كتاب تتتتتماين من انتااا كليه علوم حلوان
- 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 8 Lecture Slides
- 2. Chapter 8 Chapter 8 Marine Fishes Marine Fishes
- 3. Classification of Fishes Classification of Fishes
- 4. Marine Fish Marine Fish • Marine fish are vertebrates Marine fish are vertebrates • Some have vertebra made of cartilage, while Some have vertebra made of cartilage, while others have bony vertebra others have bony vertebra • Of the 24,000 known species of fish, about Of the 24,000 known species of fish, about 15,000 species are marine 15,000 species are marine • Fish are the oldest of vertebrates (found farther Fish are the oldest of vertebrates (found farther back in the fossil record) back in the fossil record) • Fish are by far the largest group of vertebrates Fish are by far the largest group of vertebrates in terms of species and abundance in terms of species and abundance • About half of all vertebrate species are fish About half of all vertebrate species are fish
- 5. Types of Marine Fish Types of Marine Fish 1. 1. Agnatha (jawless fish) Agnatha (jawless fish) • Hagfish Hagfish • Lampreys Lampreys 2. 2. Chondrichthyes (cartilaginous fish) Chondrichthyes (cartilaginous fish) • Sharks Sharks • Skates Skates • Rays Rays • ratfish ratfish 3. 3. Osteichthyes (bony fish) Osteichthyes (bony fish) • Lobe-finned fishes Lobe-finned fishes • Ray-finned fishes Ray-finned fishes
- 6. Types of Marine Fish Types of Marine Fish • Agnatha Agnatha – These jawless fish have a muscular, circular mouth These jawless fish have a muscular, circular mouth with rows of teeth in rings with rows of teeth in rings – Long, cylindrical body Long, cylindrical body – Lack paired fins and scales seen in other fish Lack paired fins and scales seen in other fish – Two types of jawless fish exist- hagfish and Two types of jawless fish exist- hagfish and lampreys lampreys
- 7. Types of Marine Fish Types of Marine Fish • Hagfishes Hagfishes – 20 species 20 species – Exclusively marine Exclusively marine – They feed on dead and dying fish and marine They feed on dead and dying fish and marine mammals primarily mammals primarily – Live in burrows in soft sediments Live in burrows in soft sediments – Produce large quantities of mucous from Produce large quantities of mucous from glands in the skin to protect them while feeding glands in the skin to protect them while feeding
- 9. Types of Marine Fish Types of Marine Fish • Lamprey Lamprey – 30 species 30 species – Live in freshwater and salt water Live in freshwater and salt water – Adults of some species spend a large portion of Adults of some species spend a large portion of their life in the sea, but return to freshwater to their life in the sea, but return to freshwater to breed; adults normally die after breeding. breed; adults normally die after breeding. – Other species live in freshwater lakes Other species live in freshwater lakes – They feed on living fish by rasping into the sides of They feed on living fish by rasping into the sides of fish with their sucker-like mouth and consuming fish with their sucker-like mouth and consuming blood, tissue and body fluids. blood, tissue and body fluids.
- 10. More Advanced Groups of More Advanced Groups of Fish Fish • Fishes in the Chondrichthyes and Fishes in the Chondrichthyes and Osteichthyes are considered to be more Osteichthyes are considered to be more advanced. advanced. • General Characteristics (advancements) seen General Characteristics (advancements) seen in these groups: in these groups: – Highly efficient gills Highly efficient gills – Scales cover the body Scales cover the body – Paired fins Paired fins – A wide variety of jaw and feeding types A wide variety of jaw and feeding types – Lateral line and other sensory organs Lateral line and other sensory organs – Streamlined body Streamlined body
- 12. External Anatomy of More External Anatomy of More Advanced Fish Groups Advanced Fish Groups • These representative fish show the position of fins in These representative fish show the position of fins in cartilaginous and bony fish. cartilaginous and bony fish.
- 14. Types of Marine Fish Types of Marine Fish • Chondrichthyes Chondrichthyes • General Characteristics of Group: General Characteristics of Group: – About 1000 species About 1000 species – Sharks, rays, skates and ratfishes are members of this group Sharks, rays, skates and ratfishes are members of this group – Skeleton of cartilage (as the name implies) Skeleton of cartilage (as the name implies) – Movable jaws with well-developed teeth Movable jaws with well-developed teeth – Placoid scales and paired fins Placoid scales and paired fins – 5-7 gill slits open directly into the water in most species 5-7 gill slits open directly into the water in most species – Spiracles in many species (openings on head used to bring Spiracles in many species (openings on head used to bring water directly in for respiration without opening the mouth) water directly in for respiration without opening the mouth) – Males in most species have projections of the anal fin called Males in most species have projections of the anal fin called claspers that are used in copulation claspers that are used in copulation
- 15. Types of Marine Fish Types of Marine Fish • More specific details about Sharks More specific details about Sharks – Primarily marine, but do travel up the mouths of Primarily marine, but do travel up the mouths of rivers into freshwater in some species rivers into freshwater in some species – The population numbers in many species of sharks The population numbers in many species of sharks are declining due to harvesting sharks for meat, oil, are declining due to harvesting sharks for meat, oil, skin and fins skin and fins – In addition to the lateral line, sharks have a sensory In addition to the lateral line, sharks have a sensory organ called the Organ of Lorenzini; this organ is organ called the Organ of Lorenzini; this organ is used to detect electrical currents when sharks are used to detect electrical currents when sharks are close to an object (the movement of muscles – even close to an object (the movement of muscles – even those used in respiration – emit a small electrical those used in respiration – emit a small electrical charge) – this allows sharks to detect living prey charge) – this allows sharks to detect living prey even it is hidden from their view if they can get even it is hidden from their view if they can get within a few feet of the organism within a few feet of the organism
- 17. Types of Marine Fish Types of Marine Fish More specific details about Sharks More specific details about Sharks – Most species possess 2 dorsal fins Most species possess 2 dorsal fins – Reproduction in sharks is varied – some have live Reproduction in sharks is varied – some have live birth (known as vivipary); some lay egg cases birth (known as vivipary); some lay egg cases (ovipary); while others have an internalized egg (ovipary); while others have an internalized egg that hatches while still in the female before the that hatches while still in the female before the young are expelled from the female’s reproductive young are expelled from the female’s reproductive system (ovovivipary) system (ovovivipary) – Many are carnivorous, some planktonic Many are carnivorous, some planktonic – About 350 species currently exist About 350 species currently exist
- 19. Types of Marine Fish Types of Marine Fish • More specific details about Rays More specific details about Rays – Rays always have live birth Rays always have live birth – Pectoral fins are expanded into “wings” and entire body is Pectoral fins are expanded into “wings” and entire body is dorsoventrally flattened dorsoventrally flattened – Gill slits (5 pairs) mouth are on the underside of the body Gill slits (5 pairs) mouth are on the underside of the body – Spiracles are located on the top of the body Spiracles are located on the top of the body – Rays spend much of their time on the bottom (demersal) Rays spend much of their time on the bottom (demersal) partially covered in sand partially covered in sand – Large flattened teeth for feeding on molluscs and Large flattened teeth for feeding on molluscs and arthropods arthropods – Most have long whip-like tails; in sting rays, there is a spine Most have long whip-like tails; in sting rays, there is a spine at the base of the tail with an associated poison gland at the base of the tail with an associated poison gland – Venom from this gland is delivered to other organisms if Venom from this gland is delivered to other organisms if they make contact with this spine by stepping on a ray or they make contact with this spine by stepping on a ray or making contact with the ray in some fashion making contact with the ray in some fashion – Electric rays have organs that produce electricity on either Electric rays have organs that produce electricity on either side of head side of head
- 21. Types of Marine Fish Types of Marine Fish • More specific details about Skates More specific details about Skates – Like rays, skates are dorsoventrally flattened with pectoral Like rays, skates are dorsoventrally flattened with pectoral fins modified into wings fins modified into wings – Unlike rays, skates have a fleshy tail and no spine on the tail Unlike rays, skates have a fleshy tail and no spine on the tail – Also unlike rays, skates always lay egg cases Also unlike rays, skates always lay egg cases – After fertilization, the female lays egg cases with an embryo After fertilization, the female lays egg cases with an embryo inside inside – The embryo develops within the protection of the egg case The embryo develops within the protection of the egg case for weeks to months for weeks to months – They are also demersal and feed on molluscs and arthropods They are also demersal and feed on molluscs and arthropods primarily primarily
- 22. Types of Marine Fish Types of Marine Fish • More specific details about Ratfishes More specific details about Ratfishes – Only about 30 species Only about 30 species – Mostly are deep water inhabitant Mostly are deep water inhabitant – One pair of gill slits is covered by a flap of skin One pair of gill slits is covered by a flap of skin (very unusually in the chondrichthyes) (very unusually in the chondrichthyes) – They feed on the bottom on crustaceans and They feed on the bottom on crustaceans and molluscs primarily molluscs primarily – Heterocercal tail like in sharks Heterocercal tail like in sharks – Unlike others in this group, they also have fin Unlike others in this group, they also have fin rays (tiny support rods) in the fins rays (tiny support rods) in the fins
- 24. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – As the name implies, these fish have a As the name implies, these fish have a skeleton composed of bone skeleton composed of bone – More species that all other vertebrates More species that all other vertebrates combined- over 23, 000 species worldwide combined- over 23, 000 species worldwide – Gills used for respiration Gills used for respiration – Hinged jaws allow for a variety of different Hinged jaws allow for a variety of different ways of feeding ways of feeding – Homocercal tail (two lobes of equal size) Homocercal tail (two lobes of equal size) provides forward thrust provides forward thrust
- 25. Types of Marine Fish Types of Marine Fish Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Flat bony scales (ctenoid or cycloid) protect body Flat bony scales (ctenoid or cycloid) protect body – Bony operculum covers the gills (provides better Bony operculum covers the gills (provides better protection against injury compared to gill slits for protection against injury compared to gill slits for each gill) each gill) – Lateral line used in sensory capacity and Lateral line used in sensory capacity and communication communication – Swim bladder used for buoyancy control (some Swim bladder used for buoyancy control (some bottom dwelling fish lack swim bladder) bottom dwelling fish lack swim bladder) – Variable body plans are adapted for specific Variable body plans are adapted for specific environments environments
- 26. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Coloration patterns: Coloration patterns: – Countershading is seen in virtually all fish species Countershading is seen in virtually all fish species – In countershading, the ventral (belly) area of the fish In countershading, the ventral (belly) area of the fish is lighter than the dorsal area of the fish is lighter than the dorsal area of the fish – This allows the fish to “blend in” with the environment This allows the fish to “blend in” with the environment – If a fish is seen from above, the darker coloration of If a fish is seen from above, the darker coloration of the dorsal area blends in with the darker color of the the dorsal area blends in with the darker color of the ocean bottom ocean bottom – If the fish is seen from below, the lighter coloration of If the fish is seen from below, the lighter coloration of the ventral surface blends in with the lighter the ventral surface blends in with the lighter coloration of the ocean surface coloration of the ocean surface
- 27. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Coloration patterns: Coloration patterns: – Slower swimming fish often have bars or stripes Slower swimming fish often have bars or stripes that help break up the silhouette of a fish (a form that help break up the silhouette of a fish (a form of disruptive coloration) of disruptive coloration) – This helps with predator avoidance This helps with predator avoidance – Some also have coloration that helps them blend Some also have coloration that helps them blend in with environment (known as cryptic coloration) in with environment (known as cryptic coloration)
- 29. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Coloration Patterns: Coloration Patterns: – It is also not usually to see a fish with circular patterns on It is also not usually to see a fish with circular patterns on or near the caudal fin or near the caudal fin – This confuses predators who are not sure which end of This confuses predators who are not sure which end of the fish is the head the fish is the head – If the fish at right is attacked on caudal end where the If the fish at right is attacked on caudal end where the black dot looks like an eye, he can probably get away with black dot looks like an eye, he can probably get away with minor damage minor damage – However, if he is attacked on his head region, he may However, if he is attacked on his head region, he may sustain serious, life threatening damage sustain serious, life threatening damage – Some fishes may also use color to advertise their bad taste Some fishes may also use color to advertise their bad taste or poisonous nature – this is known as warning coloration or poisonous nature – this is known as warning coloration
- 30. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Body shapes vary greatly among fish Body shapes vary greatly among fish dependent on the environment that fish dependent on the environment that fish calls home calls home – For example, flounders and soles live on For example, flounders and soles live on the bottom and cover themselves slightly the bottom and cover themselves slightly with sand to camouflage themselves from with sand to camouflage themselves from potential predators as well as prey potential predators as well as prey – The flat shape of the flounders and soles is The flat shape of the flounders and soles is well adapted to this lifestyle well adapted to this lifestyle
- 31. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Body shapes, continued Body shapes, continued – Tuna, billfish, and other fast moving predators are Tuna, billfish, and other fast moving predators are long, streamlined and most of their fins serve as long, streamlined and most of their fins serve as rudders basically (very little flexibility except in rudders basically (very little flexibility except in caudal fin) caudal fin) – This body shape allows these predators to cut This body shape allows these predators to cut through the water quickly through the water quickly – Notice, too, that the area of the body called the Notice, too, that the area of the body called the caudal peduncle (area just before the tail) is very caudal peduncle (area just before the tail) is very thin – this allows all the muscles to concentrate in thin – this allows all the muscles to concentrate in this area allowing for greater thrust of the caudal this area allowing for greater thrust of the caudal (tail) fin (this means FAST swimming capabilities) (tail) fin (this means FAST swimming capabilities)
- 32. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Body shapes, continued Body shapes, continued – By contrast, the angelfish represents the opposite By contrast, the angelfish represents the opposite environment environment – Angelfish and many other fish do not inhabit the Angelfish and many other fish do not inhabit the open waters of the ocean like tunas and billfish do open waters of the ocean like tunas and billfish do – Angelfish and the like inhabit coral reefs, oyster Angelfish and the like inhabit coral reefs, oyster reefs and other similar environments reefs and other similar environments – In these fish, the body is not as streamlined and In these fish, the body is not as streamlined and the fins are feather-like for lots of flexibility the fins are feather-like for lots of flexibility – This flexibility allows for greater control around This flexibility allows for greater control around the features that would be seen in a coral reef type the features that would be seen in a coral reef type environment (crevices, etc) environment (crevices, etc)
- 33. Types of Marine Fish Types of Marine Fish • Osteichthyes, The Bony Fish Osteichthyes, The Bony Fish – Body shapes, continued Body shapes, continued – Other fish have a shape that allows for Other fish have a shape that allows for camouflage in their environment camouflage in their environment – For example, fish like the toadfish and the For example, fish like the toadfish and the stonefish actually look like rocks or stonefish actually look like rocks or “scenery” and thus can go undetected by “scenery” and thus can go undetected by predators or prey predators or prey
- 35. Swimming Patterns Swimming Patterns • Fish exhibit an “s-shaped” swimming Fish exhibit an “s-shaped” swimming pattern pattern • Bands of muscle along the body called Bands of muscle along the body called myomeres drive this swimming motion myomeres drive this swimming motion • Depending on the type of fish, different Depending on the type of fish, different fins may be used primarily for the fins may be used primarily for the forward movement forward movement
- 38. Swimming Patterns Swimming Patterns • In sharks, a swim bladder is absent In sharks, a swim bladder is absent (although there is a large lipid-rich liver (although there is a large lipid-rich liver to help in buoyancy) – therefore, sharks to help in buoyancy) – therefore, sharks tend to sink when not in motion and tend to sink when not in motion and there is no lift from the swim bladder there is no lift from the swim bladder while swimming either while swimming either • While swimming, sharks are aided by While swimming, sharks are aided by the “lift” provided by the position and the “lift” provided by the position and stiffness of the pectoral fins stiffness of the pectoral fins
- 39. Swimming Patterns Swimming Patterns • In bony fish, pectoral fins are not needed for In bony fish, pectoral fins are not needed for lift and thus are normally not stiff in lift and thus are normally not stiff in construction (exception: fast swimming construction (exception: fast swimming species like tuna, billfish, etc) species like tuna, billfish, etc) • In contrast, the pectoral fins in many bony In contrast, the pectoral fins in many bony fins are flexible and used for maneuverability fins are flexible and used for maneuverability • In some slower-swimming species, forward In some slower-swimming species, forward movement is mainly provided primarily by the movement is mainly provided primarily by the pectoral fins pectoral fins
- 40. Swimming Patterns Swimming Patterns • In other species, all the fins may be flexible and In other species, all the fins may be flexible and highly modified for camouflage (example: sea horses highly modified for camouflage (example: sea horses and sea dragons) and sea dragons) • This means that the fins will not allow for significant This means that the fins will not allow for significant forward movement forward movement
- 41. Fish Gills Fish Gills • The construction of the gill is the same in all fish – gill The construction of the gill is the same in all fish – gill arch supports the entire structure, gill rakers are on arch supports the entire structure, gill rakers are on the forward surface of the gill arch and gill filaments the forward surface of the gill arch and gill filaments trail behind the gill arch trail behind the gill arch • Like in the human lung, exchange of oxygen and Like in the human lung, exchange of oxygen and carbon dioxide takes place on these surfaces carbon dioxide takes place on these surfaces
- 43. Acquiring and Processing Acquiring and Processing Food Food • Mouth structure also reveals the dietary Mouth structure also reveals the dietary preferences of fish preferences of fish • As an example, the “beak” (fused teeth) seen in As an example, the “beak” (fused teeth) seen in parrotfish allows for these fish to scrape algae parrotfish allows for these fish to scrape algae and other organisms off of hard surfaces and other organisms off of hard surfaces • The butterfly fish uses its long tube-like mouth The butterfly fish uses its long tube-like mouth to feed on corals to feed on corals • While the barracuda uses rows of sharp teeth While the barracuda uses rows of sharp teeth and a wide mouth to capture its prey – other and a wide mouth to capture its prey – other fish fish
- 45. Acquiring and Processing Acquiring and Processing Food Food • The position of the mouth is also The position of the mouth is also important important • A strongly forward facing mouth is A strongly forward facing mouth is important in fish who chase down their important in fish who chase down their prey (as seen in barracuda) prey (as seen in barracuda) • A downward facing mouth would be A downward facing mouth would be seen in fish feeding at/near the bottom seen in fish feeding at/near the bottom
- 46. Acquiring and Processing Acquiring and Processing Food Food • Digestion of food in fish is completed Digestion of food in fish is completed with the aid of a stomach, intestine (with with the aid of a stomach, intestine (with anus), liver, pyloric caeca and pancreas anus), liver, pyloric caeca and pancreas • The stomach is structured very similarly The stomach is structured very similarly to the human stomach – stretch to the human stomach – stretch receptors in the wall of the stomach receptors in the wall of the stomach indicate when a meal is present and indicate when a meal is present and needs to be mechanically digested by needs to be mechanically digested by the churning motion of the stomach wall the churning motion of the stomach wall
- 47. Acquiring and Processing Acquiring and Processing Food Food • The intestine, pyloric caeca, pancreas and The intestine, pyloric caeca, pancreas and liver all secrete digestive enzymes to aid in liver all secrete digestive enzymes to aid in the digestion process the digestion process • The intestines of carnivorous fish tend to be The intestines of carnivorous fish tend to be short and straight while the intestines of short and straight while the intestines of herbivorous fish are longer and more coiled herbivorous fish are longer and more coiled (plant and algae material is more difficult to (plant and algae material is more difficult to process, so it needs to stay in the intestines process, so it needs to stay in the intestines longer) longer)
- 49. The Circulatory System The Circulatory System • Fish have a two chambered heart that serves Fish have a two chambered heart that serves to pump blood throughout the body (in to pump blood throughout the body (in contrast to the 4 chambered heart seen in contrast to the 4 chambered heart seen in mammals) mammals) • A system of arteries, veins and capillaries A system of arteries, veins and capillaries takes blood to the body tissues and returns it takes blood to the body tissues and returns it for re-oxygenation by the gill filaments for re-oxygenation by the gill filaments • Oxygen and carbon dioxide will diffuse across Oxygen and carbon dioxide will diffuse across the thin membranes of the capillaries either the thin membranes of the capillaries either in the gills or at the tissues of the body in the gills or at the tissues of the body
- 51. Fluid Balance in Fish Fluid Balance in Fish • Remember from chapter 4 that the forces of Remember from chapter 4 that the forces of osmosis and diffusion are always at work in an osmosis and diffusion are always at work in an organism organism • Solutes and gases will travel from areas where Solutes and gases will travel from areas where they are more concentrated to areas where they they are more concentrated to areas where they are less concentrated are less concentrated • Since marine fish are living in an environment Since marine fish are living in an environment where the water is very solute-rich, these fish where the water is very solute-rich, these fish have a tendency to gain solutes and lose water have a tendency to gain solutes and lose water • Therefore, fish need to have mechanisms to Therefore, fish need to have mechanisms to combat this issue – this is called osmoregulation combat this issue – this is called osmoregulation
- 52. Fluid Balance in Fish Fluid Balance in Fish • Osmoregulation is the term given to the Osmoregulation is the term given to the process of managing internal water/solute process of managing internal water/solute balance balance • Fish have evolved a variety of ways to Fish have evolved a variety of ways to osmoregulate including: osmoregulate including: – Many fish swallow seawater but them expel the Many fish swallow seawater but them expel the solutes in the digestive process (this allows them to solutes in the digestive process (this allows them to keep the water and lose the solutes) keep the water and lose the solutes) – Most marine fish pass very little urine Most marine fish pass very little urine – This urine (processed by the kidneys) is highly This urine (processed by the kidneys) is highly concentrated with solutes with very little water concentrated with solutes with very little water content content
- 53. Fluid Balance in Fish Fluid Balance in Fish • Osmoregulation continued: Osmoregulation continued: – In cartilaginous fish, the blood is kept at In cartilaginous fish, the blood is kept at about the same concentration as seawater about the same concentration as seawater – This is accomplished by keeping urea in the This is accomplished by keeping urea in the bloodstream (this toxin is filtered out of the bloodstream (this toxin is filtered out of the blood by other organisms) blood by other organisms) – This means that no solutes are gained (or This means that no solutes are gained (or water lost) because the concentration water lost) because the concentration internally and externally match internally and externally match
- 55. The Fish Nervous System The Fish Nervous System • The fish have a brain, spinal cord and numerous The fish have a brain, spinal cord and numerous nerves like other vertebrates nerves like other vertebrates • Fish also possess olfactory sacs (with nostrils) for Fish also possess olfactory sacs (with nostrils) for smelling smelling • Taste buds are located in the mouth, lips, barbels and Taste buds are located in the mouth, lips, barbels and skin skin • The eyes are structured slightly differently The eyes are structured slightly differently • In humans, the lens changes In humans, the lens changes shape shape for focusing on for focusing on items items • In fish, the In fish, the position position of the lens changes like in a of the lens changes like in a camera camera
- 56. The Fish Nervous System The Fish Nervous System • In some sharks, the eye is covered by a In some sharks, the eye is covered by a nictitating membrane that covers the nictitating membrane that covers the eye – this clear membrane helps these eye – this clear membrane helps these predators protect the eye, especially predators protect the eye, especially during feeding during feeding • Incidentally, this membrane is also seen Incidentally, this membrane is also seen in some reptiles in some reptiles
- 57. The Fish Nervous System The Fish Nervous System • All fish rely heavily on the lateral line system All fish rely heavily on the lateral line system • The lateral line is a series of pores and canals The lateral line is a series of pores and canals lined with cells called neuromasts that are lined with cells called neuromasts that are specialized to detect vibrations specialized to detect vibrations • These vibrations can indicate a predator or These vibrations can indicate a predator or prey or the position of other fish in a school prey or the position of other fish in a school
- 59. The Fish Nervous System The Fish Nervous System • Cartilaginous fish also possess the Cartilaginous fish also possess the organ (or ampulla) of Lorenzini organ (or ampulla) of Lorenzini • This organ detects electrical charges This organ detects electrical charges • All muscular system of organisms relies All muscular system of organisms relies on small electrical charges on small electrical charges • Therefore, this organ can help Therefore, this organ can help cartilaginous fish detect prey, even if cartilaginous fish detect prey, even if they are not visible (buried in sand, etc) they are not visible (buried in sand, etc)
- 60. The Fish Nervous System The Fish Nervous System • The inner ears are set in fluid-filled The inner ears are set in fluid-filled canals with sensory cells similar to the canals with sensory cells similar to the lateral line system. lateral line system.
- 61. Behaviors in Fish Behaviors in Fish • Schooling Schooling – Schooling is used by a wide variety of fish Schooling is used by a wide variety of fish – Schooling makes it possible for a group of Schooling makes it possible for a group of smaller fish to appear much larger (as thus smaller fish to appear much larger (as thus avoid detection by predators avoid detection by predators – It also makes it harder for a predator to It also makes it harder for a predator to capture any one fish capture any one fish – Because of this, many fish school as juveniles Because of this, many fish school as juveniles – About 4000 species school as adults About 4000 species school as adults
- 62. Behaviors in Fish Behaviors in Fish • Territoriality Territoriality – Some fish are territorial by nature all the time, Some fish are territorial by nature all the time, others are only territorial during reproduction others are only territorial during reproduction – Fish maintain their territories normally by Fish maintain their territories normally by “posturing” to show their aggression “posturing” to show their aggression – Posturing can include raised fins, open Posturing can include raised fins, open mouth, darting, etc. mouth, darting, etc. – Fights between individuals are actually rare Fights between individuals are actually rare
- 63. Behaviors in Fish Behaviors in Fish • Some species migrate between freshwater Some species migrate between freshwater and saltwater at different times in their life and saltwater at different times in their life • Anadromous species like salmon, lampreys Anadromous species like salmon, lampreys and sturgeon live in saltwater normally but go and sturgeon live in saltwater normally but go to freshwater for reproductive purposes to freshwater for reproductive purposes • Catadromous species like the American Eel Catadromous species like the American Eel live in freshwater but travel to saltwater for live in freshwater but travel to saltwater for reproduction reproduction
- 65. Reproduction in Fish Reproduction in Fish • Sex hormones control the development of Sex hormones control the development of sperm and eggs in fish sperm and eggs in fish • The release of sex hormones can be cued by The release of sex hormones can be cued by water temperature, day length, specific tide water temperature, day length, specific tide cycles, etc. cycles, etc. • Broadcast spawning (releases eggs and sperm Broadcast spawning (releases eggs and sperm directly into water for fertilization) is most directly into water for fertilization) is most common common • Some fish do have internal fertilization (sperm Some fish do have internal fertilization (sperm is inserted directly into the female by the male) is inserted directly into the female by the male) • Complex mating behaviors are seen in some Complex mating behaviors are seen in some species species
- 67. Reproduction in Fish Reproduction in Fish • Some fish are hermaphroditic (possess Some fish are hermaphroditic (possess male and female reproductive organs) male and female reproductive organs) • Some possess these structures at the Some possess these structures at the same time (simultaneous same time (simultaneous hermaphrodites)- this is more rare hermaphrodites)- this is more rare • Other species possess these structures Other species possess these structures at different times during the life at different times during the life (sequential hermaphrodites) (sequential hermaphrodites)
- 68. Reproduction in Fish Reproduction in Fish • Types of Sequential Hermaphrodites Types of Sequential Hermaphrodites – In protandry, fish are first males and develop into In protandry, fish are first males and develop into females later in life females later in life – In protogyny, fish are first females and develop into In protogyny, fish are first females and develop into males later in life males later in life – The cues for these changes are often the result of The cues for these changes are often the result of changes in social structure or environment changes in social structure or environment – As an example, in some species, a large male keeps As an example, in some species, a large male keeps a “harem” of females and he fertilizes the eggs of all a “harem” of females and he fertilizes the eggs of all – When this male dies, the largest female develops When this male dies, the largest female develops into a functional male into a functional male
- 69. Reproduction in Fish Reproduction in Fish • Depending on the species, fish can either be: Depending on the species, fish can either be: – Viviparous – young are born live Viviparous – young are born live – Oviparous- egg layers Oviparous- egg layers – Ovoviviparous – eggs are kept inside and “hatch” before being Ovoviviparous – eggs are kept inside and “hatch” before being released from female reproductive tract released from female reproductive tract – In most bony fish, eggs are laid by the thousands or millions and In most bony fish, eggs are laid by the thousands or millions and are not protected by the parents are not protected by the parents – In other bony fish, smaller numbers of eggs are laid and the In other bony fish, smaller numbers of eggs are laid and the parent(s) protect the eggs parent(s) protect the eggs – RARE: A few species are parthenogenic- in this reproductive plan, RARE: A few species are parthenogenic- in this reproductive plan, young develop directly from the unfertilized eggs of the female young develop directly from the unfertilized eggs of the female (no DNA from males) – the young are “clones” of the female (no DNA from males) – the young are “clones” of the female
- 70. Reproduction in Fish Reproduction in Fish • In most fish, intricate behaviors are In most fish, intricate behaviors are cues for the release of eggs and sperm cues for the release of eggs and sperm (this helps ensure fertilization) (this helps ensure fertilization) • In some species, color changes or body In some species, color changes or body structure changes may indicate structure changes may indicate readiness for reproduction readiness for reproduction
- 73. Most Important Most Important Characteristics of Marine Fish Characteristics of Marine Fish