Bilaterate Phyla

Phylogeny Review Common metazoan ancestor

Simple Bilaterian Phyla

Platyhelminth Phylogeny

Phylum Platyhelminthes Triploblastic Bilaterally Symmetric Aceolomic Fig. 14.CO

Body Cavity Classification

Acoelomate Internal Organization Fig. 14.1

Platyhelminthe Taxonomic Characteriestics Free-living v parasitic Incomplete gut No circulatory system Centralized nervous system Secretory glands Excretory organs Reproductive organs Innervated musculature Pseudoceros bifurcus

Platyhelminthes Reproduction Modes Sexual Monoecious (hermaphroditic) Free living forms typically cross fertilize Schistosoma sp of flukes are dioecious Asexual Freshwater turbellarian regenerative properties Intermediate forms of parasitic classes Sporogomy of encysted miracidium and redia forms

Platyhelminthes Taxonomy Class Turbellaria Free living planarians & marine flatworms Class Trematoda Internal Flukes Class Monogenea External Flukes Class Cestoda Tapeworms All Parasitic

Class Turbellaria – Planarian Dugesia sp Fig. 14.2

Movement of Free Living Turbellarians crawling Dugesia crawling Bdellura swimming polyclad

Generalized Turbellarian Anatomy Fig. 14.3

Turbellarian Organ Systems Protonephridia – Flame cells & tube cells Fig. 14.6a

Turbellarian Organ Systems Fig. 14.6b

Orders of Class Turbellaria Order Tricladida Order Polycladida Fig. 14.9

Phylum Platyhelminthes Class Turbellaria Two tiger flatworms (Pseudoceros crozerri) on clump of orange sea squirts (Ecteinascidia turbinata: tunicates) in Bermuda Photo Copyright © Diane R. Nelson

Phlym Platyhelminthes Class Turbellaria, Order Polycladida Pseudocerus hancockanum Coral – Tubastrea aurea Tunicate – Aplidium cratiferum Fig. 14.10

Phlym Platyhelminthes Class Turbellaria, Order Polycladida Amphiscolops sp Fig. 14.11

The flatworm Mesostoma, catching and eating Daphnia Video Clip

Parasitic Life Cycles Hosts Multiple hosts Parasitic adaptations Single v multiple Multiple hosts Definitive Sexually reproductive stage of parasite Intermediate Asexually reproducing stages, larval stages of parasite Parasitic adaptations Syncytial tegument Loss of centralized nervous system Decreased digestive & excretory systems

Class Trematoda - Flukes Require 2 or more hosts Definitive host Where sexually reproducing fluke lives Intermediate hosts Intermediate larval & asexual forms encyst

Generalize Fluke Body Plan Gonopore Fig. 14.7

Fluke Hosts Definitive Hosts Intermediate Hosts Mammals, Reptiles, Birds Intermediate Hosts Arthropods Gastropods Fish

Clonorchis sinensis Life Cycle – Human Liver Fluke Fig. 14.12

Trematode Stages Adult – fluke in liver, bile ducts, respiratory tract, blood Miracidium – ciliated, swimming larvae Sporocyst – asexually reproductive stage producing redia (within sporocyst) Redia – 2nd asexual phase producing cercaria Cercaria – free swimming larval form Metacercaria – encysted cercaria

Clonorchis Stages Adult Fluke mammal Metacercarial cyst fish Redia Egg water Cercaria Sporocyst snail water

Blood Flukes: Schistosoma japonicum & Schistosoma mansoni Fig. 14.13

Swimmer’s Itch Encysted metacercaria of avian schistosomes fluke in water fowl sporocysts & redia in snail miracidium cercaria fluke in water fowl miracidium cercaria sporocysts & redia in snail

Class Monogenea Monogenea – 1 host External flukes Fish gill, amphibians No intermediate hosts Fig. 14.16

Class Cestoda - Tapeworms Two hosts Definitive host – carnivore Intermediate host – herbivore Adults live in intestine of definitive host Larval stages encyst in muscle of intermediate host

Cestode Body Plan Attach via scolex Proglottids develop from base of scolex Proglottids mature reproductively Proglottids are shed in feces or crawl from anal opening Fig. 14.18

Taenia saginata Life Cycle - Human/Beef Tapeworm Fig. 14.19

Taenia solium – Human/Pork Tapeworm

Tapeworm Stages Cysticercus Cysticercoid Coenurus Coracidium Procercoid Plerocercoid Hydatid

Broad fish Tapeworm Diphyllobothrium latum

Tapeworm Lifecycles Human pathogens FIGURE 86-4 Generalized life cycle of tapeworms. Taenia saginata, T. solium, Diphyllobothrium latum, Dipylidium caninum. Hymenolepsis nana, Cysticercus larva in cow and pig; procercoid larva in copepod, plerocercoid (sparganum) larva in fish; cysticercoid larva in insect.

Cestode Organs Each proglottid matures as an egg sack Fig. 14.20

Host Specificity Hydatid Cysts Encystment of larva in definitive rather than intermediate host Cysticercosis Taenia solium and T. saginata Echinococcus granulosus (dog tapeworm)

Hydatid Cysts in Human Heart

Hydatid Cysts in Human Brain Fig. 14.21