2 2. Cnidarians Next evolutionary jump Sometimes called coelenterates Cells form tissues that perform specific functionsSometimes called coelenteratesInclude sea anemones, jellyfish, and corals
3 Cnidarians: Structure Finally, we see a pie that can be sliced!Cnidarians actually exhibit radial symmetryin which similar body parts can be grouped around a central axis.If cut like a pizza, all slices would be similarLook the same from all sidesNo head, front, or back
5 Cnidarians: Structure and Function Oral surface and aboral surfaceCentral mouth with tentaclesMouth open into a gut (only one opening)Capture prey with nematocysts (stinging structures found within tentacles)When cells are touched, water pressure causes nematocysts to protrudeCnidocytes – cells which contain nematocysts
6 Discharged nematocysts, stingingcells used for defenseand prey capture, have beenthe plague of more than fish.Stings from certain jellyfishhave resulted in death in amatter of hours, especiallyfor infants.
7 Carukia barnesi: the badest of the bad! Irukandji syndrome:A sting from this little guy can cause the following:“It begins with a mild sting, followed by severe lower back pain,muscle cramps in arms, legs, stomach and chest. It causes sweating,anxiety, nausea, vomiting, headaches and palpitations, and has alsobeen known to cause cardiac failure.”
8 Cnidarian: Structure and Function Feeding and DigestionCarnivoresUse nematocysts to capture preyEach contain fluid filled capsule containing thread that is ejectedMay be spines or long tube that wraps around preyToxic
9 Cnidarian: Structure and Function Feeding and DigestionExtracellular digestion – outside of the cellsIntracellullar digestion – within cells in the lining of the gut
10 Cnidarian: Structure and Function BehaviorLack brain and true nervesNerve cells interconnect forming nerve net that transmits impulses in all directionsSea anemones can tell if other member is from same cloneKnown to attack and even kill anemones from other clones
11 Cnidarian: Structure and Function BehaviorSome medusae have primitive eyesMedusae have statocysts, small calcareous bodies in fluid-filled chambers surrounded by sensitive hairs, to help with balance
12 Cnidarians: Structure and Function 1. Polyp: a sac-like attached stage with a mouth and tentacles (mostly sessile)2. Medusa: a mobile bell-like upside down polyp (jellyfish).
13 Cnidarians: Structure and Function Larva is called planula, ciliated stage with two cell layersSettles and metamorphoses into a polyp or develops into medusa
15 Cnidarians: Structure and Function Two layer of cells form body wall; one is epidermis (“skin”) and other is gastrodermis (gut lining)Gelatinous middle layer is mesoglea, does not contain cellsIn medusa this layer expands to form gelatinous domed bell
17 Types of Cnidaria Cnidaria come in all shapes and sizes. Sea fanCnidaria come in all shapes and sizes.Hydrozoans- feathery hydroidsScyphozoans- large jellyfishAnthozoan-sea anemones and coralMost of the animals found within Cnidaria are all carnivores.
18 Cnidarian Types Hydrozoans (class Hydrozoa) Feathery or bushy colonies of tiny polyps attached to pilings, shells, seaweeds, and other surfacesPolyps may be specialized for feeding, defense, or reproductionReproductive polyps produce minute, planktonic medusae
19 Cnidarian Types Hydrozoans (class Hydrozoa) Medusae release gametes & fertilized eggs develop into free swimming planula larvaeEach planula larvae settles and develops into a polypThe poylp divides repeatedly and develops into a colonySome lack poylp stage and develop into a medusaeFew lack medusae stage and develop into gamete producing polyps
21 Cnidarian Types Scyphozoans (class Scyphozoa) Larger jellyfish Large medusae are dominate stage in life cyclePolyps small & release juvenile medusaeFew lack polyp stageBell diameter ranges from 2-3 meters, depending on water depth
22 Cnidarian Types Scyphozoans (class Scyphozoa) Swim with rhythmic contractions of bell but easily carried by currentsSome species stings range from rash to fatalitiesCubomedusae once classified as Scyphozoa now in own class Cubozoa (box jelly)
23 Cnidarian Types Anthozoans (class Anthozoa) Anemones and corals Solitary or colonial polyps that lack medusae stageLargest number of speciesPolyps are more complexGut contain septa increasing surface area for digestion of large preySepta provide support for larger speciesSea anemones have large polyps
25 Cnidarian Types Anthozoans (class Anthozoa) Corals – colonial anthozoansCarbonate skeletonsOccur in cold waters; tropical waters form reefsGorgonians (sea fans) secrete branching skeleton made of proteinPrecious corals gorgonians are fused with red or pink calcareous spicules in addition to protein skeletons
27 Cnidarian Types Anthozoans (class Anthozoa) Black Corals secrete hard, black protein skeletonUsed for jewelry
28 3. Comb jellies: Ctenophora Similar to cnidarians in mostrespects.Nearly 100 spp.- all marineContain ciliary combs whichassist in prey capture and mobility.
29 3. Comb jellies: Ctenophora Gelatinous body with 8 rows of combs that beat in wavesBeating of combs refracts light creating multicolor effectBody length range from few millimeters to 2 m
30 3. Comb jellies: Ctenophora Found in warm and cold watersCarnivoresSwarms consume large numbers of fish larvae and other planktonCapture prey with long tentacles with colloblasts (sticky cells)Few have nematocysts