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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
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6. Arthropods: Armored AchieversCrabs, 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
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 statocystsfor 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) • 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