Http:// Hammerhead sharks (8 species known) Sea of Cortez has the scalloped hammerhead

http://www.elasmo-research.org/education/shark_profiles/hammerhead_faq.htm

Hammerhead sharks (8 species known)Sea of Cortez has the scalloped hammerhead (Sphryrna lewini)School around seamountsSlow reproductive rate: females mature at 15 yrs, 12 month

gestation, 1 year off between pregnanciesFished for food and sport

http://www.elasmo-research.org/education/shark_profiles/hammerhead_faq.htm

Why the hammerhead shape?- spreads out sensory ability (electric, olfactory) (disadvantages: prevents jaw protusion & 3D vision)-use the hammer to pin down stingrays and eat them

(stingray spines often found in heads)

Figure 8.1

http://www.germantown.k12.il.us/html/Fishy.html

Three groups of fishes

Jawless fish (Agnatha)

Cartilagenous fish (Chondricthyes)

Bony Fish (Osteichthyes)

lamprey

Class Osteichthyes (Bony Fish)

- Dominant vertebrate in the sea

- 26,000 species (96% of all fish, 50% of all vertebrates)

http://www.germantown.k12.il.us/html/Fishy.html

Figure 8.8

Figure 8.14

Sharks (blood = seawater)- concentrate urea- excrete salt in urine,feces, rectal gland

How to cope with salt in seawater (tend to lose water)

Bony fish (blood<seawater)-kidneys conserve water-excrete salts in urine, feces,gills, skin

Figure 8.16

Figure 8.9Streamlined(fusiform)Fast-open water

Flattened topto bottom -Bottom dweller

Flattenedside to side-bottom orcoral reef

Slow -reef

Live invegetation/coral

Trunklike orround - slowmoving, reef

Figure 8.13

Maintaining buoyancy

Large oily live, light skeleton,pectoral fins for stability

Gas-filled swimBladder, pectoralfins freed for other uses-great diversity of forms

modes of swimming

Undulation flex caudal region move fins tail fin( eels) (tuna) surgeonfish boxfish

Figure 8.22

Skipjack tunaTropical speciesthat travels to temperate water tofeed. Halfway acrossglobe each year.

SalmonAnadromous =Spend lives atsea feeding, returnto rivers to breed:Magnetic field and smellof home rivers

Figure 8.22Conservation threatsPolluted rivers, damsWater harvestedIntroduced species offarmed salmon

Catadromous - breed at sea, migrate into rivers to grow (16 spp freshwater eels)

adults spawn and die in Sargasso Sea / larvae in plankton 1 yr+/ metamorphose into juveniles / grow and mature in rivers

Why do fish school?

“selfish herd theory”(middle is safest place to be)

Buoyancy - how to regulate

Cartilagenous fish (sharks, rays, chimaeras)-large oily liver, light skeleton- pectoral fins needed for stability/steering

Advantages: rapid changes in depth possible

Bony fish– Swim bladder (gas-filled sac above intestine)Advantages: freed up pectoral fins for other uses

Strange reproductive practices of fish

• Hermaphrodites

• Sex change (born one sex, become the other)

Large fish in harems are often sex-change males

Large fish in non-harem species are often sex-change

females

• Parasitic males

• “Sneaker” males that look like females

• Sex-role reversal (male pregnancy in seahorses)

• Males often do parental care in fish

http://www.geocities.com/thesciencefiles/angler/fish.html

Anglerfish adaptations for deep water habitat:

http://www.geocities.com/thesciencefiles/angler/fish.html

Anglerfish adaptations for deep sea (food and mates scarce)sit and wait predatory behaviorbioluminescent lure parasitic males

- once males encounter female, they don’t leave

http://www.oceanoasis.org/fieldguide/thal-luc.html

Rainbow wrasseThalassoma lucasanum

Two types of malesTwo types of reproduction.

1) Females(yellow/red lateral stripes)2) Primary males(look like females)3) Terminal males(blueheads) - born female, turninto males

http://www.oceanoasis.org/fieldguide/thal-luc.html

Rainbow wrasseT. lucasanum

Two types of reproduction

1) Broadcast spawning Many males and females rush

to surface and release gametes

2) Harems: one terminal maleguards group of females and mates with them individually.

Death of secondary male-large female turns into newterminal male

Mass spawning of the rainbow wrasseThalassoma lucasanum

Barred serranoSerranus psitticinusSea of Cortez

Simultaneoushermaphrodite(can act as male orfemale at any time)-dominant male in harem mates with “females”.

Serranus annularis CaribbeanOrange back basslet

http://www.qualitymarineusa.com/fish/basslets.html#top

Lecture ended here.

http://www.cnn.com/TECH/science/9812/11/seahorses.yoto/

Male pregnancy in seahorses-Placenta- Long-term pair bond-Daily dance of pair

http://www.cnn.com/TECH/science/9812/11/seahorses.yoto/

Conservation of Sea Horses20 million caught each year

- 95% chinese medicine- 5% aquarium trade

32 species (threatened status)

Coelocanth (lobe-finned fish)