Fat body
The fat body is a characteristic organ of insects , which is used to store and synthesize substances. In addition, it takes on excretory functions together with the Malpighian vessels . In terms of function, it can therefore be compared with the liver and fatty tissue of mammals. It is made up of several lobes and the hemolymph flows around it. The subdivision into several lobes increases the surface area, which ensures a better exchange of substances between fat and hemolymph.
The fat body arises from the mesoderm , more precisely the abdominal parts of the coelom sacs . This creates a network of lobules in the abdomen that usually only comprise one or two layers of cells and are surrounded by a basal lamina . The metameric structure is largely lost. The fat body can be cylindrical in the thorax and compact in the head area. The shape and size of the fat body varies depending on the species. It is particularly large in cockroaches and larvae of holometabolic insects . In the honeybee larva, it can make up to 65% of the body weight. In the honey bee larva, the fat body dissolves almost completely before pupation and the cells are distributed in the hemolymph. The color of the fat body is variable and can be transparent, white, yellow, orange or green.
The fat body consists of trophocytes (syn. Adipocytes ), which presumably arise from blood cells . In addition to trophocytes, urate cells , oenocytes and mycetocytes are also found in some species . In addition, the fat body can accommodate luminous organs . These cells have substance- specific vacuoles as their storage location .
In order to supply the animal with energy, glycogen (carbohydrates), lipids (fats) and proteins (proteins) are stored in the fat body . Both carbohydrates and fats are used for the metabolism of the fat body. The fat body grows with a good supply of food and is broken down accordingly in times of lack of food and dormancy . The proteins are primarily used to build up the cuticle during molting . In honey bees they are used to build up the forage glands . The fat body is also the synthesis site of trehalose , the "blood sugar of insects".
Fat bodies in bees
The honey bees hardly take up lipids with their food. To meet their needs, lipids are synthesized from carbohydrates, and the place of this synthesis is the fat body. The beeswax precursors are also produced there and the fat body is in direct contact with the wax glands.
Web links
Individual evidence
- ^ A b Charles F. Lytle, John R. Meyer: Practical course in general zoology . Pearson Germany, 2010, ISBN 978-3-86894-035-0 , p. 262.
- ↑ a b c K. Dettner, Werner Peters: Textbook of Entomology. Springer-Verlag, 2nd edition 2011, ISBN 978-3-8274-2618-5 , p. 121.
- ↑ a b K. Dettner, Werner Peters: Textbook of Entomology. Springer-Verlag, 2nd edition 2011, ISBN 978-3-8274-2618-5 , p. 119.