BIOL 1030 – TOPIC 12 LECTURE NOTESTopic 12: Lophotrochozoans: Platyhelminthes, Annelids, and some minor phyla (Ch. 33)I. Lophotrochozoa clade includes the following phyla that we will cover:1. Ectoprocta (or Bryozoa; clade)2. Platyhelminthes (clade?)3. Rotifera (clade)4. Annelida (clade)5. Nemertea (clade)6. Brachiopoda (clade?)7. Phoronida (clade)8. Mollusca (clade) will be covered in Topic 13II. Phylum Ectoprocta (bryozoans, or moss animals) a) ~4500 living speciesb) coelomatec) aquatic, mostly marined) use lophophore for feedinge) secrete and live in a chitinous chamber (zoecium); also may be reinforced with calcium carbonatef) adults are sessile and colonial; communicate chemically through pores in zoeciag) some non-protostome characteristics: radial cleavage, secondary mouth, deuterostome-style coelomh) appear to be a sister group to rest of the lophotrochozoansIII. Phylum Platyhelminthes – the flatworms (must exclude Acoelomorpha to have any hope of having a grade or clade)1 of 8BIOL 1030 – TOPIC 12 LECTURE NOTESa) ~20,000 living speciesb) acoelomatec) ribbon-shaped, soft-bodied, flattenedd) most are parasitic, some are scavengers and carnivorese) non-parasitic forms far more active than cnidarians or ctenophoresf) those with a digestive cavity have an incomplete gut (only one opening)g) excretory system - small tubules lined with ciliated flame cells (move water and waste into tubules and out of body)h) no circulatory system – oxygen and food must diffuse to all cellsi) some have nerve cords and simple central nervous systemj) reproduction1. most are hermaphroditic 2. most have internal fertilization: each partner deposits sperm in the other’s copulatory sac3. asexual regeneration also possible in manyk) three classes to learn (we’ll leave out the 4th class, Monogenea)l) Class Turbellaria (grade)1. only free-living flatworms2. use ciliated epithelial cells for movement3. have eyespots; usually move away from light4. have sensory pits or tentacles for detecting food, chemicals, and nearby movement5. use pharynx (muscular throat) in feeding6. abundant in many aqueous environments7. some occur in moist terrestrial areas8. include planariam) Class Trematoda (clade) – flukes1. all parasitic; resistant to digestive enzymes and host immune responses2 of 8BIOL 1030 – TOPIC 12 LECTURE NOTES2. use mouth to feed3. 1 mm to 8 cm long4. attach via suckers, anchors or hooks5. usually have two or more hosts (larvae almost always in snails, final host almost always a vertebrate)6. important pathogens of humans:• human liver fluke inhabit bile passages in the liver of humans, cats, dogs, and pigs can get them from eating raw fish can cause cirrhosis and death in high infestations• blood flukes of genus Schistosoma afflict 5% of world’s human population and cause schistosomiasis (kills ~800,000 each year)n) Class Cestoda (clade) – tapeworms1. all parasitic; resistant to digestive enzymes and host immune responses2. absorb food through skin (no mouth, no digestive tract or digestive enzymes)3. scolex - attachment organ with several suckers and possibly also hooks4. neck – unsegmented; connects scolex to proglottids5. proglottids - complete hermaphroditic units, making sperm and eggs• older ones further from neck have mature, fertilized eggs, • embryos develop and fill proglottid• proglottids shed through feces and deposited for some other animal to pickup6. human pathogen – beef tapeworm• juvenile intermuscular parasite on cows• frequent parasite of humans, can get from eating rare beef• adult in intestines of humans - to 10 m+!• 1% of cattle in U.S. are infected - don't eat rare beef!3 of 8BIOL 1030 – TOPIC 12 LECTURE NOTESIV. Phylum Rotifera – rotifers a) ~1800 species; b) pseudocoelmatec) common, small (most <1 mm), mainly aquatic animalsd) mostly free-living and found in freshwater environments; some are parasites; some terrestriale) corona - ciliated, food-gathering organ at tip of head (filter-feeders)f) sometimes called “wheel animals” because of appearance of beating ciliag) true digestive tract with separate mouth and anush) jaws in pharynxi) hydrostatic skeleton with rudimentary circulatory systemj) separate sexes; some species with parthenogensis – development of unfertilized eggsk) appear to group with true Platyhelminthes and others in a clade called PlatyzoaV. Phylum Annelida – segmented worms a) ~16,500 species in marine, freshwater and terrestrial systemsb) coelomatec) includes polychaetes, earthworms, and leechesd) unquestionably segmented1. repeated segments visible as rings2. segments separated by partitions called septa3. each segment has its own coelom4. fluid inside coelom of each acts as a hydrostatic skeleton5. muscles push against the fluid, expanding and contracting (each segment acts independently)4 of 8BIOL 1030 – TOPIC 12 LECTURE NOTES6. anterior segments often modified as heads, with sense organs, a brain, and even some with eyes7. some segments modified as copulatory organs8. connections between segments• nervous system via ventral nerve cord• circulatory system blood vessels (closed circulatory system)• digestive tract with separate mouth and anuse) most have setae – bristles of chitin used to anchor the worm to a substrate (“bristleworms”)f) closed circulatory system has some enlarged vessels that serve as heartsg) gases are exchanged at skin (no gills or lungs)h) excretory system includes nephridia (like in mollusks)1. 2 per segment2. transport waste out of coelom by excretory tubulesi) 3 classes: Polychaeta (polychaetes), Oligochaeta (earthworms), and Hirudinea (leeches)j) Class Polychaeta (grade) – polychaetes1. many unusual and colorful forms; include plumed worms, peacock worms, fan worms, and many others2. ~10,000 living species, mostly marine3. often live in burrows4. usually filter-feeders, sometimes carnivores or parasites5. distinctive characteristics:• typically more cephalized than other annelids• parapodia - paired, fleshy, paddle-like flaps on most segments- used for moving and gas exchange5 of 8BIOL 1030 – TOPIC 12 LECTURE NOTES6. sexes separate, but usually lack permanent gonads (sex organs); instead, make gametes from cells lining coelom or septa7. external fertilization8. trochophore larvae – similar to that of mollusks (ciliated)k) Class (or subclass) Oligochaeta (grade) – earthworms1. mostly terrestrial (in moist soil); a few