Amphibians [ edit ] An alpine newt larva showing the external gills, which flare just behind the head In bony fish, the gills lie in a branchial chamber covered by a bony operculum. The great majority of bony fish species have five pairs of gills, although a few have lost some over the course of evolution. The operculum can be important in adjusting the pressure of water inside of the pharynx to allow proper ventilation of the gills, so bony fish do not have to rely on ram ventilation (and hence near constant motion) to breathe. Valves inside the mouth keep the water from escaping. [9] Marine teleosts also use their gills to excrete osmolytes (e.g. Na⁺, Cl −). The gills' large surface area tends to create a problem for fish that seek to regulate the osmolarity of their internal fluids. Seawater contains more osmolytes than the fish's internal fluids, so marine fishes naturally lose water through their gills via osmosis. To regain the water, marine fishes drink large amounts of sea water while simultaneously expending energy to excrete salt through the Na +/K +-ATPase ionocytes (formerly known as mitochondrion-rich cells and chloride cells). [11] Conversely, fresh water contains less osmolytes than the fish's internal fluids. Therefore, freshwater fishes must utilize their gill ionocytes to attain ions from their environment to maintain optimal blood osmolarity. [9] [11] Cannon, L. R. G.; Lester, R. J. G. (1988). "Two turbellarians parasitic in fish". Diseases of Aquatic Organisms. 5: 15–22. doi: 10.3354/dao005015. Gills are specialized organs that are adapted for extracting oxygen from water. They are made up of thin, flat filaments that are richly supplied with blood vessels.

a b c d e M. b. v. Roberts; Michael Reiss; Grace Monger (2000). Advanced Biology. London, UK: Nelson. pp.164–165. These structures increase the surface area available for gas exchange and are rich in blood vessels, which transport oxygen to the rest of the body. As water flows over the filaments, oxygen diffuses across the thin walls of the filaments and into the bloodstream, while carbon dioxide diffuses out of the bloodstream and into the water. Justine, JL. (September 2004). "Three new species of Huffmanela Moravec, 1987 (Nematoda: Trichosomoididae) from the gills of marine fish off New Caledonia". Systematic Parasitology. 59 (1): 29–37. doi: 10.1023/B:SYPA.0000038442.25230.8b. PMID 15318018. S2CID 29105973. The structure of gills is optimized for countercurrent exchange in water, which is much denser than air. In addition, gills are not designed to prevent water loss, which would occur if they were exposed to air. What adaptations have evolved in different aquatic species to enhance gill function?Different aquatic species have evolved a variety of adaptations to enhance gill function. For example, some fish have developed specialized structures called gill rakers, which help to filter out food particles and prevent damage to the delicate gill filaments.

a b c d Dorit, R. L.; Walker, W. F.; Barnes, R. D. (1991). Zoology. Saunders College Publishing. pp. 273–276. ISBN 978-0-03-030504-7.I just watched it and will echo the comments made by others in thanking Matt for his bravery and honesty in making the video. I hope that making and sharing the video has not only helped him but also helped others.

In addition to the gill arch, fish also have an operculum, which is a bony flap that covers and protects the gills. The operculum is attached to the gill arch and can be opened and closed to regulate the flow of water over the gills. Gills Vs Lungs Gills are specialized organs that allow aquatic animals to extract oxygen from the water. The evolution of gills has played a crucial role in the adaptation of aquatic species to their environment. Gills and lungs are both respiratory organs that allow animals to extract oxygen from the air or water and release carbon dioxide. Lungs are highly efficient at extracting oxygen from air, but they are not effective at extracting oxygen from water.

Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely. Respiratory mechanism in bony fish The fish draws oxygen-rich water in through the mouth (left). It then pumps it over gills so oxygen enters the bloodstream, and allows oxygen-depleted water to exit through the gill slits (right) Aquatic arthropods usually have gills which are in most cases modified appendages. In some crustaceans these are exposed directly to the water, while in others, they are protected inside a gill chamber. [14] Horseshoe crabs have book gills which are external flaps, each with many thin leaf-like membranes. [15]

Lungs, on the other hand, are specialized organs that are adapted for extracting oxygen from air. They are made up of a network of air sacs and tubes that are lined with thin, moist membranes. Respiration in the echinoderms (such as starfish and sea urchins) is carried out using a very primitive version of gills called papulae. These thin protuberances on the surface of the body contain diverticula of the water vascular system. a b c d e f g h i j Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp.316–327. ISBN 0-03-910284-X.

This is why fish need gills

The process of respiration in gills is highly efficient due to the large surface area of the gill filaments and the constant flow of water over the lamellae. The gill filaments are covered by a thin layer of skin, which allows for the exchange of gases between the water and the fish’s blood vessels. The skin is highly vascularized, with a network of capillaries that allow for the efficient exchange of gases. Hughes, George Morgan (1963). Comparative Physiology of Vertebrate Respiration. Harvard University Press. pp. 8–9. ISBN 978-0-674-15250-2. Although most fish respire primarily using gills, some fish can at least partially respire using mechanisms that do not require gills. In some species cutaneous respiration accounts for 5 to 40 per cent of the total respiration, depending on temperature. Cutaneous respiration is more important in species that breathe air, such as mudskippers and reedfish, and in such species can account for nearly half the total respiration. [16] Scott, Thomas (1996). Concise encyclopedia biology. Walter de Gruyter. p. 542. ISBN 978-3-11-010661-9.