Sponges, Cnidarians, Flatworms,
Roundworms
Ch 26
Turboblast Version
Sponges
• Aquatic, sessile, asymmetrical, filter-feeding invertebrate
• Lack tissues, organs, organ systems (simple bodies)
• Osculum- expels water and wastes at the top of sponge (a little like a
smoke stack)
• Sponges are made of 4 types of cells:
– Pore cells (surround pores)
– Collar cells (line sponge interior, each have a flagellum that creates water
current pulling water into sponge body)
– Epithelial-like cells (contract in response to touch)
– Amoebocytes (carry nutrients, aid in reproduction, produce chemicals
that make spicules)
• Spicules are small, needlelike structures between cells that form hard
support systems
• Reproduce sexually/asexually (budding, fragmentation, gemmules/internal
buds made in response to danger)
• Hermaphroditic (can create male and female gametes): release sperm
into water, retain eggs within body, fertilization is internal
• Larvae swim from the body and land elsewhere, set up camp!
Osculum
http://youtu.be/RmPTM965-1c
Cnidarians (“Nigh-dare-ee-uhns”)
(Hydras, Jellyfishes, Corals, Anemones)
• All radially symmetrical, aquatic, invertebrate
• 2 basic forms (medusa, polyp)
http://www.infovisual.info/02/img_en/013%20Life%20cycle%20of%20a%20jellyfish.jpg
• Sting prey with cells called nematocysts located on tentacles
– Resemble tiny harpoons, inject neurotoxins into prey http://youtu.be/BpKKGB-ivQo,
http://youtu.be/6zJiBc_N1Zk
– digest food within central gastrovascular cavity
• Tentacles- ring of flexible, tubelike structures surrounding mouth;
used to capture food
• Reproduce both sexually/asexually (budding)
– Sexually- release eggs/sperm into water, external fertilization
• Nervous system composed of net of neural tissue (highly-connected
network, no centralized brain tissue)
• Hydrozoans (hydras)
http://www.youtube.com/watch?v=yqXkaZwiu6s&feature=share&list=PL9AA335CF2AC21D2F
• Scyphozoans (jellyfishes) http://youtu.be/GqdvEhI1RS0
• Anthozoans (corals and anemones) http://youtu.be/SV06sxvLx2U
– [Antho- means “flower”]
jellyfish
hydra
coral
sea
anemone
Flatworms
• Acoelomates with thin, solid bodies
• 3 classes: free-living planarians http://youtu.be/DuwDJ-eZOMc, parasitic
flukes http://youtu.be/_IC9hLsjafw, and tapeworms http://youtu.be/KWaYFC4bqL0
• Simple nervous and muscle systems
• Flukes and tapeworms have adapted structures for parasitic
lifestyle
• Clearly defined head- senses and responds to environment
• Pharynx- muscular tube that can extend out of the mouth
• Eyespots- sensitive to light, enable worm to respond to light
conditions (cannot see in detail or strong contrast)
• Sensory cells located on each side of the head, can detect
chemicals, food, movements in environment
• Flame cells- remove excess water
– (much like contractile vacuoles in paramecia; must bail out water
that is constantly diffusing into cells)
flukes
Complex mouthparts on tapeworm head
planarians
tapeworm
Roundworms
• Pseudocoelomate, cylindrical worms, lengthwise muscles
(can wriggle), relatively complex digestive system, two body
openings
• Can be parasites of plants, fungi, animals (and humans)
• Ascaris in tropical regions, found in soil, enter through
mouth, eggs hatch in intestines, move into bloodstream,
then to lungs, then eggs are coughed up (most common
roundworm infection in humans)
• Pinworms most common in US, mostly in children, eggs can
survive weeks on surfaces, eggs are ingested—worms
mature in intestinal tract—females exit host’s anus while
host is sleeping and lay eggs on surrounding skin
• http://youtu.be/PrUlhufWlIA
• Can cause trichinosis (ingesting undercooked, infested pork
meat)
• Also known as nematodes
Replica of roundworm mouth
pinworm