Answer:
In order to propose a hypothesis, there is a need to first see the function of gills in fishes. The gills of fishes comprise blood vessels that exhibit inherited tendencies of getting oxygen out of the water, which was consumed by fishes from their mouths. These gills also comprise thin walls, and when water moves over these walls of blood vessels, the oxygen from water moves into the blood, and then this oxygen-enriched blood goes to various organs.
Thus, one of the hypotheses in the given case, can be the number of blood vessels, which are found in the gills of the mentioned freshwater fish to be higher in comparison to the blood vessels found in the normal fishes, and apart from this, the surface area of the thin walls, which are found in the gills is also more in the new species of freshwater fish.
Oceanic crust or a less solid piece of oceanic crust will subduct beneath continental crust. Earthquakes occur when the oceanic plate subducts into a trench. Volcanoes are created by the melting of mantle material.
<h3>What does oceanic crust mean?</h3>
The outermost part of the Earth's lithosphere, known as oceanic crust, is created at spreading centres on oceanic ridges that are found at divergent plate boundaries and is found beneath the oceans. The oceanic crust is roughly 4 miles (6 km) thick. Even without the sediment on top, it is made up of many layers.
<h3>What is a characteristic of oceanic crust?</h3>
Compared to continental crust, oceanic crust is both thinner and denser. This is because to the oceans' weight, which has compacted it beneath it. It is also much more recent than continental crust, typically existing within the last 200 million years.
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