Phylum Porifera

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Phylum Porifera
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Porifera Characteristics

• Freshwater and marine
• Simplest of all animals
• Asymmetrical
• No systems for repro, digestion, respiration,
  sensory, excretion

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Porifera Characteristics

• 5,500 extant species
• Highest abundance in unpolluted littoral and
  tropical reefs
• 75 benthic biomass

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Porifera Characteristics

• Sessile (Adults)
• Suspension-feeders (Adults)
• Multicellular
• Flagellated cells choanocytes circulate water
  through water canals
• No tissues
• Cells totipotent

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Porifera Characteristics

• Outer and inner cell layers lack basement
  membrane
• Middle layer (mesohyl) has motile cells and
  skeletal material
• Skeletal elements (when present) are calcium
  carbonate, silicon dioxide and/or collagen fibers

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Taxonomy and classification

• Taxonomy based on skeletal elements
• Now embryological, biochemical, histological, and
  cytological methods to diagnose sponge taxa

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Three classes (Calcarea, Demospongiae,
Hexactinellida)

• Class Calcarea Calcareous sponges
• Shallow, tropical water, near shore

Leucetta
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Class Calcarea

• Spicules calcium carbonate
• Calcarean spicules lack hollow canals strong

Clathrina
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Class Hexactinellida (Glass sponges)

• Silica spicules
• Spicules join at right angles, sponge appears
  artificial

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Class Demospongiae (Demosponges)

• Largest and most diverse class of sponges, 90
  percent of sponges
• Spicules either spongin, an organic substance or
  silica, a mineralized substance

• Oscarella

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Class Demospongiae

• Genera Adocia, Halisarca, Myxilla

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Aquiferous system

• Brings water to cells
• 1 x 10 cm sponge pumps 22.5 l water daily
• Large sponge filters body mass every 10-20 s

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Sponges are single individuals

• Grow by continually adding cells that
  differentiate as needed

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Body structure and aquiferous System

• Outer layer
• Perforated by small holes - dermal pores or ostia
• Choanoderm innermost layer of flagellated cells
  choanocytes
• Mesohyl middle layer

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Body structure 3 shapes
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Asconoid sponges

• Asconoid one-cell thick choanoderm is simple and
  continuous
• 10 cm height
• Thin walls enclose central cavity atrium opens
  outside via osculum
• Pinacoderm has specialized cells porocytes
• External opening of porocyte canal is ostium or
  incurrent pore

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Asconoid sponges
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Syconoid sponges

• Syconoid choanoderm folded
• Mesohyl two layers thick
• Outer region is cortex (contains skeletal
  material)

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Leuconoid Sponge

• Leuconoid choanoderm subdivided into separate
  flagellated chambers

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Flow rate

• Flow rate not uniform throughout
• Water must move slowly over choanoderm
• Exchange nutrients, gases, and wastes
• Water leaving osculum must be carried far enough
  away to prevent fouling

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Cells that line surfaces

• Pinacocytes
• Porocytes
• Choanocytes

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Cells that line surfaces

• Porocytes
• Form ostia
• Cylindrical tube-like cells
• Contractile - open and close pore to regulate
  diameter

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Cells that line the surface

• Choanocytes
• choanoderm
• Create currents
• Not coordinated in movement

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Cells that secrete skeleton

• Fibrillar collagen
• Collencytes
• Lophocytes
• Spongocytes
• Calcareous and siliceous spicules
• Sclerocytes

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Contractile cells

• Myocytes
• Contractile cells
• Filament arrangement homologous with smooth
  muscle cell
• Unlike neurons and true muscle fibers

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Cell Aggregation

• Atlantic sponge (Microciona prolifera)
• Pieces pressed through fine cloth
• Separated cells reorganize
• 2-3 weeks
• Self-recognition

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Support

• Skeletal elements
• Organic - collagenous
• Inorganic siliceous (hydrate silicon dioxide)
• Sponges only animals that use hydrated silica as
  skeletal material

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Sponge Harvest

• Harvested for thousands of years
• Greeks harvested sponges
• Sponge fishery south of FL, Bahamas,
  Mediterranean
• 1938 2.6 million lbs

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Sponge Harvest

• Hippospongia
• Spongia

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Spicules

• Microscleres
• Megascleres
• Demosponges and Hexactinellids have both
• Calcareous sponges have only megascleres

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Nutrition, Excretion, and Gas Exchange

• Intracellular digestion
• Continuously circulate water
• Size selective feeders
• Food capture
• Phagocytosis and pinocytosis

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Excretion

• Ammonia and gas exchange
• Diffusion

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Activity and Sensitivity

• Respond to environmental stimuli
• Close ostia or oscula, canal constriction,
  backflow

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Reproduction and Development

• Sexual and asexual reproduction
• All sponges capable of sexual and asexual repro
• Processes unknown due to lack of distinct,
  localized gonads (gametes, embryos occur
  throughout mesohyl)
• Asynchrony of reproductive activity w/in
  populations

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Reproduction and Development

• Asexual Reproduction
• All sponges produce viable adults from fragments
• Cellular reorganization pinches off branch ends
  which regenerate into new adults branching
  species

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Reproduction and Development

• Asexual Reproduction
• Common in Floridas sponge farms - cuttings
  attached to cement structure
• Other processes include formation of gemmules,
  budding

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Reproduction and Development

• Gemmules
• Produced in winter as dormant bodies
• Coat and supportive cells protects from freezing
  and desiccation

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Reproduction and Development

• Gemmules

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Reproduction and Development

• Budding
• Squat or elongate club-shaped protrusions from
  sponge surface
• Buds drop, carried by current, adhere to
  substratum
• Marine species

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Reproduction and Development

• Sexual Processes
• Majority are hermaphroditic produce sperm and
  eggs at different times
• Sequential hermaphroditism
• Protogyny or protandry may occur once or many
  times during life

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Reproduction and Development

• Sexual reproduction
• Sperm from choanocytes eggs from choanocytes and
  archaeocytes

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Reproduction and Development

• Sexual process (Demospongiae and Calcarea)
• Sperm and oocytes released into environment via
  aquiferous system
• Sperm release -smoking sponges
• Fertilization in open water (oviparous)
• Few viviparous sperm into nearby sponges
  aquiferous system sperm to oocyte for
  fertilization

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Reproduction and Development

• Madsen sponge releasing sperm

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Reproduction and Development

• Release of larvae (vivipary)
• Through aquiferous system or ruptured wall
• Larvae swim hours or days, or crawl along
  substratum before settling
• Larvae are lecithotrophic use stored yolk

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Reproduction and Development

• Larval development

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Distribution and Ecology

• Calcareous sponges abundant in shallow waters lt
  200 m
• Hexactinellids deeper
• Demosponges at all depths

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Distribution and Ecology

• Sensitive to suspended sediments
• Resistant to hydrocarbon and heavy metal
  contamination
• Why?

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Symbioses

• Commensalism common (small inverts, fishes)
• Protection, habitat, water currents for suspended
  food particles
• Some organisms utilize sponge for camouflage,
  small piece on shell or carapace

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Boring Demosponges - harmful to corals and
mollusc shells

• bioerosion chemical and mechanical removal of
  fragments by etching cells