PLATYHELMINTHES ACOELA FLATWORMS ACOELA CHAPTER 8. phylum acoelomorpha marine or brackish usually found in sediments

Transcription

1 FLATWORMS? ACOELA phylum acoelomorpha marine or brackish usually found in sediments CHAPTER 8 ACOELOMORPHA ACOELA Digestion some with gastrovascular cavity Reproduction Radial nerve system proboscis sheath statocyst testes gut mouth ovary gonopore FLATWORMS Phylum Platyhelminthes platy-flat, helmins-worm Free-living or parasitic Acoelomate with primary bilateral symmetry Triploblastic Organ level of development Bilateral symmetry useful for motile, directional animals Ventral/dorsal anterior/posterior right/left

2 radial symmetry Structure and Function Excretion and Osmoregulation Protonephridia Flame cells Wastes are released through nephridiopore Nucleus of cap cell Flame bulb Cilia Interstitial fluid flow Tubule Opening in bilateral symmetry Tubules of protonephridia body wall Tubule cell Nutrition and Digestion Carnivorous or parasitic Sac-like g-v cavity with single mouth opening Gastrovascular cavity Pharynx Nervous system and sense organs Range in complexity from nerve-net pattern to cerebral ganglia / paired nerve cords Gastrovascular cavity Pharynx Mouth Mouth Eyespots Eyespots Ganglia Ventral nerve cords Ganglia Ventral nerve cords

3 Reproduction Asexual Sexual Movement most glide along mucous film using cilia rhabdites. in some, outer layer of the body is syncytial (tegument) lacks cilia. circular, longitudinal and diagonal muscles viscid glands releasing gland anchor cell microvilli epithelial cell nerve viscid gland cells parenchyma muscle releasing gland cells anchor cells cilium GROUPS CLASSIFICATION Class Turbellaria Mostly free-living using ventral cilia to crawl along mucus or sometimes swimming Marine or freshwater TURBELLARIA Predatory or detritivorous Amazing regenerative powers neoblasts Sexual Reproduction monoecious reciprocal sperm transfer direct development TREMATODA FLUKES Class Trematoda flukes Vertebrate endoparasites Adhesive sucker(s) or hooks Often with a multi-stage life cycle example life cycle overview -- egg -> miracidium -> sporocyst -> redia -> cercaria (secondary larvae) -> metacercaria (eaten by primary host)-> adult spine distal cytoplasm muscle golgi nucleus tegument cell body mitochondrion parenchymal cell

4 TREMATODA MIND CONTROL!!! liver fluke life cycle eggs passed in feces Freshwater snail eats eggs Miracidium transforms into a sporocyst Redia reproduce asexually Cercaria leave snail, burrow into fish Metacercaria are eaten Dicrocoelium dendriticum TREMATODA TREMATODA Some fluke cercariae enter humans directly schistosome dermatitis or swimmer s itch Human host Male Female 1 mm Tropical blood flukes survive and use humans as hosts dioecious gynecophoric canal larvae burrow into human Motile larva asexual reproduction in snail sexual reproduction in host Ciliated larva larvae infect snails Snail host

5 MONOGENIC FLUKES CESTODES Class Monogenea Single host oncomiracidium (ciliated larva) opisthaptor Class Cestoda tapeworms Gut parasites of vertebrates Monoecious No gut Microtriches prohaptor microtrich cytoplasm of tegument 101 mouth sucker opisthaptor anchor mitochondria CESTODES CESTODES Scolex two dorsal nerve cords Proglottids New proglottids originate behind scolex mature proglottids become egg sacs that are passed in feces life cycle Eggs hatch into larvae --> eaten by an intermediate host and encyst in muscle Larvae called cysticercus larvae Undercooked flesh eaten by the primary host Inverted scolex of larva then everts in definitive host s gut thus the area for absorption of nutriments. The bases of spine-like and blade-like microtriches have an electrondense ridge at their anterior edge. According to MacKinnon and Burt (1983 ) this ridge may function in preventing the microtriches from bending forward and thus losing their grip against the mucosal epithelium of the host intestine. The ultrastructure of microtriches can be used as a taxonomic character to be added to other characteristics (Richmond and Caira 1991; Hoberg et al ; Caira and Tracy 2002; Ivanov and Brooks 2002; Ivanov 2004 ; Gil de Pertierra 2004, 2005 ). In our opinion more information of microtriches pattern could be useful for the determination of species in proteocephalideans. circular muscle longitudinal muscle

6 CESTODES mature proglottids become egg sacs that are passed in feces life cycle Eggs hatch into larvae --> eaten by an intermediate host and encyst in muscle Larvae called cysticercus larvae Undercooked flesh eaten by the primary host Inverted scolex of larva then everts in definitive host s gut CESTODES many diverse live cycles brain from a 9 year old infected with pork tapeworm TEXT Tapeworm diet? metamerism? strobila germinative zone

7 CHAPTER 9 MESOZOA Phylum Mesozoa -- rhombozoans orthonectids orthonectid rotifera acanthocephala mollusca gnathostomulida platyhelminthes nemertea gastrotricha ectoprocta gnathifera annelida entoprocta lophotrochozoa hemichordata echinodermata nemata nematomorpha ecdysozoa tardigrada arthropoda panarthropoda onychophora chordata deuterostomia protostomia acoela cnidaria ctenophora bilateria porifera eumetazoa r o o t CHAPTER 10 Clade Gnathifera Phylum Gnathostomulida acoelomate no circulatory system ciliated epidermal cells jaws with bilateral symmetry ROTIFERS Phylum Rotifera rotifers general characteristics mastax Marine or freshwater filter-feeders some colonial may be floaters, creepers, or sessile classes bdelloidea seisonidea monogononta

8 ROTIFERS corona ROTIFERS Structure and function Foot with pedal glands 1-4 toes eutely wheel organ metachronal ciliary motion protonephridia Bilobed brain with paired nerves Paired eyespots syncytial epidermis with cuticle lorica = shell large pseudocoel circular and longitudinal muscles brain eyespot flame bulb mastax gastric gland salivary glands stomach germovitellarium anus intestine cloacal bladder pedal glands sex determination TSD GSD haplodiploidism toe ROTIFERS bimodal reproduction class monogononta Mixis Amictic females produce diploid eggs mictic stimulus -- Mictic females --> haploid eggs unfertilized eggs become haploid males Fertilized eggs become dormant ACANTHOCEPHALA Phylum Acanthocephala proboscis with spiny hooks no digestive tract protonephridia dioecious syncytial outer surface lacunar system distributes nutrients

9 GASTROTRICHS other Lophotrochozoa Phylum Gastrotricha brackish, salt, or freshwater rotifer-like -- but no corona protonephridia no flame cells solenocytes (single flagellum)