Pseudocoelomates: Nematoda and Rotifera PDF

 PSEUDOCOELOMATES ▪ Pseudocoelom, a body cavity not entirely lined by mesoderm ▪ These are the organisms that have false body cavities ▪ also known as a blastocoelomate  PHYLUM NEMATODA - Round worms - Usually lived in soil and in fresh or salt water...

 PSEUDOCOELOMATES ▪ Pseudocoelom, a body cavity not entirely lined by mesoderm ▪ These are the organisms that have false body cavities ▪ also known as a blastocoelomate  PHYLUM NEMATODA - Round worms - Usually lived in soil and in fresh or salt water - They are long and slender , smooth and have tapering ends. - They grow from 1/5 millimiter to 130 centimeters (52 inches)  PHYLUM NEMATODA Characteristics of Nematodes: Triploblastic, bitateral vermiform, unsegmented, pseudocoelomate Body wall round in cross section with longitudinal muscles only Ecdysis of the collagenous cuticle accompanies growth of juvenile stages Complete digestive tract Excretory system usually composed of collecting tubules or renette cells STRUCTURE AND FUNCTION nematode body is slender, elongate, cylindrical and tapered at both ends. Contains noncellular, collagenous cuticle STRUCTURE AND FUNCTION STRUCTURE AND FUNCTION STRUCTURE AND FUNCTION STRUCTURE AND FUNCTION Some nematodes have lips surrounding the mouth, some may have spines or teeth on or near the lips.  DIGESTIVE SYSTEM Nematodes have a complete digestive system which is consist of mouth, buccal cavity, muscular pharynx, long tubular intestine, rectum and anus.  EXCRETION Osmoregulation and excretion of nitrogenous waste products with two systems: Glandular system – which are utilized by aquatic species Tubular system – parasitic roundworms  NERVOUS SYSTEM Consist of anterior neural ring The nerve extend anteriorly and posteriorly REPRODUCTIVE DEVELOPMENT Most nematodes are dioecious and dimorphic REPRODUCTIVE DEVELOPMENT REPRODUCTIVE DEVELOPMENT REPRODUCTIVE DEVELOPMENT  Ascaris lumbricoides - Live in the intestine of pigs, horses and sometimes humans - A typical female Ascaris is prolific, producing more than 200,000 eggs daily. Ascaris lumbricoides Life Cycle Ascaris lumbricoides  Necator americanus - Hookworm - Intestinal, blood- feeding, parasitic roundworms that cause types of infection known as helminthiases.  Necator americanus - They hold into intestinal worms with teeth and feed on blood and tissue fluids. Necator americanus Life Cycle Enterobius vermicularis - Pinworm - A “threadworm” is a small, thin, white round nematode that lives in the colon and rectum of humans - Can be transmitted via fecal-oral route Life Cycle  Wuchereria bancrofti - Filarial worm - responsible for the disfiguring disease called elephantiasis - This infects the lymphatic system of its host Life Cycle Wuchereria bancrofti  Dirofilaria immitis - Dog parasite - Adult worms live in the heart and large arteries of lungs thus called “heartworm”  Trichinella spiralis - Trichina worms - Pork worm - Nematodes parasite responsible for the disease known as trichinosis Life Cycle Trichinella spiralis  PHYLUM ROTIFERA - 100-500µ𝑚 nematodes that live in marine or freshwater environment - Rotifers have crown cilia at the anterior end, corona - Complete digestive system with mouth and anus  PHYLUM ROTIFERA Characteristics of Rotifera: Triploblastic, pseudocoelomate Complete digestive system Ciliated corona (usually present) Toes with adhesive glands Epidermally derived cuticle Photonephridia with flame cells Reproduction by parthenogenesis is common  EXTERNAL FEATURES ▪ In some species, the cuticle forms a thick encasement called lorica ▪ epidermis is syncytial ▪ Three main parts: head Trunk Foot FEEDING AND DIGESTIVE SYSTEM ▪ Most of them feed on small microorganisms and suspended organic materials. ▪ Salivary and digestive glands secretes digestive enzymes into the pharynx and stomach. ▪ Complete extracellular digestion and absorption occur in the stomach.  OTHER ORGANS ▪ All visceral organs lie in the pseudocoelom ▪ Protonephridia function in osmoregulation where it empties into the cloacal bladder ▪ Rotifers exchange gases across body surface ▪ Nervous system is composed of two lateral nerves and a bilobed ganglionic brain  REPRODUCTION AND DEVELOPMENT ▪ They reproduce sexually, but several perform parthenogenesis. REPRODUCTION AND DEVELOPMENT