Question

Nerve cord of cockroach is
A. Dorsal and single
B. Dorsal and double
C. Ventral and single
D. Ventral and double

Answer 1

Hint: The brain, thoracic, and abdominal ganglia of cockroach are bound together by a pair of interganglionic connectors to form the ventral nerve cord (VNC).

Complete answer:
Cockroaches are insect species found in Phylum Arthropoda. The body of the cockroach is separated into three regions namely, head, thorax and abdomen. They have joined appendages. The body is enclosed by a hard exoskeleton made of chitin. There are hardened plates called sclerites on each segment of the exoskeleton which are connected together by a thin, flexible articular membrane.

The anterior end of the head bears the appendages containing the biting and chewing portions of the mouth. The mouthpieces consist of a labrum (upper lip), a pair of mandibles, a pair of maxillae and a labium (lower lip). Mandibles are present on most insects and are the bits that break the food into smaller pieces so that the insect can push it into its throat.

The nervous system of the cockroach includes a number of fused, segmented ganglia, linked by paired longitudinal connectors on the ventral side. Three ganglia are present on the thorax, and six in the abdomen. The nervous system of the cockroach is distributed all over the body. The head retains a bit of a nervous system, while the remainder is positioned around the ventral portion of the body. The ventral nerve cord of the cockroach comprises several very large-diameter axons that arise in the last (6th) abdominal ganglion and spread to the brain.

Hence, the correct answer is option (D)

Note: Owing to their open circulatory system and the fact that they breathe from tiny holes in each of their body parts, cockroaches do not rely on the mouth or the head to breathe.