Poriferans sponges What are Poriferans Poriferans are commonly

Poriferans (sponges)

What are Poriferans • Poriferans are commonly referred to as sponges. • Derived from two words: Pori- Pores Fera – Bearing Sponges are pore bearing animals

What are sponges • Simplest multicellular animals • Their body is described as an assemblage of cells in an extracellular matrix, supported by skeletons known as spicules. • Most sponges live in marine environments (Seas and Oceans) • A few live brackish ( e. g lagoon) and fresh water.

Unique Characteristics • Two types of openings: Ostium -Tiny in-current pore Osculum- Large ex-current opening • Radial symmetry or asymmetry • Outer surface- Pinacocytes/ Pinacoderm • Inner surface- Choanocytes/Choanoderm (Collar flagellated cells)

Unique Characteristics • Skeletal structures made of collagen fibres (proteinous) and spicles (silicaceous or calcarous). • Cells are not organized to form organs or tissues. They exist at a Cellular level of organization. • Digestion is intracellular, • Excretion & digestion via diffusion.

Unique Characteristics • Reproduction: Assexual – external bud or internal bud (gemmules) Sexual- Fusion of gametes, flagellated larvae (Parenchymula) They are suspension or filter feeders

Groups of Poriferans (3 -Canal Types) • Asconoid (flagellated canals) • Synconoid (Flagellated radial canals) • Leuconoid (Flagellated chambers) Increasing size and complexity

Synconoid Asconoid Leuconoid

Asconoid (Flagellated spongocel) • Simplest organization • One osculum numerous ostium, • E. g Leucosolenia • Exclusive to class Calcarea

Synconoid (Flagellated radial canals) • Larger and more complex than asconoids. • Presence of dermal ostia. E. g Syncon • Found in Class Calcarea & Hexacthinellida

Leuconoid (Flagellated chambers) • • Most complex. Several Oscula Dominates most Classes E. g Euplectella (Venus flower basket)

Classification • Class Calcarea • Class Hexacthinellida • Class Demospongiae

Class Calcarea (a. k. a calcispongiae) • Live in shallow marine waters • Spicles is composed of calcium carbonate • Spicules are 1 -, 3 - , or 4 rayed • Small and verse shaped • Solitary or Colonial E. g: Syncon, Leucosolenia They may be asconoid leuconoid or synconoid.

Class Hexacthinellida (Glass Sponges) • Six- rayed silicaceous spicules • Usually found in deep seas. • E. g Euplectella (Venus flower basket) • Mostly leuconoids

Class Demospongiae • 95% of all sponges, Mostly large • Spicules are silicaceous but not six -rayed. • E. g: Spongilla, Myenia • All members are leuconoids • All members are marine except Family Spongillidae which live in fresh water

Types of sponge cells • Pinacocytes – cells of the pinacoderm (external body covering). • Archaeocytes- cells that can transform into any other cell type required. • Spongocytes – secretes skeletal material called spongin. • Collencytes- secretes collagen fibres. • Sclerocytes – secretes skeletal material spicules.

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