Zoology 102 Lecture 9 PDF

‫‪Zoology102‬‬ ‫دكتور الحسيني يعقوب‬ ‫‪Lecture 9‬‬ ‫الثالثة د| عواطف‬ ‫‪Zoology 102‬‬ ‫‪1‬‬ ‫دكتور الحسيني يعقوب‬  ANNELIDA Class1 Class2. Class3: Class4:...

‫‪Zoology102‬‬ ‫دكتور الحسيني يعقوب‬ ‫‪Lecture 9‬‬ ‫الثالثة د| عواطف‬ ‫‪Zoology 102‬‬ ‫‪1‬‬ ‫دكتور الحسيني يعقوب‬  ANNELIDA Class1 Class2. Class3: Class4: Hirudinida Archiannelida Polychaeta Oligochaeta O1:Errantia O2:Sedentaria Class 1:Polychaeta General features 1. marine worms (carnivorous) 2. elongated segmented body 3. Head + prostomium + peristomium + eyes, tentacles; cirri ‫زوائد حسيو‬, palps 4. Clitellum is absent 5. spacious Coelom + intersegmental septa 6. A.C.+ buccal region + pharynx 7. segmentally paired nephridia. 8. Sex is separate 9. External Fertilization 10.+ve trochosphere larva Zoology 102 2 ‫دكتور الحسيني يعقوب‬ Polychaeta Examples : Ex.Aphrodite Ex. Sabella Ex.Arenicola Taxonomy of Polychaeta Order:Errantia Order:Sedentaria 1) Free swimming 1) Burrowing forms 2) similar segments 2) Body is two or more regions 3) Parapodia + chaetae ‫شوكو‬+cirri 3) unlike segments and parapodia 4) Head + sense organs 4) Head -ve sense organs 5) Pharynx + chitinous jaws + teeth 5) Pharynx -ve chitinous jaws -ve 6) Ex. Nereis sp teeth Gills 6) Ex. Arenicola sp. Zoology 102 3 ‫دكتور الحسيني يعقوب‬  Neanthes (Nereis sp.) Classification : Kingdom : Animalia Subkingdom : metazoan Phylum : Annelida Class: Polychaeta Order: Errantia Genus: Neanthes (Nereis sp.) 1. Shape &size long, narrow 2. bilaterally symmetrical 3. tapering ‫ مسننو او محدده‬posteriorly relatively broad anteriorly dorsoventrally flattened. 4. Segmentation head & body is divided into a series of alike segments except the last one is rounded 5. Division of body head & trunk Zoology 102 4 ‫دكتور الحسيني يعقوب‬ A. Head  Well developed head  prostomium (not a true segment )& peristomium(fusion of first two body segments).  Sensory appendages eyes (sensitive to light) ,Tentacles, Palp(tactile B. Trunk  the rest of metameric body C. Pygidium ‫العجز‬  not true segment bears 2 anal cirri D. Parapodia  Each segment, except the prostomium & pygidium, bears on either lateral side a flat one  Dorsal and ventral acicula ‫الحوسيكه‬are endoskeleton of parapodium serve for support & attachment of chaetal muscles.  aciculums has attached muscles by which retraction of the parapodium occurs  The parapodia are highly muscular for locomotion (creeping & swimming). They vascularized serve as respiratory organs Zoology 102 5 ‫دكتور الحسيني يعقوب‬ E. Chaetae ‫االشواك‬  chaetae are retracted in various directions by strands of muscular fibers present in the interior of parapodium  stiff chitinous rods which help in the locomotion It consist of basal shaft articulated with distal blade.  Three types of chaetae 1. Typical 2. Long blade 3. Oar-shaped Zoology 102 6 ‫دكتور الحسيني يعقوب‬ 6. Thick body wall  Cuticle: thin, tough chitinous & non-cellular layer  Epidermis :columnar epithelial cells; some glandular (mucous)& sensory  Muscle :circular (longer and thinner), four separate longitudinal bundles (shorter and thicker)& two pairs of oblique (dorsal of parapodium & the other to ventral part to retract it )  Peritonium: lines the muscles internally &forms somatopleure 7. Digestive system  Alimentary canal: Foregut & Midgut & Hindgut  Digestion 1. pharynx with chitinous buccal cavity are everted outside the mouth during feeding so, food grasped by jaws & teeth 2. food is digested by digestive juices (oesophageal glands + gland cells of stomach-intestine). 3. Absorption occurs in stomach-intestine by diffusion 4. undigested food passes on to rectum , egested through anus Zoology 102 7 ‫دكتور الحسيني يعقوب‬ 8. Respiration  parapodia (rich blood supply) + body wall  O2&CO2 diffuses according to great partial pressure  Blood contains respiratory pigment erythrocruorin (red) which increases the absorptive capacity 9. Blood vascular system a) closed circulatory system b) distributing collecting vessels & capillaries c) muscular vessels & circulation is maintained by peristaltic waves d) Ventral blood vessel:  fifth segment to last (anterior to posterior )  dorsal and ventral vessels are connected by a pair of transverse vessels  it supplies the blood to the stomach-intestine Zoology 102 8 ‫دكتور الحسيني يعقوب‬   distributing and non-contractile e) Dorsal blood vessel:  collecting and contractile vessel, from posterior to the anterior end, receives blood from stomach-intestine , body wall, parapodia and nephridia through lateral vessels. It carry the blood to oesophagus. f) Subneural vessel :  below the nerve cord, anterior to posterior end. It collects blood from the lower body wall and supplies blood to the ventral vessel 10. Excretory system A. No nephridia at first three & last segments B. Main characteristics of nephridium: 1. Ectodermal in origin. 2. Metamerically arranged. 3. Has two openings 4. Presence of cilia. Zoology 102 9 ‫دكتور الحسيني يعقوب‬  C. Main functions 1. Excretion of ammonia 2. Osmoregulation 3. May help in reproduction 11. Well Developed Nervous System  cerebral ganglia ( large brain)  circumpharyngeal connectives  ventral nerve cord  Main characteristics of nervous system: 1. Double,bilateral 2. Central. 3. Ventral. 4. Ladder- shape. ‫شبو السلم‬ 5. Metameric. 6. Ganglionated.‫بو عقد عصبيو‬ Zoology 102 10 ‫دكتور الحسيني يعقوب‬ 12. Reproduction 1. sexes are separate 2. temporary gonads ( breeding season from coelomic epithelium), without gonoducts 3. gametes found in the coelomic cavity till maturation 4. Mature gametes are discharged to the exterior by rupture of the body wall 5. external fertilization takes place 6. It exhibits a non-sexual Neries- phase and sexual Heteronereis- phase, free-swimming 7. (seasonal dimorphism). 8. modification of parapodia is an adaptation for swimming & increase their surface for rapid respiration 13. Trochosphere larva a) ciliated free-swimming b) metamorphose into adult c) ectodermal oesophagus d) endodermal stomach e) diploblastic stage f) -ve coelom Zoology 102 11 ‫دكتور الحسيني يعقوب‬ ANNELIDA CLASSIFICATION Polychaeta Oligochaeta Hirudinea Archannelida O1:Errantia Ex.Allolobophora Ex.Hirudo Ex.Polygordiu Ex1.Nereis Ex2.Aphrodite O2:Sedentaria Ex1.Sabella Ex2.Arenicola external +ve +ve +ve -ve segments chaetae +ve +ve -ve -ve number great few ----- ----- of chaetae Zoology 102 12 ‫دكتور الحسيني يعقوب‬