Sea spiders are often referred to as multi-legged animals. They belong to the class Cheliceraceae, the type of these creatures is Arthropods. Also acceptable is the classification by which the term "Chelicerate" is defined as the subtype from which sea spiders are separated into a class of their own. There are several more scientific names for this class - Pantopods, Pycnogonids and others.
Some general information
The concept of "sea spider" includes more than 1300 different species from a dozen families. They live in the seas all over the world. You can meet marine arthropods at different depths. Some species prefer the lower littoral (tidal section of the coast), others descend to the abyssal (deep zone). In saline and weakly saline waters, multi-elbows are much more common than in desalinated inland seas. In coastal areas, spiders settle in thickets of algae and on the ground.
Deep-sea and intertidal spider species have differences in both body structure and size. In deeper layers of water, the sea spider will be larger, it will have significantly longer and thinner legs, which may have long hairs. These devices allow you to reduce the rate of immersion. The spider does not just swim, but seems to soar in the water. To sink to the bottom, it is enough for him to compactly fold his long limbs under the body.
Coastal forms are more compact. Their legs are thicker and shorter, but they have developed tubercles and spikes necessary for hunting and protection.
Building features
Any sea spider, both deep-sea and coastal species, has a typical structure. The body is divided into two tagmas (sections). Their names are segmented prosoma and non-segmented opisome. The prosoma is characterized by a cylindrical or disc shape.
The torso of sea spiders is smaller than limbs and is covered with chitinous cuticle. There is a division into the cephalothorax and abdomen (it is rudimentary). There are from 7 to 9 segments in the cephalothorax, 4 of them are fused together. The fused part of the cephalothorax is called the head segment. The remaining segments can be either fused or dissected. In front of the head segment is a cylindrical or ovoid trunk. On the lateral parts of the trunk, 2 pairs of limbs are fixed: heliphores and palps. The third pair of limbs (ten-segmented egg-bearing legs) is fixed on the ventral side of the head section. One of the structural features of sea spiders is that the 3 front pairs of legs do not reach the ground and do not participate in walking.
The walking legs of the sea spider are attached to the lateral processes of the head segment of the body. Most often there are 4 pairs, but some representatives have 5-6 pairs.
Digestive system
The sea spider has a digestive system in the form of a poorly differentiated through tube with diverticula. The diverticulum in this case is a process of the intestine that goes into each leg. The digestion of these arthropods is combined. Both cavitary and intracellular forms are used together.
Diet
It's easy to guess what sea spiders eat. Most of them are predators. Their diet consists of sessile and inactive invertebrates. These can be polychaetes, bryozoans, ciliates, anemones, intestinal and cephalobranch mollusks, small echinoderm starfish. Prey is held by claws on heliphors. They also tear off pieces of food and go into the mouth.
Gigantomania
Not so long ago, a giant sea spider was found in the waters of Antarctica. Studying the individual, scientists drew attention to a mysterious phenomenon, which they called polar gigantism. For some as yet unknown reason, the icy waters of Antarctica are transforming common sea spider species into giants. Perhaps the increased growth is due to the amount of oxygen, which is more in cold water than in warm water.
It has been established that not only spiders, but also some mollusks, crustaceans and echinoderms suffer from gigantomania in Arctic waters. Research continues.
Starfish and Spider
Do you think we will continue to discuss the structure and life of marine animals? But you are wrong! In this section, we will talk about a fascinating book that explains the success principle of various companies.and organizations. Some of them are traditional, like spiders: they have legs growing from the body, they have a head and eyes. They can function with part of a leg or an eye missing, but without a head they will die.
Another thing is a starfish, although its body parts look ordinary, they have completely different functions: the animal has no head and brain at all, and the main organs are repeated in each limb. Moreover, if you cut off a limb of a star, it will be restored. Even if you cut the sea beauty into several parts, it will not die, and after a while the halves will become independent animals. In fact, using this unique animal as an example, we can consider companies that function like decentralized networks.
The book "Starfish and Spider" is a vivid example of the fact that everything in nature is reasonable, and many laws of development are useful to apply in other areas of human activity.
