Transcript Ch. 7, part 2: Marine Animals Without a Backbone 7.6 Arthropods

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Largest phylum (Arthropoda)
3 of 4 animals on earth are arthropods
Insects are largest group
Majority of marine arthropods are crustaceans
(phylum Crustacea)
Lobsters, shrimp, crabs and others
Flexible segmented with bilateral symmetry
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Jointed appendages moved by sets of attached
muscles
Exoskeleton composed of chitin and secreted by
underlying tissue
Provides support, protection, and increase surface
area for muscle attachment
To grow must molt exoskeleton
It is formed before molting and hardens after old
skeleton is discarded
Most are small
Largest is giant spider crab reaches 10 ft long
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http://www.youtube.com/watch?v=4f6d8crx
ZYg
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Most are marine
Most have gills for gas exchange
Chitinous skeleton hardened by
calcium carbonate
Appendages specialized for
swimming, crawling, attaching to
other animals, mating, and feeding
Two pairs of antennae involved in
sensing surrounding
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In plankton, sediment, on other organisms, and
crawling on seaweed
Copepods
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Planktonic and use mouthparts
to filter out or capture food
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Some use enlarges fist antenna to swim and
avoid sinking
Many are
parasitic
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Filter feeders that usually live attached to surfaces
including living organisms like crabs and whales
Many are very particular what they attach to
At the top of their calcareous plates is an opening
to allow cirri (feathery appendages) to sweep the
water
(Cirri are legs)
Some highly modified do not have plates and
are parasitic
Have crustacean larvae that swim and attach to
surfaces before metamorphosing into adults
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http://www.youtube.com/watch?v=1nbQIu6
0bHg
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Copepods
Barnacles
Shrimp
Krill
Lobsters
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Decapods (ten legs, or jointed appendages)
largest group AND Largest crustaceans in size
Have great commercial importance
5 pair of legs, pereopods, first pair are claws used
for feeding a defense
Maxillipeds closer to mouth, turned forward, and
specialized to sort out food and push it to mouth
Well developed carapace encloses the
cephalthorax
The rest of body is abdomen
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Laterally compressed with
elongated abdomen (tail)
Shrimp are scavengers
feeding on detritus on the
bottom
Many colorful shrimp live
in tropics on surfaces of
other invertebrates or
remove parasites from the
skin of fish while other live
in deep ocean
Ghost or mud shrimp live
in mud
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Marine and the clawless
spiny lobster are nocturnal
and hide during the day in
rock or coral crevices
Scavengers and predators
that crush molluscs and sea
urchins
Hermit crabs (not true crabs)
hide long soft abdomen in
empty shells, some cover the
shell with sea anemones and
sponges for added protection
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http://www.youtube.com/watch?v=7LJqEW756Y
Lobster colors
https://www.youtube.com/watch?v=lIuyTSX_bh
I
Lobster swimming
https://www.youtube.com/watch?v=4sHHTQ7vlo
Sea turtle eating lobster
https://www.youtube.com/watch?v=4sHHTQ7vlo
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Abdomen small tucked under compact and
typically broad cephalthorax
V-shape abdomen is male, U-shape is female
Highly mobile and walk sideways
Most diverse of the decapods
Scavengers, predators, some have specialized
diets of seaweeds, organic matter in mud, or coral
mucus
Live along rocky shores or sandy beaches
Land crabs live most of life on land but return to
ocean to release eggs
No, it has it’s own class!
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Biology of Crustaceans
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Filter feeding is common in small crustaceans
Stiff, hair-like bristles on some appendages to
capture food particles
Other appendages move food from bristles to mouth
Some appendages modified to pierce or suck in
parasitic copepods
Stomach has chitinous teeth or ridges for grinding
and bristles for sifting
Decapods has 2 chambered stomach connected to
digestive gland that secretes enzymes & absorbs
nutrients (extracellular)
Intestine ends in an anus
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Nutrient distributed by open circulatory
system
Gas exchange occurs in gills attached to
appendages
Gills lie under carapace bathed by water
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Simple crustaceans ladder-like but centralized in
decapods
Small, simple brains but well-developed sensory
organs
Compound eyes
In decapods acts like periscopes
Keen sense of smell (sensitive to chemicals in water)
Have pair of statocysts for balance
Most behaviorally complex of invert.
Have special body posture and movement of legs and
antennae
Help settle disputes between neighbors and courtship
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Sexes separate in most crustaceans
Males use specialized appendages to transfer sperm
directly to female
Hermaphroditic species transfer sperm
Barnacles have a penis that can stretch to reach others
Decapods takes place immediately after molting and
females can store sperm to use on different batches of
eggs
Amhipods and isopods eggs brooded in chamber by
lateral extensions of body
Decapods carry eggs on pleopods (simmerets) beneath
body
Most have planktonic larvae type and number of
larval stages vary widely
Other
Marine
Arthropods not in
Class Crustacea
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Only surviving members of their class
Widely represented by fossil records
5 living species and not true crabs
Live on soft bottoms of shallow waters on
Atlantic
and Gulf coasts of North America and
Southeast Asia
Emerge on beaches to reproduce
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Superficially resemble spiders
Four or more pairs of legs
Large proboscis with mouth at tip used to feed
on soft invertebrates such as sea anemones and
hydrozoans
More common in cold water but do occur
throughout oceans
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3 pairs of legs as adults
Rare in the sea
Live a waters edge scavenging for seaweeds,
barnacles, and rocks
Inhabit decaying seaweed that accumulates at
high tide
Seaweed
fly
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Special feeding structure the lophophore is
ciliated tentacles arranges in horseshoe-shaped,
circular or coiled
Suspension feeders with cilia creating current
Lack segmentation, bilateral symmetry, a
coelom and U-shaped gut
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Form colonies on seaweeds, rocks, and other
surface
Consist of minute inter connected individuals
zooids that secret skeleton of various shapes
Colonies or either encrusting or upright
Lophophore is retractable
U-shaped gut ends in anus outside edge of
lophophore
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Worm-like and build tubes made of sand
grains
Horseshoe-shape or circular lophophore and
U-shaped gut
Burrow in sand or attaching tubes to rocks in
shallow water
Most only a few cm long
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Shell w/two valves dorsal and ventral
When valves open shows lophophore w/at
least 2 coiled and ciliated
Attach to tocks or burrowing in soft sediment
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Phylum (Chaetognatha)
Smallest animal phyla
All marine only 100 species
Most common and important
member of plankton
Almost transparent streamlined
with fish-like fins and tail
Head has eyes, grasping spines
and teeth
Range from few mm to 10 cm
Voracious carnivores
w/efficient sensory structure to
detect prey
Prey on small crustaceans, eggs,
and larvae of fishes
Most of time motionless but will
swim in rapid darting
movement to grab prey
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Phylum Echinodermata
Bilateral symmetry for plantonic larvae
Pentamerous radial symmetry (five
parts) for adult
No head, anterior or ventral side
Oral surface is where the mouth is
located
Complete digestive tract, well developed
coelom & internal skeleton
(endoskeleton)
Endoskeleton is covered by thin layer of
ciliated tissue
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Spines and pointed bumps give spiny appearance
Water vascular system-water-filled canals
Tube feet are muscular extensions of canals
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When extended filled with water by the action of
muscular sacs (ampullae) that extend inside body
opposite of tube feet
Tube feet often end in a sucker used for
attachment, locomotion andreceiving chemical and
mechanical stimuli. In sea stars and sea urchins
system connects to outside through madreporite
(porous) plate
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of Echinoderms
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Starfish with most
having 5 arms radiating
from central disk
Some could have 50
arms
Tube feet radiate from
amburacural grove
Move slowly in any
direction by reaching
out tube feet and
pulling along
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Endoskeleton interconnected calcium
carbonate plates
Allow some flexibility in arms
Aboral surface covered w/spines modified
into pincer-like organs called pedicelariae that
help keep surface clean
Predators of bivalves, snails, barnacles, &
other attached or slow moving animal
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Very long flexible
and sharply
demarcated from
central disk
Has swift, snakelike movements
Feet lack suckers
& used for feeding
Eat detritus and
small animals from
bottom of water
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Particles collected
by tube feet &
passed from foot to
foot to mouth
Lack anus
Widely distributed
but hard to see
hiding under rocks
and corals or cover
themselves with
mud or sand
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Endoskeleton forms round
rigid shell-like test
w/movable spines
Locomotion by spines,
jointed to sockets in test,
and sucker-tipped tube feet
5 rows of ambulacral
groves w/tube feet extend
outer surface of sphere
Mouth on bottom and
anus on top
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Plates that make up test
can be seen cleaned of
spines & tissue
Bands of pores
correspond to bands of
tube feet
Graze on attached or
drifting seaweeds and
seagrasses
Also ingest detritus
and encrusting animals
(sponges and
bryozoans)
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Mouth has jaws and muscles (Aristotle’s
lantern) used to bite off algae and bits of food
from bottom
Common on rock shores
Heart urchins and sand dollars adapted to live
in soft bottoms having flatten bodies and short
spines
Deposit feeders use tube feet & mucus to pick
up organic matter
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Worm-like, do not have
spines, & lack radial
symmetry
Lies on side w/5 rows of
tube feet
Oral and aboral are at
ends
Endoskeleton composed
of microscopic calcareous
spicules thought warty
tough skin
Deposit feeders w/tube
feet around mouth
modified into branched
tentacles used to pick up
or scoop sediment
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Some burrow or hide and
extend only tentacles to obtain
food
Some secrete toxins
Discharge sticky sometimes
toxic filaments through anus
Evisceration- sudden
expulsion of gut or internal
organs through
mouth or anus to distract
predator
Can grow back organ
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https://www.youtub
e.com/watch?v=wXf_
YodWw40
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Suspension feeders that
use out stretched
feather arms to obtain
food
Feather stars and sea
lilies
Sea lilies restricted to
deep water & attach
permanently to bottom
Feather star perch and
crawl on hard bottoms
in both shallow and
deep water
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Upside down brittle star w/ ambulacral
grooves and mouth directed upward
Five –200 arms because of branching of
original 5
Have side branches w/tube feet secreting
mucus to catch food particles
Food gets to mouth with ciliated ambulacral
grooves
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1. Feeding a Digestion
Most sea stars carnivores
Feed by everting part of stomach inside out
through mouth envelop the food
Stomach secretes digestive enzymes made by
digestive glands that extend into arms
Food carried to glands for absorption and stomach
pulled back inside
Intestine short or missing
Brittle stars and crinoids simple short guts and
brittle stars lack anus
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Sea urchin and sea cucumber long gut
Adaptation in sea urchin to digest seaweed
because seaweed harder to digest
Sea cucumbers adapted to pick up large amount
of sediment to digest
Nutrients & oxygen transported in ceolomic fluid
Sea stars & sea urchins gas exchange take place
across small, branched projections
Sea cucumbers water drawn through anus to
respiratory trees
Respir. trees extensions of gut
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Presence of nerve net
Coordinates movement of tube feet & spines
No brain
Do have come complex behavior like sea
cucumbers righting when turned over and
camouflage
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Sexes are separate in most
5 or more gonads shed sperm or eggs into water
Spawn all at once because the gametes do not
survive long in the water
Fertilized egg develops into ciliated, bilateral larvae
in plankton and does not obtain radial symmetry
until metamorphosis
Some do not develop into larvae and are brooded in
special pouches or under body
Reproduce asexually by separation of disk and
regenerating the resulting other half
Some sea stars a severed arm can grow into a new
individual
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Get out a piece of paper and draw a star; then,
cut it out
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Pull out sides: Represents Sea Cucumber
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Fold up to top: sea urchin
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SMASH!!
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Phylum Hemichordata
Share some characteristic of echinoderms and
chordates, evolutionary linking these two groups
Some have larvae stage like echinoderms &
dorsal, hollow nerve cord and openings along
anterior part of gut like chordates
Examples acorn worms, worm like deposit feeders
that live free or in U-shaped tubes
Some found around hydrothermal vents
8-45 cm long
Ingest sediment like sea cucumbers using thick
mucus-secreting proboscis to collect organic
material
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Phylum Chordata
3 subgroups 2 invertebrates & 1 vertebrate
Invertebrates called protochordates
All developing chordates including humans
have:
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single hollow nerve cord along dorsal side
gill slits
notochord (flexible rod supports along nerve cord
and gut)
post anal tail
Have ventral heart
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Largest group
All are marine
Sea squirts
Sac like bodies attach to hard surfaced or soft
sediment
Sessile
Body protected by tunic leathery, gelatinous
outer covering
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Filter feeders water flow through incurrent
siphon filtered by ciliated sieve like sacs
U-Shaped gut where filtered water is expelled
through excurrent sipho
Some colonial forming clumps of individuals,
and other of circular, flower-like arrangement
of individuals sharing common tunic and
excurrent siphon
Planktonic larvae known as tadpole larvae
have gill slits, dorsal nerve cord, notochord,
eye, and post anal tail, but adult does not
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Larvae does not feed & sole purpose is to find
place to settle
Some are planktonic like Salps
Have incurrent and excurrent siphon
Floating colonies
Larvaceans planktonic tunics
Retain body of tadpole through life
Secretes complex, delicate gelatinous house for
protection and
filters water for food
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7 cm long
Laterally compressed
& elongated like a fish
Has all chordate
characteristic lack
only backbone
Inhabit soft bottoms
Filter feeders, use gill
slits to capture and
concentrate organic
particles