Internal Physiology of Fishes

Internal Physiology of FishesChapter 8March 2009

1FeedingMost fishes are carnivores.plankton feedersdemersal feedersopen water predators

Bony fishes teeth can be found in jaw, roof of the mouth, on gill rakers, and in pharynx

Cartilaginous fishes teeth only on jaw margin

2Gill rakers & arches

3

Digestive Systemmouthpharynxesophagusstomach J-shaped or elongatedintestineanterior pyloric caeca secretes digestive enzymesreceives inputs from pancreas and liverspiral valvecloaca/anus

4

Circulatory SystemFish have a two-chambered heart.Deoxygenated blood is pumped to the gills where gas exchange occur.5Circulation and Heat ExchangeMost fish are poikilothermic.Few large sharks and bony fish can maintain core body temperature slightly higher than their environment.rete mirabile (wonderful net)adaptation for inhabiting colder waters

6Respiratory AnatomyFish exchange O2 and CO2 through paired gills.

Cartilaginous fishes Bony fishes7Respiratory Anatomy Cartilaginous vs. Bony FishesCartilaginous FishesMost swim continuously.First pair of gill slits is modified into spiracles.Usually 5 gill slits may have 6 or 7.

Bony FishesHave a single common gill chamber.Covered by an operculum

8

Respiratory AnatomyCovered by an operculumGill archesGill filamentsLamellaeGas exchange occurs by simple diffusionCountercurrent system of flow9Osmoregulationregulation of the bodys internal salt balanceBony fishBody fresher than seawaterDrink seawaterSalt excreted by kidneySmall amount of urineChloride cellsCartilaginous fishRectal glandUrea in bloodAbsorb water through gills

10Nervous SystemFish possess a central nervous system, consisting of a brain and spinal cord.

Variation exists. Proportional size of the lobes reflects the predominant movement and feeding behaviors of particular species. (i.e. the largest area of the lamprey brain is the cerebellum and medulla which indicates the fishes reliance on grasping with its jaw and attaching to its food).

11Fish SensesSmell use sensory cells in olfactory sacs on both sides of the head. Each sac opens to the nostrils or nares.

During dissection, note the large portion of the forebrain devoted to smell particularly in the shark.

12Fish SensesTaste Taste buds can be found on the mouth, fins, skin, lips, and barbels of fish.

13Fish SensesSight used by most fishesUnlike terrestrial vertebrates, fish eyes focus by moving the lens closer or farther away from the subjectShallow water species have color vision

Sharks and deeper water species may have little color vision, but see best in contrasting light situationsSome have a nictitating membrane that can cover the eye from the bottom to reduce brightness or offer protection

14Fish SensesTouch fish possess a lateral line consisting of canals in the skin and in the bone or cartilage of the head that connect to neuromast cells that are sensitive to vibration.

15Fish SensesHearing perceive sound waves with their inner earsUse fluid filled canals on either sides of the brainSome fish amplify sounds using their swim bladderInvolved in balance use ear stones or calcified otoliths that rest on sensory hairs

16Fish Skeleton

17Shark Skeleton

18ReproductionSexes are usually separate.Some fish are hermaphroditic, but usually still reproduce with other individuals.Some fish are sequential hermaphrodites individuals begin life as one gender and later change into the other.

Sexually dimorphic sockeye salmon (male on bottom)19Simultaneous HermaphroditesFish in the Salmon and Sea bass families.

20Protygynous sequential hermaphroditism

21Protandrous sequential hermaphroditism

Initial phase: initial males and femalesTerminal phase: males22Fish Reproductive AnatomyJawless and bony fish separate urogenital opening for urination and gamete releaseCartilaginous fish duct leads from reproductive organ to the cloaca

http://www.marinebiodiversity.ca/shark/english/skull5.htm

23Reproductive behaviorTiming of reproduction controlled by sex hormones released into blood stream.In response to maturation of gametes or to environmental cuesPotential mates come together.CourtshipFertilization may be internal (most cartilaginous fish) or external (most bony fish)Some fish tend eggs or brood nests (usually males)24Early DevelopmentOviparous large number of immature eggs are laid at a single time. Larval fish hatches quickly, but still retains and absorbs yolk sac.

Ovoviviparous female retains eggs inside her reproductive tract for protectionIntrauterine cannibalism

Viviparous produce embryos that absorb nutrients through the walls of the mothers reproductive tract25Work Cited"Animals." Anatomy of animals. 12 Mar 2009 . Burgess, George. Spotted Eagle Ray.. 25 Feb. 2005 . Castro, Peter, and Michael Huber. Marine Biology 5th ed. McGraw-Hill Higher Education, Inc, Boston.Dery, Bernard. "Skeleton of a fish." The Visual Dictionary. 2009. 12 Mar 2009 . "eye." Canadian Shark Research Laboratory. 12 Mar 2009 . "Glossary of Terminology: S." Coris. National Oceanic and Atmospheric Administration: U.S. Department of Commerce. 12 Mar 2009 . Hunt, Stephen. How Stuff Works - Shark Pictures. 2009. 11 Mar. 2009 . Miller, ., and . Lea. Guide to the Coastal Marine Fishes of California. : , 1972."moray eel." Shark Tooth Gifts.com. 12 Mar 2009 . The Open University. Surviving the Winter.. 12 Mar. 2009 .Singer, Joshua. Why Do People Collect Shark Teeth? 2009. 11 Mar. 2009 ."skeleton." Canadaian Shark Research Laboratory. 12 Mar 2009 . "state fish." Nebraska Secretary of State. State of Nebraska. 12 Mar 2009 . Sunquist, Claire. A Fish with Human Teeth.. 11 Mar. 2009 . "vertebrate nervous system." The Internet Encyclopedia of Science. 12 Mar 2009 . Welcome to the Growfish Aquaculture Portal. 2006. Gippsland Aquaculture Industry Network Inc.. 12 Mar 2009 ."What are otoliths?." Shape Analysis of Fish Otoliths. AFORO (ICM-CMIMA-CSIC). 12 Mar 2009 . 26