Zoology

RADIATE ANIMALS

Phyla Cnidaria and CtenophoraPhyla Cnidaria and Ctenophora

Hysdrozoa Scyphozoa Cubozoa

Anthozoa (incl. sea anemones, stony corals, gorgonian corals, sea pen)

CNIDARIA

• More than 9000 species

Cnidaria

A Fearsome Tiny WeaponA Fearsome Tiny Weapon More highly organized than sponges; More highly organized than sponges;

most are sessile.most are sessile. Many are effective predators.Many are effective predators. Nematocysts are deadly weapons Nematocysts are deadly weapons

requiring only a small stimulus to fire.requiring only a small stimulus to fire. Can kill even very large prey.Can kill even very large prey.

The “killer” jellyfish

Eumetazoa

Planes of symmetry

spherical radial bilateral

Characteristics of Cnidaria

1.1. All are aquatic and All are aquatic and mostly marine.mostly marine.

2.2. Radial or biradial Radial or biradial symmetry forms oral symmetry forms oral and aboral ends.and aboral ends.

3.3. The polyp and The polyp and medusa forms allow medusa forms allow wider ecological wider ecological possibilities.possibilities.

4.4. The two body types The two body types are the free-are the free-swimming medusae swimming medusae and the polyps.and the polyps.

Characteristics of Cnidaria

5.5. They have a body, with two layers: epidermis and gastrodermis; They have a body, with two layers: epidermis and gastrodermis; 6.6. The gastrovascular cavity has a single opening serving as both mouth and The gastrovascular cavity has a single opening serving as both mouth and

anus.anus.7.7. Nematocysts are in epidermis or gastrodermis and abundant on tentacles. Nematocysts are in epidermis or gastrodermis and abundant on tentacles. 8.8. The nerve net may include some sensory organs.The nerve net may include some sensory organs.9.9. The muscular system has an outer layer of longitudinal fibers and an inner The muscular system has an outer layer of longitudinal fibers and an inner

layer of circular fibers.layer of circular fibers.10.10. Reproduction is either asexual or sexual; a planula larva may be present.Reproduction is either asexual or sexual; a planula larva may be present.11.11. There is no excretory or respiratory system.There is no excretory or respiratory system.

Body structure Body wallBody wall

EpidermisEpidermis Epitheliomuscular cellsEpitheliomuscular cells Interstitial cellsInterstitial cells Gland cellsGland cells CnidocytesCnidocytes Sensory CellsSensory Cells Nerve CellsNerve Cells

GastrodermisGastrodermis Nutritive muscular cellsNutritive muscular cells Gland cellsGland cells

MesogleaMesoglea

Feeding and Digestion Catch food with Catch food with

nematocysts in tentaclesnematocysts in tentacles Mouth opens into Mouth opens into

gastrovascular cavity; gastrovascular cavity; mouth may be mouth may be surrounded by an surrounded by an elevated elevated manubrium manubrium or or oral lobesoral lobes

Cnidarians prey on a Cnidarians prey on a variety of organisms, variety of organisms, often larger than often larger than themselves.themselves.

Digestion is Digestion is extracellular extracellular digestiondigestion, but , but nutritionally, is nutritionally, is intracellular digestion.intracellular digestion.

Locomotion

Hydras can move about freely, but Hydras can move about freely, but colonial polyps are permanently colonial polyps are permanently attached.attached.

Sea anemones can move on their Sea anemones can move on their basal discs; hydras can move by a basal discs; hydras can move by a “measuring worm” motion, or float “measuring worm” motion, or float to the surface on a gas bubble.to the surface on a gas bubble.

Most medusae move freely, or swim Most medusae move freely, or swim by contracting the bell, expelling by contracting the bell, expelling water from the concave oral side.water from the concave oral side.

Cubozoans are strong swimmers.Cubozoans are strong swimmers.

Nervous System

Sensory CellsSensory Cells Mechanoreceptors Mechanoreceptors

(Statocysts, Cnidocilia)(Statocysts, Cnidocilia) PhotoreceptorsPhotoreceptors ChemoreceptorsChemoreceptors

Nervous SystemNervous System No central nervous system No central nervous system

(not necessary)(not necessary) Two nerve netsTwo nerve nets

At base of epidermisAt base of epidermis At base of At base of

gastrodermisgastrodermis

Function: Coordination of Function: Coordination of swimming, tentacle and body swimming, tentacle and body retractionretraction

Reproduction

Asexual reproduction by buddingAsexual reproduction by budding Sexual reproductionSexual reproduction

in hermaphrodite formsin hermaphrodite forms in separate male female formsin separate male female forms

Gametes are shed directly into the Gametes are shed directly into the waterwater

Embryo develops into a free-Embryo develops into a free-swimming planula larvaswimming planula larva

Cnidaria

Class HydrozoaClass Hydrozoa Class ScyphozoaClass Scyphozoa Class CubozoaClass Cubozoa Class AnthozoaClass Anthozoa

Class Hydrozoa Mostly marine and colonial (asexual polyp and Mostly marine and colonial (asexual polyp and

sexual medusa stage) sexual medusa stage)

Some freshwater species (Hydra spec.) without Some freshwater species (Hydra spec.) without medusa stagemedusa stage

CNIDARIA Class Hydrozoa

Portuguese Man-o-Portuguese Man-o-War (War (Physalia Physalia physaliaphysalia))

This is a colony with This is a colony with several types of several types of polyps: gastrozooids, polyps: gastrozooids, gonozooids, and gonozooids, and dactylozooidsdactylozooids

Highly toxicHighly toxicPhoto Copyright © Diane R. Nelson

Class Scyphozoa

Larger jellyfish “cup animals” (up to 2m Larger jellyfish “cup animals” (up to 2m bell diameter, 70m tentacles)bell diameter, 70m tentacles)

E.g. E.g. Aurelia auritaAurelia aurita (moon jellyfish) (moon jellyfish)

Life cycle of Aurelia

Class Cubozoa Medusa is the Medusa is the

predominant formpredominant form In transverse section In transverse section

the bells are almost the bells are almost squaresquare

Strong swimmers and Strong swimmers and voracious predators voracious predators (feeding mostly on (feeding mostly on fish)fish)

Box jellyfish Box jellyfish The sea wasp The sea wasp

(Chironex fleckery)(Chironex fleckery)stings very dangerous stings very dangerous and sometimes fataland sometimes fatal

Class Anthozoa

Polyps with a flower like appearance Polyps with a flower like appearance “Flower animals”, no medusa stage“Flower animals”, no medusa stage

Vary greatly in sizeVary greatly in size All marineAll marine Many are supported by skeletonsMany are supported by skeletons Includes sea anemones, corals (hard corals, Includes sea anemones, corals (hard corals,

soft corals and horny corals such as sea soft corals and horny corals such as sea fans, sea pens and others)fans, sea pens and others)

Sea anemone Larger and heavy Larger and heavy

polypspolyps In coastal watersIn coastal waters Live sometimes Live sometimes

mutualistic with other mutualistic with other animals (e.g. hermit animals (e.g. hermit crabs)crabs)

Feed on fish or other Feed on fish or other live animalslive animals

body contract to small body contract to small size when animal is size when animal is endangeredendangered

CNIDARIA Class Anthozoa

The giant anemone or The giant anemone or purple-tipped purple-tipped anemone (anemone (Condylactis Condylactis giganteagigantea) often ) often harbors cleaning harbors cleaning shrimp among its shrimp among its tentaclestentacles

Common in Bermuda Common in Bermuda and the Caribbeanand the Caribbean

Photo Copyright © Diane R. Nelson

Stony corals

Miniature sea anemones Miniature sea anemones that live in calcareous that live in calcareous cupscups

Epidermis at base of Epidermis at base of column secretes a limy column secretes a limy skeletal cupskeletal cup

Polyps retract into safety Polyps retract into safety of their cup when not of their cup when not feedingfeeding


Close-up of giant star Close-up of giant star coral (coral (Montastrea Montastrea cavernosacavernosa) during the ) during the day with polyps day with polyps retractedretracted

Common in the Common in the CaribbeanCaribbean



Close-up of giant star Close-up of giant star coral (coral (Montastrea Montastrea cavernosacavernosa) with ) with polyps extended at polyps extended at night to feed on night to feed on planktonplankton



Coral Reefs Reef-building corals and coralline algaeReef-building corals and coralline algae Take dissolved calcium and carbonate ions from Take dissolved calcium and carbonate ions from

seawater and precipitate it as limestone (CaCOseawater and precipitate it as limestone (CaCO33) to ) to form reefsform reefs

Mutualistic algae (zooxanthellae) live in tissue and Mutualistic algae (zooxanthellae) live in tissue and are vital to reef-building corals but depend on lightare vital to reef-building corals but depend on light

Reef-building corals rarely live below 30m since Reef-building corals rarely live below 30m since there is not enough lightthere is not enough light

Reefs begin their growth in shallow water around Reefs begin their growth in shallow water around volcanic islands . As the islands slowly sink volcanic islands . As the islands slowly sink beneath the sea, growth of the reef is kept up with beneath the sea, growth of the reef is kept up with the rate of sinking (Charles Darwin)the rate of sinking (Charles Darwin)


Close-up of giant star Close-up of giant star coral (coral (Montastrea Montastrea cavernosacavernosa) during the ) during the day with polyps day with polyps retractedretracted




Close-up of giant star Close-up of giant star coral (coral (Montastrea Montastrea cavernosacavernosa) with ) with polyps extended at polyps extended at night to feed on night to feed on planktonplankton




Aerial view of coral Aerial view of coral reefs in Fijireefs in Fiji

Dark blue on right is Dark blue on right is deep waterdeep water

White is the edge of White is the edge of the reefthe reef

Lighter color is the Lighter color is the reef flatreef flat



Elkhorn coral Elkhorn coral ((Acropora palmataAcropora palmata), ), from the Caribbeanfrom the Caribbean

Wide branches are Wide branches are extended upward, extended upward, catching the sunlight catching the sunlight for the zooxanthellae for the zooxanthellae in the coral tissuesin the coral tissues



Brain coral (Brain coral (Diploria Diploria strigosastrigosa), common in ), common in Bermuda and the Bermuda and the CaribbeanCaribbean

Healthy coral is Healthy coral is golden-brown due to golden-brown due to the presence of the presence of symbiotic symbiotic zooxanthellaezooxanthellae



Coral aggression Coral aggression between two stony between two stony corals in Bermudacorals in Bermuda

Montastrea annularisMontastrea annularis (top) and (top) and Diploria Diploria strigosastrigosa (bottom) (bottom) compete for space, compete for space, leaving a dead zone leaving a dead zone (white) between them(white) between them



Extended slender Extended slender polyps of the stony polyps of the stony coral coral GonioporaGoniopora sp., sp., found in Fiji and the found in Fiji and the western Pacificwestern Pacific

Polyps are extended Polyps are extended during the dayduring the day



Orange cup coral Orange cup coral ((Tubastraea coccineaTubastraea coccinea) ) from Bonaire in the from Bonaire in the CaribbeanCaribbean

These ahermatypic These ahermatypic corals extend their corals extend their polyps at night to feed polyps at night to feed on planktonon plankton



Brain coral (Brain coral (Diploria Diploria strigosa)strigosa) in Bermuda, in Bermuda, with black band with black band diseasedisease

The black line marks The black line marks the cyanophyte alga the cyanophyte alga ((Phormidium Phormidium corallyticumcorallyticum) that kills ) that kills the coral colonythe coral colony



Coral bleaching in star Coral bleaching in star coral (coral (Montastrea Montastrea annularisannularis) in the ) in the CaribbeanCaribbean

Loss of zooxanthellae Loss of zooxanthellae due to higher water due to higher water temperatures results in temperatures results in lighter color lighter color


PHYLUM CTENOPHORA

1.1. This phylum has fewer than 100 species.This phylum has fewer than 100 species.2.2. All are marine species; most prefer warm waters.All are marine species; most prefer warm waters.3.3. Ctenophores have eight rows of comblike plates for Ctenophores have eight rows of comblike plates for

locomotion locomotion 4.4. Like cnidarians, they have primary radial symmetry.Like cnidarians, they have primary radial symmetry.5.5. No nematocysts!No nematocysts!6.6. Nearly all are free-swimming; only a few creep or are Nearly all are free-swimming; only a few creep or are

sessile.sessile.7.7. They use the ciliated combs to propel themselves forwardThey use the ciliated combs to propel themselves forward8.8. Many are bioluminescent.Many are bioluminescent.

Phylum CTENOPHORA (Comb jelly fish) Tentacles secrete sticky substance Tentacles secrete sticky substance

(colloblast cells) to catch small (colloblast cells) to catch small preyprey

When covered with food they When covered with food they contract and food is wiped onto contract and food is wiped onto the mouththe mouth

Gastrovascular cavity with Gastrovascular cavity with pharynx, stomach and canalspharynx, stomach and canals

Sensory cells and radial nerve netSensory cells and radial nerve net

Locomotion by cilia beating Locomotion by cilia beating (comb plates = fused cilia)(comb plates = fused cilia)

hermaphroditeshermaphrodites

CTENOPHORAClass Tentaculata

Comb jelly from Comb jelly from Roatan, HondurasRoatan, Honduras

Does not sting since it Does not sting since it has no nematocysts as has no nematocysts as in cnidarians in cnidarians

BioluminescentBioluminescent


CTENOPHORAClass Nuda

Nuda is a class of Nuda is a class of ctenophores or comb ctenophores or comb jellies. jellies. Contains a single family, Contains a single family, Beroidae, with two genera, Beroidae, with two genera, Beroe and Neis, and the Beroe and Neis, and the group is more commonly group is more commonly referred to as the “ beroids”referred to as the “ beroids”

Science

Zoology