Transcript Arthropods ppt - Currituck County Schools

6. Arthropods: Armored Achievers
Crabs, Lobster, Shrimp, Barnacles
Arthropods
• Largest phylum (3/4 of all species on earth)
• Insects – largest group
• Majority of marine arthropods are crustaceans
(subphlyum Crustacea)
• Flexible, segmented, bilateral symmetry
• Jointed appendages moved by sets of attached
muscles
Arthropods exhibit bilateral symmetry and a chitinous
exoskeleton. Provides support, protection, and increased
surface area for muscle attachment.
To grow they must molt the exoskeleton and absorb water to expand
before the new exoskeleton hardens.
Arthropods: Subphylum Crustacea
• Most marine with gills for gas exchange
• Appendages specialized for swimming, crawling,
attaching to other animals, mating, and feeding
• Two pairs of antennae involved in sensing
surrounding.
Arthropods: Subphylum Crustacea
• Small Crustaceans
– Copepods (cope-a-pod)
• Planktonic, use mouthparts to filter feed, some may
swim, many are parasitic
– Barnacles
• Filter feeders that usually live attached to surfaces,
even living organisms
• Cirri (sear-I) (feathery legs) sweep water for food
• Crustacean larvae that swim and attach before
metamorphosing into adults
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Arthropods: Subphylum Crustacea
• Small Crustaceans
– Amphipods
• Curved, flattened bodies (sideways)
• Beach hopers, common in shore debris, seaweed,
burrowing in whales, or planktonic
– Isopods
• Parasitic fish lice that are dorsoventrally flattened
• Marine pill bug
Amphipods and Isopods
Orchestoidea, a beach hopper
are often found on marine
mammals.
Sea louse: a marine pill bug
Arthropods: Subphylum Crustacea
• Small Crustaceans
– Euphausiids (yoo-fa-ze-id) (Krill)
• Planktonic, shrimp-like, filter feeders
• Common in polar waters in giant schools
• Most exclusive food source for whales, penguins and
fish
Arthropods: Subphylum Crustacea
• Shrimps, Lobsters, and Crabs
– Decapods (10 legs)
• Largest in size, great commercial importance
• 5 pairs of legs w/ first pair being claws used for
feeding and defense
• Well developed carapace encloses cephalothorax
• Rest of body called abdomen
Arthropods: Subphylum Crustacea
• Shrimps and Lobsters
– Laterally compressed
– Shrimp - scavengers feeding on detritus
• Some may remove parasites from skin of fish
– Lobsters – Marine scavengers and predators that crush
molluscs and sea urchins
– Hermit crabs – not true crabs that hide soft body in
empty shells
Arthropods: Subphylum Crustacea
• Crabs
– Abdomen small and tucked
under large cephalothorax
• V shaped abdomen = male
• U shaped abdomen = female
– Highly mobile and walk
sideways
Arthropods: Subphylum Crustacea
• Crabs
– Scavengers/predators
– Some have specialized diets of seaweeds,
organic matter, or coral mucus
– Live along rocky shores or sandy beaches
– Land crabs live most of life on land but may
return to ocean to release eggs
Biology of Crustaceans
• Feeding and Digestion
– Filter feeding common among small crustaceans
• Bristles on some appendages used to gather food
• Other appendages move food from bristles to mouth
• Some may use appendages to pierce or suck
(parasitic)
• Bristles sift, chitinous teeth in stomach grinds
Biology of Crustaceans
• Feeding and Digestion
• Decapods have 2 chambered stomach connected to
digestive gland that secretes enzymes and absorbs
nutrients (extracellular)
• Intestine ends in an anus
• Open circulatory system distributes nutrients
Biology of Crustaceans
• Nervous System and Behavior
• Small, simple brains but well-developed sensory
organs
• Compound eyes
• Keen sense of smell (chemical sensitivity)
• Have statocysts for balance
• Most behaviorally complex of all invertebrates
• Have special body posture and movement of legs and
antennae
– Helps settle disputes between neighbors and courtship
Biology of Crustaceans
• Reproduction and Life History
– Separate sexes in most crustaceans
– Males use specialized appendages to transfer sperm
directly to female
– Decapods - takes place after molting and females can
store sperm to use on different batch of eggs
– Most have planktonic larvae type and number of larval
stages vary widely
Other Marine Arthropods
• Horseshoe Crabs (class Merostomata)
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Only surviving members
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
Other Marine Arthropods
• Sea Spiders (class Pycnogonida) Pic – no – ga- ni- da
– 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 not occur throughout
oceans
Other Marine Arthropods
• Insects (class Insecta)
– 3 pairs of legs as adults
– Rare in the sea
– Live at waters edge scavenging for seaweeds, barnacles,
and rocks
– Inhabit decaying seaweed that accumulates at high tide