IB Bio Sharks

chondrichthyes

cartilaginous fish

what is a chondrichthyes’ endoskeleton like?

entirely cartilaginous

fusiform body aka

streamline body

fusiform body = _______ shaped

torpedo

where is mouth located?

ventral (on bottom of body)

countershading

* dark on top, light on bottom
* allows for camouflage

placoid scales

* scales on skin
* rough one way, smooth other way

how do placoid scales help chondrichthyes?

point toward tail & help reduce friction from surrounding water when shark swims

how many chambers in heart?

two (therefore, sharks = fish)

how many atrium(s) & ventricle(s) in sharks?

one atrium, one ventricle

flow of blood in sharks

* body ^^→^^ A ^^→^^ V ^^→^^ gills ==→== body
* ^^→^^ = deoxygenated (blue)
* ==→== = oxygenated (red)

do chondrichthyes have exposed gills slits OR an operculum covering their gills?

* separate exposed gill slits
* no operculum

how do 90% of shark species reproduce?

by internal reproduction

placoid scales can become…

teeth

chondrichthyes constantly…

grow new teeth & lose teeth

what do bony fish have that chondrichthyes DON’T?

swim bladders

swim bladders (bony fish)

used to control buoyancy (stay neutral) by filling w/ & losing air

giant livers (chondrichthyes)

* store oils to control buoyancy (stay neutral)
* buoyancy depends on amount of lipids/oil

shark senses (6)

1. smell - works farthest away
2. hearing
3. lateral line organ
4. vision
5. ampullae of Lorenzini
6. touch & taste - works closer

lateral line organ

* series of sense organs along sides of bony & cartilaginous fish

what does lateral line organ detect?

* can detect movement in water, pressure, & vibrations
* feels changes in water pressure → doesn’t bump into things swimming around them

ampullae of Lorenzini

organ that detects slight electric fields given off by living things in ocean

how do sharks eat?

open mouth → thrust jaw forward

how does internal fertilization occur?

male claspers insert into female cloaca (where waste also occurs)

ovoviviparous

* internal
* no parental support given to fertilized egg

ovoviviparous example

dogfish shark embryo

viviparous

* live young produced
* parents give extensive parental care

viviparous examples

* great whites
* porbeagle embryo

oviparous

* external eggs
* no additional parental support

oviparous example

cat shark egg

tapetum lucidum

reflects light in in back of eye to get a second chance of seeing as it reflects out

tapetum lucidum allows sharks to…

to see in dark well

whale shark

world’s largest fish (46 ft long)

where are whale sharks found?

found in worldwide tropical oceans

why are whale sharks named after whales?

b/c both are large & filter feeders (eat plankton)

why are there not many chondrichthyes fossils?

cartilage skeleton = hard to fossilize

guitarfish

one of few chondrichthyes fossils

elasmobranchii

subclass that includes familiar sharks, skates, rays, & strange fossil relatives

elasmobranchii characteristics

* upper jaw not fused to braincase
* separate slit-like gill openings

rays

* tails have barbs w/ mild toxin
* viviparous (live bearing)

skates

* tails have blunt, thorny projections; no barbs
* oviparous (egg laying)

mermaid’s purses

eggs in rectangular cases released by only skates

both rays & skates (5)

* dorsoventrally flattened; not fusiform
* gill slits open on ventral (bottom) surface of head
* spiracles
* feed primarily on mollusks & crustaceans 
* teeth modified for crushing

dorsoventrally flattened

flattened on top & bottom

spiracles

* openings on top of head
* direct water over gills → prevent sludge from clogging delicate gills

why are there no spiracles on bottom of rays & skates?

* b/c there’s sand, dirt, & sludge on bottom


* top is relatively cleaner