18.+chordata+-+osteichthyes

= Chordata - Osteichthyes (Bony fishes) by Yasmin Darvish = __ Specific species: Amia Calva (Bowfin) __



Classification/Diagnostic Characteristics - __Kingdom__: Animalia; __Phylum__: Chordata; __Class__: Actinopterygii; __Order__: Amiiformes; __Family__: Amiidae; __Genus__: Amia; __Species__: Amia Calva (13) - There are over 30,000 types included in freshwater and salt water. (16) - They have internal skeletons of calcified, rigid bone rather than flexible cartilage. (16) - Their gills open into a single chamber covered by a hard flap, called an operculum. (16) - They illustrate the structural elements common to all vertebrates. (16) - In addition to the paired pelvic fins, these fishes have paired pectoral fins on the sides of their bodies. (16) - The smallest Osteichthyes are less than 1 centimeter long as adults; the largest weigh as much as 900 kilograms. (16) -Osteichthyes have a unique characteristic called an endochondral bone or "replacement bone" (8) -This bone is ossified internally by the replacement of cartilage; allows osteoblasts to continue bone formation within the cartilage (8) -The net result of this process is that a vascularized network of bone replaces the cartilage (8) - Adult Bowfin females may reach 30 inches, obtain a weight of 8 1/2 pounds and live for about 12 years. (2) - A dorsal fin with more than 45 rays is present. This is over half the length of the fish. (9) - They have a cylindrical and heavy body with a wide bony jaw and scales. (9) -A tiny pair of barbells is present above the nostrils. (9)

Relationship to Humans - Fish are a big factor in the diet of many humans - //A. calva// are fun to catch because their strength and aggressiveness provide a fun challenge. The eggs of //A. calva// are sold as a cheap alternative for caviar and are marketed as "Choupiquet Royal". However, //A. calva// prey on many fish popular in the market, which decreases the supply of certain species for fishermen. (4) - Bowfin are near the top of the food chain in most of the ecosystems that they are in. (4)

Habitat and Niche -Amia Calva lives in freshwater lakes, rivers, and swamps in North America; during high water stages, bowfin move out into the flood plain with lower water levels. (11) - Bowfin generally prefer clear water with large amounts of aquatic vegetation, but they have also inhabited ditches, pits, and pools of slow streams (4) - They swim into river cutoffs where they are usually trapped when water level decreases; however, they can breathe air so they survive these drained ponds for a long time. (2)

Predator Avoidance - They can be eaten by other predators, but their extensive protection of their young and solidarity habits diminish that chance (3) - Don't have many predators since they are not considered a sport fish. (2) - They usually take a hook and put up a fight on light tackle. (2) - Their bullet-shaped body, armor-like plates around their head, and their sharp canine-like teeth give them an advantage towards predators. (15) - When it comes to males protecting their young, they will use their tails to create a mud screen between their kids and any approaching predator. (15)
 * -** Their main predator is a larger bowfin (3)

Nutrient Acquisition - They exploit nearly all types of aquatic food sources. (16) - In the oceans, they filter plankton from the water, rasp algae from the rocks, eat corals and other soft-bodied colonial animals, dig animals from soft sediments, and prey on virtually all kinds of other fishes. (16) - In fresh water, they eat plankton, devour insects, eat fruits that fall into the water in flooded forests, and prey on other aquatic vertebrates and occasionally, terrestrial vertebrates. (16) - A large part of their diet includes frogs, bass, other bowfin, dragonflies, sunfish, crayfish etc... (4) - They have taste buds in their skin that allow them to find food without the use of vision. (16)

Reproduction and Life Cycle - They bring their gametes together simply by releasing a large number of gametes into the water. This is known as external fertilization, or spawning, and requires the production of a massive number of gametes. (16) - Recognition mechanisms are important in aquatic species that practice external fertilization because sperm and ova of different species can be in the mix in the aquatic environment. (16) - When reproducing, males prepare a nest with a slight depression where the females will lay their eggs. The female lies on the bottom of the nest while the male encircles her. The female releases her eggs and the male releases his sperm (milt). (4) - More than one female can lay their eggs in a male's nest and females often lay eggs in several nests. (4) - Males take care of the offspring by guarding the nest and keeping the eggs supplied with fresh water. (4) - Eggs hatch in 9 days after fertilization which are continued to be overlooked by the male until they are able to swim freely by themselves (2)

Growth and Development - Takes 1,551 days for a female and 1,460 days for a male to fully mature. (6) - Bowfin live around 10-12 years in the wild, but around 30 years in captivity. (4) -Bowfin start out looking almost like tadpoles, and for the next six months, continue to grow at a rapid pace. After 3-5 years, bowfin reach sexual maturity. (4)

Integument - Their outer body surface is covered with flat, thin, lightweight scales that provide some protection or enhance movement through the water. (16) - Characteristics include stable cranial bone pattern, rooted teeth, middle mandibular insertion (10) - They have an elongated body with a dorsal fin running its entire length (12)

Movement - Fins and swim bladders improved stability and control over locomotion. (16) - Paired fins stabilize the position of jawed fishes in water and help propel them at times (16) - Their tail fin helps fish move and turn rapidly. (16) - In fish, dark trunk (slow-twitch) muscle is used for steady, continuous swimming. (16) - Slow-twitch fibers (red muscle) contains myoglobin and have many mitochondria and have lots of blood vessels. Muscles with slow-twitch fibers are good for doing long-term aerobic work. (16) - Fast twitch muscle is used for rapid spurts of activity such as escape or prey capture. (16) - Fast twitch fibers (white muscle) have few mitochondria, little to no myoglobin, and fewer blood vessels. These fibers can develop maximum tension more rapidly than slow-twitch fibers and are good for short-term work that requires maximum strength. (16)

Sensing The Environment - In their nervous system, bony fish have a central brain, spinal chord, and lots of nerves that branch out. (7) - Their nerves allow them to see and feel what is near them, this is called the peripheral nervous system (7) - In the front of their brains, bony fish have olfactory lobes, which allow them to smell very well. this is important because bowfins use smell to hunt - The brain also contains optic lobes, which help the fish to see when hunting (7) - The brain connects to the spinal chord through the myelencephalon, which functions in fish to help with osmoregulation and respiration (7) - The internal temperatures vary and match the external temperatures of the water surrounding it (10) - Some fish have internal temperatures that are slightly higher than the exterior waters (10)

Gas Exchange - Gas-filled sacs that extend from the digestive tract supplement the gas-exchange functions of the gills by giving the fish access to atmospheric oxygen. (16) - These sacs evolved into swim bladders. By adjusting the amount of gas in its swim bladder, a fish can control the depth where it remains suspended in the water while using as little energy as possible. (16) - These bladders are also known as organs of buoyancy. (16) - Fish gills use countercurrent flow to maximize gas exchange. (16) - The internal gills of fishes are supported by gill arches that lie between the mouth cavity and the protective opercular flaps on the sides of the fish just behind the eyes. (16) - Water flows unidirectionally into the fish's mouth, over the gills, and out from under the opercular flaps; the gills are continuously bathed with fresh water. (16) - This constant, one-way flow of water over the gills maximizes the PO2 on the external gill surfaces. On the internal side of the gill membranes, the circulation of blood minimizes the PO2 by sweeping O2 away as rapidly as it diffuses across. (16)

- Gills have a high surface area for gas exchange because they are so highly divided. (16) - Each gill consists of hundreds of ribbonlike gill filaments. (16) - The upper and lower flat surfaces of each gill filament are covered with rows of evenly spaced folds known as lamellae; these are the actual gas exchange surfaces. (16) - Afferent blood vessels bring deoxygenated blood to the gills, while efferent blood vessels take oxygenated blood away from the gills. (16) - Blood flows through the lamellae in the direction opposite to the flow of water over the lamellae.(16) - They ventilate their gills by means of a two-pump mechanism; closing and contracting the mouth cavity pushes water over the gills. (16) - The bowfin (//Amia calva//) is commonly known as the "mudfish" and evolved from ancestors who lived during the Jurassic and Cretaceous periods of the Mesozoic Era. Its ancestors acquired the ability to breathe air, a necessary adaptation to survive periods when fresh water bodies lost their oxygen levels or water levels. So while the bowfin will typically obtain dissolved oxygen from its aquatic environment, the bowfin also is able to breathe air by going to the surface of the water breathing air directly and storing the air in its gas bladder(used by most fish species to adjust buoyancy only). The gasbladder is connected to bowfin's circulatory system allowing it to breathe air and therefore live in habitats with low oxygen levels and, therefore, less competition. (5)

Waste Removal - Bony fishes maintain an osmolarity of 1/3 to 1/2 the osmolarity of seawater, which is around 1,000 mosm. (16) - Their only source of water is the sea around them, so they must conserve water and excrete excess solutes. (16) - They cannot produce urine that is more concentrated than their extracellular fluids, they minimize water loss by producing very little urine. (16) - Bony fishes do not absorb from their guts some of the ions they ingest; they have an additional excretory organ besides their kidney: gills. (16) - Na+ is actively excreted across gill membranes, with Cl- following. (16)

Environment Physiology - Active fish produce substantial amounts of metabolic heat, but they have difficulty retaining any of that heat due to their ectothermic characteristics of not being able to control their internal body temperature. (16) - Blood pumped from the fish heart goes directly to the gills for respiratory gas exchange. (16) - Gills are thin and have a high surface area, so blood comes into thermal equilibrium with the surrounding water; any heat the blood picks up from the metabolically active muscles is lost to the cold water flowing over the gills. (16) - Amia calva can withstand high temperatures and survives in waters unsuited to most fishes. (14)

Internal Circulation - Most fishes have a simple two-chambered heart and a single circuit. (16) - The Atrium receives and pumps blood it into the ventricle which pumps the blood to the gills, which are arranged into each gill arch in an afferent arteriole and leaves the gill in an efferent arteriole. (16) - This design places a limit on the pressure that propels blood through the non-respiratory tissues and organs (16) - Most of the pressure imparted to the blood by the contraction of the ventricle is lost as the blood travels through the narrow gill lamellae. (16)
 * -** In most fish species, the circulatory system conducts cool, oxygenated blood from the gills through a large dorsal aorta to the rest of the body

Chemical Control (Endocrine System) The gastroenteropancreatic system of Bowfin fish consists of an endocrine pancreas, or an islet organ, that is made up of abundant B cells that react to insulin; D cells that are widely distributed throughout the pancreas and contain growth hormone antibodies; A and F cells that are immunoreactive against glucagon and some polypeptides in the pancreas. This system is similar to other actinopterygian fish. (1)

Review Questions 1) What is the advantage of the Bowfin's ability to also be able to breathe in the air? How do they do this? 2) What defense mechanisms do Amia Calva use to protect their offspring? 3) Where are most bowfin located? **Answer:** Bowfin are native to North America and occupy pools of rivers, lakes, and swamps. When they are presented with high water, they swim into river cutoffs. Most times, they are trapped in cutoffs when water level decreases, however, that is not an issue since they have the ability to breathe air.  4) How do the fins of Bowfin help them with their movement? 5) How do Bowfin's secrete their waste? Why?
 * Answer**: The advantage of being able to breathe air is that they can live in habitats with low oxygen levels, which lessens their competition with other fish are marine animals. They do this since they are able to store air in their gas bladder (which most fish just use for buoyancy) that is connected to their circulatory system.
 * Answer:** Bowfin are very cautious of their young and take many safety precautions to keep them safe. With their fearful looks, male bowfins will also use their tails to create a mud screen between their kids and any approaching predator.
 * Answer: ** Their p aired fins stabilize the position of the Bowfins in water and help propel them at times. Their tail fins also help them move and turn rapidly.
 * Answer:** Bony fishes such as Bowfins, maintain an osmolarity of 1/3 to 1/2 the osmolarity of seawater, which is around 1,000 mosm. Their only source of water is the sea around them, so they must conserve water and excrete excess solutes. They cannot produce urine that is more concentrated than their extracellular fluids, they minimize water loss by producing very little urine.

Sources **:** (1) https://link.springer.com/chapter/10.1007/978-1-4899-3617-2_17 (2) https://www.floridamuseum.ufl.edu/fish/discover/species-profiles/amia-calva (3) http://www.in.gov/dnr/fishwild/files/fw-bowfin.pdf (4) http://animaldiversity.org/accounts/Amia_calva/ (5) http://www.nanfa.org/ac/Bowfin%20Amia%20calva%20Mudfish.pdf (6) http://genomics.senescence.info/species/entry.php?species=Amia_calva (7) [] (8) http://www.newworldencyclopedia.org/entry/Osteichthyes (9) http://www.bowfinanglers.com/bowfininfo.html (10) http://www.newworldencyclopedia.org/entry/Osteichthyes (11) http://www.cfr.msstate.edu/wildlife/fisheries/?a=detail&id=3&info= (12)http://www.futuredigital.com/aquarium_info/info_north_american_freshwater_fish/bowfin_info.html (13) http://animaldiversity.org/accounts/Amia_calva/classification/ (14) https://www.igfa.org/species/100-bowfin.aspx?CommonName=100-bowfin.aspx (15) https://www.fws.gov/eddies/episodeSpring2013/american_fishes/index.html (16) Hillis, D. M. (2015). Principles of life. Sunderland, MA: Sinauer Associates.