The Leydig organ , the Leydig organ is one of the hematopoietic organs of plate - branchial fish ( sharks and stingrays ). Most (but not all) have platelet-gill [1] [2] . The remaining animals, including the closest relatives of the lobar gill - whole - headed - do not have it [1] .
This organ has been known since 1685 and was initially considered the salivary gland . In 1857, a German zoologist and histologist Franz Leydig described it as a structure similar to a lymph node . In honor of Leydig, this body got its name [3] [4] .
The Leydig organ is located along the esophagus (between its muscular and mucous membranes [3] ). Usually it is more or less divided into two lobes: dorsal and abdominal. The Leydig organ can be quite large - for example, in a six-gill shark 1.8 m long, it reaches a mass of 1.6 kg [4] . It has a white color and is easily recognized among the surrounding tissues [1] . Histologically, it resembles the bone marrow of higher vertebrates (fish do not have it), but differs from it in the absence of fat cells and (at least in most species [3] ) erythroblasts [1] .
This organ is part of the lymphatic system and produces granular leukocytes , especially eosinophilic ones [1] (but not basophilic ones , which, apparently, do not exist in cartilaginous fish at all [3] ). In addition, agranulocytes (namely T-lymphocytes ) are formed there [1] . Red blood cells are usually not produced there. But the giant shark is known for the active production of red blood cells and platelets in this organ, and it can take on the hematopoietic function of the spleen if removed [3] [2] .
Also, the hematopoietic function in these fish, which do not have bone marrow and lymph nodes , is performed by the spleen , thymus , meninges and special tissues around the gonads ( epigonal organs ) and in the intestinal wall [1] .
Notes
- ↑ 1 2 3 4 5 6 7 Honma, Yoshiharu; Okabe, Kazuyuki; Chiba, Akira. Comparative histology of the Leydig and epigonal organs in some elasmobranchs (English) // Japanese Journal of Ichthyology: journal. - 1984. - Vol. 31 , no. 1 . - P. 47-54 . Archived July 6, 2011.
- ↑ 1 2 Iwama George K., Nakanishi Teruyuki. The Fish Immune System: Organism, Pathogen, and Environment . - Academic press, 1996. - P. 13-15. - 380 p. - ISBN 0-12-350439-2 .
- ↑ 1 2 3 4 5 Větvička Václav, Síma Petr. Evolutionary Mechanisms of Defense Reactions . - Springer, 1998 .-- P. 126-128. - 196 p. - ISBN 3-7643-5813-0 .
- ↑ 1 2 Aidan Martin R. Without Bones, How Do Sharks Make Red Blood Cells? . ReefQuest Center for Shark Research. Date of treatment October 14, 2012. Archived December 12, 2012.
Links
- Aidan Martin R. Without Bones, How Do Sharks Make Red Blood Cells? . ReefQuest Center for Shark Research. Date of treatment October 14, 2012. Archived December 12, 2012.