Classification • Phylum Porifera • Class Hexactinellida • Order Amphdiscophora • Order Hexasterophora • Class Demospongiae • Order Homoscleromorpha • Order Tetratinomorpha • Ceractinomorpha • Class Calcarea • Order Clacina • Order Clacaronia
Characteristics of Porifera:- • 1. No definite symmetry. • 2. Body multicellular, few tissues, no organs. • 3. Cells & tissues surround a water filled space, but no true body cavity. • 4. All are sessile
Characteristics Porifera Cont. • 5. Reproduce sexually or asexually, sexual repr. either gonochoristic or hermaphroditic. 6. no nervous system. 7. distinct larval stage-planktonic. 8. Lives in aquatic environments, mostly marine. 9. All are filter feeders. 10. Often have a skeleton of spicules.
Poriferans are commonly referred to as sponges • Appr. 5,000 living sponge species • fossil sponges are among the oldest known animal fossils, dating from the Late Precambrian • http://www.ucmp.berkeley.edu/phyla/metazoafr.html
There are three distinct groups of sponges • Hexactinellida (glass sponges), • Demospongia (Bath Sponges • Calcarea (calcareous sponges).
What's a Hexactinellid? • The hexactinellids, or glass sponges, are characterized by siliceous spicules consisting of 6 rays intersecting at right angles (toy jack) • Hexactinellids are widely viewed as an early branch within the Porifera
Demospongia • the most diverse sponge group • > 90 percent of the 5,000 species • found in many different environments, from warm high-energy intertidal settings to quiet cold abyssal depths
Calcarea • The only sponges that possess spicules composed of calcium carbonate • diversity greatest in the tropics • mainly found in shallow waters
Water enters through pores called ostia, flows through canals to a spacious chamber called a spongocoel, and finally exits through large openings called oscula.
Feeding • Poriferans don't have mouths; instead, they have tiny pores in their outer walls through which water is drawn (ostia) • Cells in the sponge walls filter goodies from the water as the water is pumped through the body • flow of water through the sponge is unidirectional, driven by the beating of flagella
Feeding ContinuedFilter feeders Collar cells lined with cilia filter tiny food particles as they flow through the sponge. (choanocytes)The cilia produce a wave-like motion which forces water up and out ofthe sponge. Water enters through Pores called Ostia exits through osculum.
Anatomy: 3 main types of canal in sponges • Asconoid: Canal runs straight through the sponge & all choanocytes line acentral cavity called “spongocoel” • Sycanoid: Canal has braches -allows water to wind through sponge body. • Leuconoid: Most complicated, Many canla that lead to chambers that contain choanocytes.
Sponges composition • skeletons of sponges can be composed of an organic substance called spongin (the stuff of an ordinary bath sponge) • or they may have calcareous or siliceous skeletons composed of chambers, or more commonly rod-like branched elements called spicules
Spicules • Large spicules (visible to the unaided eye) are termed megalascleres • small ones are called microscleres • Spicules have four basic symmetries: (i) monaxon, (ii) triaxon, (iii) tetraxon, and (iv) polyaxon
spicular symmetry serve as the primary basis in poriferan classification
Sponge type spicules • Calcarea sponges -spicules of calcium carbonate -1,3, or 4 rays • Demospongiae - spicules made of silica/Spongin -1,2 or 4 rays. • Hexactinellida –Silica spicules that are 6 rayed.
Reproduction • Hermaphroditic: no permmanent gonads, can become either egg or sperm • Sperm is released from the canals & is drawn into the canals of another sponge. • Larvae are released at a rate of 4-5/min. for 3 to 4 days. • Larvae settle in an area that has a bacteria or algae film on surface. • After settling it takes about 7 days for these minature sponges to get up and running.