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Incubation station: are hydrothermal vents speeding up skate-egg development?

Salinas-de-León, P., Phillips, B., Ebert, D., Shivji, M., Cerutti-Pereyra, F., Ruck, C., … & Marsh, L. (2018). Deep-sea hydrothermal vents as natural egg-case incubators at the Galapagos Rift. Scientific reports, 8(1), 1788.

Figure A: egg casing resembling skate egg. Source: https://commons.wikimedia.org/wiki/File:Mermaidpurse.jpg

A group of researchers have made a neat discovery at hydrothermal vent sites in the Galapagos—skate eggs (Figure A, Figure 3.f original article) potentially being incubated by the warmed fluid discharge!

When scientists visited the hydrothermal vent site, Iguanas-Pinguinos (Figure 1 original article), in 2008 with ROV Hercules, they saw 157 eggs in what they described as an ‘egg-case nursery’. The eggs were found about 150-m from sites of vigorous venting in 1660-1670 meter water depth.

During the dive, Hercules was equipped with a censor and probe to monitor the temperature of the bottom water surrounding the vent site.  Near the vent site, the water was consistently at temperatures slightly elevated (2.74-3.58˚C) above bottom water (2.67˚C).  Over 89% of the egg casings were observed in temperatures elevated above bottom water (Figures 2 & 4 original article).

Among the egg cluster, the individual eggs were at varying developmental stages.  This was evident from the apparent color spectrum of the eggs (golden to dark-brown) and the presence of old eggs casings.  The later suggests the site has been used for a long duration of time.

The egg casing species was identified from visual examination of four collected specimens. No adult skates were observed during the dive, but have been seen in the area on pervious expeditions.

Scientists concluded that the deep-sea skate population (Bathyraja spinoasissima) (Figure B) uses naturally elevated temperatures in the vent environment to incubate developing egg-cases. They suspect that the elevated temperatures may reduce the required incubation time.

FIgure B: Bathyraja spinoasissima. Left: https://commons.wikimedia.org/wiki/File:Expl6386_(9734087763).jpg. Right: https://commons.wikimedia.org/wiki/File:Bathyraja.jpg

To support their conclusion, they cite that incubation from natural heat is observed in the fossil record in reptiles and birds.  For instance, a group of Neosauropod dinosaurs used moisture and heat generated in soil for incubation during the cretaceous and some Megapode birds used volcanically heated soil to incubate their eggs.  However, the researchers also note that temperature and development time are not always correlated, as is suspected for the deep-sea octopus Granelodone boreopacifica, whose presence in warm vent areas is coincidental.

The discovery of skate egg casings at sites of hydrothermal venting is of particular interest to biologists because it is a unique opportunity to observe the role of warm fluid discharge in reproductive strategies.  It also aids in strengthening our understanding of biological development so that the most effect means of population sustainability can be utilized in the reflection of climate change.

Anne M. Hartwell

Hello, welcome to Oceanbites! My name is Annie, I’m an earth scientist (geology and oceanography). My favorite job as a scientist is working in the laboratory and the field because I love interacting with my research!


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