy Is Getting More Dangerous

Rising sea temperatures are pushing pufferfish species together, spawning hybrids that even specialist chefs cannot safely prepare

[from South China Morning Post]

by Julian Ryall

Japan’s most dangerous delicacy is getting harder to prepare safely as warming seas push different pufferfish species into the same waters, where they are inbreeding to produce hybrids whose lethal toxins are not yet fully understood.

Fugu – the collective Japanese name for several species of edible pufferfish – is prized as much for the danger surrounding its preparation as for its subtle flavour.

Many species contain tetrodotoxin, a powerful neurotoxin with no known antidote that can cause paralysis, respiratory failure and death.

Since 1958, anyone wishing to prepare pufferfish for public consumption has had to obtain a licence first, a process that takes at least two years and defeats roughly two-thirds of those who attempt it.

A restaurateur shows off a “fugu”, or pufferfish, at a restaurant in Shimonoseki, Japan. Photo: AP

Chefs learn to strip out the fish’s liver, ovaries, eyes and skin – tissues where the poison concentrates – with the precision of a brain surgeon and the nerve of a bomb-disposal technician.

But that hard-won expertise is now being undermined by climate-induced interbreeding, as experts say Japan’s coastal waters are heating up at roughly twice the global average rate.

Spotted pufferfish, once largely confined to the Sea of Japan, have spent the past decade steadily pushing northward in search of cooler currents. Some slipped through the Tsugaru Strait – the channel separating Honshu from far northern Hokkaido – where they have met and mated with the region’s native pufferfish species.

The resulting hybrids now make up as much as 40 per cent of local catches, according to a recent study of fish caught off Fukushima and Ibaraki prefectures.

“We started seeing these spotted fugu on the Pacific coast in 2012 as temperatures in the Sea of Japan became too high for them,” said Professor Hiroshi Takahashi of the National Fisheries University in Shimonoseki, Yamaguchi prefecture.

Temperatures in the waters there were “among the fastest rising anywhere in the world”, he told This Week in Asia, adding that the changes in pufferfish had been happening just as fast.

Customers visit a seafood market in Japan’s Fukushima prefecture. Photo: AP

Some spotted pufferfish had ventured down the east coast as far south as Tokyo Bay, Takahashi said, only to be driven north again as those waters also warmed.

Tiger pufferfish had likewise moved north from their usual range to interbreed with common pufferfish in and around Tokyo Bay, he added.

The trouble is not that hybrids are more toxic than their ancestors, it is that nobody yet knows how interbreeding has affected the distribution of toxins.

Each species of pufferfish stores tetrodotoxin in a different combination of organs and Japan’s health ministry has not yet been able to establish which parts of the new hybrids are safe to eat and which are not.

Until it does, the government has banned the sale or consumption of hybrid fugu – but this ban is almost impossible to enforce.

“They are very hard to identify,” said Takahashi, whose team has developed a DNA test capable of distinguishing hybrid fish and hopes to make the technology commercially available to fishermen who currently have no reliable way of screening their catch.

Pufferfish, or “fugu”, sashimi prepared for eating at a restaurant in Japan. Photo: Shutterstock

Fatal attraction

None of this is likely to diminish fugu’s deadly mystique. The dish has been eaten in Japan for centuries, enjoyed despite – or because of – the risks involved.

Every year, new tales emerge of amateur anglers preparing the fish to eat against the advice of anxious relatives and not surviving the attempt.

Diners speak of a faint numbness in the lips as evidence of a narrow escape and the emperor of Japan is barred from eating fugu altogether, lest even a licensed chef makes a mistake.

Urban legend holds that chefs who do poison a customer are honour-bound to end their own life, with their own knife, in atonement – though this is a myth.

For their part, Japanese restaurateurs are, perhaps unsurprisingly, keen to play down the risks.

A spokeswoman for Miyawaki Fugu Club, an upscale restaurant in Tokyo’s Ginza district, said its chef works exclusively with farmed tiger pufferfish from a long-established supplier, which she insisted were “completely safe”.

James Reimer, a professor of marine biology at the University of the Ryukyus, said the fugu phenomenon fit a wider pattern of marine life relocating in response to global warming.

“What happens to marine ecosystems is one of the hot-button issues of the day, particularly in Japan, because the waters here are warming at twice the global average rate,” he said.

During fieldwork off the Izu peninsula, south of Tokyo, three years ago, local fishermen told him that they had lost virtually their entire kelp crop and that the abalone once abundant in those waters had vanished.

A sea turtles in waters off Japan’s Amami Islands. Turtles are increasingly venturing farther north, fishermen say. Photo: Shutterstock

In their place, they said they were seeing far more sea turtles, as well as large schools of brightly coloured fusiliers – the prefectural fish of Okinawa, some 1,400km (870 miles) to the south.

“Last year, our summer in Okinawa was 30 days longer than average, and we had 120 days when the water temperature was around 30 degrees Celsius (86 degrees Fahrenheit),” Reimer said.

He warns that the picture is not simply one of fish and other marine life swimming steadily north in search of more comfortable temperatures, however.

Global warming is also destabilising weather patterns, making them less predictable. Waters off Kyushu, the southernmost of Japan’s main islands, that might otherwise suit certain species are increasingly prone to temperature swings that could make them unsuitable after all.

Even so, the broader direction is unmistakable. Kyushu’s waters have seen a marked rise in shark sightings in recent years, including large tiger sharks – one more sign of the changes occurring beneath the surface of Japan’s seas.

World-Watching: How Nature Paints With Color

[from Quanta Magazine]

by Yasemin Saplakoglu

When objects interact with light in particular ways — by absorbing or reflecting it — we see in color. A sunset’s orange hues and the ocean’s deep blues inspire artists and dazzle observant admirers. But colors are more than pretty decor; they also play a critical role in life. They attract mates, pollinators and seed-spreaders, and signal danger. And the same color can mean different things to different organisms: A red bird might attract a mate, while a red berry might warn off a hungry human.

For color to communicate meaning, systems to produce it had to evolve, by developing pigments to absorb certain wavelengths of light or structures to reflect them. Organisms also had to produce the machinery to perceive color. When you look out into a forest, you might see lush greenery dappled with yellowish sunlight and pink blooms. But this forest scene would look different if you were a bird or a fly. Color-perception machinery — which include photoreceptors in our eyes that recognize and distinguish light — can differ between species. While humans can’t see ultraviolet light, some birds can. While dogs can’t see red or green, many humans can. Even within species there’s some variation: People who are colorblind have trouble distinguishing some combinations, such as green and red. And many organisms can’t see color at all.

Within one planet, many colorful worlds exist. But how did colors evolve in the first place?

What’s New and Noteworthy

To pinpoint when different kinds of color signals may have evolved, researchers recently reviewed many papers, covering hundreds of millions of years of evolutionary history, to bring together information from the fossil record and phylogenetic trees (diagrams that depict evolutionary relationships between species). Their analysis across the tree of life suggested that color signals likely evolved much later than color vision. It’s likely that color vision evolved twice, developing independently in arthropods and fish, between 400 million and 500 million years ago. Then plants started using bright colors to attract pollinators and animals to disperse their seeds, and then animals started using colors to warn off predators and eventually to attract mates.

One of the most common colors that we see in nature is green. However, this isn’t a color signal: It’s a result of photosynthesis. Most plants absorb almost all the photons in the red and blue light spectra but only 90% of the green photons. The remaining 10% are reflected, making the plants appear green to our eyes. But why did they evolve to do this? According to a model, this makes photosynthetic machinery more stable, suggesting that sometimes evolution favors stability over efficiency.

The majority of colors in nature are produced by pigments that absorb or reflect different wavelengths of light. While many plants can produce these pigments on their own, most animals can’t; instead, they acquire pigments from their diet. Some pigments, though, are hard to acquire, so some animals instead rely on nanoscale structures that scatter light in particular ways to create “structural colors.” For example, the shell of the blue-rayed limpet has layers of transparent crystals, each of which diffracts and reflects a sliver of the light spectrum. When the layers grow to a precise thickness, around 100 nanometers, the wavelengths in each layer interact with one another, canceling each other out — except for blue. The result is the appearance of a bright blue limpet shell.