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04 NEKTON

04 NEKTON. I. Vertebrate Characteristics A. Backbone or vertebral column that surrounds dorsal nerve cord B. Maximum of two pairs of limbs. II. Sharks and rays A. Characteristics 1. Adaptations for buoyancy a. Light skeleton of cartilage

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04 NEKTON

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  1. 04 NEKTON

  2. I. Vertebrate Characteristics A. Backbone or vertebral column that surrounds dorsal nerve cord B. Maximum of two pairs of limbs

  3. II.Sharks and rays • A. Characteristics • 1. Adaptations for buoyancy • a. Light skeleton of cartilage • b. Body tissues contain oils and lipids (Squalene) • c. Pectoral fins provide lift • 2. Tail asymmetrical • 3. Dorsoventrally flattened • 4 Mouth ventral • a. Rows of teeth point backward • b. Continuously replaced (Lyodont)

  4. A. Characteristics (continued) • 5. Scales (Placoid) • a. Spines point backward • b. Smooth caudally, rough cranially • c. Protection from abrasion and Minimize Hydrodynamic Friction • 6. Gills exposed • 7. SPIRAL VALVE • a. Absorptive organ in gut • b. Spiral shape increases surface area (Sharks don’t chew) • 8. LATERAL LINE • a. Canals along length of body(Neuromast) • b. Detect vibrations in water (thrashing excites)

  5. 9. Ampullae of Lorenzini a. Used for Electroreception Sensory 10. Spiracles a. Supplies Oxygenated blood to brain and eyes as well as the gills during rest on the bottom

  6. B. 8 Orders of Sharks 1. Order Squaliformes (Dogfish) • 2 dorsal fins with spines (grow exponentially throughout life) • No anal fin • Ovoviviparous Reproduction www.sharkinfo.ch

  7. 2. Lamniformes (Mackerel Sharks) • No Spiracles • No Nictitating Eye Lid • Anal Fin Present • Viviparity with Uterine Cannibalism www.pelagic.org

  8. Orectolobiformes (Carpet Sharks) • Barbels Present • Anal Fin Absent • Ovoviviparous divers.neaq.org

  9. Carcharhiniformes (Requiem and Hammerhead Sharks) • Anal Fin Present • Nictitating Eye Lid • Exhibits Viviparity and Ovoviviparity oceanlink.island.net

  10. C. Whale shark 1. World’s biggest fish a. 50 ft in length b. 2 tons www.news.com.au

  11. Diver Hitching a Ride on a Whale Shark Garrison, 2005 Oceanography: An Introduction of Marine Science, p. 372

  12. A large school of cobia, Rachycentron canadum accompany an 8.5-meter whale shark. The photo was taken from a petroleum platform in the northern Gulf of Mexico south of Louisiana. Photo by Fred Andersonhttp://www.usm.edu/gcrl/whaleshark/photos.php

  13. Whale Shark Harvest in China http://www.usm.edu/gcrl/whaleshark/photos.php

  14. B. Whale shark (continued) • Not much known about them, but researchers at the Gulf Coast Research Lab in Ocean Springs, MS recently began a research program utilizing satellite tags • Current findings by Australian scientists found 300 pups in one female that were all sired from one male whale shark. • Females able to store sperm for future fertilization. • What is the advantage of staggering a litter of pups for a specific time?

  15. www.elasmodiver.com

  16. An eight- meter whale shark with a satellite position tag http://www.usm.edu/gcrl/whaleshark/photos.php

  17. B. Whale shark (continued) 5. Feed on surface plankton 6. Has also been observed following and feeding from trawl nets while being pulled toward the vessel.

  18. Whale shark filter feeding at the surface. Note the open mouth and the upper jaw extended out of the water. Photo by GCRLhttp://www.usm.edu/gcrl/whaleshark/photos.php

  19. B. Whale shark (continued) 7. Recent evidence indicates they selectively consume lipid-rich fish eggs.

  20. The plankton sample on the left was taken where 16 whale sharks were observed feeding in the northern GOM. The control sample (right) was from two miles away. Note the higher density of fish eggs in the sample from the feeding site. These data provided the first documented observation of whale sharks feeding on fish eggs in the northern Gulf of Mexico. Photo by GCRLhttp://www.usm.edu/gcrl/whaleshark/photos.php

  21. Locations of whale shark sightings in the northern Gulf of Mexico from 2006 to 2007. Map provided by Jennifer McKinney http://www.usm.edu/gcrl/whaleshark/photos.php

  22. 6. Advantages of Cephalofoil Head a. Increased Visual Field b. Increased Directional Olfaction c. Increased Surface Area for Ampullae of Lorenzini and Pit Organs

  23. Great White Shark Capturing a Sea Lion Garrison, 2005 Oceanography: An Introduction of Marine Science, p. 372

  24. Disposal of shark carcasses after sport fishing tournament http://seapics.com/cgi-bin/Panorama.cgi?searchLynx~enlarge~0.24846757100229055x344410x1x291x5?seapics

  25. Disposal of shark carcasses after sport fishing tournament http://seapics.com/cgi-bin/Panorama.cgi?searchLynx~enlarge~0.24846757100229055x344410x1x291x6?seapics

  26. Shark fins prepared for sale in Trinidad http://seapics.com/cgi-bin/Panorama.cgi?searchLynx~enlarge~0.24846757100229055x344410x1x291x2?seapics

  27. Florida Keys

  28. Chondrichthyes Mouths

  29. Sawfish trophies on sale for people who cannot catch one themselves

  30. Reduction in numbers of top predators is having an impact upon marine ecosystems, due to increase in numbers of predators that are prey to large sharks

  31. School of Cownose Rays

  32. Heat apparently degrades the toxin from stingray barbs. Dr.Richard Clark, director of the division of toxicology at UC San Diego Medical Center, recommends soaking the injured area for about 15 minutes.The ideal water temperature is warmer than a hot tub (104 degrees), but less than 114 degrees.

  33. Press Register April 20, 2008, p. 1A

  34. North Carolina bay scallop monitoring sites. Total mortality (black bars) compares August (pre–cownose ray migration) to late September and October (postmigration) densities. Low scallop densities before ray migration are indicated by asterisks (< 1 to 2 m–2) or zeroes (0 m–2). Hatched bars represent mortality within experimental stockades that exclude rays (performed in a subset of years). Scallops were free to emigrate from stockades. Arrows denote direction of ray migration.

  35. III. Bony fishes • A. ½ of all vertebrate species • B. Characteristics • 1. Bony skeleton • 2. Laterally flattened • 3. Tail symmetrical • 4. Small pectoral fins give maneuverability • 5. Mouth even with midline

  36. B. Characteristics of bony fish (continued) • 6. Scales without spines • 7. Gills covered by OPERCULUM • 8. SWIM BLADDER • a. Filled with gas • b. Attain neutral buoyancy (=lift) • 9. Lateral line

  37. Anatomical Differences between Sharks and Bony Fish Castro & Huber, 2003, Marine Biology, p. 159

  38. C. Anchovies (Family Engraulidae) 1. Elongated mouth (jaw behind eyes) 2. Filter feeders a. Swim with mouth open b. Eat copepods c. GILL RAKERS = extensions of gill arches 3. Huge numbers, important component of food chain floridasportfishing.com www.dfw.state.or.us

  39. D. Mackerel, tuna, marlin (Family Scombridae) 1. Hydrodynamic design enables bursts of speed up to 75 mph a. Tail (1) CAUDAL PEDUNCLE (= stiff projection) gives rigidity to tail enhancing ability to propel (2) Lunate (= half-moon) shape reduces drag

  40. Nybakken, 2005, Marine Biology: An Ecological Approach, Fig. 3.8, p. 110

  41. 1. Scombridae hydrodynamic design (continued) b. Caudal FINLETS reduce drag (energy not lost in eddy formation) c. Streamlined body shape (1) External structures recessed (2) Teardrop shape (3) Smooth

  42. Flat Disk Cylinder Tear Drop Drag forces on different shapes with the same cross-sectional area as they move through water Nybakken, 2005, Marine Biology: An Ecological Approach, Fig. 3.12, p. 113

  43. Lateral View Top View Nybakken, 2005, Marine Biology: An Ecological Approach, Fig. 3.13, p. 113

  44. Mackerel, tuna, marlin (continued) • 2. Muscles • a. Dark or red muscle • (1) MYOGLOBIN: Binds and stores oxygen • (2) Lipids fuel aerobic respiration • (3) Long sustained effort • b. White muscle • (1) Glucose fuels anaerobic respiration • (2) Bursts of speed • (3) Tastes sweeter than red muscle

  45. E. Cryptic coloration • 1. Counter shading • a. Dark on top • (1) The benthic region is dark • (2) Harder to see from above by a visual predator (= bird) • b. Lightly colored underneath • (1) Defense from visual predators approaching from below • (2) Predator sees light background of sky www.queposfishadventure.com

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