Parazoa Invertebrates PDF

INVERTEBRATES Parazoa Porifera  Kingdom: ANIMALIA PROTOZOA METAZOA kingdom : Prototista Eg : Ameoba PARAZOA EUMETAZOA PHY : PORIFERA...

INVERTEBRATES Parazoa Porifera  Kingdom: ANIMALIA PROTOZOA METAZOA kingdom : Prototista Eg : Ameoba PARAZOA EUMETAZOA PHY : PORIFERA Eg : Sponges DIPLOBLASTIC RADIATA TRIPLOBLASTIC PHY : COELENTERATA BILATERIA Eg : Hydra Acoelomata Pseudocoelomata EUCOELOMATA Phy : Platyhelminthes Phy : Aschelminthes(nematoda) Eg : Ascaris Phy : Phy : Phy : Phy : PHY : Annelida Arthropoda Mollusca Echinodermata CHORDATA Classificatin Kingdom – Animalia Subkingdom – Parazoa (lacks tissues) Phylum – Porifera (pores)  Characteristics of phylum Porifera ▪ The 9,000 or so species of sponges range in height from about 1 cm to 2 m and most are marine and take bright color. ▪ About 100 species live in fresh water, they are green in color. ▪ Multicellular, They lack true tissues and organs– loose aggregation of cells, different cell types. ▪ The body of a simple sponge resembles a sac perforated with holes. ▪ Body with pores, canals and chamber for water transport. ▪ Water is drawn through the pores into a central cavity, the spongocoel, and flows out through a larger opening, the osculum. ▪ More complex sponges contain branched canals and several oscula.  Skeletal structure of collagen (a protein) and calcerous or siliceous crystalline spines. No organs or true tissues; digestion intracellular; excretion and respiration by diffusion. No nervous system. All adults sessile and attached to substratum Asexual reproduction by budding or fragmentation. sexual reproduction by eggs and sperm; flagellated, swimming larvae )amphiblastula stage). Sponge Body Structure ▪ The body of a sponge is asymmrtrical and consists of two cell layers: ▪ Outer epidermis and inner endoderm, separated by Jelly-like material (mesenchyme) which form a gelatinous region, the mesohyl. ▪ Mesenchyme (mesohyl) in sponges: is a gelatinous matrix that contains skeletal elements and archaeocytes or amebocytes. Cell types of the Sponge: 1-Pinacocytes: are thin, flat, epithelial-type cells that cover the exterior and some interior surfaces of most sponge. 2-Porocytes: Some pinacocytes forms tube like contractile porocytes. They regulate water circulation. 3-Amebocytes (archaeocyte): are present in mesohyl layer. They take up food from water and from choanocytes, digest it, and carry nutrients to other cells. 4- Choanocytes, or collar cells: Flagellated, line the spongocoel (hollow internal water chambers) create a flow of water through the sponge with their flagella, and trap food with their collars. Other cell types secrete spicules (sclerocytes) and spongin (spongocytes). Nearly all sponges are suspension feeders, collecting food particles from water passing through food-trapping equipment. Choanocytes line the gastrovascular cavity & capture food Amebocytes digest & distribute food Skeletal Structure of the Sponge The skeletal framework of a sponge may be fibrous or rigid: 1- The fibrous part comes from collagen fibrils called spongin, it is more flexible, in the intercellular matrix. 2- Rigid skeletons consist of needlelike spicules of calcareous (limestone)(calcium carbonate CaCO3 ( or silicaeous (glass). Spicules are hard spear or star-shaped structures Sponge Skeletons Silica Spicules Limestone Spicules SPONGIN Sponge Reproduction Most sponges are hermaphrodites, with each individual producing both sperm and eggs. Sponge can reproduce 1- Sexual reproduction ▪ Gametes arise from choanocytes or amoebocytes. ▪ The eggs are retained, but sperm are carried out the osculum by the water current. ▪ Sperm are drawn into neighboring individuals (Cross- fertilize) and fertilize eggs in the mesohyl. ▪ The zygotes develop into flagellated, swimming larvae that disperse from the parent ) amphiblastula stage(. ▪ When a larva finds a suitable substratum, it develops into a sessile adult. 2- Asexual reproduction A- Sponges are capable of extensive regeneration, the replacement of lost parts through mitotic division. They use regeneration not only for repair but also to reproduce asexually from fragments broken off a parent sponge. B- by budding  Surviving Harsh Conditions Gemmules Are specialized buds made to survive harsh weather (hot or cold) Contain food, amebocytes, and a protective covering of spicules. Released when a sponge dies. Resist dessication (drying out) Become adult sponge when conditions become favorable Porifera have three types of canal systems Tiny body openings (ostia) for incoming water. Few large openings (oscula) for water outlet. Sponges consist of a series of water canals called the aquiferous system. ▪ The choanoderm (cell layer composed of choanocytes) may remain simple and continuous with one main chamber, the spongocoel (asconoid condition) ▪ It may become folded (syconoid). ▪ It may become greatly subdivided into separate flagellated chambers (leuconoid). 1- Asconoid Asconoid sponges have specialized cells called porocytes: cylindrical tubular cells that form each incurrent pore (ostium), extend through the mesohyl, and into the choanoderm where it opens into the spongocoel that is entirely lined by choanocytes. 2-Syconoid Syconoid sponges display simple folding of the pinacoderm and choanoderm; Complexity increases, with the thickness of the mesohyl. Dermal pores in those with a cortex are comprised of more than one cell and are called dermal pores Prosopyle ; Choanocytes are restricted to choanocytes chambers, and each chamber opens to the spongocoel. Prosopyle :a pore through which water is drawn from the outside into one of the saclike chambers formed by the evagination of the body wall. Apopyle: a pore in each of the saclike chambers formed by the evagination of the body wall, through which water passes into the excurrent canals.  3-Leuconoid Leuconoid sponges have additional folding of the choanoderm and a further thickening of the mesohyl by cortical growth; Flagellated surfaces are further subdivided into smaller, discrete choanocyte chambers (i.e. smaller in size, but larger in number). Water Flow Through Sponge  Copyright e The McGraw-HillCompanies, Inc. Permission required for reproduction or display. A B A-C: Larry S. Roberts; B: C William C. Ober c