How to draw a crab step by step

How to draw a crab in 2 variants will be told in this article! In the process of evolution, ten-legged crayfish repeatedly became crabs – acquiring a characteristic flattened wide body shape with a short abdomen. What is even more surprising is that they just as often lost “crabbiness,” again approaching in the form of the usual river crayfish.

Scientists have even coined special terms for these changes and are trying to understand their causes with the help of modern technology. Several hypotheses have been proposed, but so far, none of them can be recognized as satisfactory due to data gaps.

Traditionally, “crabs” are understood to be a suborder of Brachyura, a member of the decapod crayfish (Decapoda). In taxonomic terms, they are often contrasted with the suborder Anomura, or “false crabs,” differing from them by the number of walking legs.

However, these two suborders have much more in common than differences. They have very similar anatomy – the cephalothorax is wide and covered with a flat shield – the carapax. The abdomen (pleon), which in crustaceans is usually long and looks like a thick “tail” of a crab, in crabs – and “true” and “false” – is reduced and tucked under the cephalothorax. External morphological features of crabs are accompanied by internal ones – some abdominal ganglia are merged into one, and abdominal muscles are reduced. It is reasonable to assume that the two suborders in parallel (convergent) acquired such a structure in the process of evolution.

The reality turns out to be much more interesting – paleontological and phylogenetic studies show that in each suborder, the body plan characteristic of crabs developed independently several times: twice in “true” crabs and twice in false crabs. This process was repeated so often by evolutionary standards that a special term was coined for it: carcinization.

Moreover, in the same taxa – Brachyura and Anomura – the “crabness” disappeared many times: the carapax again became long and narrow, and the abdomen lengthened and straightened. There is also a separate term for this process – decarbonization. It seems as if natural selection was constantly experimenting on the ten-legged crayfish on how to make crabs better – and remaking everything back if it “didn’t like it.”

Draw and enjoy drawing crabs with us the main thing is to follow our recommendations! In general, convergent development of the same trait in a certain taxon, as well as its loss, is a rather common thing for evolutionary biology, even in such epochal things as multicellularity. For example, in the Wolvox green algae – that is, in a rather small taxon (about 60 species in 15 genera) – multicellularity managed to occur twice, and cell differentiation – as many as four times! What can we say about carcinization, which implies a much smaller change in body plan?

Interest in carcinization (and decarbonization) is fueled, first, by the “age” of the problem: the term itself was introduced as early as 1916. Second, crabs are much more “tangible” and culturally relevant to a wide audience than multicellularity.
In general, the topic of crab evolution is quite “evergreen,” so scientists continue to deal with it and, in particular, to search for an answer to the question: why does evolution so often come to the “crab” structure and just as easily “abandon” it?

So, let’s get to drawing the crab right now!