General characteristics of invertebrate phyla

General characters of some invertebrate phyla(porifera, cnidaria,ctenophora,platyhelminthes,aschelminthes,annelida, arthopoda,mollusca,echinodermata and hemichordata).Reference -INVERTEBRATES(R.L. KOTPAL)

1. General Charactristics of major Invertebrates phyla Presented by:- Uttama Tungkhang B.Sc in Zoology

2. WHAT IS INVERTEBRATE ? Over the 5million described animals, about 5% of them possess a vertebral column or backbone and are known as vertebrates. The remaining animals which lack a vertebral column are called invertebrate.

3. Phylum- Porifera (sponges) General Characters- Multicellular organism with cellular level of body organisation. Mostly marine, a few fresh water, all aquatic. All sessile. Symmetry- radial or asymmetrical. Body wall with outer pinacoderm, inner choanoderm and mesenchyme in between. Chaonocytes or flagellated collar cells are the distinguishing feature of phylum porifera. All hermephrodite. Reproduction- both sexual and asexual. Body with many pores called ostia, serves for flow of water. Exit is osculum.

4. Examples – Sycon (scypha) Euspongia(bath sponges) Spongilla(fresh water sponges)

5. Phylum - Coelenterata General characters- All aquatic, some fresh water, mostly marine. Sessile or free swimming. Symmetry- Radial or Biradial. Body organisation of cell tissue grade. Exoskeleton chitinous or calcareous. Body wall diploblastic. Two types of individuals- free swimming medusae and attached polyps. Single internal cavity. Digestion intracellular as well as extracellular. Both body layers with nematocytes. Reproduction-both sexual and asexual. Development indirect, with a larval stage of free swimming planula larva.

6. Examples- Physalia (Portuguese man of war) Adansia ( sea anemone) Pennatula (sea pen) Gorgonia (sea fan) Meandrina (brain coral).

7. Phylum- Ctenophora General characters- Marine, solitary, free swimming or pelagic. Body transparent. Symmetry biradial. External surface with 8 vertical rows of comb plates. A pair of long , solid tentacles present. Cell tissue grade of body organization. Body acoelomate and triploblastic. Special adhesive and sensory cells called colloblasts present. All hermaphrodite. Development usually includes a characteristic cydippid larva. Asexual reproduction absent. Regeneration and paedogenesis common.

8. Example- Pleurobrachia and ctenoplona.

9. Phylum - Platyhelminthes General characters- Free living commensal or parasite. Tissue- organ grade of organization. Triploblastic. Bilaterally symmetrical. Dorso-ventrally flattened. Body unsegmented. Acoelomate body. Adhesive structures like hooks, spines and suckers, and adhesive secretion common in parasitic form. Muscular system of mesoderm origin. Mostly monocious with complex reproductive system. Fertilization internal. Development direct or indirect. EXAMPLE- Tania and fasciola.

10. Phylum- Aschelminthes General characters- Mostly aquatic, free living or parasite. Usually small, even microscopic. Body slender, vermiform,unsegmented,flat or cylindrical. Organ system grade of body organization. Body cavity is pseudocoel. Digestive canal complete. No circulatory and respiratory system. Mostly dioecious, female usually larger than male. Development usually direct. EXAMPLE- Ascaris( round worm) wucheria( filarial worm) Anclyostoma( hookworm)

11. Phylum- Annelida General characters- Mostly aquatic, some terrestrial, some parasitic and commensal. Body elongated, bilaterally symmetrical,triploblastic, truly coelomate, metamerically segmented. Body wall dermomuscular. Locomotion- satae or chaetae. Digestive system straight and complete. Blood vascular system closed. Hermaphroditic. Example- hirudina, sipunculuc.

12. Phylum - Arthopoda General characters- Organ system level of body organization. Body bilaterally symmetrical, triploblastic and metamerically segmented . Jointed appendages. Exoskeleton of dead chitinous cuticle , that is shed at intervals called ecdysis. Body divisible into head, thorax and abdomen. True coelom reduced and largely replace by a blood filled haemocoel. Digestive system complete with mouth and anus. Respiration by body surface , gills, tracheae or by book lungs. Sexes usually sperated. Development direct or indirect with one or many larval stages. Parthenogenesis in some. Parental care well marked. EXAMPLE-honeybee, lac insect, butterfly, ants, cockroach etc.

13. Phylum - Mollusca General characteristics- Tissue- system grade of body organization. Triploblastic, coeleomate, bilaterally symmetrical and unsegmented. Body divisible into head, mantle, foot and visceral mass. Shell, when present usually univalve or bivalve. Coelom reduced and represented mainly by pericardial cavity, gonadial cavity and kidney. Digestive system complete. Respiration or by gills or by lungs or both. Dioecious or monocious. Terrestrial or aquatic. EXAMPLE- Pila, Pinctada,Sepia,Loligo,Octopus etc.

14. Phylum- Echinodermata General characters- Organ system grade of body organization. Triplobastic, coelomate and radially symmetrical. Body unsegmented with globular, star like , spherical or elongated in shape. Head absent. Body surface marked with five symmetrical areas and five alternating interradii. Exoskeleton of dermal calcareous, ossicles with spine. Water vascular system of coelomic origin. Alimentary canal straight or coiled. Usually dioecious . Regeneration of lost parts. Exclusively marine. EXAMPLE-Asterias, E chinus, Antedon, Cucumaria, etc.

15. Phylum- Hemichordata General characters- Exclusively marine. Body soft, fragile ,vermiform, unsegmented , bilaterally symmetrical and triploblastic. Body wall of single layer epidermis with mucous glands. Digestive tube complete, straight or U-shaped. Foregut gives out a hollow buccal diverticulum into proboscis. Dorso lateral pharyngeal gill slits when present, one to several pairs. Reproduction usually sexual, sexes are separate. Fertilization external in sea water. Development direct or indirect. EXAMPLE- Balanoglossus, Saccoglossus.