Q. 2. What is metagenesis? Describe the life-cycle of Obelia.
Ans.2. Reproductive System
The animal is hermaphrodite but cross fertilisation occurs as a rule.
A. The Male Reproductive Organs
The male reproductive organs are: testes, vasa deferentia, seminal vesicle. ejaculatory duct, cirrus and cirrus sac.
1. Testes: These are highly branched and tubular structures. A pair of them are situated in the middle part of the body, one behind the other in tandem arrangement.
2. Vasa deferentia: A narrow delicate vas deferens arises from each testes and runs forward forming the common sperm duct just below the ventral sucker.
3. Seminal vesicle: The common sperm duct leads into a large muscular pear-shaped sac, the seminal vesicle, which lies in front of ventral sucker.
4. Ejaculatory duct: It arises as a fine convoluted tube from the seminal vesicle and runs forward in a zigzag fashion through the cirrus to open into the genital chamber through the male genital pore.
5. Cirrus and cirrus sac: The cirrus or penis is a muscular cylindrical structure traversed internally by the passage of ejaculatory duct. It can be everted out and drawn in through the genital pore and thus helps in copulation. The cirrus, prostate glands and the seminal vesicle are enclosed in a bag-like cirrus sac or cirrus sheath.
6 Prostate glands: Numerous unicellular prostate glands surround the ejaculatory duct and open into it. The alkaline prostatic secretion helps in the movement of sperms.
(B) Female Reproductive Organs
These are ovary, oviduct, ootype, uterus, shell glands, vitelline glands and Laurer’s canal.
1. Ovary: Fasciola has single ovary. It is a large, highly branched tubular structure, situated on the right side in front of testes. It occupies the anterior one third of the body.
2. Oviduct: From the inner side of ovary arises a short, narrow and convoluted oviduct. It runs downwards and backwards to join the uterus. During its course it gives out Laurer’s canal and receives the common vitelline duct.
3. Ootype: The union of oviduct with the vitelline duct is markedly swollen to form the ootype. It is surrounded by numerous shell glands or Mehlis glands. Inside the ootype the eggs are collected and stored. The ootype is said to be absent in F. hapatica.(BSc Lower Non-chordates Fasciola Hepatica Question Answers)
4. Uterus: The uterus arises from the ootype as a wide convoluted tube and runs forward to open into the genital atrium on the left side by the female genital pore. It is filled with fertilised eggs. The terminal part of uterus is muscular and helps in ejecting out the eggs.
5. Shell gland: Encircling the ootype are found numerous unicellular shell glands or Mehlis glands. Their secretion is deposited inside the ootype. It forms the shell around the eggs and lubricates their passage in the uterus.
6. Vitelline glands and vitelline ducts : The vitelline glands or the yolk glands are in the form of numerous minute vesicles or follicles arranged on either side of the body from one end to the other. A fine duct arises from each vesicle and after uniting with similar ducts from other vesicles opens into the lateral longitudinal ducts. The two longitudinal ducts are connected in the middle line by a transverse vitelline duct. A median duct arises mesially from the transverse vitelline duct and joins the oviduct.
7. Laurer’s canal: The Laurer’s canal arises from the oviduct and acts as a sperm duct. It develops a temporary opening on the dorsal body surface during the breeding season.
BSc 1st Year Lower Non-chordates Fasciola Hepatica Sample Model Practice Question Answer Papers