Biology COCKROACH: REPRODUCTION

KEY TOPICS

`star` Reproductive System
`star` Development
`star` Economic Importance

REPRODUCTIVE SYSTEM

● Cockroaches are `color{Brown}"dioecious"` and both sexes have `color{Violet}"well developed"` `color{Violet}"reproductive organs"`.

● `color{Violet}"Male reproductive system"` consists of a `color{Violet}"pair of testes"` lying one on each lateral side in the `color{Violet}"4th -6th abdominal segments"`.

● From each testis arises a `color{Brown}"thin vas deferens"`, which opens into `color{Violet}"ejaculatory duct"` through seminal vesicle.

● The `color{Violet}"ejaculatory duct"` opens into `color{Violet}"male gonopore"` situated ventral to anus.

● A characteristic `color{Violet}"mushroom shaped gland"` is present in the 6th-7th abdominal segments which functions as an `color{Violet}"accessory reproductive gland"`.

● The `color{Violet}"external genitalia"` are represented by `color{Brown}"male gonapophysis or phallomere"` (chitinous asymmetrical structures, surrounding the male gonopore).

● The sperms are stored in the `color{Violet}"seminal vesicles"` and are glued together in the form of bundles called `color{Violet}"spermatophores"` which are discharged during copulation.

● The `color{Brwon}"female reproductive sysytem"` consists of two `color{Violet}"large ovaries"`, lying laterally in the 2nd – 6th abdominal segments.

● Each ovary is formed of a group of `color{Violet}"eight ovarian tubules or ovarioles"`, containing a chain of developing ova.

● Oviducts of each ovary unite into a `color{Violet}"single median oviduct"` (also called `color{Brown}"vagina"`) which opens into the `color{Violet}"genital chamber"`.

● A `color{Violet}"pair of spermatheca"` is present in the 6th segment which opens into the `color{Violet}"genital chamber"`.

● `color{Violet}"Sperms"` are transferred through `color{Violet}"spermatophores"`.

● Their `color{Violet}"fertilised eggs"` are encased in `color{Violet}"capsules"` called oothecae.



DEVELOPMENT

● `color{BBrown}"Ootheca"` is a dark `color{Violet}"reddish to blackish brown"` capsule, about 3/8" (8 mm) long.

● They are `color{Violet}"dropped or glued"` to a suitable surface, usually in a crack or crevice of `color{Violet}"high relative humidity"` near a food source.

● On an average, females produce `color{Violet}"9-10 oothecae"`, each containing `color{Violet}"14-16 eggs"`.

● The development of `color{Violet}"P. Americana"` is `color{Violet}"paurometabolous"`, meaning there is development through `color{brown}"nymphal stage"`.

● The `color{Violet}"nymphs look"` very much like adults.

● The nymph grows by `color{Violet}"moulting about 13 times"` to reach the adult form.

● The next to last nymphal stage has `color{Violet}"wing pads"` but only `color{Violet}"adult cockroaches have wings"`.



ECONOMIC IMPORTANCE

● Many species of `color{Violet}"cockroaches are wild"` and are of `color{Violet}"no economic importance"`.

● A few species thrive in and around `color{Violet}"human habitat"`.

● They are `color{Violet}"pests"` because they `color{Violet}"destroy food and contaminate it"` with their smelly excreta.

● They can transmit a `color{Violet}"variety of bacterial diseases"` by contaminating food material.

 
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