11. Study of Animal Type - Cockroach - part 07 - Reproduction system

 

11. Study of Animal Type - Cockroach - part 07 - Reproduction system


Reproduction system :

  • Cockroach is dioecious organism i.e. male and female individuals are separate.

1. Male Reproductive System : 


  • Male reproductive system consists of - 
  1. primary reproductive organs
  2. secondary reproductive organs. 
  • Primary sex organs (male gonads) are called testes which are paired and located in the 4th to 6th abdominal segments. 
  • They produce sperms which are carried by vasa deferentia. 
  • It is a pair of thin tubular structure arising from the testes and opening into the ejaculatory duct through seminal vesicle. 
  • They carry sperms to the ejaculatory duct. 
  • Ejaculatory duct opens into male gonopore situated ventral to anus.
  • Mushroom shaped gland or Utricular gland is accessory reproductive gland. 
  • It is present in the 6th to 7th abdominal segments.
  • Male gonapophyses or phallomere are external genitalia of male. These are three asymmetrical chitinous structures surrounding the male gonophore.
  • The sperms produced by the testes are stored in seminal vesicles and are glued together in the form of bundles called spermatophores.
  • These spermatophores are deposited in female reproductive tract during copulation.

2. Female Reproductive System : 


  • Female reproductive system consists of -  
  1. primary reproductive organs
  2. secondary reproductive organs. 
  • Primary reproductive organs are ovaries. 
  • There is a pair of large ovaries, lying laterally in the 2nd to 6th abdominal segments. 
  • Each ovary is formed of a group of 8 ovarian tubules or ovarioles, containing a chain of developing ova.
  • All ovarioles of an ovary open in lateral oviduct of respective side. 
  • Both lateral oviducts unite to form common oviduct or vagina.
  • Common oviduct or vagina opens into the genital chamber (bursa copulatrix), the female organ of copulation.
  • A sperm storing structure called spermatheca is present in the 6th segment that open into the genital chamber. 
  • Besides, paired accessory glands-collaterial glands are also present that open in genital chamber.
  • Female gonapophyses consist of six chitinous plates surrounding the genital pore.



Fertilization and formation of ootheca :

  • Male and female cockroaches come together by their posterior ends and with the help of phallomeres. 
  • The spermatophores are transferred to the genital chamber of female cockroach.
  • The sperms are released from spermatophore and they reach the spermatheca.
  • The eggs are discharged from both the ovaries alternately into the common oviduct and pass into the genital chamber where they are fertilized by the sperms coming from the spermatheca. 
  • The process of fertilization is internal.

Ootheca : 

  • The secretion of collaterial glands forms a capsule around them is called as ootheca or egg case. 
  • Ootheca is dark reddish to blackish brown capsule about 8 mm long, containing 14 to 16 fertilized eggs in two rows.
  • Ootheca are dropped or glued to a suitable surface like a crack or crevice of good humidity near the food source. 
  • On an average, a female produces 9 to 10 oothecae.

Development of Eggs : 


  • The development of Periplaneta americana is paurometabolous i.e.there is development through nymphal stage.
  • Embryonic period varies as per temperature and humidity. 
  • At 24oC, duration is about 58 days and at 30oC, the duration is about 32 days.

Fertilized egg-- Nymph --Adult

  • The nymph looks like the adult but far smaller and is sexually immature. 
  • After sufficient growth, nymph undergoes moulting and enters into next instar (a stage between two successive moults).
  • Cockroach may undergo moulting for about 13 times before reaching the adult stage. 
  • The nymphal stages have wing pads but only adult cockroaches have wings.

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