Before entering fully to define the term aquatic animal, we will proceed to determine its etymological origin. In doing so we discover that the two words that shape it emanate from the Latin:
• Animal, comes from “animal” that can be translated as any being that has breathing.
• Aquatic, meanwhile, derives from “aquaticus”. A term this that is made up of two clearly differentiated parts: the noun “aqua”, which is synonymous with “water”, and the suffix “-tico”, which is used to indicate “relative to”.
The animals are those living beings that are part of the kingdom Animalia, can mobilize on their own, they reproduce sexually way, absorb oxygen to breathe and ingest food. The concept, in its broadest sense, includes Homo sapiens although, in general, the use of the term is limited to non-rational animals.
According to DigoPaul, aquatic, meanwhile, is an adjective that refers to what is linked to water. The word is often used with reference to those beings that live in it or to objects that, by their nature, remain in the water constantly.
The aquatic animals, therefore, are those living beings belonging to the kingdom Animalia who spend most of their livelihood in the water. This does not mean, however, that they are only animals capable of breathing underwater, but that there are aquatic animals that must appear on the surface to capture oxygen.
Although there are many different types of aquatic animals, it is important to know that they all have a series of common characteristics such as the ones shown below:
• They have had to adapt to the sea, specifically its tides and the different water currents that are produced. Hence some have fins, others have basal discs, some have shells…
• No less important is that the diet of these living beings, in one way or another, depends on phytoplankton, which is a species of plant that lives in the sea and that it is microscopic. And it is located in the nutritional base of these animals.
• It should also be noted that they have also had to adapt to the water temperatures, so each class has mechanisms that do so: scales, pale blood…
The fish are the most representative example of aquatic animals. These vertebrates have gills to breathe underwater, so they do not need to get out of the water: in fact, when they are removed from their environment, they die. The fish have fins for swimming and usually have a covered body with scales.
Other aquatic animals, however, must rise to the surface to breathe. This is the case of the dolphin, a mammal that has a single blowhole to absorb oxygen from the air.
It is important to note that there are aquatic animals that also spend a good amount of time on land, which is why they are usually classified as semi-aquatic. The Beavers and hippopotamus, for example, are in this group.
It should be borne in mind that within the group of aquatic animals there are several that are in danger of extinction, such as the Mediterranean monk seal, sea otter, gray whale or napoleon fish, among others.