Ikigai Daily
Menu
WonderDeep-sea vision fact

The barreleye Macropinna microstoma has tubular eyes beneath a transparent, fluid-filled shield, and can rotate them from looking upward to looking forward.

Barreleye

OceanBiologyNatureScience

The story behind the card

The barreleye lives about 600 to 800 metres down in the northern Pacific and grows to around 15 centimetres. It was described in 1939, but for decades it was known only from specimens hauled up in nets, which destroyed the soft shield, and its eyes were thought to be fixed, pointing straight up. Bruce Robison and Kim Reisenbichler of the Monterey Bay Aquarium Research Institute filmed living barreleyes off California with a remotely operated submersible and, in a 2008 paper, showed the green eyes turning inside the intact dome. The two dark spots above the mouth that look like eyes are in fact its organs of smell. Robison has suggested that the fish may steal food from siphonophores, stinging relatives of jellyfish, with the shield protecting its eyes.

Türkçe oku
Fıçı gözlü balık Macropinna microstoma'nın tüp biçimli gözleri, başındaki saydam ve sıvı dolu bir kalkanın altındadır. Balık bu gözleri yukarı bakar konumdan ileri bakar konuma çevirebilir.

Fıçı gözlü balık Kuzey Pasifik'te 600-800 metre derinlikte yaşar ve 15 santimetre kadar büyür. 1939'da tanımlandı, ama onlarca yıl yalnızca ağlarla yukarı çekilen örneklerden tanındı. Ağlar yumuşak kalkanı parçaladığı için gözlerin kıpırdamadan hep yukarı baktığı sanılıyordu. Monterey Körfezi Akvaryumu Araştırma Enstitüsü'nden Bruce Robison ile Kim Reisenbichler, Kaliforniya açıklarında uzaktan kumandalı bir denizaltıyla canlı fıçı gözlü balıkları görüntüledi ve 2008'de yayımladıkları makalede yeşil gözlerin sağlam kubbenin içinde döndüğünü gösterdi. Ağzın üstünde göz gibi duran iki koyu nokta aslında koku organlarıdır. Robison, balığın denizanalarının sokan akrabaları olan sifonoforların yiyeceğini çalıyor olabileceğini, kalkanın da gözlerini onların dokunaçlarından koruduğunu düşünüyor.

Sources and further reading

Background reading: Barreleye
Get the mobile appAbout our cards

Related cards

These cards share a subject or reading mode with the card above.

WonderNature

Great frigatebirds can sleep while soaring over the ocean, sometimes with one half of the brain and sometimes with both. In flight, though, they sleep only about 40 minutes a day, against more than 12 hours a day on land.

The finding comes from a 2016 study led by Niels Rattenborg of the Max Planck Institute for Ornithology in Germany. His team fitted great frigatebirds nesting in the Galápagos Islands with small devices that recorded brain activity during flights lasting up to ten days. Most sleep came in bursts of about twelve seconds, often while the birds circled upward in rising warm air. When only one half of the brain slept, the eye linked to the awake half usually looked in the direction of flight. Frigatebirds hunt far out at sea, yet their feathers are not waterproof, so they cannot rest on the water. How they cope with so little sleep is still not known.

Great frigatebirdRead card
StillnessOcean

Mangroves, salt marshes and seagrass meadows draw carbon dioxide from the air and lock it away in waterlogged coastal mud, often for centuries. Scientists call this stored carbon 'blue carbon'.

The term was popularised by a 2009 United Nations report. Coastal mud holds so little oxygen that dead roots and leaves rot very slowly, so carbon keeps building up in the soil instead of returning to the air. These habitats cover only a small fraction of the seabed, yet they are thought to account for about half of all the carbon buried in ocean sediments. Mangroves also break waves, trap sediment and shelter young fish and crabs among their roots. When the wetlands are drained or cleared for shrimp farms or building, the stored carbon can escape back into the atmosphere.

Mangrove blue carbonRead card
StillnessScience

Kelp forests grow in cool coastal seas from giant brown algae, not plants, and shelter a great variety of fish, invertebrates, seals and sea otters.

Kelp are large brown algae. Instead of roots they have a grip-like base called a holdfast, and gas-filled bulbs hold their fronds up towards the light. Giant kelp can grow up to about 60 centimetres a day and reach more than 30 metres, forming a canopy at the surface like the treetops of a forest. Kelp forests grow along cool coasts from California and Chile to South Africa, Australia and Norway. In the North Pacific, sea otters help protect them by eating sea urchins, which graze on kelp. Where otters were hunted out for their fur, urchins multiplied and stripped forests down to bare rock, leaving what are called urchin barrens.

NOAA Ocean ServiceRead card
WonderOcean

Coral reefs cover less than 1 per cent of the ocean floor, yet they support about a quarter of all known marine species. They also shield coasts from storm waves.

A reef is built by coral polyps, tiny animals related to jellyfish that lay down skeletons of limestone. Most reef corals carry single-celled algae inside their tissue; the algae photosynthesise and pass food to the coral in return for shelter, and they also give it its colour. When the water stays too warm for too long, corals expel the algae and turn white, which is called bleaching; if the heat lasts, they starve and die. A global bleaching event from 2014 to 2017 hit about two-thirds of the world's reefs, and a fourth, from 2023 to 2025, the most severe on record, reached about 84 per cent of reef area.

Coral reefsRead card
WonderMigration

European eels live in the rivers of Europe and North Africa but begin life some 5,000 kilometres away in the Sargasso Sea, in the western Atlantic. Adults swim back there to breed, yet no one has ever seen them spawn.

How eels breed puzzled people for more than 2,000 years; Aristotle thought they arose from mud. In the early 1900s the Danish biologist Johannes Schmidt spent almost two decades netting eel larvae across the Atlantic and found that they grew smaller the further west he went, until the tiniest turned up only in the Sargasso Sea. The larvae drift to Europe with the Gulf Stream and turn into transparent 'glass eels' as they near the coast. In 2022 researchers reported the first direct evidence of adults reaching the Sargasso Sea, after tracking satellite-tagged eels released in the Azores. No eggs or spawning adults have yet been found. The species is now critically endangered.

European eel migrationRead card
Next card in the archiveA siphonophore, a relative of jellyfish, grows from a single fertilised egg into a colony of connected parts. Each part, called a zooid, takes on one job: swimming, feeding, defence or reproduction.Read next →