Fish Biology and Evolution Quiz

The Fishes: Vertebrate Success in Water

• Fishes are vertebrates adapted to aquatic life.
• Hagfishes (Class Myxini) have cartilaginous head support, lack vertebrae, and have a notochord. They have sensory tentacles and slime glands. They are cold-water marine scavengers, feeding on soft-bodied invertebrates and dead fish. Some species are endangered due to overfishing.

Infraphylum Hyperotreti: Class Myxini

• Hagfishes have a unique characteristic, a slime-producing ability for defense.

• Hagfishes are marine organisms and inhabit cold-water environments globally.

• Hagfishes are scavengers, feeding on dead, soft-bodied organisms and dead fish.

• Some species are facing endangerment due to overfishing.

Class Petromyzontida

• Lampreys have a sucker-like mouth with sensory organs and attachment functions.

• Lampreys have epidermal teeth and use their tongue to rasp away scales from prey, primarily feeding on the blood of their prey.

• Reproduction involves females attaching their nest to a stone, while males wrap around the female, resulting in external fertilization of sticky eggs coated with sand.

Classes of Gnathostomes

• There are three main groups: cartilaginous fishes, bony fishes (Actinopterygii and Sarcopterygii).

Evolution of Jaws and Paired Appendages

• Jaws evolved from anterior pharyngeal arches, improving feeding efficiency.
• Paired appendages enhanced locomotion and stability in early fish.
• The development of jaws and appendages drove predatory lifestyles and species diversification.

Class Chondrichthyes

• Includes sharks, skates, rays, and ratfishes; characterized by cartilaginous endoskeleton and placoid scales.

• Most are carnivorous or scavengers in marine environments

• Teeth are modified placoid scales, constantly replacing worn or damaged teeth.

• Some, like skates and rays, have modified tails for defense and hunt invertebrates in shallow water, featuring blunt teeth and venomous spines.

Pectoral Fins

• Pectoral fins can be expanded into wing-like appendages.
• They can also assist in locomotion via muscular waves.
• Some species, such as stingrays, have elaborate dorsal patterns for camouflage.

Cartilaginous Fishes (Basic Morphology)

• Key features include a caudal peduncle, external gill openings, eyes, snout, cloaca, lateral line, spiracle, and a mouth.

Comparison of Cartilaginous and Bony Fishes

• Cartilaginous fishes are usually characterized by their upper tail lobe, placoid scales and a mouth that's located ventrally.

• Bony fishes have operculum (gill cover), a mouth position that is terminal, and cycloid or ctenoid scales.

Bony Fishes (Osteichthyes)

• Have bony skeletons and scales (cycloid or ctenoid).
• Operculum covers gill openings.
• Many have lungs or swim bladders for buoyancy control.

Bony Fishes (Basics)

• Key features include a caudal fin, lateral line, opercle, preopercle, nape cheek, snout, anus, pectoral fin, mouth, eye, belly, caudal peduncle, pelvic fin.

External Anatomy of Bony Fish

• Features such as nares (nostrils), eye, mouth, pectoral fins, pelvic fins, scales, soft dorsal fin, spiny dorsal fin, vent, caudal tail fin, and lateral line.

Class Sarcopterygii (Lobed-Finned Fishes)

• Characterized by muscular lobes associated with their fins.
• Some exhibit lung use for gas exchange.
• The lungfish group has the ability to remain dormant (aestivate) in dry seasons by burrowing in the mud.

Related Classes of Fish

• Hagfishes are marine scavengers with slime glands
• Lampreys are predatory with sucking mouths.
• Gnathostomes have jaws and paired appendages.
• Chondrichthyes (sharks, skates, rays) are cartilaginous with placoid scales.
• Bony fishes possess bony skeletons.

Evolutionary Pressures on Fishes (Locomotion)

• Streamlined body shape and mucous secretions reduce water resistance
• Fins (vertical caudal fins that are thin and forked) and body wall aid in propulsion.
• Muscle arrangement enhances swimming efficiency.
• Fast-swimming fishes (tuna, mackerel) show adaptation for speed.

Fish Fins

• Describes various fin types including pectoral, pelvic, anal, dorsal, caudal.

• Types of caudal fins includes heterocercal, diphycercal, homocercal, and protocercal, classifying them based on shape and vertebral placement.

Nutrition and the Digestive System

• Early fishes were filter feeders and scavengers.
• Jaws evolved leading to predation.
• Feeding strategies encompass predation, filter feeding, and herbivory.
• Fish digestive tracts include stomachs and intestines with specific functions.
• Gill rakers aid in filtering plankton.

How do fish get enough oxygen?

• Large surface area of gill filaments and lamellae maximizes gas exchange (oxygen and carbon dioxide )
• Counter-current flow enables efficient oxygen uptake. Water flows in the opposite direction to blood.

Circulation and Gas Exchange

• Oxygen and carbon dioxide dissolve in water and fishes exchange gases via gills.
• Gills are composed of filaments and lamellae that support blood vessels to facilitate gas exchange.
• The circulatory system includes a heart, arteries, capillaries, and veins to transport oxygenated and deoxygenated blood throughout the body.

Swim bladder and Lungs

• Pneumatic sacs function as lungs and help regulate buoyancy.
• Fish use buoyancy based on gas regulation within their swim bladder, while other fish use oily, dense tissues to maintain their buoyancy .
• Fish can manage their buoyancy control by controlling the amount of gas in the swim bladder for maintaining buoyancy.

Fishes - Buoyancy

• Bony fish use swim bladders for buoyancy.
• Cartilaginous fish use stiff fins, large oil-filled livers, and low-density cartilage for buoyancy.

Test your knowledge on the biology and evolution of various fish species, including hagfishes, lampreys, and bony fishes. This quiz covers key features such as skeletal structures, feeding adaptations, and ecological roles of these fascinating aquatic animals.