
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
30-1


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
30-2


Fig. 30.3
30-3




Cnidarians
◦ Multicellular, tubular or bell-shaped animalsradial symmetry
◦ All aquatic, mostly marine
2 germ layers during development
◦ Organized at tissue level
Nematocysts
◦ stinging cells unique to cnidarians
30-4

cont’d

2 body typespolyps 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
30-5


Fig. 30.4
30-6

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
30-7

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
30-8


Fig. 30.5
30-9




Flatworms
Bilateral symmetry, three germ layers, acoelomate
Mesoderm gives greater complexity
◦ Muscles, excretory, reproductive, and digestive systems in some
◦ Respiration by diffusion and circulation
30-10


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
30-11


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
30-12


Fig. 30.6
30-13


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?
30-14

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
30-15


Fig. 30.7
30-16

Parasitic Platyhelminthes cont’d

Class Trematoda - Flukes
◦ Endoparasites of many species
◦ Body Structure
 Tegument
 Oral sucker and posterior sucker
◦ Digestion
 Well-developed digestive canal
30-17

Parasitic Platyhelminthes cont’d

Class Trematoda - Flukes cont’d
◦ Muscles and excretory system much like freeliving flatworms
 Poorly developed sense organs- why might that be?
◦ Reproduction
 Hermaphroditic
 Complex life cycle involving two intermediate hosts
30-18

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
30-19


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
30-20


Fig. 30.8
30-21

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
30-22


Fig. 30.9
30-23


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
30-24

Parasitic Nematodes cont’d

Wuchereria bancrofti
◦ filarial worm that causes elephantiasis
◦ Migrates into lymphatic vessels and prevents lymph drainage
◦ Edema occurs
30-
25

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
30-26