Transcript Phylum: Porifera “The sponges”

Phylum Porifera
Porifera Characteristics
• Freshwater and marine
• Simplest of all animals
• Asymmetrical
• No systems for repro, digestion,
respiration, sensory, excretion
Porifera Characteristics
• ~ 5,500 extant species
• Highest abundance in unpolluted littoral
and tropical reefs
• ~ 75% benthic biomass
Porifera Characteristics
• Sessile (Adults)
• Suspension-feeders (Adults)
• Multicellular
• Flagellated cells = choanocytes circulate
water through water canals
• No tissues
• Cells totipotent
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
Taxonomy and classification
• Taxonomy based on skeletal elements
• Now embryological, biochemical,
histological, and cytological methods to
diagnose sponge taxa
Three classes (Calcarea,
Demospongiae, Hexactinellida)
• Class Calcarea: Calcareous sponges
• Shallow, tropical water, near shore
Leucetta
Class Calcarea
• Spicules = calcium carbonate
• Calcarean spicules lack hollow canals =
strong
Clathrina
Class Hexactinellida (Glass
sponges)
– Silica spicules
– Spicules join at right angles, sponge appears
artificial
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
Class Demospongiae
• Genera Adocia, Halisarca, Myxilla
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
Sponges are single individuals
• Grow by continually adding cells that
differentiate as needed
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
Body structure: 3 shapes
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
Asconoid sponges
Syconoid sponges
• Syconoid: choanoderm folded
– Mesohyl two layers thick:
• Outer region is cortex (contains skeletal material)
Leuconoid Sponge
• Leuconoid: choanoderm subdivided into
separate flagellated chambers
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
Cells that line surfaces
• Pinacocytes
• Porocytes
• Choanocytes
Cells that line surfaces
• Porocytes
– Form ostia
– Cylindrical tube-like cells
– Contractile - open and close pore to regulate
diameter
Cells that line the surface
• Choanocytes
– = choanoderm
– Create currents
– Not coordinated in movement
Cells that secrete skeleton
• Fibrillar collagen
– Collencytes
– Lophocytes
– Spongocytes
• Calcareous and siliceous spicules
– Sclerocytes
Contractile cells
• Myocytes
– Contractile cells
– Filament arrangement
homologous with smooth
muscle cell
– Unlike neurons and true
muscle fibers
Cell Aggregation
• Atlantic sponge (Microciona prolifera)
– Pieces pressed through fine cloth
– Separated cells reorganize
– 2-3 weeks
– Self-recognition
Support
• Skeletal elements
– Organic - collagenous
– Inorganic – siliceous (hydrate silicon dioxide)
• Sponges only animals that use hydrated
silica as skeletal material
Sponge Harvest
• Harvested for thousands of years
• Greeks harvested sponges
• Sponge fishery south of FL, Bahamas,
Mediterranean
– 1938: 2.6 million lbs
Sponge Harvest
• Hippospongia
• Spongia
Spicules
• Microscleres
• Megascleres
– Demosponges and
Hexactinellids have both
– Calcareous sponges
have only megascleres
Nutrition, Excretion, and Gas
Exchange
• Intracellular digestion
• Continuously circulate water
– Size selective feeders
• Food capture
– Phagocytosis and pinocytosis
Excretion
• Ammonia and gas exchange
– Diffusion
Activity and Sensitivity
• Respond to environmental stimuli:
– Close ostia or oscula, canal constriction,
backflow
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
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
Reproduction and Development
• Asexual Reproduction
– Common in Florida’s sponge farms - cuttings attached
to cement structure
– Other processes include formation of gemmules,
budding
Reproduction and Development
• Gemmules
– Produced in winter as dormant bodies
– Coat and supportive cells protects from
freezing and desiccation
Reproduction and Development
• Gemmules
Reproduction and Development
• Budding
– Squat or elongate club-shaped protrusions from
sponge surface
– Buds drop, carried by current, adhere to substratum
– Marine species
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
Reproduction and Development
• Sexual reproduction
• Sperm from choanocytes; eggs from choanocytes
and archaeocytes
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 sponge’s aquiferous
system; sperm to oocyte for fertilization
Reproduction and Development
Madsen sponge
releasing sperm
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
Reproduction and Development
• Larval development
Distribution and Ecology
• Calcareous sponges abundant in shallow
waters < 200 m
• Hexactinellids deeper
• Demosponges at all depths
Distribution and Ecology
• Sensitive to suspended sediments
• Resistant to hydrocarbon and heavy metal
contamination
– Why?
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
Boring Demosponges - harmful to
corals and mollusc shells
• = bioerosion; chemical and mechanical removal
of fragments by etching cells