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Freshwater Macroinvertebrate Diversity ENVIRON 311 / EEB 320 Winter 2007 Phylum Platyhelminthes Class Turbellaria • Flatworms • Habitat: widespread in marine and freshwater • Notes: – Class Turbellaria free-living (Some others are parasites) – Dorsoventrally flattened; no body cavity – Not segmented – Some marine species are brilliantly colored – One of first animals to display bilateral symmetry Phylum Platyhelminthes Class Turbellaria • Anatomy/Physiology: – Displays primitive cephalization (development of a head) – Feeding is through ventral mouth – No digestive outlet: wastes diffuse across body membranes – Can reproduce asexually through fragmentation Phylum Annelida Class Oligochaeta • Bristle worms • Habitat: Widespread in marine and fresh waters – In fresh water, commonly prefers fine sediments with plentiful organic carbon • Notes: – Cylindrical, multisegmented body – Setae present – Anterior mouth for eating and anus for excretion – Abundance of certain species may be indicator of pollution Phylum Annelida Class Hirudinea • Leeches • Habitat: Vegetated spots in lakes and sluggish parts of rivers • Notes: – Dorsoventrally flattened – Multisegmented – Parasite of vertebrates and predator of small invertebrates – Three “teeth” in mouth allow it to cut into host • Anticoagulants keep blood flowing • After decent meal, may not need to feed for 100 days Class Hirudinea • Leech locomotion – Use anterior and posterior suckers in sequence to anchor body while muscles selectively contract – Needs hard substrate for locomotion: cannot live in disturbed, silty habitats Credit: Josee Soucie, Biodidac Phylum Mollusca • Molluscs (Mollusks) – Class Gastropoda • Snails • Univalve shell covers soft, unsegmented body with foot and tentacles • Highly mobile • Subclass Prosobranchia has gills and operculum • Subclass Pulmonata has lungs and no operculum • Prefer hard waters (used to maintain calcareous shell) Phylum Mollusca Class Gastropoda, Family Ancylidae Web • Limpets • Habitat: Well-aerated hardwater streams; other waters with emergent rocks or vegetation • Notes: Courtesy of: UM Museum Animal Diversity – Univalve shell does not spiral – Feeds mainly on algae Phylum Mollusca Class Gastropoda, Family Lymnaeidae • Pond snails • Habitat: varies; common in lakes and ponds • Notes: – Pointy, spiraled shell opens to the right (dextral) – Feeds on periphyton Ecophenotypes in Snails • Snails at top left and right are different species of lymnaeids • When placed together in the aquarium, the offspring (at bottom of photo) appeared to be intermediate Courtesy of: UM Museum Animal Diversity Web – They turned out to be the species on the top left but their development had been altered by a changed environment Phylum Mollusca Class Gastropoda, Family Physidae • Pouch snails • Habitat: varies; common in lakes and ponds • Notes: – Pointed, spiraled shell opens to left (sinistral) – Feeds on periphyton Phylum Mollusca Class Gastropoda, Family Planorbidae Courtesy of: UM Museum Animal Diversity Web • Orb snails • Habitat: common in lakes and ponds • Notes: – Shell spiraled but not pointed; roughly in one plane – Like most other freshwater gastropods, feeds largely on periphyton Phylum Mollusca • Class Bivalvia – Clams and Mussels – Found in marine and fresh waters – Bivalve shell encloses soft body with foot that can project for movement – Mainly filter feeders – Prefer hard waters to preserve calcareous shell – Almost 1/3 of all freshwater mussels found in the US (most in SE) Phylum Mollusca Class Bivalvia, Family Dreissenidae Dreissena polymorpha • Zebra mussel – Introduced to Great Lakes in 1988; now occurs throughout most of Ohio/Mississippi River system – Occurs on hard substrates – Invasive species that competes with rare native mussels and may exclude other invertebrates – May also increase bioaccumulation of harmful pollutants in smallmouth bass • Via another introduced species: the round goby Phylum Mollusca Class Bivalvia, Families Corbiculidae and Sphaeriidae • Asian and Fingernail Clams • Habitat: Found in wide variety of lentic and lotic sediments – Corbiculids introduced from Asia • Show fewer and more pronounced ridging on exterior of valves – Sphaeriids native • Show shallow ridging • Gradually disappearing from many areas Phylum Mollusca Class Bivalvia, Family Unionidae • Freshwater mussels • Habitat: clean streams, lakes • Notes: – One of the most threatened animal groups in North America due to pollution, habitat loss, overharvesting and zebra mussel (which may seal valves shut) – Many lotic species seriously affected by dams Courtesy of: UM Museum Animal Diversity Web Phylum Arthropoda Courtesy of: UM Museum Animal Diversity Web • Extremely diverse group – Includes the crustaceans, myriapods, arachnids and insects – Wide variety of adaptations • Have colonized freshwater, marine, and terrestrial habitats around the world • Found everywhere from tar pits to the Antarctic ice sheets to ocean trenches Dominance of the Arthropods • Arthropods make up an enormous proportion of all species of life • The insects themselves make up more than half of all species diversity on the planet • Major advantages of being an insect: – Flight – Size (relative strength, general ease of diffusive respiration) – Rapid reproductive rate Characteristics of Arthropods • Possess hard exoskeleton – In order to grow, must molt • Segmented body, legs, mouthparts and antennae – Reflects specialization and reduction of segments from earlier forms (e.g. segmented worms) – Head, thorax and abdomen present (though sometimes fused) • Eyes (usually) Phylum Arthropoda Superclass Crustacea • Characteristics of crustaceans – Two pairs of antennae – Head and thorax usually fused into cephalothorax – Three pairs of mouthparts – Usually > three pairs of legs • Habitat: – Primarily aquatic and mostly marine Phylum Arthropoda Superclass Crustacea, Order Ostracoda • Seed shrimp • Habitat: shallow wetlands to sea floor depths • Notes: – Feed on detritus, plankton – Body protected by bivalve carapace Phylum Arthropoda Superclass Crustacea, Order Amphipoda • Scuds, sideswimmers • Habitat: Widespread in marine and fresh waters • Notes: – Laterally compressed body – Seven pairs of “walking” appendages – Feed mainly on detritus – Abundant and important food source for many fishes; where amphipods are in decline, some fish species will follow – Prolific; will often be found mating Phylum Arthropoda Superclass Crustacea, Order Isopoda • Sowbugs • Habitat: mostly marine but a few freshwater • Notes – Dorsoventrally compressed – Seven pairs of legs – Tend to prefer vegetated lentic or sluggish lotic habitats – Consume detritus – Related to terrestrial pillbugs Phylum Arthropoda Superclass Crustacea, Order Anostraca • Fairy shrimp • Habitat: Ephemeral and permanent wetlands/ponds • Notes: – Lacks carapace – Stalked eyes – Uses many appendages to swim on its back – Many populations only around for short periods of time each year…and may vary greatly in number from year to year – Filter feeders Phylum Arthropoda Superclass Crustacea, Order Decapoda • Crayfishes and shrimps • Habitat: Ubiquitous in fresh and marine waters; some are quasi-terrestrial • Notes: – Cylindrical body – Three anterior leg pairs equipped with chelae (moveable fingers) – When startled, raises claws or swims backward using telson – Omnivorous: eats everything from macrophytes to small fish Phylum Arthropoda Superclass Hexapoda, Class Parainsecta, Order Collembola • Springtails • Habitat: surface film of fresh water • Notes: – – – – – Possess six legs, like the insects, but do not develop wings Head, thorax and abdomen distinct Posterior jumping organ (furcula) present Mainly a terrestrial order Usually very small (<2 mm) Phylum Arthropoda Superclass Hexapoda, Class Insecta • Aquatic insects are ubiquitous in aquatic ecosystems, mostly in the larval stage • Because the adults are able to fly, they have easily colonized almost all terrestrial and freshwater ecosystems – Less successful in the oceans, where flight is not as advantageous Basic Insect Anatomy 1. 2. 3. 4. 5. Tarsus/tarsal claw Cercus Pronotum Mesonotum Metanotum Class Insecta Exopterygotes • Include those insects that possess wingpads in larval (nymphal) stage • Larvae resemble adults (though sometimes loosely), have compound eyes and chitinous (hard) bodies • Pass from egg to nymph to adult stage (no pupal stage) • Aquatic members: – Ephemeroptera, Odonata, Plecoptera and Hemiptera Class Insecta Order Ephemeroptera • Mayflies • Habitat: mostly cool lotic waters; some also live in lentic waters • Notes: – Very important source of food for many fish – Usually fairly intolerant of pollution; good indicator taxon – Adults do not feed; only mate and die – Some nymphs are predators, most are grazers or filterers Courtesy of: UM Museum Animal Diversity Web Class Insecta Order Ephemeroptera • Many species can move their gills to ventilate when dissolved oxygen levels are low • ID: • usually three terminal filaments • One tarsal claw • Gills may be present on sides of abdomen Class Insecta Order Odonata, Suborder Anisoptera • Dragonflies • Habitat: lentic and lotic • Notes: – Obligate predator as both nymph and adult – Nymphs characterized by large extensible labium (lower lip), wide body and tiny cerci on last abdominal segment – Adults hold wings to sides, may be brightly colored Class Insecta Order Odonata, Suborder Zygoptera • Damselflies • Habitat: lentic and lotic • Notes: – Obligate predator in all life stages – Nymph characterized by head wider than body and three terminal lamellae (gills) • Also has extensible labium – Adult holds wings up over body; may be highly colored Dragonfly Feeding Class Insecta Order Plecoptera • Stoneflies • Habitat: cool, fast streams • Notes: – Generally sensitive to environmental perturbations; good indicator taxon – Nymphs may be shredders, grazers or predators – Nymphs have two filamentous cerci and two tarsal claws – Adult able to fold wings onto body, generally short-lived and dull-colored Class Insecta Order Hemiptera • True Bugs • Habitat: mainly lentic and sluggish lotic • Notes: – Nymph and adult hard to tell apart – Mostly predators; use piercing mouthpart and raptorial forelegs to attack prey – Some forms skate on water surface; others swim below surface Class Insecta Order Hemiptera • Unique features: – Males in Family Belostomatidae carry eggs on back until they hatch – Members of Family Notonectidae swim on their backs— hence their common name: backswimmers Class Insecta Endopterygotes • Include those insects that do not possess wingpads in larval stage • Larvae have simple eyes, bear little resemblance to adults, and have generally softer bodies • Pass from egg to larval to pupal to adult stage • Aquatic members: – Megaloptera, Neuroptera (lacewings), Trichoptera, Lepidoptera (butterflies/moths), Coleoptera, Diptera, Hymenoptera (wasps) Class Insecta Order Megaloptera • Dobsonflies, Hellgrammites, Fishflies • Habitat: Mainly swift lotic • Notes: – May grow quite large – Larvae are predatory, characterized by large mandibles, lateral filaments – Adult males grow large tusks, used in mating; usually short-lived – Relatively small group Class Insecta Order Megaloptera • Video of a vicious larval dobsonfly • Note display of large mandibles • Also, lateral filaments not used in locomotion Class Insecta Order Trichoptera • Caddisflies • Habitat: wide variety of lentic/lotic ecosystems • Notes: – Some larval caddisflies build cases, others are free-living – Note soft abdomen – Wide range of feeding types, from predatory to filter feeding – Characterized by two anal prolegs, in addition to thoracic legs – Adults are dull, resemble moths Class Insecta Order Trichoptera • Wide variety of cases among species that build them – May consist of mineral or organic materials – Utilized mainly to allow ventilation; sometimes for protection – Many taxa can be identified by unique cases Class Insecta Order Trichoptera • Case building caddisflies spend a lot of time in their cases EPT • Ephemeroptera, Plecoptera, Trichoptera – Index for streams: the count of EPT taxa (often at the genus level) • AKA: EPT Richness E, P, T = 3 orders of aquatic insects that tend to be most abundant in relatively unpolluted waters, so more is better Usually do % EPT per total Class Insecta Order Coleoptera • Beetles • Habitat: wide variety of lentic and lotic • Notes: – Larvae entirely aquatic – Larvae are variable in form but usually elongate and often with unsegmented terminal filaments – Adults often predacious or scavengers – Adults characterized by very hard body and covered first pair of wings Class Insecta Order Diptera • True Flies • Habitat: extremely variable; sometimes found in marine ecosystems • Notes: – Very diverse family – Larvae have no segmented legs and often reduced head; may have one or more pairs of prolegs – Larvae have variety of feeding habits – Adults have only one pair of wings – Adults may be parasitic or nectar feeding Dipteran Photos The End