This document provides an overview of the phylum Aschemlinthes. It discusses their key features including their cylindrical body shape without segmentation, bilateral symmetry, triploblastic germ layer, and tube within tube organ system level of organization. Their body wall has a cuticle, epidermis, and longitudinal muscle layers. They have a pseudocoel body cavity and hydrostatic skeleton. Their digestive system is complete with a mouth, pharynx, intestine, and anus. Respiration occurs through the body surface and circulation is undeveloped. Their nervous system includes a circum pharyngeal ring and sensory structures. Excretion involves protonephridia. Reproduction involves separate sexes with internal fertilization and mostly

1. ANIMAL KINGDOM
ASCHELMINTHES

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4. Introduction, Other features, Body wall, Body cavity and
skeleton, Digestion, Respiration and circulation, Nervous
system, Excretion, Reproduction
Synopsis

5. Introduction

6. INTRODUCTION
◈ Earlier round worms or thread worm were classified
as Achelminthes by Grobben.
◈ Gegenbour established the Phylum Nemathelminthes.
Phylum included round worm.
◈ Nematods are found everywhere in fresh water, sea
water, soil humus - rich soil. Many as a parasite and
cause health problems.

7. Other features

8. OTHER FEATURES
◈ Animal of this phylum are cylindrical, tapering at both
end without segmentation.
◈ Symmetry - Bilateral, Germ layer - Triploblastic, Level
of organisation - Organ system level and having tube
within tube plan.
◈ Anterior end does not show distinct head.
◈ No appendage

9. Body wall

10. BODY WALL
◈ 1. Cuticle - Firm, non living, resistant to digestive
enzymes of host.
◈ Moulted (changed) many time during growth period
(usually four times).
◈ 2. Epidermis - Without cilia. Syncytial i.e. a continuous
layer of cytoplasm having scattered nuclei.
◈ 3. Muscle layer - Longitudinal fibre divided into four
quadrants.

11. Body cavity and
skeleton

12. BODY CAVITY AND SKELETON
◈ Body cavity is there between body wall and digestive
tract. Which is not lined by mesothelium i.e.
Pseudocoel (developed from blastocoel) and contain
Pseudocoelomic fluid.
◈ Skeleton is not mineralized.
◈ High fluid pressure in the pseudocoelom maintains the
body shape. It is called Hydro skeleton.

13. Digestion

14. DIGESTION
◈ Digestive tract is complete
and differentiated into
mouth, pharynx, intestine
& Anus.
◈ Mouth is surrounded by 3 -
lips having sensory papillae
and amphids.
◈ Pharynx is muscular. It is
used to suck of food.
◈ Intestine is non muscular.

15. Respiration and
Circulation

16. RESPIRATION AND CIRCULATION
◈ Respiration is through body surface by diffusion.
◈ Circulatory system is undeveloped

17. Nervous system

18. NERVOUS SYSTEM
◈ Nervous system comprises
of circum pharyngeal ring
(Brain).
◈ Sense organs like Papilalae
(Tangoreceptors) Amphids
(Chemoreceptor) are present
on lip
◈ Paired unicellular Phasmids
(chemoreceptor) are found
near hind end of body.

19. Excretion

20. EXCRETION
◈ Excretory system is H-shape
of gland cells or intracellular
canal or Protonephiridia -
(Renettle cell).
◈ Excretory matter is ammonia.

21. Reproduction

22. REPRODUCTION
◈ Reproduction system is developed as sexes are
generally separate.
◈ Sexual dimorphism is present.
◈ Male is smaller than female and curved from its caudal
end.
◈ Male has penial spiculas for copulation.
◈ Genital tract joins digestive track to form cloaca.
Female is larger than male and straight.

23. REPRODUCTION
◈ Female lays numerous eggs with Chitinous
shell.
◈ Fertilization is internal and development
is mostly direct.
◈ Cleavage is Holoblastic spiral and
determinate type.
◈ Number of cells are fixed from larva to
adult development knows as Eutely.

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