30.1 Section Objectives – page 793 Relate the structural adaptations of fishes to their environments. Compare and contrast the characteristics of the different groups of fishes. Interpret the phylogeny of fishes. 30.1 Section Objectives – page 793

Section 30.1 Summary – pages 793-802 What is a fish? Fishes, like all vertebrates, are classified in the phylum Chordata. Fishes belong to the subphylum Vertebrata. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 What is a fish? In addition to fishes, subphylum Vertebrata includes amphibians, reptiles, birds, and mammals. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 What is a fish? In vertebrates, the embryo’s notochord is replaced by a backbone in adult animals. All vertebrates are bilaterally symmetrical, coelomates that have endoskeletons, closed circulatory systems, nervous systems with complex brains and sense organs, and efficient respiratory systems. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Classes of fishes Fishes Class Organisms Characteristics Jawless, cartilaginous skeleton, gills Myxini Hagfishes Jawless, cartilaginous skeleton, gills Cephalaspidomorphi Lampreys Jaws, cartilaginous skeleton, paired fins, gills, scales, internal fertilization Chondrichthyes Sharks, skates, rays Jaws, bony skeleton, paired fins, gills, scales, swim bladder Osteichthyes Lobe-finned fishes, ray-finned fishes Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes breathe using gills Fishes have gills made up of feathery gill filaments that contain tiny blood vessels. Gill Filaments Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes breathe using gills As a fish takes water in through its mouth, water passes over the gills and then out through slits at the side of the fish. Gill Filaments Capillary networks in filament Water Gill filaments Artery Vein Water Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes breathe using gills Oxygen and carbon dioxide are exchanged through the capillaries in the gill filaments. Gill Filaments Capillary networks in filament Water Gill filaments Artery Vein Water Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes have two-chambered hearts Aorta Capillary network Gills Heart Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes reproduce sexually Although the method may vary, all fishes reproduce sexually. Fertilization and development is external in most fishes. Eggs and sperm can be released directly into the water, or deposited in more protected areas, such as on floating aquatic plants. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes reproduce sexually Most bony fishes have external fertilization and development. This type of external reproduction in fishes and some other animals is called spawning. Salmon spawning Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes reproduce sexually In some bony fishes, such as guppies and mollies, fertilization and development is internal. Most fishes that produce millions of eggs provide no care for their offspring after spawning. Some fishes, such as the mouth-brooding cichlids, stay with their young after they hatch. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Most fishes have paired fins Fishes in the classes Chondrichthyes and Osteichthyes have paired fins. Fins are fan-shaped membranes that are used for balance, swimming, and steering. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Most fishes have paired fins Fins are attached to and supported by the endoskeleton and are important in locomotion. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Most fishes have paired fins The paired fins of fishes foreshadowed the development of limbs for movement on land and ultimately of wings for flying. Dorsal fins Pectoral fin Anal fin Caudal fin Pelvic fins Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems Cartilaginous and bony fishes have an adaptation called the lateral line system that enables them to sense objects and changes in their environment. Lateral line Gelatin-like fluid Receptor cells Nerve Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems The lateral line system is a line of fluid-filled canals running along the sides of a fish that enable it to detect movement and vibrations in the water. Lateral line Gelatin-like fluid Receptor cells Nerve Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems Fishes have eyes that allow them to see objects and contrasts between light and dark in the water as well. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems Some fishes that live in areas of the ocean where there is no light may have reduced, almost nonfunctional eyes. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Fishes have developed sensory systems Some fishes also have an extremely sensitive sense of smell and can detect small amounts of chemicals in the water. Sharks can follow a trail of blood through the water for several hundred meters. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Most fishes have scales Scales are thin bony plates formed from the skin. Scales can be toothlike, diamond-shaped, cone-shaped, or round. Shark scales are similar to teeth found in other vertebrates. Section 30.1 Summary – pages 793-802

Types of Scales Cycloid Scales: have a smooth outer edge, and are most common on fish with soft fin rays, such as salmon Ctenoid Scales: have a toothed outer edge, and are usually found on fish with spiny fin rays, such as bass and crappie Placoid Scales: are found on cartilaginous fish including sharks. Ganoid Scales: can be found on Gars. They have a diamond-shaped, shiny, and hard scale.

Section 30.1 Summary – pages 793-802 Jaws evolved in fishes Gill arches Gill slits Jawless, filter-feeding fish Jaws Skull Gill slits Gill arches Beginning of jaw formation Fish with jaws The advantage of jaws is that they enable an animal to grasp and crush its prey with great force. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Jaws evolved in fishes Gill arches Gill slits Jawless, filter-feeding fish Jaws Skull Gill slits Gill arches Beginning of jaw formation Fish with jaws Jaws also allowed early fishes to prey on a greater variety of organisms. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Most fishes have bony skeletons Bony fishes, a successful and widely distributed class, differ greatly in habitat, size, feeding behavior, and shape. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Bony fishes have separate vertebrae that provide flexibility A mackerel flexes the posterior end of its body to accentuate the tail -fin movement. A tuna keeps its body rigid, moving only its powerful tail. Fishes that use this method move faster than all others. An eel moves its entire body in an S-shaped pattern. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Bony fishes evolved swim bladders Swim bladder A fish with a swim bladder can control its depth by regulating the amount of gas in the bladder. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 Bony fishes evolved swim bladders Some fishes remove gases from the swim bladder by expelling them through a special duct that attaches the swim bladder to the esophagus. In fishes that do not have this duct their swim bladders empty when gases diffuse back into the blood. Section 30.1 Summary – pages 793-802

Section 30.1 Summary – pages 793-802 A Bony Fish Lateral line system Swim bladder Kidney Scales Urinary bladder Reproductive organ Fins Stomach Intestine Liver Heart Gills Section 30.1 Summary – pages 793-802

Summary of Ray-Finned Fishes Class Actinopterygii (Ray-finned fishes) Skeleton made of bone. Scales can be ganoid, cycloid, ctenoid or absent. Paired and median fins present. Jaws present. Teeth usually present with enamaloid covering. Respiration by gills and covered with an operculum. Swim bladder often present with or without a duct connecting to esophagus. Two chambered heart. Sexes usually separate. Fertilization usually external. Nervous system of a brain with small cerebrum, optic lobes, and cerebellum.  

Summary of Lobe-Finned fishes Class Sarcopterygii (Lobe-finned fishes) Skeleton made of bone. Paired and median fins present. Jaws present, teeth are covered with true enamel and typically are crushing plates restricted to palate. Gills supported by bony arches and covered by an operculum. Swim bladder vascularized and used for respiration and buoyancy. Nervous system with a cerebrum, cerebellum, and optic lobe. Sexes separate; fertilization external or internal.