Phylum: Aschelminthes : General features and Example

Defination of Aschelminthes

Aschelminthes are  Pseudocoelomate , Triploblastic, bilateral symmetrical roud worms with  organ level of organisation . 

General features 

• The body of the aschelminthes is circular in cross-section, hence, the name roundworm. 

• They may be freeliving, aquatic and terrestrial or parasitic in plants and animals. 

• Roundworms have organ-system level of body organisation. 

• They are bilaterally symmetrical, triploblastic and pseudocoelomate animals. 

• Alimentary canal is complete with a well- developed muscular pharynx. 

• An excretory tube removes body wastes from the body cavity through the excretory pore. 

• Sexes are separate (dioecious), i.e., males and females are distinct. Often females are longer than males.

• Fertilisation is internal and development may be direct or indirect. the young ones resemble the adult 

• Body of Round worms are covered by the syncytial cuticle to protect the body from digestive enzyme in body of host.

• They have  nervous system including nerve ring around the Oesophagus and branches nerves through out the body.

• Respiratory system is absent . They Respire through their body surface.

Examples of Platyhelminthes  

1. Ascaris 

• Ascaris is long round worm which can be up to more than 30 cm but female is always longer than male. 

•  Ascaris show sexual dimorphism. Male is usually shorter with folded end at one side.

• Ascaris has non cellular cuticle covering on body to get protection from digestive enzyme of host.

• Digestive system is well developed in with various digestive organs.

• Nerrvous system include nerve ring with numerous nerve cords.

•  Embryonated egg is infective stage of Ascaris. These eggs are passed out with the stool of infective person and make contaminated the soil.

• Egg is ingested by host when it comes contact with contaminated soil into host body. 

• Egg is developed into Rhabditiform larva and than into adult Ascaris.

2.Wuchereria 

• It is commonly called as Filaria worm.

• It show sexual dimorphism. Adult female is usually longer  with rounded  ends and male is shorter than female. The tail of male is centrally curved.

• Wuchereria has 15 pairs of sensory organs.

• It resides in lymphatic system of Human but may also found in blood.

• Alimentary canal include Muscular pharynx oesophagus intestine and anus. The mouth is present without oral lips.

• Female genital pore is present as vulva whereas male has cloaca.

• Penial setae or copulatory Spicules are present in male.

• Microfilareae is larval stage of wuchereria found in blood of human.

3.Ancylostoma

• It is commonly called as Hook worm.

• Adult female is usually longer  with rounded  ends and male is shorter than female

• Hook worm is small cylinder and white or pinkish in color.

• It has sharp teeth or cutting plate in their buccal capsule.

• Male Hook worm has bursa with two Spicules.

• Female Hook worm has vulva. It lay 10000 to 30000 eggs per day

• It create various health complex like anemia , Malnutrition and protein loss.