by256 lecture exam 2

hagfish mouth

-no jaws
-muscular tongue w/ keratinized teeth

what do hagfish eat?

live/dead fish
marine worms
crustaceans on ocean floor

do hagfish have good eyesight?

no, but they have a good sense of smell and touch
-also have tentacles around mouth for touch!

hagfish lateral line

degenerate but still useful!

what kind of kidneys do hagfish have?

primitive (pronephros) that are retained into adulthood

isoosmothic

osmolarity the same as environment!
-seen in hagfish

osmosis

diffusion of water through a selectively permeable membrane

osmolarity

measure of total concentration of solute particles

osmolarity of sea water

1000 mOsm/L

osmolarity of freshwater

less than 20 mOsm/L

osmolarity of mammal's body fluids

300 mOsm/L

isoosmotic groups

hagfish, protochordates

accessory hearts of hagfish

help pump blood back to main heart
-heart rates are all endogenous with no neural inputs to hearts

knotting behavior of hagfish

helps them get rid of slime produced as a defense mechanism

hagfish reproduction

- single long gonad
- some hermaphrodites
- no reproductive ducts
- external fertilization
- NO LARVAL STAGE

lamprey general characteristics

-one nostril for olfaction
- well-developed eyes and lateral system

do lamprey have accessory hearts?

no!
- single two-chambered heart w/ neural innvervation

lamprey osmoregulation

300 mOsm
- hypoosmotic in seawater
- hyperosmotic in freshwater

anadromous life cycle

live in marine water and travel to freshwater to reproduce
-lamprey

lamprey feeding

parasitic, feed on dead fish
- produce anticoagulant
- filter feed in larval stage

lamprey reproduction

-separate sexes w/ external fertilization

how long does lamprey larval stage last?

3 to 8 years

how long will parasitic lamprey feed before reproducing?

1-3 years

lamprey non-parasitic lifecycle

adults breed soon after they undergo metamorphosis and then die

how may jaws have developed?

through modifications of several sets of anterior gill arches

When did jawed vertebrates appear?

silurian period

what developed alongside jaws?

paired fins

two groups of early jawed fishes

1. Acanthodians
2. Placoderms

acanthodians

-first jawed fishes
- spines!
- most closely related to modern jawed fishes

placoderms

- heavily armored
- ranged many sizes
- placo \= plate/ derm\=skin

when did the early jawed fishes flourish/go extinct?

placoderms and acanthodians flourished during Devonian and went extinct during Carboniferous and Permian

examples of large placoderms

dinichthys and dunkleosteus, grew up to 20ft

chondrichthyes

cartilaginous fish, date back to Devonian
- sharks, skates, rays, and chimera

cladoselache

earliest group of sharks!
- went extinct during carboniferous
- fast and predatory
- up to 2m length

Chondrichthyes morphology

- jawed w/ cartilaginous skeletons
- paired fins
- heterocercal tail
- placoid scales
- mucous glands in skin

what are teeth in sharks a modified version of?

placoid scales

attachment of jaws in chondrichthyes

jaw is not attached to cranium except in chimeras!
- jaws can be enlarged during feeding

do sharks have a swim bladder?

no! have an oily liver
- oil is squalene

shark nervous system

brain has distinct lobes
- 10 pairs of cranial nerves
- semicircular canals have three loops
- well-developed olfaction and lateral line

Ampullae of Lorenzini

sensory pits on head that act as electroreceptors
- also detect temperature changes

how do ampullae of lorenzini detect temp changes?

gel in ampullae generate electrical currents

do sharks have good vision?

yes, have advanced eyes
- have a nictitating membrane to protect eyes during feeding

shark digestive system

- spiral valve in intestine slows passage of food
- large liver

shark circulatory system

- two-chambered heart (one atrium/one ventricle)
- blood goes from heart to gills then to body
- rectal gland secretes conc. salt solution into cloaca

osmoregulation of sharks

isoosmotic to sea water (1000 mOsm)
- retain high levels of urea to help maintain high osmolarity

shark reproduction

- separate sexe, internal fertilization
- ducts connect to the cloaca (except in holocephalii)

claspers

modified pelvic fins on a male shark that allows for transfer of sperm to female

oviparous

egg laying
- mermaid's purses
-eggs take 6 months-1yr to hatch

ovoviviparous

producing living young from eggs that hatch within the body
-develop for 9 months to over a year
ex. whale sharks

viviparous

live birth
- maternal connection
- primitive placenta
-develop for 8 months to over a year
ex. hammerhead!!

how do sharks focus their eyes?

move lens back and forth

when are sharks active?

at night; nocturnal

sharks are \______ to grow, \_______ to mature

slow, slow

holocephalii

chimaeras and ratfish
- Paleozoic/Devonian
-large venomous spine on 1st dorsal fin

how many living species of holocephalii?

~50 living species

why are holocephalians considered chondrichthyes?

similarities to sharks, skates, + rays:
-cartilaginous skeleton
-spiral valve in intestine
-oil-filled liver
-claspers in males

where do holocephali live

deep ocean!
-ALL marine

Holocephali differences from sharks, skates, rays

-firmly attached upper jaw
-single gill flap/no spiracle
-no scales
-no cloaca

Holocephali ecology

-found in the deep parts of most oceans
-feed mainly on shellfish and other inverts
-large plate like teeth for crushing shellfish
-large eyes for detecting bioluminescence

what does holocephali mean?

whole head

Holocephali reproduction

oviparous

Elasmobranchs

1. Batoids (55%)
2. Sharks (45%)

Batoids general facts

skates, rays, sawfish, guitar fish
-600 species
-55% elasmobranchs
-date back to jurassic (newer than sharks)

Batoid morphology

-flattened dorsoventrally w/ large pectoral fins
-spiracle on dorsal surface
-gill slits on ventral surface
-reduced tail
-plate like teeth for crushing prey, not sharp

Batoid ecology

-most marine but some can travel to freshwater
-mostly bottom dwellers

euryhaline

species that can tolerate a wide range of salinities
ex. batoids can travel from marine to freshwater

guitar fish (batoid)

aka shovel-nosed ray
-has ampullae of Lorenzini
-ovoviparous!
-shallow costal waters

sawfish (batoid)

-spiracle dorsally, gill slits ventrally
-elongated snout w/ teeth
-saw has ampullae of lorenzini
-euryhaline
-ovoviparous
-only 7 species

skates (batoid)

-tail more elaborate than rays
-no sharp spine
-more kite-like head
-oviparous

most common skate in alabama?

clearnose skate

rays (batoid)

-more whip-like tail w/ sharp spine
-ovoviparous

stingrays (batoid)

-sharp spine on tail
-spine covered w/ sheath, contains toxins

examples of stingrays

-bluntnose, atlantic, southern: AL
-eagle, cownose: swim in water column

manta ray (batoid)

"devil ray"
-filter feeds on plankton
-cephalic fins guide food into mouth
-migrate!
-largest rays
-can breach water
-ovoviparous

electric ray (batoid)

-flat body, well developed tail
-electric organ!
-bottom dwellers
-ovoviviparous

electric organ of electric rays

-connected to brain via large nerves (so it is under
voluntary control).
-composed of specialized muscle cells that
act like a series of batteries and they generate action
potentials (thousands of cells).
-Some can generate 220 volts or more.
-used to deter predators and stun prey and
possibly used for species recognition

torpedo ray (electric ray)

-largest!
-atlantic and pacific coasts
-high voltage shocks (ex. 200 volts)

lesser electric ray

-gulf of Mexico
-Atlantic coast
-produce 35 volt shock

SHARKS !

-very diverse
-sharp teeth in multiple rows
-top carnivores

how often are sharks' teeth replaced?

every 2 weeks in some

nurse shark

-shallow water bottom dweller
-has barbels @ nose
-can grow over 10 ft
-ovoviviparous but development in egg

thresher shark

-tail longer than body
-uses tail like a whip + for herding
-breaches
-ovoviviparous
-oophagous

oophagous

-egg eating
-embryos may eat unfertilized eggs in oviduct

great white shark

-largest predatory shark!
-can grow over 20ft and 2000 lbs
-feed on about anything and attack humans
-colder waters
ovoviviparous/oophagous

carcharodon megalodon

megalodon\=mega tooth
-extinct about 3.6 mya
-up to 50 ft

tiger shark

-blunt snout
-aggressive eater
-ovoviviparous
-attacks humans

hammerhead shark

-flattened head enhances senses
-warm water
-large groups
-viviparous

whale shark

-largest living fish
-pelagic feeder
-ovoviviparous

where do whale sharks live?

tropical/subtropical waters including gulf of mexico

bull shark

-common in G.o.M
-salt and freshwater
-euryhaline

euryhaline species

-travel up river
-tolerate different salinities
-have adapted to freshwater

what are the most modern bony fishes?

acanthodians

former classification of bony fishes

osteichthyes
-not used in cladistics

when did acanthodians appear?

Silurian period!

how much of fish species do bony fishes make up?

-28,000 species
-96% of all fish are teleosts

two cladistic groups of bony fishes

1. actinopterygii: ray finned
2. sarcopterygii: fleshy

general characteristics of bony fishes

-bony skeletons
-skin w/ dermal scales (vs epidermal)
-fins
-jaws
-respiratory system
-lungs

when did bone appear in fishes?

jawless fishes
ex. ostracoderms

functions of bone

-strong skeletons
-protection of brain and spinal cord
-location for Ca++ storage

dermal scales in bony fishes

ganoid, cycloid, ctenoid