Question

Which of these differences between male and female cockroaches (Periplaneta americana) is correct?

• A. The testis in male cockroach is longer than the ovary in female cockroach.
• B. The male cockroach has anal cerci while female cockroach has an anal style.
• C. The male cockroach has one chromosome less than the female cockroach.
• D. The spermatheca is found in male cockroach while ootheca is found in the female cockroach.

Answer 1

Answer: (C)

The male reproductive system of cockroach consists of a pair of testes lying on each lateral side in the 4^th -6^th abdominal segments. The female reproductive system of cockroach consists of two large ovaries, lying laterally in the 2^nd - 6^th abdominal segments. Thus ovaries are longer than testes. Males bear a pair of short, threadlike anal styles which are absent in females. In both sexes, the 10^th segment bears a pair of jointed filamentous structures called anal cerci. A pair of spermatheca is present in the 6th segment of female cockroach which opens into the genital chamber. Their fertilized eggs are encased in capsules called oothecae. Periplaneta americana has a $XX-XO$ type of sex determination. Females have 34 chromosomes $(32+XX)$ and males have 33 chromosomes $(32+X).$