6. arthropods: armored achievers crabs, lobster, shrimp, barnacles

6. Arthropods: Armored Achievers6. Arthropods: Armored Achievers

Crabs, Lobster, Shrimp, BarnaclesCrabs, Lobster, Shrimp, Barnacles

ArthropodsArthropods

• Largest phylum (3/4 of all species on earth)Largest phylum (3/4 of all species on earth)• Insects – largest groupInsects – largest group• Majority of marine arthropods are crustaceans Majority of marine arthropods are crustaceans

(subphlyum Crustacea) (subphlyum Crustacea) • Flexible, segmented, bilateral symmetryFlexible, segmented, bilateral symmetry• Jointed appendages moved by sets of attached Jointed appendages moved by sets of attached

musclesmuscles

Arthropods exhibit bilateral symmetry and a chitinous Arthropods exhibit bilateral symmetry and a chitinous exoskeleton. Provides support, protection, and increased exoskeleton. Provides support, protection, and increased surface area for muscle attachment.surface area for muscle attachment.

To grow they must To grow they must moltmolt the exoskeleton and absorb water to expand the exoskeleton and absorb water to expandbefore the new exoskeleton hardens.before the new exoskeleton hardens.

Arthropods: Subphylum CrustaceaArthropods: Subphylum Crustacea

• Most marine with gills for gas exchangeMost marine with gills for gas exchange• Appendages specialized for swimming, crawling, Appendages specialized for swimming, crawling,

attaching to other animals, mating, and feedingattaching to other animals, mating, and feeding• Two pairs of antennae involved in sensing Two pairs of antennae involved in sensing

surrounding.surrounding.


• Small CrustaceansSmall Crustaceans– Copepods Copepods (cope-a-pod)(cope-a-pod)

• Planktonic, use mouthparts to filter feed, some may Planktonic, use mouthparts to filter feed, some may swim, many are parasitic swim, many are parasitic

– BarnaclesBarnacles• Filter feeders that usually live attached to surfaces, Filter feeders that usually live attached to surfaces,

even living organismseven living organisms

• CirriCirri (sear-I) (feathery legs) sweep water for food (sear-I) (feathery legs) sweep water for food

• Crustacean larvae that swim and attach before Crustacean larvae that swim and attach before metamorphosing into adultsmetamorphosing into adults

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• Small CrustaceansSmall Crustaceans– AmphipodsAmphipods

• Curved, flattened bodies (sideways)Curved, flattened bodies (sideways)

• Beach hopers, common in shore debris, seaweed, Beach hopers, common in shore debris, seaweed, burrowing in whales, or planktonicburrowing in whales, or planktonic

– IsopodsIsopods• Parasitic fish lice that are dorsoventrally flattenedParasitic fish lice that are dorsoventrally flattened

• Marine pill bugMarine pill bug

Amphipods and IsopodsAmphipods and Isopods

Sea louse: a marine pill bugSea louse: a marine pill bug

OrchestoideaOrchestoidea, a beach hopper, a beach hopperare often found on marine are often found on marine mammals.mammals.


• Small CrustaceansSmall Crustaceans– Euphausiids (yoo-fa-ze-id) (Krill)Euphausiids (yoo-fa-ze-id) (Krill)

• Planktonic, shrimp-like, filter feedersPlanktonic, shrimp-like, filter feeders

• Common in polar waters in giant schoolsCommon in polar waters in giant schools

• Most exclusive food source for whales, penguins and Most exclusive food source for whales, penguins and fishfish


• Shrimps, Lobsters, and CrabsShrimps, Lobsters, and Crabs– Decapods Decapods (10 legs)(10 legs)

• Largest in size, great commercial importanceLargest in size, great commercial importance

• 5 pairs of legs w/ first pair being claws used for 5 pairs of legs w/ first pair being claws used for feeding and defensefeeding and defense

• Well developed carapace encloses Well developed carapace encloses cephalothoraxcephalothorax

• Rest of body called Rest of body called abdomen abdomen


• Shrimps and LobstersShrimps and Lobsters– Laterally compressed Laterally compressed

– ShrimpShrimp - scavengers feeding on detritus - scavengers feeding on detritus• Some may remove parasites from skin of fishSome may remove parasites from skin of fish

– LobstersLobsters – Marine scavengers and predators that crush – Marine scavengers and predators that crush molluscs and sea urchinsmolluscs and sea urchins

– Hermit crabs Hermit crabs – not true crabs that hide soft body in – not true crabs that hide soft body in empty shellsempty shells


• CrabsCrabs– Abdomen small and tucked Abdomen small and tucked

under large cephalothoraxunder large cephalothorax• V shaped abdomen = maleV shaped abdomen = male

• U shaped abdomen = femaleU shaped abdomen = female

– Highly mobile and walk Highly mobile and walk sidewayssideways


• CrabsCrabs– Scavengers/predatorsScavengers/predators– Some have specialized diets of seaweeds, Some have specialized diets of seaweeds,

organic matter, or coral mucusorganic matter, or coral mucus– Live along rocky shores or sandy beachesLive along rocky shores or sandy beaches– Land crabs live most of life on land but may Land crabs live most of life on land but may

return to ocean to release eggsreturn to ocean to release eggs

Biology of CrustaceansBiology of Crustaceans

• Feeding and DigestionFeeding and Digestion– Filter feeding common among small crustaceansFilter feeding common among small crustaceans

• Bristles on some appendages used to gather foodBristles on some appendages used to gather food

• Other appendages move food from bristles to mouthOther appendages move food from bristles to mouth

• Some may use appendages to pierce or suck Some may use appendages to pierce or suck (parasitic)(parasitic)

• Bristles sift, chitinous teeth in stomach grindsBristles sift, chitinous teeth in stomach grinds


• Feeding and DigestionFeeding and Digestion• Decapods have 2 chambered stomach connected to Decapods have 2 chambered stomach connected to

digestive gland that secretes enzymes and absorbs digestive gland that secretes enzymes and absorbs nutrients (extracellular)nutrients (extracellular)

• Intestine ends in an anusIntestine ends in an anus

• Open circulatory system distributes nutrientsOpen circulatory system distributes nutrients


• Nervous System and BehaviorNervous System and Behavior• Small, simple brains but well-developed sensory Small, simple brains but well-developed sensory

organsorgans

• Compound eyesCompound eyes

• Keen sense of smell (chemical sensitivity)Keen sense of smell (chemical sensitivity)

• Have Have statocysts statocysts for balancefor balance

• Most behaviorally complex of all invertebratesMost behaviorally complex of all invertebrates

• Have special body posture and movement of legs Have special body posture and movement of legs and antennaeand antennae

– Helps settle disputes between neighbors and courtshipHelps settle disputes between neighbors and courtship


• Reproduction and Life HistoryReproduction and Life History– Separate sexes in most crustaceansSeparate sexes in most crustaceans

– Males use specialized appendages to transfer sperm Males use specialized appendages to transfer sperm directly to femaledirectly to female

– Decapods - takes place after molting and females can Decapods - takes place after molting and females can store sperm to use on different batch of eggsstore sperm to use on different batch of eggs

– Most have planktonic larvae type and number of larval Most have planktonic larvae type and number of larval stages vary widelystages vary widely

Other Marine ArthropodsOther Marine Arthropods

• Horseshoe Crabs (class Merostomata)Horseshoe Crabs (class Merostomata)– Only surviving membersOnly surviving members

– Widely represented by fossil recordsWidely represented by fossil records

– 5 living species and not true crabs5 living species and not true crabs

– Live on soft bottoms of shallow waters on Atlantic and Live on soft bottoms of shallow waters on Atlantic and Gulf coasts of North America and Southeast AsiaGulf coasts of North America and Southeast Asia

– Emerge on beaches to reproduceEmerge on beaches to reproduce


• Sea Spiders (class Pycnogonida)Sea Spiders (class Pycnogonida) Pic – no – ga- ni- da Pic – no – ga- ni- da– Superficially resemble spidersSuperficially resemble spiders

– Four or more pairs of legsFour or more pairs of legs

– Large proboscis with mouth at tip used to feed on soft Large proboscis with mouth at tip used to feed on soft invertebrates such as sea anemones and hydrozoansinvertebrates such as sea anemones and hydrozoans

– More common in cold water but do not occur throughout More common in cold water but do not occur throughout oceansoceans


• Insects (class Insecta)Insects (class Insecta)– 3 pairs of legs as adults3 pairs of legs as adults

– Rare in the seaRare in the sea

– Live at waters edge scavenging for seaweeds, barnacles, Live at waters edge scavenging for seaweeds, barnacles, and rocksand rocks

– Inhabit decaying seaweed that accumulates at high tideInhabit decaying seaweed that accumulates at high tide

6. arthropods: armored achievers crabs, lobster, shrimp, barnacles

Documents

subphylum crustaceashrimps

subphylum crustaceamost

abdomen arthropods

marine mammals

marine pill bugorchestoidea

shrimp scavengers

foodother appendages

chitinous exoskeleton