Question

Number of chambers in the heart of cockroach is
a. 5
b. 9
c. 13
d. 16

Answer 1

Hint: Cockroach is a terrestrial and cosmopolitan insect found in places with warmth, moisture, darkness and plenty of food. It is a nocturnal and omnivorous organism. The blood circulatory system in cockroaches is of open or lacunar type.

Complete answer:
- The haemocoel of cockroach is divided into three interconnected chambers- dorsal or pericardial sinus, middle or perivisceral sinus and ventral or perineural sinus.
- Heart of the cockroach is elongated, thick, muscular and 13-chambered. Each chamber represents one heart. It lies in the pericardial sinus of the haemocoel.
- Each chamber of the heart receives oxygenated blood from the dorsal sinus through one pair of slit-like apertures called ostia which are valvular apertures.
- Heart contracts postero-anteriorly at the rate of 100-120 times/ minute so the blood also flows postero-anteriorly. Muscles responsible for blood circulation in cockroaches are alary muscles, one pair in each segment, one on either side of the heart.
- Pointed ends of the alary muscles are attached to the terga. The first chamber leads into an aorta that opens in head sinuses which are connected to pericardial sinus through perineural and perivisceral sinuses.
- Blood of the cockroach is colorless as it has no haemoglobin so is also called hemolymph. It is formed of a transparent liquid called plasma and numerous corpuscles called haemocytes. Blood corpuscles are of two types- circular pro leukocytes and amoeboid phagocytes.

Hence, the correct answer is option (C).

Note: Each chamber of the heart receives hemolymph from the dorsal sinus through one pair of slit-like apertures called ostia which are valvular apertures. The body of the cockroach contains blood which bathes viscera in it.