The spiral valve is an internal organ characteristic of several orders of fish and cyclostomes . It is a spiral fold of the middle intestine, spirally curled inward, forming up to 40 [1] and even 45 turns [2] .
A spiral valve is present in fish of ancestral origin - cartilaginous ( sharks , rays and chimeras ) and some bony - lobed - nosed and ganoid ( sturgeon-shaped , multi - fin- shaped , amyiform-like , armored ) [3] [4] . Cyclostomata have a small spiral valve, although it is very poorly developed [3] . In the form of an insignificant rudiment, it is also found in some herring-like ( Chirocentrus ) [3] .
It is especially developed in sharks and stingrays. In all these fish, the intestinal length is small: for sharks 3 m long, it is only 2.7 m (in humans about 8 m), so the spiral valve significantly increases the intestinal suction surface [2] . In addition, this organ significantly slows the passage of food through the intestine, which increases the duration of absorption [1] . In sharks and stingrays, the stomach usually passes almost immediately into a spiral valve, which, in turn, opens into the rectum [5] . A highly developed spiral valve is one of the most characteristic anatomical features of sharks and rays.
Notes
- ↑ 1 2 Spiral valve . Great Soviet Encyclopedia. Electronic version. Date of treatment July 25, 2011. Archived on August 15, 2012.
- ↑ 1 2 F. Ommany. Fish. - M .: "The World", 1975. - S. 81. - 192 p.
- ↑ 1 2 3 Animal Life / Ed. S.P. Naumov and A.P. Kuzyakin. - M .: "Enlightenment", 1971. - T. 4 (part one). - S. 25-27, 84, 100, 123. - 300,000 copies.
- ↑ Soldatov V.K. Commercial ichthyology: a textbook for STR . - Yurayt, 2019 .-- S. 97 .-- 595 p. - ISBN 978-5-534-10648-0 .
- ↑ Sharks and Rays. Anatomy and Physiology . Seaworld.org. Date of treatment July 25, 2011. Archived on August 15, 2012.