Download Arthropods - Bowie Aquatic Science

Phylum Arthropoda
aka: Arthropods
• Literally means
“Jointed foot” animals
• Includes crabs,
shrimps, barnacles,
spiders, insects,
horseshoe crabs, etc…
Common Characteristics of all
Arthropods
• Exoskeleton-tough outer
covering made of chitincarbohydrate. Some chitin
may contain calcium to
strengthen the skeleton.
Protection and muscle
attachment.
• Jointed appendages that
are specialized for
feeding, movement,
protection, and
reproduction.
Class Crustacea
a.k.a. Crustaceans
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Bilateral Symmetry
2 main segments-cephalothorax and abdomen
Cephalothorax-head and chest region; covered with carapace
Abdomen-posterior region often including a tail.
Decapods (lobster, crabs, shrimps) 5 pr of legs under carapace.
(not barnacle)
1st pair= claws for food getting; 2nd-5th pr walking
Head-two eyes, 2 pr. Antennae, special mouth parts for feeding.
Thorax-chilipeds (claws), and walking legs.
Abdomen-swimmerets (paddle-like appendages for swimming).
Anatomy of Crayfish
Molting
• Shedding of the exoskeleton
• Occurs once or more per year
• Soft-shelled crabs are newly
molted crabs
Lobsters
• Northern lobster (Homarus
americanus)- American or Maine
lobster w/ 2 large claws
• Spiny lobster (Planularis aragas)no large claws; CA, FL, and Gulf of
Mexico
Feeding and Digestion
• Predators that eat mussels and sea urchins;
scavengers
• One-way digestive tract-mouth, esophagus,
stomach, intestines, and anus
Respiration
• Uses gills-featherlike structures
located in the water-filled chamber
under the carapace.
• Each gill is attached to the upper
end of a walking leg.
• Rapid beating of mouth parts
sends currents of water over the
gills.
• O2 diffuses in and CO2 out.
Circulation
• Open circulatory system (no
capillaries so blood just passes
through tissue spaces)
• Blood is blue b/c of pigment called
hemocyanin (contains copper)
• Blood is pumped through the body
by a one-chambered heart.
Nervous System
• Have a brain and
ventral nerve cord to
carry impulses and
messages from the
eyes and antennae.
Reproductive System
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Sexually
Internal fertilization
External development
Male deposits sperm cells into
the female’s abdomen in the
seminal receptacle
• As the eggs are released, they
are fertilized by the sperm.
• Holds eggs on her
swimmerets for nearly one
year.
• Plankton when they hatch.
Lobsters
• One in a million
lobsters are blue.
• Mutant of the brown
lobster
• DNA codes for a
special protein that
mixes with the red
pigment to create blue.
Crabs
Mole Crab (Emertia)
• Lives in turbulent surf
zone along sunny
beaches.
• Has smooth body to
burrow w/ its
swimmerets.
• Feathery antennae to
catch microscopic
organisms in the sand.
Fiddler Crab (Uca)
• Digs tunnels in sand
along shores of bays
and inlets.
• Males have one large
claw and one small.
• Females have 2 small
claws.
Hermit Crab (Pagarus
longicarpus)
• Lives in shallow
coastal waters.
• Has soft abdomen
w/o exoskeleton so it
finds an empty shell to
live in.
• Changes shells as it
grows.
Spider Crabs (Libinia
emarginata)
• Slow moving due to
lack of paddle-like
appendages
• So slow that algae and
barnacles grow on it.
• Giant spider crab of
Japan can grow up to
4m long from leg to
tip.
Life Activities
• Similar to lobster
• Abdomen folded up
between walking legs.
• V-shaped abdomen is
a male; U-shaped
abdomen female.
• Mostly eat dead plant
and animal matter.
Shrimp: Common Species
• Pink Gulf Shrimp (Penaeus duorarum)- popular
seafood; 17cm in length
• Common Shore Shrimp (Palaemonetes
vulgaris)- smaller; scavenges in marshes
• Mantis Shrimp (Spuilla empusa)- largest shrimp
(25 cm in length); eat worms and small fish; found
from Cape Cod to Brazil.
• Cleaner Shrimp (Periclimenes)- lives on coral
reefs and rides tropical fish in Caribbean and Gulf
waters and eats parasites that are found on their
skin.
Examples of Shrimp
• Mantis Shrimp 
• Cleaner Shrimp
(below)
Copepods
• Copepods (Calanus)1000’s of species.
Less that ½ cm long;
eats diatoms;
important part of
zooplankton
community; abundant
in spring and winter
Krill
Krill (Euphasia)-cold
water (Antarctica)
relative of copepod;
grow 5 cm in length;
principal food source
for filter-feeding
(baleen) whales
Amphipods and Isopods
• Amphipods- crustaceans
that look like tiny shrimp
that have flattened sides;
scuds and beach fleas
• Isopods- small
crustaceans with flattened
bodies (dorsoventrally)
and seven pairs of legs;
sea roach.
Giant Isopod
Barnacles
• Acorn Barnacle (Balanus)- have overlapping, sharp
calcium carbonate plates; live in uppertidal zone, attached
to rocks and other hard surfaces
• Filter Feeders- Have cirri to feed-six pairs of feathery
appendages extend to catch phytoplankton and other food
particles.
• No gills- O2 in water diffuses into skin
• Hermaphrodite- contains both testes and ovaries;
internal fertilization- penis from one barnacle is inserted
into another barnacle. Internal development- fertilized
eggs develop into larvae and enter the plankton population.
Example of Barnacle
• Gooseberry barnacle
Class Merostomata- Horseshoe
Crabs (Limulus polyphemus)
• Most closely related to spiders and scorpions
• Lack antennae and mouthparts; have 2 compound
eyes and 2 simple eyes
• Have 6 prs of appendages; 1st pr are pinching
claws (cheliceras); and the other 5 are for walking
Horseshoe Crab cont.
• Scavenge and feeds on
dead matter
• Book Gills- used for
breathing and
locomotion
• Telson (tail)- helps it
right itself if it is
tossed over by a wave.
Life Cycle
• Late Spring high tide, female HS crabs w/ smaller
males clutched to their backs come to shore
• Females dig holes and lay eggs; males fertilize
them externally while still attached to their backs.
• In two weeks, the eggs hatch into juvenile HS
crabs (no larval phase)
• Can live 20 yrs. Living fossil. (no change in 400
million years!)
Horseshoe Crab Mating
• Eggs (below)
Marine Insects- Class Insecta
• Live in bays and marshes; have chitinous
exoskeleton and jointed appendages but
only have 3prs of legs and have 3 body
segments (head, thorax and abdomen)
• Marsh Mosquito- use proboscis to draw
blood from host; (only female bite)
• Sand Fly- “no-see-um” very tiny!