Phylum Cnidaria & Ctenophora

(ny-dar’ e-a) & (te-nof’ o-ra)

Phylum Cnidaria & Ctenophora

(ny-dar’ e-a) & (te-nof’ o-ra)

The RADIATE MetazoaThe RADIATE Metazoa

Cnidaria (cnidos=nettle like)

Cnidaria (cnidos=nettle like)

9000+ species Primary radial or biradial symmetry 700 million+ year fossil record 2 Germ layers ectoderm (epidermis), endoderm (gastrodermis), & mesoglea

Gastrovascular cavity (extracellular digestion) Coelenerata (hollow gut)

Nerve net (no CNS) Locomotion via epitheliomuscular cells Polymorphism (one species, multiple forms)

Nematocysts (unique to Cnideria)

9000+ species Primary radial or biradial symmetry 700 million+ year fossil record 2 Germ layers ectoderm (epidermis), endoderm (gastrodermis), & mesoglea

Gastrovascular cavity (extracellular digestion) Coelenerata (hollow gut)

Nerve net (no CNS) Locomotion via epitheliomuscular cells Polymorphism (one species, multiple forms)

Nematocysts (unique to Cnideria)

Cnideria contd.Cnideria contd.

Usually shallow marine habitats Some on the open ocean or at depth Many have bioluminescence. Symbiosis: commensals (anemonies), mutuals (zooanthellae)

More on polymorphism Polyps Medusae

Usually shallow marine habitats Some on the open ocean or at depth Many have bioluminescence. Symbiosis: commensals (anemonies), mutuals (zooanthellae)

More on polymorphism Polyps Medusae

Life cycleLife cycle

Hydrozoa Scyphozoa

Hydrozoa Scyphozoa

Medusae are specialized for dispersal.Polyps are specialized for colonial life.

CnidocytesCnidocytes

Cnidoblast (developing) Nematocyst Osmotic pressure

Leads to hydrostatic pressure Operculum (covering) Cnidocil (trigger) Venomous or adhesive

Cnidoblast (developing) Nematocyst Osmotic pressure

Leads to hydrostatic pressure Operculum (covering) Cnidocil (trigger) Venomous or adhesive

Hydra Cnidocyte

Sometimes nematocysts are stolen and used by other invertebrates.-nudibranchs-comb jellies

Nervous systemNervous system

No CNS Nerve net or plexus No myelin Nerve signals transmitted in both directions at the synapse

Statocyst (equilibrium) Ocelli (simple eyes)

No CNS Nerve net or plexus No myelin Nerve signals transmitted in both directions at the synapse

Statocyst (equilibrium) Ocelli (simple eyes)

4 Classes of Cnidaria4 Classes of Cnidaria1. Hydrozoa (e.g.. hydroids, fire

corals, Portuguese man-o-war)2. Scyphozoa (true jellies: e.g..

moon jellies, other bell-shaped jellies )

3. Cubozoa (cube jellies:e.g.. Chironex fleckeri..or Sea wasp)

4. Anthozoa (e.g.. anemones, stony corals, & soft corals such as sea pens)

1. Hydrozoa (e.g.. hydroids, fire corals, Portuguese man-o-war)

2. Scyphozoa (true jellies: e.g.. moon jellies, other bell-shaped jellies )

3. Cubozoa (cube jellies:e.g.. Chironex fleckeri..or Sea wasp)

4. Anthozoa (e.g.. anemones, stony corals, & soft corals such as sea pens)

Class Hydrozoa • Includes the solitary freshwater hydra; Most are Includes the solitary freshwater hydra; Most are colonialcolonial and marine and marine • Typical life cycle includes both asexual polyps Typical life cycle includes both asexual polyps and sexual medusa stages; however, freshwater and sexual medusa stages; however, freshwater hydras and some marine hydroids do not have a hydras and some marine hydroids do not have a medusa stage.medusa stage.Hydras• Solitary freshwater hydras are found in ponds and streams occurring on the underside of vegetation.• They possess a pedal disc, mouth on a hypostome, surrounded by 6-10 tenetacles.• Mouth leads to a gastrovascular cavity* • Sexual reproduction: Ovaries and testes form on the body wall. Sperm are released into the water, and fertilize eggs within the ovaries. Resulting blastula falls off the parent as a cyst which can last the winter.• Asexual reproduction: budding

* Extracellular & intracellular digestion

Hydrozoa cont.

Colonial Hydrozoans - e.g., Obelia

• Colonial stalk called hydrocauli•Skeleton of chitin that is secreted by the epidermis (perisarc)• Two different kinds of individuals or zooids that comprise the colony: feeding polyps called hydranths or gastrozooids and, reproductive polyps or gonangia

Hydrozoa cont.Life Cycle of Obelia• Gonozooids release free swimming medusae.• Zygotes become planula larvae, which eventually settle to become polyp colonies.

Also, the margin of the bell projects inward forming a shelf-like velum.

The medusae of hydroids are smaller than those of true jellyfishes (Scyphozoa).

Hydrozoa cont. The Portuguese man-of-war (Genus Physalia) is another example of colonial Hydrozoa.

The colony is suspended on a gas-filled floatformed from one of the polyps.

The tentacles house the polyps and modified medusae of the colony, including the dactylozooids or “fishing tentacles”.

A mutualistic relationship exists between Physalia and a small fish (Nomeus) which feeds off of the tentacles.

Class Scyphozoa“Jellyfish” have the most conspicuous medusae.• The medusae are large and contain large amounts of mesoglea (the jelly).• They differ from the hydrozoan medusa in that they lack a velum.•They possess four gastric pouches lined with nematocysts to further subdue prey. Pouches are connected with the mouth as part of the gastrovascular system.•They have many rhopalia for sensory function (vision & gravity)

Moon Jellyfish

Scyphozoan Life Cycle - Aurelia• Gametes develop in the Gametes develop in the gastrodermisgastrodermis of gastric of gastric pouches; eggs and sperm are shed through the mouth.pouches; eggs and sperm are shed through the mouth.• Fertilized eggs develop into a Fertilized eggs develop into a planula larvaplanula larva which settles on substrate and develops into a which settles on substrate and develops into a polyppolyp - scyphistoma. - scyphistoma.• ScyphistomaScyphistoma produces a series of polyps by produces a series of polyps by budding - budding - StrobilaStrobila• The polyps undergo The polyps undergo differentiationdifferentiation and are and are released from the released from the strobilastrobila as free swimming as free swimming ephyraephyra• EphyraEphyra matures into an adult jellyfish matures into an adult jellyfish

Illustration from page 266 of the text

Aurelia Life Cycle

Class Cubozoa (box jellies)Class Cubozoa (box jellies) Medusae are the

dominant form (2-25cm)

Good swimmers (eyes) More ocelli

Bells are squared (hence box jellies)

Pedalium at the base of each tentacle

Polyps small, little known

Subumbrella forms a velarium similar to a velum in Hydromedusae

Sting can be severe or even fatal…Sea Wasp

Medusae are the dominant form (2-25cm)

Good swimmers (eyes) More ocelli

Bells are squared (hence box jellies)

Pedalium at the base of each tentacle

Polyps small, little known

Subumbrella forms a velarium similar to a velum in Hydromedusae

Sting can be severe or even fatal…Sea Wasp

The eye of a box

jellyfish, class

Cubozoa

The eye of a box

jellyfish, class

Cubozoa

Class Anthozoa (anemonies, corals, sea pens, etc.)• Exclusively marine; there is no medusa stage• At one or both ends of the mouth is a ciliated groove called the siphonoglyph, which generates a water current and brings food to the gastrovascular cavity• They possess a well developed pharynx

“Flower”animals

The The gastrovascular gastrovascular cavitycavity is large is large and partitioned by and partitioned by septasepta or or mesenteriesmesenteries; These ; These increase surface increase surface area for digestion area for digestion or support.or support.

Edges of the septa usually have acontia threads, equipped with nemat-ocysts that protrude from the mouth and pores for defense and prey capture.

Anthozoa cont.• Solitary anthozoans include sea anemones• Most anthozoans are colonial (e.g. corals) and secrete external skeletons composed of calcium carbonate.•Hexamerous or Octamerous symmetry•Recognize prey through chem-ical detection (glutathione or asparagine) and vibration freq.• Many corals obtain much of their energy from microscopic, photosynthetic dinoflagellates (zooxanthellae) that live symbiotically inside the cells of the coral.

Anthozoa contd.

ReproductionReproduction

Anemonies Monoecious and dioecious

Protandrous if monoecious

Asexual reproduction by Budding Longitudinal fission

Pedal laceration

Anemonies Monoecious and dioecious

Protandrous if monoecious

Asexual reproduction by Budding Longitudinal fission

Pedal laceration

Hard Corals (hexacorallian)

Sexual repro. Moneceous & dioecious

Spawning Planula larva

Asexual repro. Budding Fission

Transverse Longitudinal

Hard Corals (hexacorallian)

Sexual repro. Moneceous & dioecious

Spawning Planula larva

Asexual repro. Budding Fission

Transverse Longitudinal

Coral Reef types (more)

Coral Reef types (more)

Fringing reef Close to land; narrow or no lagoon

Barrier Parallel to shore; wide, deep lagoon

Patch Located on the leeward side of a barrier reef or atoll

Atoll Encircle a lagoon, but not an island

Fringing reef Close to land; narrow or no lagoon

Barrier Parallel to shore; wide, deep lagoon

Patch Located on the leeward side of a barrier reef or atoll

Atoll Encircle a lagoon, but not an island

Hermatypic (reef building) corals

Coraline algae Shallow water (<30m) & warmth (+ 30° Lat.)

Large formations of calcium carbonate (CaCO3)

Tremendous diversity of life (Islands of life)

Hermatypic (reef building) corals

Coraline algae Shallow water (<30m) & warmth (+ 30° Lat.)

Large formations of calcium carbonate (CaCO3)

Tremendous diversity of life (Islands of life)

The little-known fifth class of Cnidaria, the

Ostrizoa

The little-known fifth class of Cnidaria, the

Ostrizoa

Ctenophora(Comb Jellies)Ctenophora

(Comb Jellies) Colloblasts (glue-secreting cells - prey capture)

Cilliated Comb rows (swims mouth first) Marine, < 100 species; many deep water sp. Two tentacles which retract into sheaths No nematocysts (H. rubra steals them) Aboral organ senses gravity (statocyst) Aboral canal voids waste (complete gut) Epidermis, gastrodermis, and collenchyme which contains distinct muscle fibers.

Respiration & excretion through cell membranes

Bioluminescence

Colloblasts (glue-secreting cells - prey capture)

Cilliated Comb rows (swims mouth first) Marine, < 100 species; many deep water sp. Two tentacles which retract into sheaths No nematocysts (H. rubra steals them) Aboral organ senses gravity (statocyst) Aboral canal voids waste (complete gut) Epidermis, gastrodermis, and collenchyme which contains distinct muscle fibers.

Respiration & excretion through cell membranes

Bioluminescence

Ctenophora life cycleCtenophora life cycle

Monoeceous Eggs and sperm released into the water

Free swimming cydippid larva No polyp stage

Monoeceous Eggs and sperm released into the water

Free swimming cydippid larva No polyp stage

The EndBrought to you by…The End

Brought to you by…

Hydrozoa

& Scyphozoa