Characteristics of all Arthropods• Hard exterior (exoskeleton)• Joined appendages• Highly evolved nervous systems• Segmented body• 2 main groups – Chelicerates and mandibulates
Chelicerates• Primitive Arthropods• Characteristics – 6 pairs of appendages • 1 oral appendage (chelicerae) used for feeding – Lack actual mouth parts for chewing so “suck up predigested food” – Cephalothorax-largest – Abdomen –contains gills
• Representative species – Horseshoe crabs and sea spiders• Reproduction – Sexual: separate sexes • Sea spiders: males carry fertilized eggs ( only marine invert to do this!!!!!) • Horseshoe crabs: external fertilization; females lay eggs in sand and when hatch carried to sea by high tide• Digestion – Horseshoe crab: scavengers; will eat anything – Sea spiders: carnivores; feed on cnidarian juice!!• http://www.youtube.com/watch?v=wA-NoH_G330
Mandibulates (Crustaceans)• Characteristics – Mandible: pair of appendages at anterior end used for feeding – 3 main body regions: head, thorax and abdomen – 2 pairs of antennae – Remaining appendages used for locomotion – Molting: as animals grows, new exoskeleton is formed and old one is shed • The shell does not grow with the crustacean • http://www.youtube.com/watc h?v=4QIgW639Oog&safety_mo de=true&persist_safety_mode= 1&safe=active
Order Decopoda (“decopods”)• Representative species – Crabs, lobster, and shrimps• Characteristics – 5 pairs of walking legs • 1st pair pinchers for food and defense• http://www.youtube.com/watch?v=flnMoSghUzs&feature=related&safety_mode=true&persist_safety_m ode=1&safe=active
• Digestion • Reproduction – Variety of feeding – Separate sexes/internal habits(depend on species) fertilization • Majority are predatory • Males special appendage scavengers modified for holding onto – Large inverts are prey for female and depositing most sperm. » Ex Alaskan king crab • Eggs are incubated by feed on bivalves female; larvae stage when » Hermit Crabs and hatched shrimp-scavengers feed on detritus » Fiddler crabs- deposit filter feeders
Order Euphausiacea• Representative species – Krill• Characteristics – Pelagic – Shrimp-like (3-6 cm) – Photospheres: Organ producing bioluminescent • Used to attract mates; so what is reproduction? – Can molt so quick that will “jump out of their shells!• Digestion- filter feeders; eat zooplankton and diatoms
• Ecological Role – Main diet of certain marine mammals • Keystone species of Antarctic food web • Blue whales eat 40 million krill a day – So why havent krill gone extinct? – http://www.youtube.com/watch?v=OPMQaP- Yj1Y&safety_mode=true&persist_safety_mode=1 &safe=active
– Reproduction • Sexual – Separate sexes – Some species internal fertilization/ others spawners – Life cycle 6 months to 6 years• Copepods – Most abundant of zooplankton – Suspension feeders – Carnivorous – Sexual reproduction
Class Cirripedia “barnacles”• Characteristics – Only sessile crustaceans – Shell of calcium carbonate• Digestion – Filter feeders: use appendage “cirriped”• Reproduction – Hermaphrodites: cross fertilize – Larvae move until finds a substrate and metamorphoses into adult-> remain sessile
Ecological Roles of Arthropods• Essential links in food chains• Nutrient recycling• Food sources for humans and many other animals• Symbiotic relationships – Some can remove parasites – cleaner shrimp• Some have become invasive when introduced
Compete for space* as a scientist, how would you determine population density of the barnacle species on this dock post?
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