Deep-sea volcanic vents incubate eggs for this underwater mothers

The robot “hand” of the Hercules ROV picks up a skate egg pod.

(Ocean Exploration Trust)

Ice skating — flat, diamond-shaped fish related to sharks and rays — brooding their eggs for as much as four years or more, longer than most animals on Earth. But scientists recently discovered that ice skating could speed up the lengthy process by turning the heat on their egg cases.

And they do this in the most badass way possible — by making use of the warmth of the deep sea volcanoes.

The Pacific white skate (Bathyraja spinosissima) deposits much of the development of egg cases, each about the size of a mobile phone close to hydrothermal vents, where they enjoy the extra warmth. While nesting behavior that makes use of an active volcanic source to incubate eggs is known from a few species on land, it is never seen in a marine environment for the researchers reported in a new study. [Extreme Life on Earth: 8 Bizarre Creatures]

“This is the first record of a hydrothermal vent habitat and an egg-case, nursery site, a discrete habitat with an extremely high densities of egg cases, when compared to the surrounding similar habitats,” the study’s lead author, Pelayo Salinas-de-León, a senior marine ecologist with the Charles Darwin Foundation in Galapagos, Ecuador, told Science in an e-mail.

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White skates are cartilaginous fishes, lacking a hard, bony material in their skeletons. They belong to the deepest-dwelling ice-skating in the ocean, is home to more than 9,843 feet (3,000 meters) below the surface, and its preference for rocky parts of the seabed, according to the International Union for Conservation of Nature and Natural Resources (IUCN).

The skates reproduce by laying groups of eggs is enclosed in a rectangular pods that resemble large and leathery ravioli, each angle tipped with four slender, tapering “horns.” Made of collagen separated from a fallopian tube, the water-permeable pods — which sometimes wash ashore on the beach after the eggs are hatched — are just known as “mermaid purses,” according to a study published in 1980 in the Journal of Experimental Biology.

In the pods, the eggs incubate for years at a stretch — at least 1500 days in the waters where the average temperature was 36.9 degrees Fahrenheit (2.7 degrees Celsius), the authors of the research reported.

To learn more about how skates interact with their deep-sea environment, the scientists explored a hydrothermal vent field — a collection of fissures in the seabed in the vicinity of a volcanic active area in the eastern tropical Pacific ocean in the vicinity of the galapágos, north of the Islands of Darwin. At the beginning of the expedition in 2015, “we hardly knew anything about the Galapagos deep-sea ecosystems,” Salinas-de-León said.

With the help of a remotely operated vehicle (ROV) named “Hercules,” the researchers observed caches of skate egg pods, but they saw no skates. In total, they counted 157 egg cases in the area, of which the majority (58 percent) were placed no more than 66 feet (20 meters) of the hottest vents known as “black smoker chimneys,” Salinas-de-León said.

Elevated temperatures of the water in these volcanic zones measured around 40 degrees Fahrenheit (4.5 degrees Celsius) in a location — can heat up the skates’ eggs enough to the speed of their incubation, according to the study.

Evidence from the fossil record suggests that some sauropod dinosaursduring the Cretaceous period, incubated their eggs in volcanically heated soil. And the bird known as the Polynesian megapode (Megapodius pritchardii) nests by burrowing in the earth, warmed by volcanoes on the island of Tonga.

However, for this study, there was no evidence that the marine creature incubated the eggs with volcanic heat, the study authors reported.

“It shows how little we have studied and therefore understand about the deep sea,” Salinas-de-León, wrote in an e-mail.

Ice skating, as well as stingrays and sharks belong to the fish group known as Chondrichthyans, which is particularly hard hit by overfishing in the last decades — about 25 percent of the species in this group are threatened with extinction, the scientists wrote in the research. Who lives in the deep water are more at risk, because they tend to grow slower and mature later, making it difficult for populations to rebound when their numbers are depleted.

The understanding of the reproduction and habitat requirements of these vulnerable deep-sea skate is therefore of great importance for strategizing their continued protection and preservation, in particular in a warming world, the researchers wrote.

“Further research should focus on identifying and promoting the protection of the additional Chondrichthyan and deep-sea nurseries, given the constant expansion of the fishery in the direction of the deep sea and the intrinsic vulnerability of this group of species,” the authors of the study concluded.

The findings are published online today (Feb. 8) in the journal Nature.

Original article on Live Science.

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