Lecture 4. - Wednesday, September 3, 2008.

1. Discuss next weekend - Illinois River Trip - Who can make it?2. Discuss Fish Friday presentations - Sign up for Slots3. Distinguishing Traits of Chondrichthyes4. Traits that Distinguish Elasmobranchii & Holocephali5. SHARKS & RAYS

a. ecology & life-historyb. reproductionc. conservationd. notable shark & ray orders

IB Student Picnic Hosted by the School of Integrative Biology

Thursday, Sept 4

5-8 PM

Illini Grove Pavilion

(corner of Lincoln and Pennsylvania Ave)

Free Food

Free T-shirt

Meet Faculty

Find out what SIB is all about and meet other IB majors!

Illini Grove Pavilion5-8 pm

• Food served 5:30 to 7:30 pm

• Hamburgers, cheeseburgers, veggie burgers

• Ranch beans, potato salad, watermelon

• Cookies

• Pop and water

• RSVP to Debbie Lanter, 333-3044 or email dlanter@life.uiuc.edu

Chondrichthyes synapomorphies

1. Pelvic claspers • Derived from the margin of the pelvic fin

Mating Sharks Video 1

Mating Sharks Video 2

Cool Shark Videos to Checkout

Chondrichthyes synapomorphies

Teeth not fused to jaws

• Replaced serially in whorls

Chondrichthyes synapomorphies

3. Skull (chondrocranium) lacks sutures

Elasmoid

Ganoid

Placoid

Cosmoid

9

bone

dentindentinee

enamel

heterocercal abbreviate

d heterocercal

homocercal

isocercal

8

Bull Shark with heterocercal tail

Major living gnathostome lineages

Subclass HolocephaliRatfishes, rabbitfishes, or chimeras

Order Chimaeriformes (58 species)

Subclass HolocephaliRatfishes, rabbitfishes, or chimeras

Subclass Holocephali

• lacking gill slits - a single gill covering over 4 gill openings

• Upper jaw fused to cranium

• skin is naked in adults

• Some males have cephalic claspers in addition to pelvic ones

Differ from sharks and rays by:

Order Chimaeriformes

Ecology, Life History

• Reproduction, oviparous (egg-laying), internal fertilization

• Benthic, deep sea (80 to 2600 m), around the world

• Nocturnal

• Feed mainly on benthic invertebrates

mermaid’s purses

Lemon Shark Giving Birth

• http://www.youtube.com/watch?v=LfQgRCg1bNA

Whale Shark

whale shark video

• http://www.youtube.com/watch?v=uQrBwN39LJI

goblin shark

megamouth

megamouth video

• http://www.youtube.com/watch?v=RxhqBmnZv8Q

• start at 2:10

thresher shark (Alopiidae)

thresher shark video

• http://www.youtube.com/watch?v=BQrrW9VRMFQ

• start at 5:30

basking sharks

great white shark

great white shark video

• http://www.youtube.com/watch?v=O2FInaOCqoo

Order Carcharhiniformes (ground sharks)

• Family Carcharhinidae (requiem sharks) Largest Order - 8 families, 210 species

Tiger shark Hammerhead shark

Order Carcharhiniformes (ground sharks)

• Family Carcharhinidae (requiem sharks)

Bull shark

Oceanic white tip shark

Silky shark

Shark attacks on humans

• 35 to 55 unprovoked attacks each year

• 6 to 11 fatalities per year

• 54% of attacks on surfers/windsurfers 38% on swimmers/waders 6% on divers/snorkelers

Regions with most shark attacks:

Shark attacks on humans

• 35 to 55 unprovoked attacks each year

• 6 to 11 fatalities per year

• 54% of attacks on surfers/windsurfers 38% on swimmers/waders 6% on divers/snorkelers

Regions with most shark attacks:South Africa - 63 attacks from 1990 to 2003Brazil - 57 “ “ “ “Australia - 51

Shark attacks on humans

• 35 to 55 unprovoked attacks each year

• 6 to 11 fatalities per year

• 54% of attacks on surfers/windsurfers 38% on swimmers/waders 6% on divers/snorkelers

Regions with most shark attacks:South Africa - 63 attacks from 1990 to 2003Brazil - 57 “ “ “ “Australia - 51Florida - 311

dogfish sharks (Squalidae)

dogfish shark

http://www.flmnh.ufl.edu/fish/sharks/SpinyDogfish/spinydogfish.html

saw sharks

pointed snout used to thrash and incapacitate small fishes

electric rays (Torpedinidae)

sawfish (Pristidae)

More sawfish pictures

Skates (Rajidae)

Myliobatiformes

Sting rays (Dasyatidae)

Myliobatiformes

Sting rays

Myliobatiformes

Manta rays (Myliobatidae)

Weblinks:

great white : http://www.flmnh.ufl.edu/fish/sharks/whaleshark/whaleshark.html

megamouth: http://www.flmnh.ufl.edu/fish/Sharks/Megamouth/mega.htm

thresher: http://www.new-brunswick.net/new-brunswick/sharks/species/thresher.html

hammerhead: http://www.flmnh.ufl.edu/fish/Gallery/Descript/SmHammer/SmoothHammerhead.html

sawfish: http://www.flmnh.ufl.edu/fish/education/sawfishbrochure.pdf

manta ray: http://www.flmnh.ufl.edu/fish/gallery/Descript/MantaRay/MantaRay.html

for ground and requiem sharks (family Carcharinidae), skates (family Rajidae), and sting rays (Dasyatidae) go to the following website and look up some details about one or two species.

http://www.flmnh.ufl.edu/fish/Education/bioprofile.htm

There is tons of really cool stuff on sharks at the Florida Museum of Natural History website.

We could spend a lot of time on each of the various orders and families in the Elasmobranchii. Instead, I want you to look up something about each of the following groups. Find one or two facts that are of interest to you.

Review Questions

1. List the characters that distinguish between Elasmobranchii and Holocephali. Whoare the Elasmobranchii and who are the Holocephali? Where do Holocepahli generallylive?

2. We covered a lot of sharks and rays in a short amount of time. For each of the following groups, list one or two interesting facts about their biology. You can use your book, any book in the library, or the links I provided on the powerpoint file.

3. Describe the adaptations that Elasmobranchs have for maintaining neutral buoyancy. Explain how they work.

4. One could argue that Elasmobranch life-history reflects selection for high efficiency in their use of resources. What evidence supports this notion? Discussboth the life-history data (clutch sizes, when they mature, lifespan) as well as dataon metabolism and feeding rates.

5. Although all Chondrichthyes have internal fertilization, they vary quite a bit in thedevelopment of the embryos. Describe this variation (oviparity, retained oviparity,ovoviviparity (and the variations on this theme), placental viviparity, and uterineviviparity). Can you propose a general model for how these reproductive strategies evolved?

Review Questions Cont’d.

6. Why can sharks hunt so good at night? Hint: what sensory systems are well-developed in this group.

7. How does the general pattern in Elasmobranch life-history predispose them to being easily overharvested and endangered? What is the general pattern forshark fisheries? How do other fisheries endanger shark populations?