Reproduction system :
The cockroach is a uni sexual animal & it exhibits sexual dimorphism.
Male reproductive organs :
The male cockroach has following reproductive organs-
- Testes : There is a pair of testes in 4th. 5th & 6th abdominal segments. Each testis is tri-lobed. Each lobe has 20 tubular lobules.
- Vas deferens : Each testis leads into a vas deferens. Both the vas deferens open separately at the base of the mushroom gland.
- Mushroom or Utricular gland : It is found in 7th abdominal segment & opens into an ejaculatory duct. It consists of three types of structures—
(a) Seminal Vesicles : They are small & round structures which store the sperms.
(b) Short central tubules or Utricular minores: They are small tubules which secrete nutrients for the sperms.
(c) Long peripheral tubules of Utriculi majors : They are long & thin tubules. Which secrete inner layer of the spermatophore.
- Ejaculatory duct : The male cockroach has a thin, glandular & contractile ejaculatory duct. It is attached to the ventral phallomere. It opens outside through the male gonopore. It secretes teh middle layer of the spermatophore.
- Phallic or Conglobate gland : It is a white & bag-like gland which is situated ventral to the ejaculatory duct from 6th to 9th abdominal segments. Its anterior end is broad & the posterior end is narrow tube-like. It opens outside through the male gonopore withe help of a duct. The duct is attached to the right
- Phallomeres of Gonapophyses :
The male gonopore is provided with three irregular chitinous plates which are called as phallomeres. They are as follows
(a) Left phallomere : It has 4 lobes viz.—asperate lobe, titilator. acutolobus & pseudopenis.
(b) Right phallomere : It includes a hook, a serrated lobe & two opposite lobes.
(c) Ventral phallomere : It is a small & flat plate. The ejaculatory duct is attached to it.
Female reproductive organs :
They female reproductive include –
- Ovaries :
There is a pair of ovaries which are found in 3rd to 6th abdominal segments. Each ovary has eight long, light yellow & tubular ovarioles.
Each ovariole has 5 parts –
(i) Suspensory ligament
(ii) Gennarium
(iii) Vitellarium
(iv) Ovarium or Egg chamber
(v) Pedicle
The suspensory ligaments of all the 8 ovarioles remain joined.
- Oviduct & common oviduct :
All the eight ovarioles of one ovary open into an oviduct. Both the oviducts join to form a common oviduct or vagina which is found in 7th segment & opens into a genital chamber.
- Gynatrium :
It is also called as brood pouch. It is formed by the modification of the 8th & 9th stemites. It is divisible into 2 parts—
(a) Genital chamber—Anterior & small
(b) Oothecal chamber—Posterior & large
The gynatrium opens outside through the female gonopore.
- Spermathecae :
There is a pair of spermathecae which are unequal i.e. right spermatheca is comparatively small. They open through a common duct into the genital chamber. The opening is situated on a spermathecae papilla. They store sperms after the copulation.
- Colleterial glands :
There is a pair of colleterial glands which are shiny, branched & uneuqal. The left gland is large & more branched.
Both the glands open through a common duct into the oothecal chamber. The right gland secretes dihydroxy phenol & the left gland secretes a protein. Both these substances react to form a scleroprotein which is dark brown in colour.
- Female gonopophysis :
It has 6 chitinous plates attached to the roof of the oothecal chamber which are called as ovipositors. The female gonopore is covered by two gynovalvular plates which arc large & oval. They are formed by the modification of 7th sternum.
Reproduction physiology :
(i) Formation of spermatophore
It is formed in the male reproductive organs. It is a bag-like structure which is three-layered. It is full of sperms. The inner layer is secreted by the long peripheral tubules of the mushroom gland, the middle layer is secreted by the ejaculatory duct & the outer layer is secreted by the phallic gland
(ii) Copulation
The copulation in cockroach takes place in the night in tail to tail position. It’s duration is of one hour. The copulation takes place during breeding season & the breeding season extends from March to September. During copulation, the male opens the female gonopore with the help of phallomeres and insert one spermatophore into the genital chamber. The spermatophore gets attached to the spermathecal papilla and the sperms get stored into the spermathecae. It takes about 20 hours. The empty spermatophore is forced out which is consumed as food by any cockroach. During breeding season, the male is attracted by the pheromone secreted by female cockroach.
(iii) Fertilization
As a result of copulation. 16 ova are released from both the ovaries in the oothecal chamber. The ovipositors arrange the ova into two rows of 8-8 ova. Now the sperms are released on the ova from the spermathecae. Hence, the fertilization takes place in the genital chamber.
(iv) Formation of Ootheca
The ovipositors push the fertilized eggs into the oothecal chamber in 2 rows of 8 in each row. In the oothecal chamber. the secretions of the collecterial glands form a dark brown colored covering around the fertilized eggs. The resulting structure is called as ootheca. The formation of ootheca takes about 20 hours.
The length of the ootheca is 8-10 mm. It’s one end is serrated. A female cockroach forms about 20-40 oothecae in it’s life span. The female carries the ootheca for few days & finally it deposits the ootheca in some dark, dry & warm place. The eggs of the cockroach are centrolecithal & are covered by chitinous shell. Every egg has a minute micropyle.
