phylum Porifera - The sponges

1. FUNCTION OF CANAL SYSTEM

1.1. Water current flow through the canal system brings in food and oxygen

1.2. and carry away co2 and nitrogenous waste material

1.3. thus canal system help in nutrition, respiration and excretion

2. strange

3. Plant like creature commonly called as sponges

4. they are vase like or cylindrical, but majority form flat, globular or irregular,branching masses

5. Symmetry - cylindrical sponges have radial symmetry , other are asymmetrical

6. DIPLOBLASTIC ANIMALS - Two germ layer

7. Cellular level of organisation

8. no head and appendages are missing

9. BODY WALL - Two layer outer dermal or pinacoderm and inner choanocytes .

9.1. dermal layer consist of flat cells called pinacocytes and oval porocytes

9.2. Choanocytic layer consists of characteristic flagelated collar cells or choanocytes

9.3. b/w these layers a gelatinous material named mesophyl or mesenchyme

9.3.1. It contain numerous free amoeboid cells, AMOEBOCYTES, of several kinds such as

9.3.1.1. SCLEROBLASTS

9.3.1.2. SPONGIOBLASTS

9.3.1.3. THESOCYTES

9.3.1.4. PHAGOCYTES

9.3.1.5. TROPHOCYTES

9.3.1.6. ARCHAEOCYTES

9.3.1.7. COLLENCYTES

9.3.1.8. CHROMOCYTES AND POROCYTES

10. body cavity - spongeocoel and in most cases also contain in its thickness numerous small cavities , the canal

11. Canal is lined by choanocytes with flagella .

11.1. The ceaseless beating of flagella main a steady current of water through the canal in body of sponge

11.1.1. the current of water enter through small pores , the DERMAl OSTIA ,performing the porocytes and after passing through various canal ,the enter into spongeocoel and finally leave through a larger aperture , the OSCULUM or oscula

11.2. all cavities of sponge is intercommunicating and are collectively referred as canal system

12. ENTIRE BODY CONTAIN PORES HENCE CALLED PORIFERA

13. 3 MAIN TYPE OF CANAL SYSTEM

13.1. 1. SIMPLEST : Asconoid

13.1.1. LEUCSOLENIA

13.2. 2. SIMPLE : Syconoid

13.2.1. SYCON

13.3. 3.COMPLEX : LECONOID

13.3.1. SPONGILLA

14. SKETETON : internal skeleton consist of tiny calcareous or siliceous spicules secreted by scleroblast

15. DIGESTIVE TRACT : mouth and digestive system is lacking

15.1. nutrition is holozoic

15.2. digestion is intracellular and occur in food vacuoles as in protozoan

15.3. sponges are filter feeder or suspension feeders

15.4. food is stored in the mesenchymal cell , the THESOCYTES

15.5. PLANKTON is an important food source for sponges

16. CIRCULATION ; distribution of food from ingesting cells to other is brought about by wandering amoeboid cells, the TROPHOCYTES , of mesenchyma

17. RESPIRATION AND EXCRETION BY DIFFUSION . SPONGES ARE ammoniotelic animal

18. only animal without NERVOUS SYSTEM AND SENSE ORGAN

19. REPRODUCTION : is SEXUAL AND ASEXUAL

19.1. BY GEMMULES IN ASEXUAL REPRODUCTION

19.2. SEXUAL REPRODUCTION involves formation of ova and spermatozoa

19.2.1. these are develop from ARCHEAOCYTES OR CHOANOCYTES OR BOTH

19.2.2. FERTILISATION IS INTERNAL

19.3. MOST of sponges are HERMAPHRODITES

20. DEVELOPMENT : ZYGOTE develops into a new sponge by HOLOBLASTIC SEGMENTATION

20.1. life cycle involve a free swimming larva

20.1.1. AMBHIBLASTULA in SCYPHA

20.1.2. PARENCHYMULA in LECOSOLENIA for dispersal