1. Chapter 10
Marine Fishes

2. Fishes and Other Vertebrates
Fishes are vertebrates—animals that possess vertebrae, a series of bones or cartilages that surround the spinal cord and help support the body
Primitive fishes lacked paired fins and jaws
Adaptation of jaws and paired fins allowed fish to more efficiently obtain food ultimately replacing all but a few jawless forms.

3. Jawless Fishes Hagfish - lampreys Lack both jaws and paired appendages
Have skeletons of cartilage (no bone)
Lack scales
Hagfish also lack vertebrae

4. Hagfishes Bottom dwelling “slime eels”
Skins are used to make leather goods
Slime glands produce abundant milky, gelatinous fluid for protection if hagfish is disturbed

5. Figure 10-1 (b) HAGFISH.

6. Lampreys
Have oral disk and rasping tongue covered with horny dentacles to grasp prey, rasp hole in the body and suck out tissue and fluid.

7. Cartilaginous Fishes Class Chondrichthyes Skeleton of cartilage
e.g. sharks, skates, rays, chimaeras
Skeleton of cartilage
Possess jaws and paired fins
Placoid scales cover skin

8. Sharks Top predators of ocean’s food webs
Excellent swimmers with streamlined bodies
swim with powerful, sideways sweeps of the caudal fin (tail)
heterocercal tail: caudal fin in which the dorsal lobe is longer than the ventral
Males have claspers—modified pelvic fins which transfer sperm from the male to the female

9. Caudal fin Clasper Pelvic fin Rectal gland Spleen Cloaca Dorsal fin
Intestine
Kidney
Spine
Stomach
Testis
Gill slits
Mouth
Pharynx
Heart
Pectoral fin
Liver
Pancreas
Placoid
scales
Stepped Art
Fig. 10-3, p. 266

10. Sharks
Ventral mouth with multiple rows of teeth which are constantly replaced
Found in all oceans with the greatest numbers in temperate and tropical waters
Humans exploit shark populations for fins, meat, oil, leather, cartilage and sport

11. Skates and Rays Have flattened bodies adapted to a bottom existence
Greatly enlarged pectoral fins that attach to the head
Reduced dorsal and caudal fins
Eyes and spiracles (openings for the passage of water) on top of the head
Gill slits on the ventral side
Lack anal fin
Specialized teeth are used to crush prey (e.g. benthic invertebrates)

12. Skates and Rays
Electric rays have electric organs that can deliver up to 220 V
Stingrays have hollow barbs connected to poison glands
treatment for stingray wounds: submerge in hot water to break down protein toxin
Sawfishes and guitarfishes have a series of (non-venomous) barbs along their pointed rostrums
Fished commercially for food, many are considered threatened

13. Figure 10-8 (b) SKATE EGG CASE.

14. Lobefins
Coelacanths – classified as lobefins due to presence of rod-shaped bones surrounded by thick muscle in the pelvic and pectoral fins
Only known as fossils until discovery of living specimen in 1938

15. Lobefins Live in Indian Ocean at depths of 150 to 250 meters
Skeleton made of bone and cartilage (vertebral column is cartilage)
Rostral organ in head detects weak electrical currents, may aid in prey detection
Life span is 60 years, reach sexual maturity at ~ 20 years, produce 5 to 26 live young
Considered to be in danger of extinction

16. Ray-Finned Fishes
Possess unpaired and paired fins, providing better control of movements
1 or more dorsal fins, caudal fin, and usually anal fin
help maintain stability while swimming
Paired fins consist of pectoral and pelvic fins
both used in steering
pectoral fins also help to stabilize the fish

17. Figure 10-13 (b) ANATOMY OF RAY-FINNED FISHES.

18. Figure 10-13 (c) ANATOMY OF RAY-FINNED FISHES.

19. The Biology of Fishes: Body Shape
Shape of body determined by characteristics of habitat
Fusiform body shape: streamlined shape with a very high and narrow tail
efficient movement for active swimmers
Figure (a) FISH SHAPES.

20. Body Shape Laterally compressed or deep body allows navigation through
complex habitat, e.g., grass or corals
Figure (b) FISH SHAPES.

21. Body Shape Depressed or flattened bodies bottom-dwelling fishes
Figure (c) FISH SHAPES.

22. Body Shape Globular bodies, enlarged pectoral fins
appropriate for sedentary lifestyle
Figure (d) FISH SHAPES.

23. Body Shape
Long, snake-like bodies, absent or reduced pelvic and pectoral fins
useful for burrowing, living in tight spaces
Figure (e) FISH SHAPES.

24. Fish Coloration and Patterning
Countershading is seen in open ocean fish
when viewed from above, dark color blends in with surrounding water; when viewed from below, white belly blends in with lit surface waters
Disruptive coloration—background color of the body is usually interrupted by vertical lines; may be a dark dot (“eyespot”) present in tail area
more difficult for predators to see the fish

25. Figure 10-16 DISRUPTIVE COLORATION.

26. Fish Coloration and Patterning
Poster colors: bright, showy color patterns
may advertise territorial ownership, aid foraging individuals to keep in contact, or be important in sexual displays
warning coloration: bright coloration to warn predators that the fish is too venomous or spiny to eat

27. Figure 110-17 WARNING (APOSEMATIC) COLORATION.

28. Fish Coloration and Patterning
Cryptic coloration: coloration which blends with the environment
used for camouflage

29. Figure 10-18 (b) CAMOUFLAGE.

30. Locomotion
muscles contract alternately from one side of the body to the other

31. Figure 10-19 (a) FISH LOCOMOTION.

32. Locomotion Fish with different body forms swim in different ways
elongate fish undulate the entire body
swift swimmers flex only the posterior portion of the body
other fish are somewhere in between
fish with a dermal skeleton can only flex the area before the caudal fin
some fish swim using their fins alone without body flexure

33. Figure 10-19 (c) FISH LOCOMOTION.

34. The Biology of Fishes Respiration and Osmoregulation
Gills often used to extract O2, eliminate CO2, and aid in salt balance
gill filaments: highly vascularized, rod-like structures which compose the gills

35. Figure 10-21(b) THE FISH GILL.

36. Operculum (gill cover)
rakers
filaments
Operculum (gill cover)
Water +
CO2
Deoxygenated
blood
entering
gill
Oxygenated
blood leaving gill
Water + O2
Water
and O2
and CO2
Gill
filament
Blood
capillaries
Deoxygenated
blood entering
gill
Blood
flow
Stepped Art
Fig , p. 278

37. Respiration and Osmoregulation
Water must be continuously moved past the gills to keep blood oxygenated
most ray-finned fishes ventilate gills by pumping water across them using gill pumps
very active fishes, e.g., sharks, tuna, and swordfish use ram ventilation—continuously swimming forward at high velocity with the mouth open

38. Respiration and Osmoregulation
Osmoregulation refers to process by which organisms maintain proper concentration of solutes and water in body fluids
Blood’s salt concentration is about 1/3 that of seawater, so water is lost
Fish drink seawater to compensate

39. Water gain by osmosis Salt-excreting Salts diffuse in gland
Some
salt water
swallowed
with food
Salt-excreting
gland
Salts diffuse in
through gills
Kidney with
large glomeruli—
reabsorbs urea
Large volume of
hypotonic urine
Gains salts
by diffusion
Water loss by osmosis
Drinks
salt water
Salt excreted
through gills
Kidney with small
or no glomeruli
Small volume of
isotonic urine
Stepped Art
Fig , p. 279

40. The Biology of Fishes Cardiovascular System
Consists of heart, arteries, veins, and capillaries

41. Cardiovascular System
maintain body-core temperature at 2-10oC above seawater, increasing efficiency of swimming muscles

42. Figure 10-23 COUNTERCURRENT HEAT EXCHANGE IN TUNA.

43. The Biology of Fishes Buoyancy Regulation
Maintaining buoyancy
sharks sink if they stop swimming
large livers produce squalene—an oily material with a density less than seawater

44. Buoyancy Regulation
Most fish use a swim bladder—a gas-filled sac that helps offset the density of the body and regulates buoyancy
the fish can adjust the amount of gas in the swim bladder to maintain depth

45. Buoyancy Regulation
Active swimmers do not have swim bladders, and must swim to avoid sinking
Bottom dwelling fish lack swim bladder, do not need to maintain buoyancy in water column

46. The Biology of Fishes Nervous System and Senses
Nervous system consists of: brain, spinal cord, peripheral nerves, and various sensory receptors
Olfaction and Taste
olfactory receptors in sharks (“swimming noses”) well developed
ray-finned fishes have olfactory pits—blind sacs opening to the external environment that contain olfactory receptors
taste receptors may be located on the surface of the head, jaws, tongue, mouth and barbels (whisker-like processes about the mouth)

47. Nervous System and Senses
Lateral line system and hearing
ray-finned fishes have a lateral line system for detecting movement in the water – aids in locating prey and avoiding predators
lateral lines consist of canals running along the length of the fish’s body and over the head

48. Nervous System and Senses
Lateral line system and hearing
ears are internal and have a detection range of 200 to 13,000 hertz
human range = 20 to 20,000 hertz

49. Nervous System and Senses
Vision
no eyelids (or poorly developed)
usually don’t need to adjust pupil size because of the low quantity of light
eyes are usually set on the sides of the head
shallow-water species can perceive color

50. Nervous System and Senses
Ampullae of Lorenzini
organs scattered over the top and sides of shark (and relatives) head
sense electrical currents in water

51. The Biology of Fishes: Digestion
Digestive system consists of mouth, pharynx, esophagus, stomach and intestine

52. Digestion All cartilaginous fish are carnivores
Ray-finned fishes exploit all food resources and can be carnivores, herbivores or omnivores
Prey of carnivorous fish is swallowed whole, chewing would block water flow past gills
Filter feeding fish (e.g., basking sharks) use gill rakers to filter plankton

53. Figure PARROTFISH.

54. The Biology of Fishes Adaptations to Avoid Predation
Many exhibit elaborate camouflage
Pufferfishes and porcupinefish inflate their bodies to deter predators
Flying fishes use enlarged pectoral fins to glide through the air and escape
Parrotfish secrete a mucus cocoon
Surgeonfish are armed with razor-sharp spines

55. Adaptations to Avoid Predation
Clingfishes use a sucker to attach to rocks so predators can’t dislodge it
Triggerfish projects spines to deter predators or wedge itself into cracks
Scorpionfish and stonefish have venom glands for self-protection

56. The Biology of Fishes: Reproduction
Sexes are typically separate
Sperm and eggs pass to the outside through ducts

57. Reproduction Three reproductive modes:
Oviparity – eggs are shed into the water column and embryo develops outside the mother’s body
common in ray-finned fishes
Ovoviviparity – fertilization is internal and eggs hatch within mother’s uterus, where they are nourished by yolk stored in egg
common in sharks
Viviparity – young attach directly to mother’s uterine wall or uterus produces “uterine milk” that is absorbed by embryo
occurs in some sharks and some ray-finned fishes

58. Reproductive Strategies
Hermaphroditism: individuals have both testes and ovaries at some time in their lives
occurs in at least 14 bony fish families
synchronous: possessing functional gonads of both sexes at one time
sequential: changing from one sex to another

59. The Biology of Fishes: Schooling
School of fish = group of individuals that operates in a polarized, synchronized fashion
Reasons for schooling:
more eyes increases food finding abilities and predator avoidance
predators can’t focus on an individual

60. The Biology of Fishes: Fish Migrations
Daily migrations usually associated with feeding and predator avoidance
Seasonal migrations usually associated with spawning, changing temperatures or feeding
Migrations may occur within seawater or between seawater and fresh water to spawn

61. Figure 10-33 (upper left) LIFE CYCLE OF THE AMERICAN AND EUROPEAN EELS.