Transcript Chapter 8: Sponges, Cnidarians, Comb Jellies, and Marine Worms

Sponges, Cnidarians,
Comb Jellies, and
Marine Worms
What are Animals?
• Multicellular
• Eukaryotic (lack cell walls)
• Cannot produce their own food
(heterotrophs)
• Can move (exception: adult sponges)
• Vertebrates: have a
backbone (vertebral
column)
• Invertebrates: do not
have a backbone (no
vertebral column)
– Majority of marine animals
Sponges (Phylum Porifera)
• Simple
• Asymmetric
• Sessile (cannot move)
Structure and Function
• Full of tiny holes/pores
called ostia
– Water circulation
(nutrients and oxygen)
– Carries away wastes
• Lack tissues and organs
• Size is limited by ability
to circulate water
through its body
• 3 possible body plans
– Asconoid (simplest)-tubular and small
– Syconoid (body-wall folding)-internal
pockets
– Leuconoid (highest degree of folding)
• Nutrition and digestion:
– Suspension feeders
(filter feeders)  Get
food from water
• Reproduction
– Sexual
• Hermaphrodites
– Asexual
• Budding  pinching off to
form new organism
• Fragmentation  pieces form
new organism
• Ecological roles
– Can produce chemicals that can kill coral or
inhibit growth
– Can provide camouflage and protection for
animals
– Can produce chemicals that prevent organisms
from settling on their surface or to deter grazing
– Hosts to other organisms
– Recycles calcium to seawater
Cnidarians (Phylum Coelenterata)
• Ex: jellyfish, hydra, coral, and sea
anemones
• Radial symmetry
Structure and Function:
• 2 different body plans
– Polyp: benthic form
• Cylindrical body with an
opening a 1 end (mouth)
• Surrounded by tentacles
– Medusa: free-floating stage
– Gelatinous material between
layers of body called mesoglea
• Stinging cells (cnidocytes)
–Common on tentacles and outer body
wall
–Can also release toxins
• Nutrition and
digestion
– Digests prey in
gastrovascular
cavity
– Filter-feeders
– Can be
carnivores
• Paralyze prey
with toxins
• Reproduction
– Asexual  polyp stage
– Sexual  medusa stage
• Ecological relationships
– Predators that feed on a variety of prey
– Provide habitats for organisms (ex:
corals)
– Host symbionts that aid in nutrition and
help them grow
Ctenophores (Comb Jellies)
• Structure and Function:
– Transparent bodies
– Lack stinging cells
– Planktonic
– Eight rows of comb plates
used for locomotion
• Made of large cilia
– Weak swimmers
– Found mostly in surface
water
– Radial symmetry
– Luminescent at night
• Nutrition and Digestion
– Carnivorous
• Reproduction
– Hermaphrodites
– Shed eggs and sperm
directly into the water
column
– Few species can brood
eggs in their bodies
Marine Worms
• Most are benthic
Structure:
• Elongated bodies
• Lack external hard covering
• Gain support for body from fluid in body
compartments
– Hydrostatic skeleton
Flatworms
• Flattened bodies
Structure:
• Head and posterior end
• Free-living or parasitic
• Bilateral symmetry
Ex: flukes and tapeworms
• Nutrition and digestion:
– Chemical-detecting
organs called
chemoreceptors
– Carnivorous
– Can subdue prey by
entangling it in mucus
and suffocating it
– Can stab prey
– Digestion in
gastrovascular cavity
• Reproduction:
– Asexually 
regeneration
– Sexually
• Hermaphrodites
• Can fertilize each
other
• Internal fertilization
• No larval stage
Nematodes
• Roundworms
– 12,000 species
• Structure: Round, slender body
– Elongated
– Tapered at both ends
• Nutrition/Digestion:
– Scavengers, parasites
– Carnivorous, free-living
• Reproduction:
– Most are hermaphroditic
– Some can have separate sexes
Annelids
• Segmented
Structure and Function:
• Body wall has muscle
• Skin has setae (small bristles used for
locomotion, digging, anchorage, and
protection)
• Feeding and
digestion:
– Can have jaws or
teeth
– Active predators
– Chemoreceptors
monitor water
currents
– Filter-feeders
• Reproduction
– Asexual
• Budding
• Regeneration
• Fragmentation
– Sexual
• Separate sexes
• Gametes shed into body
cavity where they
mature
• Ecological roles:
– Burrowing aids in nutrient cycling
– Burrows provide habitats for other
species
– Feed on microorganisms and detritus
Examples of Annelids
polychaetes
echiurans
pogonophorans