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• SegmentedStructure 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