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Phylum Phylum PoriferaPorifera

Phylum Porifera (Sponges)

5000 - 90000 spp.

mostly marine some freshwater

none terrestrial

3 classes, most important

distinctions are skeletal

Most primitive animal group

DistributionThere are approximately 9,000 living

species and above 2200 fossil forms.All are aquatic–most are marine; found at all depths

from intertidal to the abyssal zone, – a few occur in freshwater (~150 spp.)–most range from <1/2 inch to over 6 ft. tall

(loggerhead sponges),– some are round, flat, grow as crusts or vase-

like,– some are radially symmetrical; most are,– Assymetrical, often brightly colored: yellows,

reds, greens, oranges, lavenders

SimplicityThey are closely related to the group of protozoan protists, called the choanoflagellates,

The protozoan protists cells closely resemble the collar cells of sponges,

Approximately, 1/4th of Sponges genes are shared by all other animals,

All sponges are sessile, but multicellular their structure is unlike any other animal group.

Ecology• Growth is entirely dependent on the following:-• shape of the substratum to which they attach,• the direction or speed of water currents,• Space availabilityTherefore environment plays significance in

growth patterns.

Sponge Biological Associations

Excoriations by sponges into shells and Carapace of Bivalves and Brachipods

Abundance of fossil recordsIn 2010, newly discovered fossils were found

in old rocks that were 635-659 million years old.

About 400 million years ago, sponges dominated the oceans as reef builders,

Some fossil sponge reefs are much larger than the great barrier reef,

Sponges covered an arc across most of Northern Europe some 200 million years ago.

They were fossilized into hard rock for building castles in the Middle age.

Spindle diagram showing Originating Era

Stromatoporoids

A

B

Stromatoporoids Showing calcareous Layers

Phylogenetics of Porifera• Diagnostic feature of the Porifera was the

presence of spicules,• Groups with a solid calcareous skeleton such as

the Archaeocyatha, chaetetids, sphinctozoans, stromatoporoids, and receptaculids were problematic.

• 15 extant species of sponges having a solid calcareous skeleton were recently added,

• With living sponges in hand, histological, cytological, and larval characteristics were observed.

• Calcarea and the Demospongia are more closely related to each other than they were to the Hexactinellida.

• chaetetids, stromatoporoids, and sphinctozoans were living with a fourth class was erected and called sclero-spongia,

• Sclero-spongia is not a natural monophyletic group and thus has being abandoned,

• The Archaeocyatha pose a special case because no living representative of this group has been discovered but their organization is consistent with that of living sponges.

• Phylogenetic analysis included archaeocyaths with other sponges and grouped them as sisters to the demosponges due to the presence of choanoflagellates.

• On the contrary, sponges only achieve collar cells after embryological development.

Phylogenetics of Porifera

Adaptive Radiation in Poriferans• The enormous diversification centres on

a unique ability of members to use a perfect water-current system to channel food, oxygen and eliminate waste via the same system.

• The proliferation of the flagellated

chamber observed in the leuconoid sponges favoured them because of the largeness in size of this group as compared to the asconoid and synconoid.

Morphology

Arrows shows water flow directions

Microscopic view of Porifera cells

Choanocytes (collar cells) They line the flagellated

canals and chambersThey are ovoid with one

end embedded in the mesohyl

Adjacent Microvilli are connected to each other by microfibrils

They act as a pump to bring water into the sponge

Food engulfed is passed to archeocyte for digestion

flagellum

Nucleus

Collar microvilli

Food Vacuole

Collagen - Support Collagen is found between the

inner canals and chambers Mesohyl

Amoeboid cells located in the mesohyl, have different roles:-

1.Archeocytes: motile in the mesohyl:– Phagocytize particles in the

pinacoderm,– Recieves particles for digestion

2.Sclerocytes: Specialized, secrete spicules

3.Spongocytes: Secrete spongin fibres for skeleton

4.Collencytes: Secrete fibrillar collagen

5.Lophocytes: Secrete large quantities of Collagen distinguishable from collencytes

Body wall: Support

Small Section through Sponge wall

Types of SpiculesDemospongiae &

Sclerospongiae secrete siliceous spongin silicon dioxide (SiO2).

Calcareous sponges secrete crystalline calcium carbonate (CaCO3) spicules with one to four rays

Collagen is stiffened by addition of microscopic mineral accretions or additional protein fibers (spongin) or both

Types of Spicules

Types of Canal Systems

Osculum

ChoanocytesSpongocoel

Ascon

Ostium

Osculum

Ostium

Sycon Leucon

Spongocoel

Choanocytes

Porocytes

Anatomy of Ascon & Sycon

Leuconoid Anatomy

• The most common network of water channels

Asconoids• Flagellated

spongocoels,• Simplest organization,• Small, branched and

tube shaped,• Spongocoels allow

water into the cells lined with choanocytes,

• Present only in Calcarea

• E.g. Leucosolenia, Clathrina canariensis,

Syconoids • Flagellated canals• larger editions of asconoids,• Tubular body but single

osculum,• Thicker & complex body

wall containing radial canals lined with choanocytes

• Spongocoels lined with epithelia & not flagella

• Water enters through dermal ostia and filters through Prosophyles,

• Food is forced through internal pores called apopyles,

• No branched colonies• E.g. Calcarea, hexactinellida

In flux & Out flux of Water in Syconoid

Leuconoids• Flagellated chambers,• Complex organization• Suitably adapted for

increasing size,• Forms large masses

with numerous oscula,• Flagellated cluster

chambers filled from incurrent canals, and opens into excurrent canals,

• Most are leuconoids,• Clear adaptive value,• E.g. Calcarea,

Classification

Phylum Porifera

Class Calcarea,

Class Demospongiae,

Class Hexactinellida,

Sclerospongiae (no longer

considered a class)

ClassificationClass Calcarea (calcareous sponges)

small, vase shaped, primitive group,

mostly drab coloured; a few are yellow, red, green, lavender,

all marine, especially shallow waters,

show all 3 types of canal systems; mostly asconoid canals,

spicules of CaCO3, needle shaped or 3-4 rayed, monaxons,

Grows in coloniesStraight spicules around the

osculum that discourages small animals from entering

Class Demospongiae (Most sponges)• Possess spicules made of silicon

dioxide (SiO2) or spongin or a combination of both

• Most sponges belong to this class (90%) Nearly all are leuconoid body type,

• 95% are living, encrusting plants• Mostly found on the continental

shelf in well oxygenated habitats• Spongilla spp. (Bath sponge),

present in midsummer and later form gemmules after disintegration

Class Hexactinellida (Glass sponges)

• Spicules are made of silica, • Usually found in deep water on soft

substrates in the tropics 200-1,000m.• Spicules are six- rayed, pointed and

have a lattice-like structure,• Cup, vase or urn shape,• Radially symmetrical,• Formed as one by trabecular net of

living tissues from fusion of pseudopodia of archaeocytes,

• E.g. Euplectella (Venus flower)

Reproduction in SpongesSEXUAL•Male & female gametes are formed (monoecious). •Archeocytes become eggs•Choanocytes filter sperm out of the water•Fertilization is involved.•Planktonic larvae or mini flagellated colonies are released to colonize new areas.•Most are viviparous

ASEXUALMarine sponges•Budding•Fragmentation•Regeneration

Freshwater sponges•Gemmules •Budding•Fragmentation•Regeneration

Development during Reproduction (Demosponges)

• Parenchymula larva is free – swimming,• Outward flagellated cells invaginates

and becomes the choanocytes,

Development during Reproduction (Calcarea)

A hollow blastula (Amphiblastula) develops with flagellated cells interiorly,

Blastula turns inside-out,

Flagellated end appears outward (micromeres),

Larger nonflagellated end (macromeres) turns into pinacoderm & Sclerocytes,

Flagellated cells become the choanocytes, archeocytes & collencytes

Larvae of SpongesAsexual•Asexual budding•Formation of internal buds/Gemmules by freshwater sponges•Regeneration: can regenerate from broken pieces•AllorecognitionSexual•Sexual usually hermaphroditic with male and female cells scattered throughout the connective tissue.

A Gemmule of Spongillidae

Human Impacts of Sponges

Bath sponges

•In use since bronze age (4000 yrs.)

•Holds up to X 35s its weight in water

•Takes 5 yrs. to reach marketable size

•Creates job opportunities for harvesters &

collectors

•Sponges were challenged by red tides and a fungal

disease that wiped out the sponge beds

•Synthetic sponges were introduced to the market

Human Impacts of SpongesProduction of a wide variety of bioactive compounds•Pharmaceuticals: Antibiotics, Asthma, Arthritis, Anticancer drugs, Chemicals that promote wound healing, Anti-inflammatories

Examplesantibiotics against bacteria such as E. coli and Staph aureus, e.g. Acyclovirfrom Caribbean sponge1st antiviral compound approved for human use fights herpes infections (in use since 1982), e.g. Vidabarine.may attack AIDS virus, e.g. a species of S/Pacific sponge produces chemicals that is bactericidal against Candida albicans (thrush and vaginal infections)

Human Impacts of Sponges

• In 2009, a new chemical derived from sponge has the ability to re-sensitize bacterial pathogens to antibiotics (Ensures loss of resistance to all antibiotics and die)

Material Science• The strongest glass structure derived

from Euplectella (Venus flower) is a source for study due to its strength

Aquarium Trade

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