Diversity • Fishes are dated back to over 480 million years • Fish evolved in fresh water • Now fish live in ALL water areas – fresh and salt • Fish are the dominant, free-swimming animals of the seas. • Diet: • Some are herbivores (eat plant material) • Others are carnivores(eat meat material)
Diversity • The structure of the body is designed for ease of movement • This has enabled fishes to live in most parts of the world's water bodies • Come in all shapes and sizes • Active life style: • Some are free swimming, • While others rest on the bottom of the sea
General Characteristics • Fish Anatomy • Fins • Made up of stiff rays covered by skin. • Some may be jointed • Some separate near the edge of the fin. • Functions : • Each fin on a fish is designed to perform a specific function.
General Characteristics • Fish Anatomy • Fins • Dorsal fin: lends stability in swimming, controls roll • Ventral fin: lends stability in swimming. • Caudal fin: main propelling fin, provides thrust and controls direction • Anal fin: lends stability in swimming, increase speed • Pectoral fins: Locomotion and side to side movement, acts as rudder and brakes or as feet (mudskippers)
General Characteristics • Skin • Made of collagen and blood vessels. • The skin of fish is divided into two layers, the Epidermis (outer) layer and the Dermis. • The Epidermis is made of epithelial cells, • Constantly shed and replaced with new ones. • Between the epithelial cells are slime cells • Produce mucous secretions that form the very important protective covering (slime coat) • The dermis lies under the epidermis
General Characteristics • Swim Bladder • Helps maintain buoyancy in the water. • A sac inside the abdomen that contains gas. • Scales • Scales do not stick out of a fish • The scales overlap • Form a protective flexible armor • Capable of withstanding blows and bumping
General Characteristics • Lateral line system • Def—a series of scales, which connects with a system of canals containing sensory cells and nerve fibers • It runs in a semi-line from the gills to the tail fin • Seen as a band of darker looking scales running along the side • VERY important sensory organ in fish • It can detect minute electrical currents • Also functions to help the fish identify its surroundings.
General Characteristics • Swimming (Two types) • Cruisers: Swim continuously in search for food, such as the tuna. • Burst Swimmers: stay relatively in the same place (most reef fish) • Internal Body Temperature • Cold blooded (exotherms) • Derive their body heat from their environment and conform to its temperature
General Characteristics • Three Modes of Reproduction: • Oviparous– • Lay undeveloped eggs, • External fertilization (90% of bony fish), Internal fertilization (some sharks and rays) • Ovoviviparous • Internal development- without direct maternal nourishment • Advanced at birth (most sharks + rays) • Viviparous • Internal development- direct nourishment from mother • Fully advanced at birth (some sharks, surf perches)
General Characteristics • In fishes, oviparous is most common • Parental care: • Parental care is very rare as most fish are broadcast spawners, but there are a few instances of parental care. • Methods of Parenting • Egg Scatters- scatter eggs on bottom • Nest Builders- arrange protection for eggs • Egg depositors- selectively place eggs • Mouthbreeders- house eggs in mouth • Egg buriers – bury eggs • Livebearers- give live birth
General Characteristics • Respiration • Gills • Located under the gill covers. • Five gill slits and four gill arches. • Gills are actually mounted/located on gill arches • Circulation • Heart only has two chambers, in contrast to our heart which has four. • Heart only pumps blood in one direction. • A very simple closed-circle circulatory system.
General Characteristics • Digestion • Some have a spiral valves in intestine (shark) • Slows food for better absorbtion • Most have complete system • Excretion • Oily liver to help with water retention, salt levels and excretory purposes
General Characteristics • Sensory • Fish can sense light, chemicals, vibrations and electricity. • Senses (in addition to lateral line) • 1) Vision: • Vision underwater poses many special problems. The most significant is the small amount of light • Vision is limited to a few yards at best
General Characteristics • Senses, cont. • 2) Smell • Used in the location of food • 3) Hearing • It has been shown that fish can hear, but not very well • 4) Taste • Taste buds in fish are located in the mouth and also in the skin covering the head, body fins, and lips. • 5) Touch • Nothing of importance
General Characteristics • Senses, cont. • 6) Chemicals: • Some fish (such as sharks, rays, eels, and salmon) can detect chemical levels as low as 1 part per billion. • 7) Vibrations: • Do have ears located within their bodies • Also have lateral line system that actually lets them feel their surroundings. • 8) Electricity: • Sharks and rays posses special organs for detecting electrical potential [voltage].
Classification • Kingdom Animalia • Phylum Chordata(Subphylum Vertebrata) • Fish Classes: • Modern fish are divided into three classes. • Superclass AGNATHA • Class CHONDRICHTHYES • Class OSTEICHTHYES
SuperclassAgnatha “Jawless” Fish • The most "primitive" of the fishes; • Lack a jaw and a bony skeleton. • Very flexible • Smooth, scaleless skin and are soft to the touch. • In place of the jaws is an oral sucker • Many are highly predatory, attaching to other fish by their suckerlike mouths,
Found in both fresh and salt water and some are anadromous • Def: living in both fresh and salt water at different times in its life cycle • The hagfish has no eyes, while the lamprey has well-developed eyes. • Cartilaginous and fibrous skeleton • Ex: Hagfish and Lamprey
Class Chondrichthyes • Members include the sharks, skates, rays, and ratfish. • Have cartilaginous skeleton, but their ancestors were bony animals. • These were the first fish to exhibit paired fins. • Pelvic fins in males are modified (claspers) used in copulation • Chondrichthyes lack swim bladders,
Internal fertilization • posses 5-7 gill arches (most have 5). • Exposed gill slits • They have cartilaginous upper and loosely attached lower jaws with a significant array of teeth. • Their skin is covered with teethlikedenticles which gives it the texture and abrasive quality of sandpaper. • Separate sexes with paired gonads • Cloaca • All modes of reproduction
Class Ostieichthyes • Comprise the largest section of the vertebrates, with over 20,000 species worldwide. This compares to 51,000 total vertebrate species. • They are called bony fish because: • Their skeletons are calcified, endochondral (start out as cartilage) • Makes them much harder than the cartilage bones of the chondrichthyes.
Have great maneuverability and speed, • Have highly specialized mouths equipped with protrusiblejaws • Pharyngeal jaws for chewing, grinding, crushing • Contain a swim bladder to control buoyancy. • Operculum covers gills • Live in mostmarine and freshwater habitats on earth. • Ex: perch, bass, bluegill, flying fish, sea horse, clown fish, catfish