Download Marine Animals Without a Backbone

Invertebrates
Sponges, Cnidarians,
& Comb Jellies
Ch. 7
Objecitves
1. Understand the most important
morphological characters of the major
groups of marine invertebrates (inverts).
2. Suspension vs. deposit feeding
3. Compare and contrast body structures
between gastropods, bivalves, and
cephalopods.
4. Compare and contrast body structures
between sea stars and sea urchins
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Sponges
• Structurally simplest
multicellular animals
• Cellular level of
organization
– No true tissues or organs
• Amazing variety of
shapes, sizes, colors, but
simple body plan
Sponges: simple body plan
• Sessile: live permanently attached to bottom
• Numerous pores (ostias)—allow water to enter
• water filtered through collar cells, food ingested, water
leaves through osculum
Sponges: feeding
• Suspension feeders:
– Eating food particles suspended in water
• Filter feeders:
– Actively filter food particles
Sponges feeding
Sponge Sex: They do it all!
• Hermaphrodites:
– Male and female gonads
• Asexual
– Branches or buds break
off, grow into identical
sponge
• Sexual
– Broadcast spawning
Cnidarians
• Sea anemones, jellies,
corals, and realatives
• Tissues that perform
specific functions
– Huge evolutionary step!
– Able to swim, respond to
stimuli, engulf prey, and
more.
• Radial symmetry
– Like a pizza-all slices
similar
Mexican Anemone
Cnidarians: aboral vs. oral
• Oral surface
– Mouth located here
• Aboral
– Opposite side
Nematocysts
• Microscopic needles
housed within a tiny cell
• Both mechanical and
chemical stimuli may
trigger needles
• Fire from housing and
drill into victim
• Needles contain a
neurotoxin, designed to
paralyze the prey.
Nematocysts in action!
Polyp vs. Medusa
Cnidarians are usually one or the other---but sometimes spend
time as both.
Types of Cnidarians: Hydrozoans
• Feathery or bushy colonies or tiny polyps
• Interesting life cycle
• Life cycle animation
Types of Cnidarians: Siphonophores
• Form drifting
colonies of polyps
• Some have
specialized gas
filled float
• Portuguese manof-war
• Up to 165 ft
tentacles!
• Deadly
Types of Cnidarians: Cubozoa
• Box jellies
– a.k.a. sea wasps
• Venom attacks heart,
nervous system, and
skin cells dead w/in
minutes
• One of the deadliest
venoms on earth
• Northern Australia,
Southeast Asia, and the
Indian Ocean
Box Jellies
Comb Jellies
• a.k.a. ctenophores
• Have 8 rows of ciliary
combs
– Refracts light, creates a
prism-like multicolor
effect
• Carnivores