Question

5.a) Describe the parts of the body of a tapeworm.

5.b) Tapeworms are hermaphroditic. What is the meaning of this term?

Answer 1

5) a. The body of tapeworm consists of the following parts

Parts for attachment : head and neck

Parts for reproduction : Proglottids

• Head or Scolex : It is knob like and consists of hooks , rostellum and sucker. Hooks are arranged as a ring on rostellum which is present at the tip of the scolex. Rostellum is the part of the scolex which gets attached to the intestine of the host. The sharp hooks present in the rostellum imbed into the intestinal lining of the host and provide a grip to the tapeworm to hold on to the intestine of the host. The suckers are present below the rostellum. There are four suckers. They also helps in anchoring. In some species of tapeworm, the hooks may be absent. In such cases the suckers help them to anchor on to the intestine of the host.
• Neck : Neck connects between the scolex and first body segment. It extends from scolex and connects to the first segment of immature proglottid.
• Proglottid : The remaining part of the body of the tape worm consists of a series of rectangular body segments which are flat. They are generated by neck. They can have a length of about 4.6 to 6.1 metre. The proglottids which are close to the neck are immature and the proglottids away from the neck are mature. The proglottids at the distal end of scolex are the old ones. They are regularly sheded by the tapeworm along with faeces. New proglottids are formed at the proximal end of the head. Male and female sex organs are present in the mature proglottids. The mature proglottid also consists of genital openings for the release of fertilised eggs called gravids.

The outer covering of the tapeworm is the cuticle through which it absorbs nutrients from the host. Hence digestive system is absent. Along the length of the body of the tapeworm, runs the rudimentary nervous system and excretory system.

5) b. Hermaphrodite means an organism having both the male and female organs. Which means an organism which is capable of reproducing on it's own, without the help of a partner. A single organism is capable of producing both the gametes ( eggs and sperms ). 5% of the known animal species are hermaphrodites (6500 species) .Many of the invertebrates and plants are hermaphrodites.

Hermaphrodites can be divided into 3:

• Sequential hermaphrodites : In which an organism is born in one sex and later it changes to the another sex. This change in sex happens only once. It can be seen in fish, gastropods etc.
• Simultaneous hermaphrodites: In this type of hermaphrodites, both the male and female sex organs are present completely throughout their lifecycle. Tape worm is an example of this.
• Pseudohermaphroditism: They are not actually hermaphrodites. For example, in hyenas, the identification of male and female is difficult until it reaches the sexual maturity.