1 Animal Kingdom Phylum : Porifera ● Study of porifers or sponges : Parazoology. ● Sponges are also called Republic of cells. ● Sponges form sideline of evolution. ● It appears to be quite lifeless & plant like. ● In parazoa,ectoderm develops from vegetal pore & endoderm develops from animal pore (reverse in metazoa). ● The sponge differs from other animals by collar cells / choanocytes. ● Proterospongia is a connecting link between protozoa & porifera. ● Cellular grade of organization.Acoelomate. ● Multicellular (1 st ) & cell aggregate body plan. ● No appendages. ● All sponges are aquatic ;mostly marine & few freshwater forms. ● Sponges are not found in cold water. ● Sponges may be solitary (sycon) or colonial (leucosolenia). ● Larva is active & floating but adult is sedentary or sessile. ● Most are asymmetrical but very few have radial symmetry (sycon & leucosolenia) . ● All poriferans are filter feeder & suspension feeder. Few imp. filter feeders :
2 1.Ciliates - Eg : Paramecium 2.Sponges - Specially Sycon. 3.Mollusca - Bivalvia. Eg : Unio. 4.Hemichordata 5.Protochordata ● Body is perforated with large number of smaller inhalent pores called ostia ( Mouthlets) & single larger exhalent pore called osculum (anus). ● If a foreign particle is put on the ostia of a living sponge, it will be ingested & enters in spongocoel and if on the osculum , it will be thrown away with waste water. ● Ostia is non-valvular & osculum is valvular due to presence of oscular fringes. ● Diameter of ostia is regulated by myocyte cell. ● Diploblastic. ☆ Outer layer pinacoderm (ectoderm) having 2 types of cells. 1. Pinacocytes (flattened cells, multicellular) 2. Porocytes (Tubular cells, unicellular) ☆ Inner layer choanoderm (endoderm) having flagellated cells called choanocytes which are nutritive cells. ● In between pinacoderm & choanoderm, is a cellular layer (gelatinous matrix) called mesenchyme or mesohyl which consist of skeletal elements (spicules) , collagen fibres & free amoebocytes. ● Amoebocyte is also called as wandering cell.
3 ● The cavity common to all sponges is spongocoel or paragastric cavity lined with flagellated choanocytes. ● In sponges, food is ingested by choanocytes/collar cells. Also the water current through the body of sponge is maintained by choanocytes. ● Choanocytes or collar cells are present only in sponges. ● Choanocyte cell feeds holozoically. AMOEBOCYTE ● They're of 10 types : 1. Archaencytes ☆ Largest amoebocytes called totipotent cell. ☆ Can be converted to other types of cells, specially germ / sex cells. ☆ Helps in regeneration called morpholaxis . ☆ Helps in formation of internal bud called gemmule for asexual reproduction. 2. Tropocytes ☆ Called Nurse cells or nutritive cells. provide food to developing cells. 3. Thescocyte ☆ Contain reserve food material in the form of glycogen granules, 4. Collenocytes cells/Connecting cells
4 ☆ Uninucleate with fibres. ☆ Secrete collagen fibres i.e. Calcareous spicules (CaCO3) ; ☆ Siliceous spicules (Silica) ; Spongin fibres (Protein). 5. Scleroblasts ☆ Multinucleate, secretes spicules. 6. Myocytes/Contrcactile cells ☆ Present at ostia & osculum (but mainly at osculum) ☆ Helps in closing & opening of osculum. 7. Chromocytes/Pigment cells ☆ Gives colour as well as excretory in nature. 8. Phagocvtes ☆ Phagocytic in nature. ☆ Also helps in elimination of excretory product. 9. Germcells ☆ Helps in reproduction, produce sperm & ova. 10. Glandcells ☆ Serve for attachment by secreting slimy substance (mucus) . ● Sponges have a canal system, also called aquiferous system & they need a continuous current of water flowing through their bodies for respiration, excretion, nutrition and reproduction ● Canal system may be
5 Types Explanation Flow Of water Ascon type (Leucosolenia) Simplest & primitive type. Paragastric cavity is lined by choanocytes. Water ➝ Ostia ➝ Spongocoel ➝ Osculum ➝ Out Sycon type (Sycon) Paragastric cavity is lined by pinacocyte. Water ➝ Ostia ➝ Incurrent canal ➝ prosopyle ➝ radial canal ➝ apopyle ➝ spongocoel ➝ osculum ➝ out Leucon type / Rhagon type (Spongilla) This type is found in few sponges during larval stage & will be transformed to leucon type during adulthood. Water ➝ Ostia➝ Incurrent canal ➝ prosopyle ➝ radial canal ➝ apopyle excurrent canal ➝ spongocoel ➝ osculum ➝ out ● Sponges have skeleton consisting of spicules or spongin fibres which may be either calcareous or silicious. Skeleton of sponges is secreted by scleroblasts. ● There are three types of scleroblasts i.e. • Calcoblasts : CaC03 • Silicoblasts : Silica • Spongioblasts : Spongin fibres ● Digestion is intracellular & holozoic. ● Digestion of food takes place partially in choanocytes & partially in wandering amoebocytes.
6 ● Circulation takes place by wandering of amoebocyte cells (Trophocytes) . ● Excretion (primarily ammonia) & gas exchange are by simple diffusion occurs across the choanoderm. ● Respiration is performed by both choanoderm and body surface, but mainly by choanoderm. ● Reproduction may be sexual or asexual. All sponges are hermaphrodite but crossfertilization is the rule due to protogynous. ● Asexual reproduction is either by fragmentation or through the production of gemmules or buds . ● Gemmules are internal buds containing archeocytes, mostly produced by freshwater sponges of the family spongillidae, concerned with asexual reproduction. ● Asexual reproduction in leucosolenia is by external budding and not by internal budding, ● Gemmule passout through prosopyle. ● Prosopyle is a smaller which connects incurrent canal with radial canal. ● Sexual reproduction by sex cells ( sperm & ova) arise from undifferentiated archeocytes at different times, protogyny ( mostly) or protandry. ● Sponges are hermaphrodite ; cross fertilization & internal in spongocoel. ● Development indirect. Larval forms are 8 • Amphiblastula (hollow) Of Sycon • Parenchymula (solid) Of Leucosolenia • Parenchymula is the larva Of many sponges. ● Cleavage of zygote holoblastic & equal.
7 ● Sponges have great regenerating power due to archeocytes which are highly totipotent cells. Classification On the basis of skeleton / spicules. Calcarea/Limy Sponges Hexactinellida Demospongia (Largest Class) Exclusively marine. AII marine. Marine as well as fresh water. Inhabits shallow water. Deep water. Shallow water. Presence Of calcerous spicules. Presence Of silicious spicules. Pesence Of silicious spicules. Canal system ascon or sycon. Canal system Leucon. Canal system Leucon. Choanocytes are large. Small Small Examples: Sycon,Leucosolenia Examples : Euplectella (Venus flower basket) , Hyalonema, Pheronema. Examples: Spongilla (Fresh water sponge), Euspongia (Bath sponge). ● Euplectella ( Venus flower basket) famous for beauty of a skeleton, a traditional wedding gift in Japan.
8 ● Euplectella shows commensalism with shrimps of the genus spongicola. ● Gemmules are formed by the aggregation of archeocyte cells. ● Body of Leucosolenia is cylindrical & radially symmetrical. ● Nerve cells are not found in sponges. ● Evolutionary sequence of canal system in sponge is ascon, sycon, leucon. ● In sponges, digestion takes place in food vacuoles. 10 ● The characteristics features of sponges is canal system. ● Cliona is sponge harmful to oyster industry. ● Hypothetic ancestral stage of sponge is Olynthus. ● Spongin fibres is left after a bath sponge disintegrates & dries. ● Bath sponge is found in red Sea, Gulf of Mexico, Mediterranean Sea. ● Natural sponge is prepared from Euspongia. ● The life-line of sponge is canal system. ● Chalina is an example ofthe group which is considered as blind allay in animal kingdom. ● Sponge is devoid of respiratory, excretory & circulatory organs. ● Exogenous budding of asexual reproduction in sponges is known as Gemmation. ● Freshwater sponges form internal asexual products called Gemmule. ● Largest sponge : Speciospongia. ● Smallest sponge : Leucosolenia. ● Tallest sponge : Posterion patera.
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