I. Arthropoda

B. Crustacea1. Decapoda (order)

• Crabs, true shrimp, lobsters• Most species in Crustacea (~10,000)

• Scavengers/Predators/Both• Five pairs of walking legs

• First pair usually modified as claws for feeding/defense• Well-developed carapace = cephalothorax

• Rest of body = abdomen• Lobsters, shrimp – Usually laterally compressed

• Tail/Abdomen behind thorax• Crabs – Usually dorsoventrally compressed

• Tail/Abdomen curled underneath thorax• Largest crustaceans

• Lobster > 42 lbs• Crab > 13 feet “tall”

Decorator crab

Hermit crab

I. Arthropoda

B. Crustacea1. Decapoda (order)

• Crabs, true shrimp, lobsters• Most species in Crustacea (~10,000)

• Scavengers/Predators/Both• Five pairs of walking legs

• First pair usually modified as claws for feeding/defense• Well-developed carapace = cephalothorax

• Rest of body = abdomen• Lobsters, shrimp – Usually laterally compressed

• Tail/Abdomen behind thorax• Crabs – Usually dorsoventrally compressed

• Tail/Abdomen curled underneath thorax• Largest crustaceans

• Lobster > 42 lbs• Crab > 13 feet “tall”

Fig. 9-35

I. Arthropoda

B. Crustacea1. Decapoda (order)

• Diverse nutritional modes: predators (Ex: lobsters), deposit feeders (Ex: fiddler crabs), suspension feeders (Ex: mole crabs)

• Dioecious• May exhibit courtship behavior, territoriality• Males often transfer spermatophores to female with

modified copulatory pleopods• Fertilization usually internal• Eggs usually brooded• Larvae pelagic

• Nauplius – shrimp, other crustaceans• Zoea – crabs

Nauplius

ZoeaFig. 9-36 Megalopa

I. Arthropoda

B. Crustacea2. Copepoda• Extremely abundant and important plankton

• Among most abundant animals on earth• Benthic forms also important

• Important primary consumers of phytoplankton• Many exhibit DVM• Some parasitic forms

Harpacticoid copepods

Parasitic copepods

Herbivorous vs. Predatory Copepod

I. Arthropoda

B. Crustacea3. Euphausiacea (krill)• Laterally compressed

• Up to 10 cm long (usually smaller)

• Head and anterior segments fused to form distinct carapace

• Widespread distribution• Important primary consumers and predators• Important prey for larger consumers• Keystone species in some ecosystems (Southern

Ocean)

• Aggregate in schools• May be immense (450 sq km x 200 m @ >1000 m-3)• May molt rapidly; predator avoidance?

I. Arthropoda

B. Crustacea4. Amphipoda• Laterally compressed

• Generally small (< 2 cm), but larger in deep ocean

• Widespread distribution• Generally free living• Important scavengers

• Often highly mobile• Some sedentary forms• Diverse lifestyles

• Brood young

I. Arthropoda

B. Crustacea6. Isopoda• Dorsoventrally compressedDorsoventrally compressed

• Generally small (< 2 cm), but larger in deep oceanGenerally small (< 2 cm), but larger in deep ocean

• Related to terrestrial pill bugsRelated to terrestrial pill bugs• Widespread distributionWidespread distribution

• Generally free livingGenerally free living• Important scavengersImportant scavengers

• Often highly mobileOften highly mobile• Some parasitic formsSome parasitic forms

• Brood youngBrood young

I. Arthropoda

B. Crustacea6. Cirripedia (barnacles)• Active suspension feeders (filter feeders)

• Use feathery cirripeds (modified swimming appendages)

• Sessile (attached to surfaces)• Fouling organisms (boats, hard surfaces,

whales)• Resemble mollusks superficially• Some parasitic forms• Simultaneous hermaphrodites

• Internal fertilization (How??)

Fig. 9-41

StalkedSessile

I. Arthropoda

B. Crustacea6. Cirripedia (barnacles)• Active suspension feeders (filter feeders)

• Use feathery cirripeds (modified swimming appendages)

• Sessile (attached to surfaces)• Fouling organisms (boats, hard surfaces,

whales)• Resemble mollusks superficially• Some parasitic forms• Simultaneous hermaphrodites

• Internal fertilization (How??)

I. Arthropoda

B. Crustacea7. Stomatopoda (mantis shrimp)

• Specialized predators• Modified second pair of thoracic appendages

• Smashers (eat mollusks, crabs) Video Video• Spearers (eat shrimp, fishes)

• Sophisticated eyes• Three lobes (midband for color vision)• Up to 16 photoreceptor types (humans have four)• Can see ultraviolet & polarized light

• Reproduction• Female lays egg mass• Zoea larvae in plankton up to three months