Deep-Sea Creature Uses Hydrothermal Vents As A Nursery

The skate's egg sac, called a 'mermaid's purse”, is about the size of a cell phone. Ocean Exploration Trust

A deep-sea volcanic trench might seem like a dreadful home, but for the Pacific white skate it’s an absolutely dreamy nursery.

Researchers studying the rocky, deep-sea hydrothermal vent field called Iguanas-Piguinos – 48 kilometers (30 miles) offshore of the Galapagos and 1,675 meters (5,500 feet) beneath the surface – found a species of skate that scientists believe uses the vents to incubate its eggs.

Scientists aren't totally sure why the skates lay their eggs in such a seemingly precarious spot, but believe it might speed up incubation time, increase survival rates, and perpetuate their parents' DNA. The study is published in Scientific Reports.

Embryos can take up to four years to develop, but a little hydrothermal help could shorten that period by several months.  

"Water temperature elevating even half a degree Celsius probably speeds up development time," said co-author Dave Ebert, program director of the Pacific Shark Research Center at Moss Landing Marine Labs in California, in an interview with IFLScience. 

The video was captured using a remotely operated vehicle. A fiber-optic cable tethered from the ROV to a research vessel provides a live feed for researchers to view – and ultimately capture – seafloor samples. It was at this point the rare stingray-like creature was seen laying its eggs on hot plumes coming out of the hydrothermal vents. 

“This is one of the few vertebrates we know of – certainly the only deep-sea vertebrates – that use these hydrothermal vents as nursery area,” said Ebert.

He says it’s the first recorded marine animal to use hydrothermal vents for this purpose, but it’s not the first time he’s seen it. The Pacific white skate has now been recorded laying eggs along the Ring of Fire, from British Columbia to California, and the species might not be as rare as once believed. 

“What I’ve seen is that if they have the right habitat, they’re actually quite common,” he says.

Skates are part of a diverse family of fish called elasmobranchs and, like their ray and shark cousins, are most vulnerable while they’re incubating in an egg sac called a “mermaid’s purse”.

Skate parents, it seems, are intentional with where they place their eggs. Certain concentrations of egg sacks were found at certain distances – almost always in places where water was hotter than the average 2.8°C (37°F) and within 30 meters (65 feet) of the chimney.

“If they’re too close, they would probably just become scrambled eggs,” said Ebert.

Ebert says a survey for the Pacific white skate helped describe three new species including the fine spine skate, a rare species found at 2,000 meters (6,500 feet) or deeper, and the more common broad skate.

Hydrothermal vents in the Galapagos were first discovered in 1977. Ocean Exploration Trust



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