Biology

Deep-sea fish hijack hydrothermal vents to incubate their young

Deep-sea fish hijack hydrother...
Deep-sea hydrothermal vent (Framegrab from the Remotely operated underwater vehicle)
Deep-sea hydrothermal vent (Framegrab from the Remotely operated underwater vehicle)
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Hercules ROV being lowered into the water
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Hercules ROV being lowered into the water
Skate egg-cases
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Skate egg-cases
Hercules' robotic arm gently collects a skate egg case for further investigation (Framegrab from the Remotely operated underwater vehicle)
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Hercules' robotic arm gently collects a skate egg case for further investigation (Framegrab from the Remotely operated underwater vehicle)
Deep-sea hydrothermal vent (Framegrab from the Remotely operated underwater vehicle)
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Deep-sea hydrothermal vent (Framegrab from the Remotely operated underwater vehicle)
Skate egg-cases scattered around deep-sea hydrothermal vent (Framegrab from the Remotely operated underwater vehicle)
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Skate egg-cases scattered around deep-sea hydrothermal vent (Framegrab from the Remotely operated underwater vehicle)
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Research teams from the Ocean Exploration Trust, the Charles Darwin Foundation and the Galapagos National Park Directorate have discovered that some species of skate incubate their eggs in deep-sea hydrothermal vents, a behavior never before observed in marine animals.

Using a Hercules remotely operated underwater vehicle (ROV), which can perform close-up inspections at depths of up to 13,124 ft (4,000 m), the researchers surveyed an active hydrothermal field 28 miles (45 km) north of Darwin Island in the Galapagos archipelago in June 2015. There they happened upon 157 smartphone-sized, horned, yellow-to-brown skate egg-cases tucked into crevices near plumes of volcanic heat.

Of these egg-cases, 58 percent they found were within 65 ft (20 m) of sulfurous, chimney-like "black smokers", which are the hottest kind of hydrothermal vent, and overall 89 percent were laid in places where the water was hotter than average.

Hercules' robotic arm gently collects a skate egg case for further investigation (Framegrab from the Remotely operated underwater vehicle)
Hercules' robotic arm gently collects a skate egg case for further investigation (Framegrab from the Remotely operated underwater vehicle)

The team used the ROV to collect four egg-cases and later conducted DNA analysis that revealed that the skate species Bathyraja spinosissima was the ingenious mastermind that had outsourced its incubation duties. Why this behavior has been adopted over normal methods remains uncertain, but the scientists theorize the fish could be using the heat emitted from the vents to speed up the developmental process. This wouldn't be a surprise considering deep-water skates have some of the longest egg incubation periods, which generally span over a few years.

Although this is a new discovery for marine animals, similar behaviors have been noted in land animals, such as the Polynesian megapode, a Tongan bird that nests in volcanically heated soils, and fossils of certain Cretaceous-era sauropod dinosaurs.

The study can be found in Scientific Reports and footage from the Hercules ROV can be seen below.

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Footage from Hercules ROV. Credit: Salinas-de-León et al.

Source: Springer Nature

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