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

OscarellaOscarella

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