Aransbuilding class (Helitseri) and crustacean (toads) class belong to representatives of the same type: type of arthropods. This type of living organisms is the most numerous on our planet (there are only more than a million species), and these organisms are found almost anywhere in the planet and its atmosphere.
The same signs of both types
Both spiders and crustaceans belong to the type of arthropods, which means they have a fairly large number of similar features:
Appearance: in both of them and others, a segmented body, which is divided into two main segments: the head and abdomen, as well as the joint limbs.
Skin: Both crayfish and spiders are covered with a chitin shell.
Blood system: both species are distinguished by an unmarked type of blood supply, and the location of its main organ (heart tube) in the back of the back.
The presence of a winding nerve ring, and the same abdominal nervous chain.
Distinctive features of spiders and crustaceans
Crayfish and spiders have a number of distinguishing features:
Relative to the legs: in crayfish, 10 legs are usually formed, and spiders have four pairs.
Regarding the eyes: crayfish have faceted eyes of a complex type (they consist of a large number of simple organs), and spiders have the eyes of a conventional structure.
Regarding the mustache: crayfish are equipped with two pairs of antennae, and spiders are generally dispensed with without them.
Regarding life support systems (primarily blood and respiratory): crayfish formed gills for breathing, and a blood system that actively spreads oxygen, and spiders breathe light with the help of trachea, and their blood supply system is not developed so well. If we talk about the excretory system, then crayfish has the presence of metanefridia.
Regarding the cover: crayfish have a calcified chitin carapace, and in spiders, chitin is covered with sensitive hairs.
Spiders are equipped with Helitsers and Pedipalpas for eating and hunting, but crayfish formed for this purpose.
Both spiders and crustaceans have a fairly large number of similar features, but you can notice much more differences, and such a number of distinguishing features automatically means different conditions of existence for these types: first of all, this will touch the food, movement and the process of reproduction.