1. Chapter 8
Marine Fishes

2. Phylum Chordata
Subphylum Vertebrata

3. Classification of Fishes

4. Marine Fish First vertebrates - 500 million years ago
Oldest and largest group of vertebrates
24,000 known species of fish, 15,000 marine
Bilateral symmetry
Endoskeleton

5. Vertebrates: An Introduction
Have a backbone (also called vertebral column or spine)
The backbone encloses and protects the nerve cord or spinal cord
The spinal cord ends in a brain protected by a skull

6. Types of Marine Fish Agnatha (jawless fish)
Hagfish
Lampreys
Chondrichthyes (cartilaginous fish)
Sharks
Skates
Rays
ratfish
Osteichthyes (bony fish)
Lobe-finned fishes
Ray-finned fishes

7. Types of Marine Fish Class Agnatha (Hagfish and Lampreys)
Most primitive fishes living today
These jawless fish have a muscular, circular mouth with rows of teeth in rings and feed by suction
Long, cylindrical body
Lack paired fins and scales seen in other fish

8. Types of Marine Fish A. Hagfishes or “slime eels” 20 species
Exclusively marine
They feed on dead and dying fish and marine mammals
Live in burrows in soft sediments
Produce large quantities of mucous from glands in the skin to protect them while feeding

9. Hagfish

11. Hagfish video

12. Types of Marine Fish B. Lamprey 30 species
Freshwater (most) and Marine
Adults of some species live in sea, but return to freshwater to breed
Adults normally die after breeding.
Other species live in freshwater lakes
Attach to other fish and suck their blood

13. Lamprey

14. Lamprey

15. Advanced Groups of Fish
Fishes in the Chondrichthyes and Osteichthyes are considered to be more advanced.
General Characteristics (advancements) seen in these groups:
Highly efficient gills
Scales cover the body
Paired fins
A wide variety of jaw and feeding types
Lateral line and other sensory organs
Streamlined body

17. External Anatomy of More Advanced Fish Groups
These representative fish show the position of fins in cartilaginous and bony fish.

18. Types of Marine Fish 2. Class Chondrichthyes – Cartilaginous fish
General Characteristics of Group:
About 1000 species
Sharks, rays, skates and ratfishes
Skeleton of cartilage -lighter and more flexible than bone
Movable jaws with well-developed teeth
Placoid scales and paired fins
scales cause rough, sandpaper skin
Spiracles in many species (openings on head used to bring water directly in for respiration without opening the mouth)
Males in most species have projections of the anal fin called claspers that are used in copulation

19. Placoid scales
Paired fins

20. Class Chondrichthyes Sharks
350 species well adapted for fast swimming (fusiform shape) and predatory feeding
Some have not changed for 100 my
Caudal fin (tail) well developed and powerful
Heterocercal – upper lobe longer than lower
Two dorsal fins and paired pectoral fins
5-7 gill slits behind head on either side
Powerful jaws with several rows of teeth that move forward

21. Shark Diversity

22. Shark Diversity

23. Class Chondrichthyes Shark Diversity – found in all oceans and depths
Hammerhead – wide flattened head acts as rudder and widens sensory organs for better reception
Sawsharks – long, flattened head with teeth
Thresher sharks – long upper lobe on tail to herd and stun fish
Spined pigmy shark – 10 inches
Whale shark – 60 feet filter feeders (plankton)
Great white shark – 20 feet

24. Class Chondrichthyes Rays and Skates 500 species
Dorsoventrally flattened
Demersal – bottom dwellers (some cover with sand and hide)
Pectoral fins flat and expanded – wings
5 pairs of gills slits on ventral side
Spiracles on dorsal side

25. Class Chondrichthyes Rays
Large flattened teeth for feeding on molluscs and arthropods
Have long whip-like tails; in sting rays, there is a spine (barb) at the base of the tail with an associated poison gland
Stepping on a ray or making contact with the ray may eject venomous spine
Electric rays have organs that produce electricity on either side of head

26. Types of Rays and Skates
Stingrays
Bat ray
Cow nosed ray
Electric rays
Eagle ray
Bull ray (killed Steve Irwin)
skates

27. Cow nose ray

28. Bat ray

29. Eagle ray

30. Bull ray

31. Sting ray

32. Ray and Skate Video Stingray national geographic

33. Class Chondrichthyes Skates
Dorsoventrally flattened with pectoral fins modified into wings
Rays are less mobile than skates
Skates have a fleshy tail and no spine on the tail
Major difference:
Rays are viviparous (bearing live young)
Skates are oviparous (laying eggs)
After fertilization, the female lays egg cases with an embryo inside
The embryo develops within the protection of the egg case for weeks to months
They are also demersal and feed on molluscs and arthropods primarily

34. Mermaid’s Purse

35. Class Chondrichthyes Ratfishes (Chimaeras) 30 species
Deep water inhabitant
One pair of gill slits is covered by a flap of skin
They feed on the bottom on crustaceans and molluscs primarily
Heterocercal tail like in sharks
Unlike others in this group, they also have fin rays (tiny support rods) in the fins

36. Ratfishes or chimaeras
Hydrolagus colliei

37. Types of Marine Fish Class Osteichthyes - The Bony Fish
Skeleton composed of bone
Over 23, 000 species worldwide
Gills used for respiration
Homocercal tail (two lobes of equal size) provides forward thrust
Cycloid (smooth) or ctenoid (spiny) scales
Operculum – boney flap protecting gills
Swim bladder – change depths (heavy skeleton)

38. Swim Bladder
Swim bladder used for buoyancy control (some bottom dwelling fish lack swim bladder)
Sound, pressure detection
Bony fish ONLY- (ex. NOT in sharks)

39. Biology of Fishes Ichthyology – study of fishes
Body shape – related to lifestyle
Fusiform – streamlined, strong, fast
Compressed- thin, easy, quick short bursts
Depressed – flat, demersal, “fly” through water
Some irregular shapes can act as camouflage among seaweed, or rocks

41. Coloration

42. Biology of Fish - Coloration
Cryptic coloration – color to blend in with environment
Bright colored – chromatophores
Structural colors – skin reflects only certain colors
Shiny iridescent fishes
Warning colors – advertise they are dangerous, poisonous, or taste bad
Disruptive coloration – stripes break up outline of fish
Difficult to pick out single fish from group
Countershading – light ventral and dark dorsal

43. Cryptic Coloration

44. Bright Coloration

45. Structural Coloration

46. Warning Colors

47. Disruptive Coloration

48. Biology of Fish - Locomotion
Most fish exhibit an “s-shaped” swimming pattern
Pushes against water to move body forward
Some move a) whole body, b) tail end, C) other fins, d) caudal fin
Myomeres – muscles run along sides of body

51. Biology of Fish - Locomotion
Sharks use fins for lift
Bony fish use swim bladder
Dorsal and anal fins provide steering and stability (no rolling)
Pectoral and pelvic fins help turn, balance, and brake

52. Biology of Fish - Feeding
Most sharks are carnivores – bite prey larger than themselves
Many cartilaginous fish are filter feeders
Bony fish are diverse in how they feed, though most are carnivorous
Protrusible jaws allow more flexibility in feeding habits

54. Biology of Fish - Feeding
Different mouths have evolved for different diets
Teeth for rasping prey or biting off chunks
Huge mouths swallow large prey or filter feed
Beaks for biting hard coral
Downward pointing mouth – bottom feeders

55. Biology of Fish - Digestion
Digestion accomplished with stomach, intestine (with anus or cloaca), liver, pyloric caeca and pancreas
Cloaca – one exit for feces, urine and gametes
The stomach– stretch receptors in the wall of the stomach indicate when a meal is present

56. Biology of Fish - Digestion
The intestine, pyloric caeca, pancreas and liver all secrete digestive enzymes
The intestines of carnivorous fish=short and straight
Intestines of herbivorous fish = longer and more coiled

58. Biology of Fish -Circulatory System
Fish have a two chambered heart that serves to pump blood throughout the body (in contrast to the 4 chambered heart seen in mammals)

60. Biology of Fish – Respiratory System
Irrigation of the Gills
Extract oxygen from water; water flows over gills

61. Biology of Fish – Respiratory System
Structure of Gills
Gill arch – supports two gill filaments
Gill rakers – block food from entering gills
Filter feeders use them to gather food
Gill filaments have lots of capillaries for gas exchange
Lamellae – discs that increase surface area

63. Biology of Fish – Respiratory System
Gas Exchange
Oxygen diffuses from water into capillary blood
Blood flows in opposite direction of water flow called Countercurrent System of flow or Countercurrent Exchange
Dismisses CO2 at same time
O2 and CO2 carried by hemoglobin
Muscles use lots of O2 and use myoglobin to store O2

64. Biology of Fish – Regulation of Internal Environment
Water is very solute-rich, fish have a tendency to gain solutes and lose water
Fish need to have mechanisms to combat this issue – this is called osmoregulation

65. Fluid Balance in Fish Methods of Osmoregulation:
Swallow seawater but them expel the solutes in the digestive process (keep the water and lose the solutes)
Pass very little urine highly concentrated with solutes with very little water content

66. Fluid Balance in Fish Osmoregulation cont:
In cartilaginous fish, the blood is kept at about the same concentration as seawater
Keep urea in the bloodstream (this toxin is filtered out of the blood by other organs)
If salt enters through gills or feeding – rectal gland expels salt

67. Osmoregulation Freshwater fish: Water diffuses in Ions diffuse out
Drink little
Lots of dilute urine
Actively reabsorb ions by kidneys and gills

68. Osmoregulation Saltwater fish Water diffuses out Ions diffuse in
Drink a lot
Concentrated urine
Actively excrete ions by kidneys, gills, and gut

70. Biology of Fish - Nervous System
CNS – brain and spinal cord; nerves connect
Fish also possess olfactory sacs (with nostrils) for smelling
Sharks can smell blood 1 part/million
Salmon – recognize smells for migration
Taste buds are located in the mouth, lips, barbels (organs near mouth of bottom feeders) and skin

71. Biology of Fish - Nervous System
All fish rely heavily on the lateral line system
Pores and canals lined with cells called neuromasts that are specialized to detect vibrations
These vibrations can indicate a predator or prey or the position of other fish in a school
Cartilaginous fish have ampullae of Lorenzini
Detect electrical fields
Help some detect hidden prey in sediment

73. Lateral Line
nerves

74. Biology of Fish - Nervous System
In humans, the lens changes shape for focusing on items
In fish, the position of the lens changes like in a camera
In some sharks, the eye is covered by a nictitating membrane that covers the eye –protect the eye, especially during feeding

75. The Fish Nervous System
The inner ears are set in fluid-filled canals with sensory cells similar to the lateral line system.

76. Behaviors in Fish Territoriality
Some territorial all the time, others only during reproduction
Maintain territories by “posturing”
Raised fins, open mouth, darting, etc.
Fights are actually rare

77. Territoriality

78. Behaviors in Fish Schooling
Schooling is used by a wide variety of fish
Fish appear much larger (as thus avoid detection by predators)
Harder for a predator to capture any one fish
Because of this, many fish school as juveniles
More efficient swimming?

79. Fish Schooling

80. Behaviors in Fish Migrations Mass movement from one place to another
Once per day, year, or lifetime
Onshore to/from outshore
Vertical migration
Transoceanic – tuna, salmon

81. Behaviors in Fish Migrations
Anadromous –sea, migrate fresh for reproduction – Pacific salmon and the Skipjack tuna
Homing behavior – sexual maturity swim up rivers or stream where they were born
Catadromous – fresh, migrate marine for reproduction – freshwater eels (Anguilla)

83. Reproduction and Life History
Cartilaginous fish use cloaca; bony fish use urogential opening
Sex hormones control the development of sperm and eggs in fish
The release of sex hormones cued by environment
Broadcast spawning is most common
Internal fertilization
Typical among cartilaginous fish using claspers

85. Reproduction and Life History
Some fish are hermaphroditic
Simultaneous hermaphrodites- produce both – can even fertilize themselves
Other species possess these structures at different times during the life (sequential hermaphrodites)

86. Reproduction and Life History
Types of Sequential Hermaphrodites
Protandry - male to female
Protogyny –female to male

87. Reproduction and Life History
Behaviors are cues for the release of eggs and sperm (this helps ensure fertilization)
Color changes or body structure changes may indicate readiness for reproduction
Courtship behavior – dances, displays, etc

89. Reproduction in Fish Depending on the species, fish can either be:
Viviparous – young are born live
Oviparous- egg layers
Ovoviviparous – eggs are kept inside and “hatch” before being released from female reproductive tract
Most laying eggs in large numbers to not protect
Some laying eggs in small numbers will protect