Cancer is an animal of the crustacean class. It is difficult to imagine a reservoir in which there would be no owner of a pair of powerful claws. And what gambling can be hunting for crayfish! No, we are not talking about banal fishing with the help of "crabs", we are talking about a real fight, one on one. When you are chasing a barbel escaping from you in a mask and fins (and where did the talk about the sluggishness and slowness of crayfish come from?), And now, when you have already practically managed to grab him, he quickly hides in a hole … hand there, and here it is - the moment of truth! I want to scream in pain, but I can’t… and the crayfish tightly grabbed the fingers of its offender with its claws. The goal is achieved - the victim is in the cage, but who caught whom still needs to be figured out. However, we got carried away a little, because you don’t need to start with this. First, let's talk about what cancer is, what are its features. So, in this article we will look at the parts of the bodycrustaceans, their way of life, and along the way - habits.
Remember the lessons of zoology: the structure of arthropods
Cancer is an invertebrate animal, its body is clearly divided into the front part - a fused cephalothorax, covered with a brown-green and very strong shell; and the back - a jointed abdomen, ending in a wide fin. On his head are two pairs of mustaches. The first short pair are the organs of smell. The second, long mustache, is responsible for touch. The eyes of a cancer are, as it were, planted on processes-stalks; with the help of muscles, they can move outward and retract inward. From above, the organs of vision are covered with frontal spiny processes, which make up the anterior end of the cephalothorax shell. The oral cavity is surrounded by several pairs of jaw appendages of a very complex structure, due to which food is finely ground before entering the mouth. The lower part of the cephalothorax has five pairs of limbs. The first of these are large claws. With their help, cancer holds food in front of it, and also protects itself from enemies. Claws are not used for walking. Cancer moves with the help of the so-called walking legs (the remaining four pairs). The ends of the first and second pairs contain rudimentary claws, while the third and fourth end with claws.
What do they have inside?
The internal structure of crustaceans includes the following systems: digestive, circulatory, respiratory, excretory. The first of them looks like a straight tube and, like all arthropods, consists of an anterior, middle, and posterior ectodermal gut. The circulatory system in crayfish is of an open type, that is, the hemolymph flows through the sinuses and vessels of the mixocel. The heart is located above the intestines, in the dorsal part. The respiratory system of crustaceans is represented by gills, which are formed in a special cavity under the carapace. They are located in three rows. The excretory system is represented by the kidneys, which are modified coelomoducts. Cancer is an animal whose muscles are striated muscle tissue. It does not have a skin-muscular sac, the muscles are represented by separate large bundles.
Gender separation
Female and male crustaceans are slightly different in body structure. For example, males have large and powerful claws, their abdomen is as wide as the cephalothorax, and the anterior abdominal legs are well developed. Females have small claws, their abdomen is slightly wider than the cephalothorax, and the front legs are underdeveloped. However, these differences are only noticeable to the experienced eye. A person who understands crustaceans solely from a gastronomic point of view is unlikely to be able to distinguish a male from a female.
The armor is strong and our tanks are fast
As mentioned earlier, cancer is an invertebrate animal, but it has a strong chitinous exoskeleton. Its strong shell provides reliable protection from enemies, but prevents cancer from developing and restrains its growth. Therefore, from time to time, crustaceans shed their hard cover (this process can be compared with molting). With great difficulty, the animal pulls legs and claws out of the shell, it happenseven that they come off, but the lost limbs grow back. True, they differ in size and appearance. The shedding of the shell lasts from a few minutes to a full day. After that, cancer becomes helpless and hides from numerous enemies. While its body is covered with soft skin, the animal grows intensively in length. Hardening of the shell is carried out within one and a half months. Moulting in young crayfish occurs more often than in adults.
Habitat conditions
Crustaceans live mainly in the coastal zone, where they master depths of up to three to five meters. They do not form continuous settlements, they concentrate on areas that are located near steep and steep banks, composed of clay, silt, peat or sandy soil, in which it is very convenient to dig holes. Crayfish are very sensitive to the quality of water, as well as the amount of oxygen dissolved in it. If a water body is polluted with municipal industrial wastewater and agricultural pesticides (herbicides, insecticides, etc.), then crustaceans disappear from such waters.
Crustaceans
There are three main species in our country: thick-clawed, long-clawed and broad-clawed crayfish. As their names indicate, they all differ only in the structure of the claws. The most common are long-clawed crustaceans. Individuals of this animal in different water bodies may differ slightly in both biology and body structure. Often, only representatives of one species settle in one water area, but they canbe exceptions. Broad-toed crayfish are found mainly in fresh waters of streams and rivers, as well as in clean lakes. This species of decapod crustaceans arranges colonies-settlements on steep and steep banks. Thick-clawed crayfish, on the contrary, practically do not live in fresh water bodies, they prefer brackish waters of estuaries and desalinated areas of the seas. And long-toed crustaceans are inhabitants of both brackish and fresh water bodies, they are less demanding on environmental conditions, therefore they are more common than other species. They can settle even in stagnant waters with a significantly lower oxygen content. As shelters, these representatives of arthropods use depressions between stones, under sunken trees, among the roots and stems of aquatic plants. In addition, these crayfish often burrow into the mud, thus distinguishing them from their broad-toed counterparts.
