The biological wealth of our planet is very wide. This has led to the presence of a multitude of animals and particular characteristics within them. One of the most interesting characteristics is related to the way they move or move. In this way, we find a multitude of different forms, from the hydrodynamic movements of fish and cetaceans, to the wings of birds, through the legs of most mammals and insects, as well as other really ingenious forms. In fact, one of the most striking ways that some animals move is by crawling, that is, dragging their belly against the ground when they do so.
What is crawling and origin of crawling animals
When we speak of crawling we are referring to a way of moving that many animals have. The name makes a clear reference to reptiles , since, in this group of animals, we will be able to find many of the animals that move by crawling . However, although reptiles are common crawlers, they are by no means the only ones that move in this way.
When it comes to specifically defining what is crawling, we are going to find the problem that there is no specific limitation on when to consider crawling and when to walk. In general, crawling animals are all those that drag their belly against the ground during movement . However, there is no single way to do this, since you can find animals that move with the muscles of their belly (such as snakes), or animals that have legs to carry out movements of movement but that In practice, they also drag their belly when moving (as is the case with crocodiles).
In this way, although a priori it might seem that the absence of legs is one of the characteristics common to all animals that crawl, we will be able to see that, in reality, it is not always the case.
Origin of creeping or crawling animals
If we focus on talking about reptiles that crawl , since they are one of the largest groups of animals that move like this, we can say that their origin is in the first amniotes . These appeared on the face of the Earth from the Cotilosaurs in the Carboniferous period , which came from a group of amphibians. The first amniotes were divided into two groups: the Synapsids (related to current mammals) and the Sauropsids (related to current reptiles, which are the only vertebrate animals that crawl ).
Without a doubt, of all the animals that crawl, reptiles have the characteristic of being the most numerous in this sense. In the case of reptiles, we find clearly crawling animals, such as snakes. Snakes are reptiles that are characterized by having an elongated body devoid of legs of any kind. In this way, the snakes move by crawling using the muscles that run throughout their body, including their belly, and that allow them to move at speeds fast enough to be excellent hunters. Some of the best known snakes include the cobra, viper, anaconda, snakes, etc.
On the other hand, within reptiles, we will also find crawling animals with legs, such as crocodiles , some lizards and many species of turtles . How is it possible for animals with legs to crawl around? Because actually, they can move in a number of different ways. In fact, most of these animals, in addition to walking and crawling, can also swim easily and with great agility, which shows that they are versatile animals that adapt very easily to the environment in which they are found.
The way legged reptiles crawl is done through the strength of their legs. In this case, they place their legs in a forward position and then drag their body forward. Afterwards, they repeat the process and, in this way, they manage to move by crawling despite the presence of their legs. A good example of this type of crawling is found in the leatherback turtle., a marine reptile that spends most of its life in water. In fact, this makes your body hydrodynamic and adapted to swimming. However, when the leatherback turtle mates, it lays its eggs in the sand on the beach. To move to the mainland, it uses its front legs, which allow it to crawl to the future nest and, later, return to the ocean. All this, without taking your belly off the ground, and without the need for muscles in your lower body.
Although the ability to crawl is one of the most widespread characteristics in reptiles, we can also find animals that crawl that do not belong to this type of animal. Some of the most common that we can find are gastropod mollusks . In fact, the very name gastropod literally means “that walks with the stomach”. Some of these animals are snails and slugs . In addition, all sea snails would also fall within this type of animal, so we can see that the ability to crawl is not limited only to the terrestrial environment.
On the other hand, we can also find, for example, some insects that crawl . One of the characteristics of insects is the presence of six legs, which allows them to walk and, when they have wings, also to fly. However, some insects in their younger stages look completely different. This would be the case of caterpillars that, despite having legs that allow them to move, in many cases, also drag their belly, in the same way that happens with crocodiles or turtles . In addition, another important group that should be mentioned are the annelids, such as the earthworm.. So, as you can see, the ability to crawl is much more common than it might appear at first.