Fishes

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.

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: 1. Oviparous–

Lay undeveloped eggs, External fertilization (90% of bony fish), Internal

fertilization (some sharks and rays)

2. Ovoviviparous Internal development- without direct maternal

nourishment Advanced at birth (most sharks + rays)

3. 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].

General Characteristics

Classification› Kingdom Animalia › Phylum Chordata (Subphylum Vertebrata)› Fish Classes:

Modern fish are divided into three classes. 1. Superclass AGNATHA2. Class CHONDRICHTHYES3. Class OSTEICHTHYES

Superclass Agnatha “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

Superclass Agnatha – Class Petromyzontida Lamprey

Superclass Agnatha – Class Myxinoidea Hagfish

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 teethlike denticles which gives it the texture and abrasive quality of sandpaper.

› Separate sexes with paired gonads› Cloaca› All modes of reproduction

Class Chondrichthyes - Shark

Class Chondrichthyes - Ray

Class Chondrichthyes - Skate

Class Chondrichthyes - Ratfish

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 protrusible jaws› Pharyngeal jaws for chewing, grinding,

crushing› Contain a swim bladder to control

buoyancy.› Operculum covers gills› Live in most marine and freshwater

habitats on earth.› Ex: perch, bass, bluegill, flying fish, sea

horse, clown fish, catfish

Class Osteichthyes - Various