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Home , Cnidaria, Starfish

often beautiful and graceful “-like” or “flower- (= & ) like” forms with one or more rows of large extending from body

9,000 living, 9,300 like , ancient scholars considered them some kind of

plant include: jellyfish not considered until 1700’s sea anemones corals but some (eg. jellyfish) swim weakly as part of the sea fans sea whips another very ancient group with lots of fossil though sessile almost all are extremely effective representatives predators

longest fossil history of any jellyfish are among the longest of animals up to 9’ diameter with 120’ tentacles known are even more ancient than sponges some colonial forms can grow up to 150’ long

going back at least 700 M as a , they rank as some of the longest – lived (plenty of hard parts – corals) animals on earth

in terms of evolutionary history they were the 1st eg. a gold colony off the coast of was recently animals to appear that had a definite shape (2009) dated at 2742 years old

eg. a in the same area was dated at 4265 years old all known animals at that time were sessile ; cnidaria (jellyfish) may have been all are aquatic the first animals to swim widespread in radial ! especially shallow , warmer most members of the phylum (eg. corals) are sessile a few found in freshwaters

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 1 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 2

tubular body all but 1 of fw cnidarians are polyps usually sessile – though some can move

but there is one small fw jellyfish: upward facing mouth surrounded by tentacles many are colonial medusa umbrella shaped ! groups of individuals usually living together and interconnected eg corals mouth facing downward often, thick jelly-like layer in body wall eg. a single coral colony can contain millions of individuals ! jellyfish motile: contractions of “bell” tissue level of organization free floating, pelagic planktonic

more complex than sponges but still very simple medusa

do have true tissues sessile motile asexual sexual only a few very simple organs benthic pelagic

Cells & Tissues Body Forms

two true tissue layers, not the 3 typical of many cnidarians are polymorphic animals

! with 2 or more separate body forms =diploblastic

epidermis & gastrodermis with an alternation between forms

2 well defined germ layers: !the same species has 2 distinct forms endoderm polyp (=) become two adult tissues medusa (=jellyfish) epidermis gastrodermis polyp

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 3 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 4 between the two tissues is a jelly layer called most epidermal cells contain contractile fibers and act like muscle cells to produce movement

! very thick in “jellyfish” Cells of Epidermis:

nontissue layer of mesoglea in between a. epitheliomuscular cells covers outside of body in a few species this mesoglea is replaced by 3rd tall T shaped, columnar cells true tissue: base elongated with myofibrils muscular contractions ! b. interstitial cells Body Wall undifferentiated cells can form , cells, sex cells, etc but not epitheliomuscular cells epidermis – tissue layer that lines outer surface c. gland cells around basal disc and mouth mesoglea – jellylike middle layer; not tissue layer secretes and adhesives those in basal disc can secrete gas bubble for floating gastrodermis – tissue layer that lines GVC d. cnidocytes stinging cells, more later 1. Epidermis e. sensory cells outer “skin” of the animal scattered but especially near mouth and tentacles respond to chemical and tactile stimuli

consists of cells that cover and protect f. nerve cells most multipolar (3 or more processes) also contain special stinging cells form synapses with sensory cells and other nerve cells connect to epitheliomuscular cells and cnidocytes

some areas also have gland cells for attachment 2. Mesoglea

contain nervous and sensory cells not really a tissue layer, just a layer of jelly-like

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 5 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 6

very thin layer in polyps; much thicker in medusa cavity in which it thus “jellyfish” muscle layers in body wall contract against 3. Gastrodermis hydrostatic

inner lining of the digestive sac some polyps of noncolonial forms are motile

mademostly of cells that digest and absorb food eg. fw hydras are not permanently attached ! can glide on pedal disc ! inchworm movements using tentacles these cells also contain contractile fibers for ! gas bubbles and float to surface movement medusae are more mobile Cells of Gastrodermis: have a. nutritive muscular cells tall T shaped, columnar cells ciliated controls contractions of bell for base elongated with myofibrils swimming lines GVC in some freshwater species cells contain green algal symbionts Feeding and in some marine species cells contain algal symbionts all are

b. Interstitial cells scattered most species have one or more rings of tentacles transform into other cells as needed, see above surrounding mouth

c. gland cells in hypostome and scattered throughout armed with cnidocytes (=stinging cells) for some secrete digestive capturing prey mucous glands around mouth

Stinging Cells (cnidocytes) Movement

one of the most characteristic features of the typically polyp is sessile and often secretes a cup like phylum Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 7 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 8 most are not harmful to humans used for feeding and defense eg. most sea anemones stings are harmless inside each is harpoon-like nematocyst but a few are very painful ! highly coiled tubular thread !contained within a capsule like eg. Portuguese Man-O-War and some corals

! triggerlike cnidocil (tactile trigger) a few can be fatal

when triggered can fire in a fraction of a second eg. cubomedusae (box jellies)

discharge due to: digestive system is a mouth that opens into a saclike cavity high osmotic pressure within (140 atm; 10x’s sea level) when stimulated to discharge rushes in = lined with gastrodermis forces thread out with great force – turns inside-out as it extends at 2m/sec causes barb to flick out like tiny switchblades to impale prey single opening = mouth

each cell operates independently incomplete digestive tract ! mouth only

digestion mostly extracellular, but some intracellular can differentiate between animate and inanimate objects most are predatory

! doesn’t just fire at anything use cnidocytes to capture and paralyze prey use tentacles to move prey toward mouth cnidoblast must grow new nematocyst after firing engulf prey with mouth

over 20 different kinds inside GVC gland cells secrete digestive enzymes

some wrap around prey or are sticky nutritive muscular cells take in particles by some with tiny barbs that impale prey & inject poison pseudopodia

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 9 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 10

completes the process at margins of bell often between lappets indigestible material is expelled through mouth contains ocelli ! detect light ! balance organs sensory pits ! chemoreceptors No respiratory or Coordination and Control both sexual and no head, no , no CNS asexual: very simple , no asexual reproduction usually by

= nerve net if buds remain connected = colonial mostly for coordinating contractions in body fission sea anemones only diffuse network of nerve fibers connect to: pedal laceration sensory cells cnidocytes sexual: epitheliomuscular cells most are dioecious nutritive muscular cells many shed into water gonads are epidermal in some simple sense organs: gonads are gastrodermal in other groups statocysts ! balance ocelli ! light little is know of lifespans but one kept in an lived for 80 years until the tank polyp was accidentally drained simple sensory cells scattered in epidermis some jellyfish can live up to 10 years medusae clusters of sense organs = rhopalium Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 11 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 12 in marine species is usually a Classification in many members of the group there is an : Hydrozoa alternation of generations between most are marine, a few are freshwater individuals usually small and inconspicuous polyp which reproduces asexually and the polyp is dominant stage, some completely lack medusa medusa when present has velum around margin medusae which reproduces sexually no septae in GVC, no pharynx (=throat), no cells in mesoglea most are colonial - small plant-like appearance most have with alternation of generations

Class: (true jellyfish)

most of the larger jellyfish belong to this group medusae without velum, cells in mesoglea all are marine solitary polyp stage reduced or completely absent thick jelly layer (=mesoglea)

Class: Cubomedusa (, sea wasps)

cubical jellyfish with extremely potent toxins - some lethal

Class: (Corals and Sea Anemones)

=”flower animals” all are marine polyp only; no medusa stage many cells in mesoglea polyp with septae and pharynx some are solitary = sea anemones, usually larger most are colonial = corals, polyps usually small most secrete skeleton of or

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 13 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 14

A. Class Hydrozoa usually mature 1 at a time eggs fertilized by , then shed cyst forms around embryo – overwinters most are marine, a few are freshwater no larval stage young hydras hatch from cyst in spring some are colonial eg. common in nearshore marine habitats most have polymorphism with alternation of generations more representative of class

have both polyp and medusa stage polyp is dominant stage colonial hydrozoan ! interconnected hydroid colony some, eg , lack medusa stage attaches to substrate by rootlike hydrorhiza colonial species often have more than two body forms branching body = hydrocaulus in same living tissue = coenosarc

different forms act like separate organs and chitinous protective covering = perisarc are specialized for feeding, stinging, reproduction attached to hydrocaulus are individual polyps

two types of polyps: eg. Hydra (hydra)

freshwater species 1. hydranths = feeding polyps very common in ponds and creeks tubular or vaselike feeds on small mouth surrounded by tentacles seems to “prefer” Daphnia capture and ingest prey: worms, crustaceans, no medusa stage larvae ! polyp reproduces both asexually and sexually provide nutrition for whole colony asexual: ! digested broth passes thru common GVC budding as outpockets of body wall of whole colony continuous GVC cilia of nutritive muscular cells move it eventually detach

sexual: 2. gonangia = reproductive polyps dioecious ovaries or testes are temporary no tentacles organs on side of polyp medusa bud off sides usually appear in autumn (low temp, low O ) 2 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 15 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 16 medusae B. Class Scyphozoa (true Jellyfish) produced by gonangia small; 2-3mm velum surrounds inside of bell margin most of the larger jellyfish belong to this group mouth at end of manubrium a few up to 2 m in diameter radial canals extend from GVC to margins of bell and ring canal GVC also extends into tentacles from ring canal contains one of the longest animals; lion’s mane jellyfish ! over 120’ eg. Craspedacusta all are marine the only freshwater medusa hydroid colony is microscopic in size; <2mm medusa .5 – 1” in diameter with few or many tentacles around margin of bell eg. Physalia (Portuguese Man-O-War) medusa stage is dominant colonial hydroid form irridescent purple color solitary polyp stage reduced or absent common on gulf coast can produce painful sting even if dead but with several different kinds of polyps thick jelly layer (=mesoglea) float = swimming bell filled with gas may contain amoeboid cells and fibers gastrozoid polyps = each with single long dactylozoids = fishing tentacles gonophores = sacs of ovaries or testes medusa has no velum

a symbiotic , Nomeus, swims among the tentacles Movement

jellyfish are the most motile members of the phylum

more complicated muscle layers:

muscles arranged in radiating and circular bands

contractions of these muscles allow the organism to propel itself to some degree

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 17 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 18

still, jellyfish are considered part of the zooplankton (the largest members) since they are not strong enough Nervous system & senses swimmers to go against the current watching some jellyfish swim looks like they’re not since jellyfish are motile their sense organs are going anywhere better developed than other members in the phylum but contractions of bell creates water currents that draw food through tentacles and toward mouth ! its not ‘trying to go anywhere’ jellyfish in this class have a greater variety of sense organs than other jellyfish in a few species the medusa is sessile and spends its laying upsidedown on the scalloped margins of bell with indentations bearing lappets and rhopalia Feeding with ocelli, statocysts and sensory pits mouth hangs down under umbrella on the end of a throat-like manubrium reproduction & life cycle:

GVC extends into radiating canals or pouches medusa stage is the sexual stage

all jellyfish are carnivorous polyp is asexual stage buds off small medusa they eat mostly zooplankton, smaller fish and other jellyfish jellyfish life cycle: medusa

larger ones may eat shrimp and other ephyra planula crustaceans strobila scyphistoma jellyfish are eaten by spadefish, sunfish and loggerhead turtules many jellyfish live less than a

only a few dozen of the 500 or so species of but a few species live up to 10 years jellyfish are dangerous to humans Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 19 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 20 eg. (moon jelly) the most poisonous sea creatures known

common off Texas coast since 1884, it has killed more people along the northern Australian coast than have sharks in the 7-10 cm diameter; some up to 2 feet area scalloped margin with indentations bearing lappets and rhopalium with ocelli, statocysts and sensory pits mouth on manubrium drawn out into 4 frilly oral arms feeds on small planktonic organisms

male releases sperm threads into water

female collects and eats them to fertilize eggs

eg.

eg. Lion’s mane jellyfish

one of largest can be 8’ in diameter tentacles can extend to 200’

C. Class Cubozoa (box Jellyfish, sea wasps)

poorly known group

once considered as a group of scyphozoa

medusa is dominant form, polyp is inconspicuous

most are relatively small; <1”

tentacles are at each corner of cubical bell

eg. sea wasp ( fleckeri)

ranges from Indian to coral sea

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 21 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 22

D. Class Anthozoa (Corals and Sea Anemones) pores in body wall to help catch prey =”flower animals” 3 major groups in class: all are marine 1. sea anemones and stony corals 2. sea fans, sea pansies, sea pens, soft corals !range from deep to shallow water 3. tube anemones and thorny corals

some are solitary = sea anemones, usually larger eg. anemones

especially common in tropical waters most are colonial = corals, polyps usually small much larger than their coral relatives; some 3’ dia polyp only; no medusa stage mostly sessile, but some can glide on pedal disc

GVC large some form interesting mutualistic relationships with other organisms muscular infolding of mouth = pharynx almost every specimen is a host to a variety of fish and other animals (shrimp, crab, fish) GVC partitioned by septa (=mesenteries) immune to the lethal stinging cells

mesenteries can be complete or eg. clown fish incomplete over 50 species of fish associated with anemones (also some shrimp) free edge of incomplete septae form fish symbionts are stung on first contact (on tail septal filaments with nematocysts or nonvital body part)

in some, lower septal filament prolonged ! then body mucous or slime is chemically altered so the fish is not affected by into acontia further stings

also with nematocysts must continually refresh mucus layer

eg. – ! can be extruded thru mouth or Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 23 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 24 eg. sea pens, sea pansies, sea fans, whip corals, pipe corals eg. attach to shells of hermit crabs toxins from soft corals, reproduce by fragmentation; they leave pieces behind as ! used as antitumor medication they move sea whips & sea pens eg. hard corals (stony corals) sea fans colonial polyps eg. tube anemones produce rock-like cups (=theca) secrete tubes secreted by lower half of polyp

= for support and protection

form extensive structures in warm shallow waters

reef structure consists of compressed & welded together: calcium carbonate coral encrusting coralline algae foraminiferan shells bivalves plates

continually destroyed by:

sponges, worms & bore into reef

waves reduce it to white

crown of thorns () feeds on polyps and decimates populations

highly resilient communities ! regenerate quickly eg. soft corals ()

secrete a flexible of spicules or keratin-like protein

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 25 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 26

Ecological Interactions fish symbionts are stung on first contact (on tail or nonvital body part)

1. most are aggressive predators ! then body mucous or slime is chemically altered so the fish is not affected by further eg. a single lions mane jellyfish was found with >200 fish within stings its tentacles must continually refresh mucus layer many jellyfish species congregate into large swarms of up to 1000’s of individuals and can devastate prey in an area eg. most corals are mutualistic with

-often triggered by eutrophication zooxanthellae (dinoflagellate algae)

2. also prey for a variety of specialized predators 4. Coral Reefs (see separate set) eg. parrot fish, butterfly fish, tangs eat coral polyps

eg. sea like jellyfish

unfortunately many are suffocated by eating plastic bags floating in the ocean

eg. a number of sea slugs (nudibranchs) eat them but store unfired nematyocysts in their skin and use them for defense

3. numerous symbioses within this phylum

many live as commensals on shelled animals

eg. anemones form interesting mutualistic relationships with other organism

eg. decorator crabs

eg. clown fish (immune to nematocysts)

over 50 species of fish associated with anemones (also some shrimp)

Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 27 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 28 Economic Importance: 5. a green fluorescent protein extracted from jellyfish 1. in orient a few jellyfish are eaten (also found in fireflies) and used to build tiny fuel cells which could be useful in powering eg. people in China and Japan eat the mushroom jellyfish; fresh nannodevices used to diagnose and treat diseases or pickled in the body 2. stinging cells of some cnidaria are lethal to humans 6. in 1991 2500 moon jellies flew aboard the eg. box jelly or sea wasp () Columbia space shuttle

from Indian ocean to coral sea - esp around coast of to study how their balance organs develop under Australia weightlessness can have up to 60 tentacles as long as 15 feet.

most poisonous sea creature known

stings can kill a human in 5 minutes

each has enough toxin to kill 50 humans

since 1884 at least 5,567 deaths have been attributed to these creatures.

3. Pharmaceuticals

anti-inflammatories, painkillers for arthritis, antimicrobials

cardiac stimulant from sea anemone

4. in clinical trials (2009) is a process developed to harvest stinging cells, remove their and then use them to inject painkillers or insulin into the skin Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 29 Animals: Phylum Cnidaria; Ziser Lecture Notes, 2012.9 30