Invertebrates: Phylum Porifera Sponges Multicellular; body a loose aggregate of cells All aquatic, mostly marine Body with pores (ostia), canals, and chambers for circulation of water Epidermis of flat cells, some with contractile fibers Middle layer is semi-fluid, with wandering amebocytes Inner layer of choanocytes-flagellated to move water

Phylum Porifera cont’d Filter feeders- intracellular digestion Cells get food from circulating water Classified based on skeleton Composed of spicules Chalk sponges - spicules of calcium carbonate Glass sponges - spicules of silica Proteinaceous sponges - spongin fibers Reproduction asexual by budding, sexual by fusion of gametes

Sponge Fig. 30.3

Invertebrates: Phylum Cnidaria Cnidarians Multicellular, tubular or bell-shaped animals- radial symmetry All aquatic, mostly marine 2 germ layers during development Organized at tissue level Nematocysts stinging cells unique to cnidarians

Cnidarians cont’d 2 body types-polyps and medusae Life cycle alternates between both forms in some; in others one form is reduced or absent Gastrovascular cavity-sac-like body plan Includes corals, jellyfish, and hydrozoans Corals- polyps Jellyfish-medusae Hydrozoans-may have both forms

Cnidarian diversity Fig. 30.4

Cnidarians cont’d Hydra Representative organism (Class Hydrozoa) Freshwater, attaches to rocks, leaf litter Small tubular polyp, sac-like body plan with a single opening Outer tissue layer – epidermis from ectoderm Inner layer – gastrodermis from endoderm Longitudinal and circular muscle fibers present Diffuse nerve net between layers

Cnidarians cont’d Digestion begins in gastrovascular cavity, completed in cells Can reproduce sexually and asexually (budding) Sexual reproduction- hydra develops an ovary or testis in body wall-produces gametes

Anatomy of Hydra Fig. 30.5

Invertebrates: Phylum Platyhelminthes Flatworms Bilateral symmetry, three germ layers, acoelomate Mesoderm gives greater complexity Muscles, excretory, reproductive, and digestive systems in some Respiration by diffusion and circulation

Platyhelminthes cont’d Class Turbellaria - Planarians Free-living flatworms freshwater, feed on small living and dead organisms Ladder-like nervous system Ganglia and eyespots anterior Auricles – chemosensitive receptores Digestion: Feed through muscular pharynx Specialized cells for excretion: flame cells

Platyhelminthes cont’d Class Turbellaria - Planarians cont’d 3 muscle layers- circular, longitudinal, and diagonal Allows for more complex movements Cephalization Organized to have an anterior end and a posterior end Hermaphroditic

Planarian Fig. 30.6

Parasitic Platyhelminthes Class Cestoda (Tapeworms) Internal parasites as adults Body Structure Tegument: tough outer covering protect from host’s enzymes Scolex - head Barbs/hooks for attachment Proglottids: segments Each contains organs of both sexes Lack a digestive system- why?

Parasitic Platyhelminthes cont’d Class Cestoda (Tapeworms) (cont’d) Reproduction Fertilization is internal proglottids filled with fertilized eggs are called gravid Gravid proglottids drop off and pass out in feces Ingested by intermediate host larvae become encysted Intermediate host is then eaten by definitive host Larvae mature to adults Representative Organism: Tanea solium Pork tapeworm

Life cycle of a tapeworm, Taenia Fig. 30.7

Parasitic Platyhelminthes cont’d Class Trematoda - Flukes Endoparasites of many species Body Structure Tegument Oral sucker and posterior sucker Digestion Well-developed digestive canal

Parasitic Platyhelminthes cont’d Class Trematoda - Flukes cont’d Muscles and excretory system much like free- living flatworms Poorly developed sense organs- why might that be? Reproduction Hermaphroditic Complex life cycle involving two intermediate hosts

Parasitic Platyhelminthes cont’d Class Trematoda - Flukes cont’d Representative Organism: Clonorchis sinensis Liver Fluke Transmission Snails ingest eggs Develop in to larvae, which leave the snail and burrow into muscles of a fish Humans ingest fish Larvae moves into bile ducts where adults develop Eggs pass out of human in feces, cycle continues

Invertebrates: Phylum Nematoda Roundworms First appearance of Tube-within-a-tube body plan 2 openings, mouth and anus Body Cavity Pseudocoelomates Pseudocoel -filled with fluid, acts as hydrostatic skeleton Many species; some are free-living in soil and water, others are parasitic

Coelom structure and function Fig. 30.8

Parasitic Nematodes Ascaris Move with whip-like motion Intestinal parasites in many animal species Females are much longer than males and highly prolific Eggs enter host in uncooked vegetables, soil, or feces Larvae burrow out of intestine and migrate to heart and lungs Larvae are coughed up and swallowed Mature to adults in intestines Estimated to infect 25% of world population

Roundworm anatomy Fig. 30.9

Parasitic Nematodes cont’d Trichinella spiralis the trichina worm Causes trichinosis Humans contract the worm by eating undercooked pork Larvae migrate out of intestines and form painful cysts in the muscles

Parasitic Nematodes cont’d Wuchereria bancrofti filarial worm that causes elephantiasis Migrates into lymphatic vessels and prevents lymph drainage Edema occurs

Parasitic Nematodes cont’d Pinworms and hookworms Roundworm parasites which cause problems in children Much more common in U.S. Pinworms are primarily an annoyance Hookworms cause skin irritations and in some cases debilitating disease