Characteristics of Animals

Sponges and Cnidarians

Invertebrates make up over 95% of all named phyla of animals. There are

over 30 different phyla.

Animals started an explosion of evolutionary differentiation during the Cambrian Period. This

was possible by mutations in Hox genes allowing for new traits/physiology to

emerge.

Animals are placed in groups based on characteristics such as Body Symmetry; Tissue

Layers; and Development Patterns

Symmetry

Asymmetrical BilaterialRadial

• the arrangement of body structures relative to some axis of the body

Body Plan Symmetry:Bilateral Symmetry – can be divided equally along one plane, forms mirror-image sides

Radial Symmetry – body parts are arranged in a circle around a central axis

Asymmetrical - no symmetry (typically found in Porifera)

Body Plan Terms

ANIMAL SYMMETRY:

The Animal Kingdom

• Multicellular

• Eukaryotic

• Heterotrophs

• Cells lack cell walls

• 95% are invertebrates

What Animals Do to Survive

• Feeding

• Respiration

• Circulation

• Excretion

• Response

• Movement

• Reproduction

Trends in Animal Evolution

• Cell specialization and levels of organization

• Early development

• Body symmetry

• Cephalization

• Body cavity formation

Phylum Porifera

• Sponges

• Have tiny openings, or pores, all over their bodies

• Sessile: they live their entire life attached to a single spot

• They are animals! Why…?

SPONGES

Sponges

• Sponges are really nothing but a loose aggregation of specialized cells.

• Of the 6,000 known spp. nearly all are marine.

• Amazingly enough, these cells don’t actually form organs, but do serve similar functions, keeping the animal(s) alive.

James FatherreeJames Fatherree

Sponges are Animals!!!

• Multicellular

• Heterotrophic

• No cell walls

• Contain a few specialized cells

Form and Function in Sponges

• Have nothing resembling a mouth or gut

• Have no tissues or organ systems

• Simple functions are carried out by a few specialized cells

General Sponge TypesSponges fall into several basic categories, mostly depending on Sponges fall into several basic categories, mostly depending on shape:shape:

branchingbranching

tubulartubular

roundround

encrustingencrusting

glassglass

boring (destructive)boring (destructive)

Hawaiian encrusting spongeHawaiian encrusting sponge

Sclerosponge (CaCOSclerosponge (CaCO33))

Ceratoporella nicholsoniCeratoporella nicholsoni

Harvested spongesHarvested sponges

Asymmetrical Symmetry

• Have no front or back ends, no left and right sides

• A large, cylindrical water pump

• The body forms a wall around a large central cavity through which water flows continually

Choanocytes

• Specialized cells that use flagella to move a steady current of water through the sponge

• Filters several thousand liters/day

Osculum

• A large hole at the top of the sponge, through which water exits

• The movement of water provides a simple mechanism for feeding, respiration, circulation and excretion

Simple Skeleton

• Spicule: a spike-shaped structure made of chalk-like calcium carbonate or glasslike silica in hard sponges

• Archaeocytes: specialized cells that make spicules

Feeding

• Filter feeders

• Sift microscopic food from the water

• Particles are engulfed by choanocytes that line the body cavity

Respiration, Circulation, & Excretion

• Rely on the movement of water through their bodies to carry out body functions

• As water moves through the cavity:

• Oxygen dissolved in the water diffuses into the surrounding cells

• Carbon dioxide and other wastes, diffuse into the water and are carried away

Response

• No nervous system

• Many sponges protect themselves by producing toxins that make them unpalatable or poisonous to potential predators

Reproduction

• Sexually or asexually

• A single spore forms both eggs and sperm; usually at different times

Sexual Reproduction

• Internal fertilization: Eggs are fertilized inside the sponge’s body

• Sperm are released from one sponge and carried by currents to the pores of another sponge

Sexual reproduction

• Many sponges are Many sponges are hermaphrodites, containing hermaphrodites, containing male and female reproductive male and female reproductive capabilities, yet do not self-capabilities, yet do not self- fertilize.fertilize.

•Tube sponges, such as this Tube sponges, such as this Verongia archeriVerongia archeri which is which is common in Caribbean waterscommon in Caribbean waters use broadcast spawning to use broadcast spawning to disperse sperm and eggs in disperse sperm and eggs in a flurry of activity that isa flurry of activity that is often coordinated with lunaroften coordinated with lunar cycles.cycles.

Asexual Reproduction

• Budding

• Gemmules: groups of archaeocytes surrounded by spicules

Still, if you carve ‘em up, they come back for more!!

It’s more amazing than that. If you mix groups of sponges together, It’s more amazing than that. If you mix groups of sponges together, they will usually reorganize into their original groups. they will usually reorganize into their original groups.

Ecology of Sponges

• Ideal habitats for marine animals such as snails, sea stars, sea cucumbers, and shrimp

• Mutually beneficial relationships with bacteria, algae and plant-like protists

– Many are green due to these organisms living in their tissues

Ecology of Sponges

• Attached to the seafloor and may receive little sunlight

• Some have spicules that look like cross-shaped antennae

• Like a lens or magnifying glass, they focus and direct incoming sunlight

Phylum Cnidaria

Sea anemones, jellyfishes, coral, etc.

Cnidarians• Phylum Cnidaria

• Hydras, jellies, sea anemones, and corals

• Soft-bodied

• Carnivorous

• Stinging tentacles arranged in circles around their mouths

• Simplest animals to have body symmetry and specialized cells

General Cnidarian Structureand Function

• Centrally located mouthCentrally located mouth

• Oral surface (mouth)Oral surface (mouth)

• Aboral surface (opposite end)Aboral surface (opposite end)

• TentaclesTentacles

• GutGut

• Nematocysts (cnidae)!Nematocysts (cnidae)!

• Polyp and Medusa: reproductivePolyp and Medusa: reproductive stagesstages

Beautiful, but deadly! This colonialBeautiful, but deadly! This colonialhydrozoan still contains cnidae.hydrozoan still contains cnidae.

Macrorhynchia phillipina

Cnidocytes

• Stinging cells that are located on their tentacles

• Used for defense and to capture prey

Nematocyst

• A poison-filled, stinging structure that contains a tightly coiled dart

• Found within cnidocytes

Form and Function in Cnidarians

• Only a few cells thick

• Simple body systems

• Most of their responses to the environment are carried out by specialized cells and tissues

Radially Symmetrical

• Central mouth surrounded by numerous tentacles that extend outward from the body

• Life cycles includes a polyp and a medusa stage

Body Plan

• Polyp: cylindrical body with arm-like tentacles; mouth points upward

• Medusa: motile, bell-shaped body; mouth on the bottom

Feeding

• Polyps and medusas have a body wall that surrounds an internal space: the gastrovascular cavity

• Gastrovascular cavity: a digestive chamber with one opening

– Food enters and wastes leave the body

Respiration, Circulation, & Excretion

• Following digestion, nutrients are usually transported throughout the body by diffusion

• Respire and eliminate wastes by diffusion through body walls

Response• Specialized sensory cells are used to gather

information from the environment

• Nerve net: loosely organized network of nerve cells that together allow cnidarians to detect stimuli

– Distributed uniformly throughout the body in most species

– In some species it is concentrated around the mouth or in rings around the body

Response

• Statocysts: groups of sensory cells that help determine the direction of gravity

• Ocelli: eyespots made of cells that detect light

Portuguese Man of War - cnidarian that floats in the water and has long tentacles

Irukandji syndrome:Irukandji syndrome:

A sting from this little guy can cause the following:A sting from this little guy can cause the following:

““It begins with a mild sting, followed by severe lower back pain, It begins with a mild sting, followed by severe lower back pain, muscle cramps in arms, legs, stomach and chest. It causes sweating,muscle cramps in arms, legs, stomach and chest. It causes sweating,anxiety, nausea, vomiting, headaches and palpitations, and has alsoanxiety, nausea, vomiting, headaches and palpitations, and has alsobeen known to cause cardiac failure.”been known to cause cardiac failure.”

Carukia barnesi: the baddest of the bad!Carukia barnesi: the baddest of the bad!

Movement

• Hydrostatic skeleton: a layer of circular muscles and a layer of longitudinal muscles that enable cnidarians to move

Reproduction: Sexually and Asexually

• Polyps can reproduce asexually by budding

• External sexual reproduction

– The sexes are separate-each individual is either male or female

– Both egg and sperm are released into the water

CNIDARIANS

Groups of Cnidarians

• Jellies (formerly jellyfishes)

• Hydras and their relatives

• Sea anemones

• Corals

Types of Cnidaria

Sea fanSea fan

Cnidaria come in all shapes and sizes.Cnidaria come in all shapes and sizes.

•Hydrozoans- feathey hydroidsHydrozoans- feathey hydroids

•Siphonophores- man-o-warSiphonophores- man-o-war

•Scyphozoans- large jellyfishScyphozoans- large jellyfish

•Anthozoan-sea anemones and coralAnthozoan-sea anemones and coral

•Most of the animals found within Cnidaria Most of the animals found within Cnidaria are all carnivores.are all carnivores.

multiple comb jelliesmultiple comb jellies

Ecology of Corals• The worldwide distribution is determined by:

– Temperature

– Water depth

– Light intensity

• Many suffer from human activity• Coral bleaching has become common • Global warming may add to the problem

http://video.nationalgeographic.com/video/animals/invertebrates-animals/other-invertebrates/manowar_portuguese/

Multimedia

Sponge Images and Videos - http://www.junglewalk.com/video/Sponge-movie.htm 

Cnidarian Images and Videos - http://www.junglewalk.com/video/Coelantrate-movie.htm

General Invertebrate Movies at National Geographic --- really good video on the portuguese man of war (under invertebrates) Hydra Video at  http://www.schooltube.com/video/55045/Hydra