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Marine Invertebrates
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Who are the Invertebrates?
Any animal lacking a backbone Lamarck (1809) 98% of all animal species (Fig. 7.1) Diversity rules in all aspects of their life feeding (filter, predator, parasitic…) morphology (stars, threads, torpedoes…) reproduction(sexual, asexual) habitats (benthic, pelagic, intertidal, open ocean)
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Why study Invertebrates?
Ecological importance Economic importance Medical importance Learning Strategy: From simplest to most complex in terms of body organization. Major taxa only Unique (defining) features of each taxa
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Phylum Porifera (The sponges)
Latin “Pore-bearers” Body plan simple: Multicellular, but without tissues encrusting, globular, vaselike…
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Sessile lifestyle feeding - forced water flow through flagellated channels two cell layers choanocytes = flagellated cells pinacocytes = outer covering spicules of SiO3 or CaCO3 give support ostia = incurrent pores osculum = excurrent pore
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Phylum Cnidaria Greek “stinging thread” Body plan (Fig. 7.3)
tissue level of construction (2 layers with mesoglea between) 2 alternate body plans: polyp = sessile (anemone, corals) medusa = free-floating (jellyfish) Many species possess both body plans in their life cycle (Fig. 7.4) Many species are colonial (polyp or medusa) (Fig. 7.5)
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Regardless of body plan type, all have:
radial symmetry gastrovascular cavity with one opening tentacles surrounding mouth batteries of stinging cells (cnidocytes) each cnidocyte contains a nematocyst barbed sticky toxic nematocysts discarged explosively for defense or prey capture
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Class Hydrozoa Greek “water animals” Ex. Physalia
medusa with gas (N) filled pneumatophore colonial organism with polyp members dangling beneath medusa reproduction digestion offense/defense
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Class Anthozoa Greek “flower animals” Ex. Hard corals
polypoid body plan colonial organization secrete hard “cup” of CaCO3 layers of calcium carbonate build up to form reefs endosymbiotic algae provide nutrients Healthy reefs - clear, clean, shallow water
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Class Scyphozoa Greek “cup animals” Ex. Moon jelly Aurelia
almost exclusively medusa form solitary predatory
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Phylum Ctenophora Greek “comb bearer” (Fig. 7.6)
Very similar to Cnidarians no nematocysts rows of fused cilia called combs or “ctenes” for locomotion
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Marine Worms Since they belong to 13 different phyla, many differences exist between these organisms. Shared characteristics: worm-like (vermiform) bilateral symmetry with cephalization efficient swimming, burrowing, tube-dwelling, and parasitic lifestyles
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Phylum Annelida Latin: annulus or “ring”
Most common group of marine worms Body - segments (metamerism) with repeating body parts. Possess tissues / organs / organ systems (nervous, digestive, reproductive, excretory) and extensive musculature. Fig. 7.7a
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Burrowing lifestyle: ex. Arenicola
lives in a L-shaped burrow in intertidal mud and sand ingest sand/food at bottom of burrow and defecate undigestible parts at surface
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Tube-dwelling lifestyle Ex. Feather dusters
secrete parchment-like tubes to inhabit. extend tentacles to collect particles (suspension feeders). Retract tentacles into tube for protection
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Free-living lifestyle Ex. Fireworms
swim (although not particularly speedy) often using modified flaps of skin called parapodia. Usually deposit feeders Predatory species often use jaws (annelids) (Fig. 7.7a) special harpoon devices (nemerteans) (Fig. 7.7e)
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ex. Nematodes, tapeworms and flukes
Parasitic lifestyle ex. Nematodes, tapeworms and flukes complex life cycles often including multiple hosts definitive hosts usually vertebrate (in muscles, digestive tract, nasal and bronchial areas)
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Phylum Mollusca Latin “soft”
Second largest animal phylum (after arthropods) Extreme variation in size and shape
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Shared characteristics: (Fig. 7.9)
visceral mass containing organ systems heart in pericardial cavity ganglia and nerve cords usually separate sexes (dioecious) Mantle = secretes shell foot = modified for movement and food acquisition radula = tongue-like structure with teeth for scraping food
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Radula movie
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Class Gastropoda (Fig. 7.11)
Greek “stomach foot” ex. Snails, conchs, limpets, nudibranchs single, coiled shell when present may graze using radula to scrape diatoms and algae, set mucus nets, or be predaceous. Trochophore and veliger larvae swim to allow dispersal (adults heavy, slow)
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Class Bivalvia (Fig. 7.12) Latin “two shells”
ex. Clams, oysters, scallops no radula, collect debris on leaf-like gills = ctenidia (in mantle cavity) and stuff into mouth. bacteria and viruses (from sewage), and pollutants, concentrated in visceral mass significant health risk to humans if poorly cooked prior to consumption.
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Class Cephalopoda (Fig. 7.13)
Greek “head foot” ex. Squid, octopus, nautilus shell variable (reduced, absent, present) most highly cephalized of all marine invertebrates eyes highly developed rapid swimmers (some) by jet propulsion multiple muscular arms with suckers all predaceous carnivores able to learn and problem-solve
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Squid swimming
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Class Polyphacophora (Fig. 7.14)
Greek “many plate-bearer” ex. chitons shells of 8 overlapping plates grazers using radula
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