Download PORIFERA _ CNIDARIA - Doral Academy Preparatory

PORIFERA & CNIDARIA
Tissue Levels of organization
Origins of Multicellularity
• Multicellular organisms first appeared 600 million years
ago
• Arose quickly 100 million years prior to the cambrian
period
• Two hypothesis on the origin of multicellularity
– Colonial hypothesis- cells of a dividing protist remained
together, cell invagination formed two cell layers, supported by
the colonial organization of some protozoa with radial symmetry
– Syncytial hypothesis- a large multinucleated protista developed
plasma membranes separating into multiple cells, multinucleate
bilateral ciliates support this hypothesis
• Animal kingdom is monophyletic and the most likely
protista ancestor is the Choanocyte ( collar cell )
Phylum Porifera
• Sponges- mostly marine animals consisting of loosely
organized cells
• No tissues or organs, 9000 species, Asymetrical or
radially symmetrical, Sessile
• Filter feed by a series of canals and chambers thru
body wall where water circulates
• Three Classes
– Calcarea- Calcium carbonate spicules, 3-4 rays
– Hexactinellida – Silica spicules, 6 rays, deep water sponges
– Demospongia- Brillantly colored, Siliceous spicules, needle
or 4 rayed or spongin or both, Bath sponges
CALCAREA
HEXACTINELLIDA
DEMOSPONGIA
Sponge Anatomy
• Simple but more than colonies of independent cells
• Division of labor- cells specialized for particular
functions
• Pinacocytes- flat cells line outer surface, can change
shape ( contraction ), can regulate water circulation
• Mesohyl- Jellylike layer, contains Ameboid cells which
are specialized for reproduction, secrete spicules,
Transport and store food, form contractile rings
• Choanocytes ( collar cells)- flagellated cells with a collar
like ring of microvilli forming a mesh, Line inner
chambers
CHOANOCYTES
Water Currents and Body forms
• Water currents created by Choanocytes beating
their Flagella bring food and oxygen, carry away
wastes
• Food consists of bacteria, microscopic Algae,
protists, and suspended organic matter, some
deepwater sponges capture small crustaceans
using spicule covered filaments
• Large populations of sponges help reduce turbidity
of coastal waters
• Pinacocytes in incurrent canals may phagocytize
larger food particles
• Sponges absorb dissolved nutrients from seawater
by active transport
Body forms
– Ascon- Simplest, Vase shaped, Outer opening ostia
lead to spongocoel chambers and then osculum
inside exit
– Sycon- Folded body wall, water enters thru dermal
pores to incurrent canals then to radial canals with
choanocytes, exits to spongocoel and out osculum
– Leucon- Extensively branched canal system, water
enters thru ostia to branched canals to choanocyte
lined chambers, multiple exit points osculum
Body Functions
• No nerve cells so reactions result from cells
responding to a stimulus
• Water circulation minimal at sunrise and
maximum at sunset, light inhibitits
constriction of pinacocytes
• Water circulation can cease suddenly,
choanocytes stop together
• Internal communication is present by chemical
messages
Reproduction
• Most sponges Monocious, both sexes, no self
fertilization, produce egg and sperm at different times
• Some choanocytes can loose collar and flagella, or
ameboid cells undergo meiosis and form sperm or eggs
• Choanocytes capture sperm and transport it to egg,
early development in mesohyl, Flagellated larva
blastula released, 2 days settles to bottom, turns inside
out
• Asexual reproduction, release gemmule capsules of
ameboid cells, Fragmentation of adult
GEMMULE
Sponge Ecology
• Few animals feed on sponges, few bony fish,
molluscs and Hawksbill sea turtles feed almost
exclusively on sponges.
• Many species of sponge contain cyanobacteria
in their bodies, sponge provides protection
and sunlight and get nutrients and oxygen in
return
• Boring sponges burrow into coral and mollusc
shells to hold on, return calcium to seawater
Cnidarians
• Radial or Biradial symmetry, no anterior or
posterior, direction based on mouth position,
oral mouth and aboral opposite
• Over 9000 species mostly marine, important
ecosystems ( coral Reefs )
• No Brain, nerve net system
• Gastrovascular Cavity
• Diploblastic tissue layers, Epidermis and
Gastrodermis, mesoglea (jelly) in between
Cnidarian Anatomy
• Ectoderm, epidermis- protection, food
gathering
• Endoderm, gastroderm- coordination,
movement, digestion, absorption and
reproduction
• Mesoglea- Jelly Layer, May be noncellular or
contain wandering mesenchyme cells.
Cnidocytes
• Found in epiderm and gastroderm, 30 types
• Used for attachment, defense and feeding
• Cnidia- fluid filled intracellular capsule attached
to a hollow tube
• Operculum- lidlike cap on cnidia
• Cnidocil- modified cilium trigger discharges
harpoon using water pressure
• Nematocyst- harpoon, uses spines-barbs and
long tube to inject paralyzing toxins into prey,
ejects from cell by inverting like a sweater sleeve
CNIDOCYTES
Scyphozoa
• All marine, “True Jellyfish” because dominant
stage in life is Medusa
• Mesoglea contains ameboid cells
• Cnidocytes in gastrodermis and epidermis
• Most harmless to Humans others can cause
painful stings
• Gastrodermal cells possess cilia to circulate
seawater and digested food
Scyphozoa
• Aurelia Libiata- very common Atlantic and Pacific
• A plankton feeder, cilia on bottom carry food to
mouth
• Mouth leads to 4 gastric pouches then to radial
canals out to margin of bell
• Rhopalium (notches) along bell contain olfactory
sensory pits, statocyst and photorecptors
• Exhibits distinct phototaxis
SCYPHOZOANS
Hydrozoan
• Small common cnidarians, some freshwater
• Usually anchor to bottom substrate, Polyp
stage dominates in most
• Nematocysts only in epidermis
• Gametes epidermal released outside body
• Mesoglea acellular
• Many have colonial polyps, specialized for
feeding, budding, or defending the colony
HYDROZOAN
Cubozoan
• Medusa is cuboidal, tentacles hang from each
corner of bell
• Active swimmers and feeders
• Polyp stage very small or absent
• Warm tropical waters
• “Box Jellyfish” or “sea Wasp” (Chironex
Fleckeri)seasonally abundant in Austrailian waters
• Contains photoreceptors
CUBOZOAN
BOX JELLYFISH STINGS
Physailia, Hydrozoan
• Portuguese man-of-war, large gas sac up to 12
inches acts as a float, filled with CO2, developed
from larval polyp
• Floating colony of specialized cells, individuals
• Feeding polyps- have single long tentacle used for
digestion
• Fishing polyps- tentacles with stinging cells
capture prey
• Modified medusa-contain ovaries and testes for
reproduction
PORTUGUESE MAN OF WAR
PORTUGUESE MAN OF WAR
PORTUGUESE MAN OF WAR STING
Anthozoa
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•
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Include Anemones, and Stony and soft corals
Are colonial or solitary and lack Medusa
Cnidocytes lack cnidocils ( triggers )
Mouth leads to pharnyx then gastrovascular
cavity
• Mesenteries divide gastrovascular cavity into
sections
• Mesoglea contains ameboid cells
• Externally show radial symmetry, internally
biradial
Sea Anemones
• Solitary or large colorful colonies
• Attach to solid substrate, some burrow in
sand, some symbiotic relationships
• Attaches to substrate with pedal disk
• Oral disk contains mouth and tentacles
• Slitlike mouth ends have siphonoglyph
“ciliated tract” to move water into
gastrovascular cavity for hydrostatic skeleton
Sea Anemones cont.
• Locomotion by gliding on their pedal disk,
crawl on sides, walk on tentacles, some swim,
some float with bubble in pedal disk
• Feed on invertebrates and fish
• Large species of anemone form symbiotic
relationships with Clown Fish, clown fish
attracts other fish, keeps anemone free of
sediment, fecal pellets from clown fish nourish
anemone, ventilate anemone with movement
ANTHOZOA
Stony and Soft Corals
• Similar to Anemones, lack siphonoglyphs
• Calcium carbonate cup exoskeleton secreted by
epithelial cells, polyps retract into cup when
threatened
• Symbiotic relationship with photosynthetic
dinoflagellate Zooxanthellae Algae
• Coral provides nitrogen and phosphorous for the
Algae and get carbon compounds in return
• Zooxanthellae promote calcium carbonate
deposition
Stony and Soft Corals
• Cover 0.17% of ocean bottom hold 25% of
oceans species
• Environmental disturbances, warm water,
stress corals causing them to loose
zooxanthellea and bleach
• Stony corals are connected to each other
under the cup, can share food
• Florida and Bahama reefs are 60% degraded
ANTHOZOA CORALS
Ctenophora
• Comb Jellies, Eight bands of cilia from oral to
aboral sides for locomotion
• Mesoglea is highly cellular, muscle cells
contained here, may be triploblastic
• Tentacles contain colloblasts adhesive cells to
capture prey, wipe tentacles across mouth
CTENOPHORA
Coral Reefs
• Sponge and Jellyfish fossils are found in the
oldest fossil deposits, the Ediacaran Formation
• Coral Reefs are one of the most endangered
habitats on earth
• Coral covers 0.17% of the ocean and yields
10% of the fish caught
• Contribute $375 Billion to the worlds economy
• Corals grow very slowly, are disturbed easily
Coral Reefs
• formed from hard and soft corals, coralline red
algae and calcified green algae as well as sponges
• Hard coral polyps reproduce by budding, each
polyp remains attached to the parent by thin
tissue
• The colony grows upward and outward in layers
and assumes genetically determined shape, some
polyps develop gonads for sexual reproduction