PORIFERA CNIDARIA Tissue Levels of organization Origins of

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 CO 2, 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

Glaucus Atlanticus

PORTUGUESE MAN OF WAR STING

Anthozoa 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

Coral Destroyers • Ocean Acidification, sediments (Turbidity), Dredging and construction, • Coral mining for decoration and building material, • dynamite fishing, clorox lobstering, Boat anchoring, • Runoff from land- Cars leaking oil, chemicals from factories, fertilizer from farms and golf courses • Global warming increasing ocean temp

Coral Savers • Marine parks and sanctuaries • Construction barriers to prevent sediment runoff • Permanent moorings for boats • NSU and UM have coral restoration programs to grow and replant broken pieces

Coral Savers • U. S. - Artifical reef programs- sinking old ships offshore, dumping concrete from deconstructed bridges, large pipes • Cayman Islands- Marine protection zones, areas along shoreline where you cannot enter. Serves as a place for fish corals to regenerate • Japan- Research into what juvenal fish prefer, design concrete structures with appropriate sized holes and depth