FISH

A. Adaptation 1.Definition- is a behavioral, structural or physiological trait that increases a species’ chance of survival in a specific environment. a. Behavioral-Migration b. Structural-shape of the body, fin location and mouth size and orientation. c. Physiological-temperature tolerance, salt tolerance, the ability to breath air when needed, and in body form.

2. Examples a. Ectothermic 1.Definition-organisms that have internal body temperatures at or near the same temperature as the environment in which it lives. 2. Fish, amphibians, and reptiles 3. Most of the fish in Texas are warm water fish due to the geographical location.

b. Osmoregulation 1.Definition-a physiological adaptation allowing fish to live in freshwater or saltwater while maintaining an electrolyte balance.

2. Comparisons a. freshwater fish °water diffuses in °ions diffuse out °drink little °lots of dilute urine °actively reabsorb ions °kidneys °gills b. saltwater fish °water diffuses out °ions diffuse in °drink a lot °concentrated urine °actively excrete ions °kidneys °gills °gut

B. The Anatomy of a Fish

1. External Structures of a Fish

A. Fins 1. supported by rays a. two types of rays 1. soft 2. spines

2. Fin Identification and Function a. unpaired fins 1. dorsal-keeps the fish upright and stable 2. caudal-helps with speed and movement 3. anal-maintain stable equilibrium 4. adipose fin- contains a network of nerves that likely serves as a sensory organ. b. paired fins-can move independently 1. pectoral-used to steer or maneuver 2. pelvic-used to steer or maneuver 3. aides in moving quickly in any direction

B. Skin 1.epidermis-contains mucous glands which secrete mucous to reduce friction while swimming and helps in disease prevention. 2. dermis- made up of fibroblast, collagen, blood vessels and contains scales in pockets. The four types are placoid, ganoid, cycloid ctenoid, or there are none.

3. Examples of scales 4. Fish do not produce additional scales. 5. Scales grow larger over time and age can be determined by counting the rings.

6. Color a. cells 1.chromatophores- pigments cells 2. iridophores-reflective crystals=metallic b. biolumination 1. self –luminous- due to photophores 2. symbiotic bacteria c. control 1. endocrine system 2. nervous system

C. Sensory Mechanisms 1. Lateral line a. line of special hair-like cell on the sides of fish leading to mechanoreceptors b. function- gathers environmental information such as pressure, vibrations, sound c. importance- detecting prey, schooling and orientation to objects in the water

2. Eyes a. placement and shape allow fish to see in all directions b. can see color c. are near-sighted 3. Ears a. located beneath the skin on the head b. hear low-frequency sounds caused by the lateral line 4. Taste-taste buds in the mouth 5. Smell-nares or nostrils on the head

E. Electrical System 1. electric organs 2. electroreceptors 3. examples a. electric eel b. electric catfish c. electric ray

2. Internal Structures

A. Respiratory System 1. gills a. three bilateral layers b. covered with capillaries c. process- water enters in the mouth, moves over the gills, taking in dissolved O 2 and releasing CO 2, then water exits the fish. d. can remove 85% of dissolved O 2 in clean water. 2. operculum- protective gill cover 3. A few species have lungs.

B. Cardiovascular System 1. heart has 2 chambers- one atrium and one ventricle. 2. blood a. red blood cellsfrom the head and kidney- no bone marrow b. white blood cells-similar to ours C. Excretory System 1. gills 2. anterior and posterior kidney

D. Digestive System 1. Structures-primarily like ours 2. Nutrition a. Species vary 1. food 2.feeding behavior a. time b. location c. obtaining food b. general fish nutrition- consume more protein and lipids > carbohydrates

E. Swim Bladder 1. Functions a. buoyancy b. sound, pressure detection F. Neuroendocrine System 1. brain-forebrain,midbrain,cerebellum 2. spinal cord G. Muscular System 1. Muscles makeup 85% of the fish’s body 2. located on the sides of the body for power

C. Classes of Fish 1. Agnatha- Jawless fish a. Examples: Lampreys Hagfish

b. Characteristics 1. No true jaws-round mouth. 2. No true teeth-horny teeth composed of protein located in the roof of the mouth. Used to rasp the scales and skin from the fish surface exposing blood vessel to suck the blood pair of unprotected gill slits. 4. Adults parasitic feeding on blood and the larvae filter feeders. 5. No scales -leathery skin. 6. No paired fins-single mid-dorsal fin. 7. No swim bladder.

2. Chondrichthyes-Cartilage fish a. Examples: Sharks Rays Skates

b. Characteristics 1. true jaws 2. placoid scales cover the body 3. true teeth composed of calcium and grown in rows in the life of the shark 4. 5 pair of unprotected gill slits. 5. paired Fins-pectoral fins and anal or pelvic fins. 6. No swim bladder, instead oil filled liver 7. Sensory pits along the side forming the lateral line. 8. Ampullae of Lorenzinii (electroreceptors that detect low level electrical fields)

3. Osteichthyes-bony fish Types: soft rayed spiny rayed

b. Characteristics 1. true jaws. 2. true teeth composed of calcium. 3. paired fins. 4. ctenoid, cycloid, or ganoid scales. 5.one pair of gill slits protected by the operculum. 6.a swim bladder which provides buoyancy.