Isopods have a body flattened in the dorso-abdominal direction. Carapax is absent. On the head are seated faceted eyes. The thoracic section consists of 6–7 segments. Chest legs are single-branched, walking, having the same structure (hence the name of the detachment). The abdominal legs are two-branched, leaf-shaped, perform respiratory function.
Woodlice - crustaceans, adapted to the terrestrial image. Herbivorous. In some species of woodlice, gill respiration is preserved, these species live in places with high humidity, and they have devices for constant hydration of the gills. In other species, the anterior abdominal legs have air breathing organs - pseudotracheas similar to tracheal insects. Pseudotracheas begin with respiratory openings, which lead into deep and branched protrusions of the integument. Through the walls of these impressions, oxygen penetrates into the hemolymph.
Females have eggs in the brood chamber on the thoracic region from the bottom. In our region, species of the genera Porcelio, Oniscus are most often found.
The species of woodlice living in the desert dig deep holes.
Detachment Legged, or Amphipoda (Amphipoda)
Different-legged crustaceans have a flattened lateral body. Carapax is absent. On the head are seated faceted eyes. The chest legs are seven pairs, they are single-branched, carry gills and have a different structure (hence the name of the detachment). The first two pairs are grasping, ending with claws serving to capture food. The next two pairs end with claws pointing back. The last three pairs are longer than the rest of the limbs and are directed forward with claws.
The limbs with claws are used for swimming and crawling. The abdomen consists of six segments and telson. The first three pairs of abdominal legs are two-branched, multi-segmented, serve for swimming. The next three pairs are directed back and are used for jumping. Reproduction is sexual. Development without transformation. Females have eggs in the brood chamber, located on the thoracic part from below.
Most of the species of amphipods lead a benthic lifestyle, feeds on organic residues. Some species are planktonic.
► Description of other classes and subclasses of type Arthropods:
► The Bilateria Section of the Multicellular Sub Kingdom also includes:
The structure and reproduction of isopods
These arthropods have a flattened in the dorsal-abdominal direction, a wide body with an average size of 1-2 cm. The length of the smallest isopods is 1 mm, the largest representatives are 25 cm. The body is divided into head, abdomen and chest. One thoracic segment (in some species, two) motionlessly fuses with the head. Fusion of the anal lobe with one or more abdominal segments is characteristic.
Only the first pair of chest limbs is transformed into the maxilla. The remaining seven pairs of thoracic and abdominal extremities are relatively equal in length and almost identical in structure. Hence the name of the detachment - isopods.
The sensory organs are located on the head: complex sessile eyes (reduced in parasites), antennas (organs of touch and smell), as well as oral appendages. The oral apparatus in most cancers of this detachment is gnawing. Only in parasites and rare predators, the oral apparatus is transformed into a piercing-sucking proboscis with stylet-shaped jaws.
Respiration of water forms of isopods of gill, with partially abdominal limbs transformed into gills. The heart is displaced into the abdominal region, while in decapod higher cancers it is located in the thoracic region.Reproduction. Most of the species of this group are dioecious, rare forms are hermaphrodites. The development of crustaceans in the vast majority of species is direct. Typically, the female carries eggs and young, recently hatched crustaceans in a brood bag, which is formed from the processes of the thoracic limbs. In parasitic species, larval stages can be free-floating. After several links, young crustaceans turn into adults.
In nature, they occupy important positions in food chains, since these organisms are omnivores. Many isopods themselves serve as the main food for fish. Woodlice are valuable saprophages in biocenoses. Some species harm the human economy by damaging wooden structures - woodworms from the genus Limnoria. A sea cockroach destroys nets and spoils caught fish, causing damage to fisheries.
Ligida Family - Lighdae
Fig. 176. Ligia gray
Lygia gray - Ligia cinerascens Budde-Lund. Large wood lice with a long oval body, its length more than 2 times the width. The dorsal surface of the body is dark gray, shiny, fine-grained, vaulted-convex. The eyes are large, oval, black, located on the sides of the head. The abdominal region is somewhat narrower than the thoracic, consists of 5 free abdominal segments and pleotelson. The posterior-lateral corners of the caudal segment are drawn into pointed processes, the posterior margin is obtuse. I antennas are short and not visible from above, II antennas are long, with a multi-segmented flagellum, when bent back, they reach the posterior edge of the chest. The abdominal legs of all 5 pairs are well developed, bifurcated, adapted for air breathing, their inner branches are tender, spongy, the outer ones are rougher, without air cavities or pseudotrache, cover the inner branches from above. Steering legs attached to the posterior end of pleotelson, long, bifurcated, both branches narrow, rod-shaped. Length up to 40 mm.
Authentically known from the coast of the Yellow Sea and about. Hokkaido in the south to the hall. Syauhu in Primorye, the southern coast of Sakhalin and the southern Kuril Islands. Terrestrial animal, but lives in the zone of sea spray and storm splashes. Lives on coastal cliffs and between stones. He runs very fast. In summer, females hatched eggs and juveniles in brood bags.