The cappings of fish are bones that have the primary mission of protecting the gill structures or gills. They are also responsible for ensuring the circulation of water through the gills in only one direction, in order to comply with the respiratory process of the body.
The operculum in many species of fish is the broadest bone lamina of the skeleton, for this reason it is frequently used by scientists in biological research as a measurement parameter for estimating the age of the individual.
Location of the operculum. By Internet Archive Book Images, via Wikimedia Commons
Cranial skeletal malformations, specifically those suffered in the gills, have been reported mainly in captive-bred fish, occurring in the first stages of growth and attributed to unfavorable conditions of the environment in which they are found.
Betta splendens fighting fish, originating from the Asian continent, have been widely studied due to the common aggressive reaction that male individuals develop towards other males, showing striking aptitudes such as the extension of the fins and the particular opening of the glands, where even gills protrude.
General characteristics
Since the gills are soft structures in constant contact with water and the environment, they need to be protected by the gills that are formed by a calcareous composition. Bony fish have four pairs of gills, each supported by a gill arch.
The process of respiration or gas exchange between oxygen O 2 and carbon dioxide CO 2 in the blood in fish begins with the opening of the mouth, allowing water to enter the body.
Later they close it, conducting the water towards the gills for its filtration and oxygen extraction, and finally it is expelled without being able to return through the caps.
The blood circulation is countercurrent to the water, thus achieving that the gas exchange is approximately 80%, otherwise it would only be 50%, fulfilling the capture of oxygen and the elimination of carbon dioxide.
Compared with air-breathing organisms, energy expenditure is very high, especially when oxygen concentrations in the water are low, for this reason the respiratory system must be highly efficient.
The determination of the age of the fish is generally more exact in the operculum than in the scales, with the exception of older specimens. Growth rings can be clearly seen on its surface.
Operculums are unique to bony fish, so cartilaginous fish like sharks and rays lack these.
Features
The covers serve two primary functions in bony fish:
- Protect the gills, which are very sensitive organs and prone to physical damage or diseases caused by bacteria, parasites and fungi.
- Actively contribute to the respiratory process, where they function as pumps and gates that regulate the exit of water from the body, prevent its entry and establish a single flow direction.
Anatomy
The covers are located in the anterior part of the fish, establishing the limit of the head. They are mostly trapezoidal or rectangular in shape, having a slightly concave inner face.
They are divided into four margins: the anterior or preopercular, the superior, the posterior and the inferior or subopercular.
To achieve its constant movement, the operculum has three powerful muscles inserted dorsally on its surface.
By Jlikes2Fish, from Wikimedia Commons
Moonfish Mola mola
(https://www.publicdomainpictures.net/es/view-image.php?image=16852&picture=peces-luna-mola-mola)
Angiliform fish, family Muraenidae
(https://pxhere.com/es/photo/650471)
Seahorse Hippocampus sp.
By Jon Bragg (https://www.flickr.com/photos/festivefrog/3208805703/in/photostream/)
Salmon Salmo sp.
Source: pixabay.com
Betta fish Betta splendens
Source: pixabay.com
Gold carp fish Carassius auratus
(https://www.peceswiki.com/imagenes-fish-carpa-dorada-jpg)
Shaker Electrophorus electricus
By KoS, from Wikimedia Commons
Piranha Pygocentrus sp.
By Rinaldo Wurglitsch (https://www.flickr.com/photos/wurglitsch/2629145976)
References
- rguello, W., M. Bohórquez and A. Silva. (2014). Cranial malformations in larvae and juveniles of cultured fish. The t. Am. J. Aquat. Res. Vol. 42 (5): 950-962.
- Bioinnova. Gaseous exchange in fish. Innovation group on teaching in biological diversity. Recovered from:
- Mancini, M. (2002). Introduction to the biology of fish. Introductory courses on animal production and animal production I, FAV UNRC. 19 pp.
- Martínez, I. (2008). Aggressive behavior in the Siamese fighting fish (Betta splender). University Annals of Ethology. Vol. 2: 98-105.
- Miranda, R. and M. Escala. (2002). Identification guide for cyprinid bone remains. Publ. Biol. Univ. Navarra, Ser. Zool. Vol. 28: 98-114.
- Werlinger, C. (2005). Marine biology and oceanography: concepts and processes. Volume I. 253-285 pp.