Test: Cockroach (NCERT) - NEET MCQ

Leg of the cockroach is articulated with its thoracic by a stout flattened, basal coxa, followed by a triangular trochanter. The latter is fused to a stout spiny femur followed by a slender spiny tibia, which is the longest segment of leg. Finally, the tarsus is made of 5 very small movable podomeres or tarsomeres bearing fine hairs.

Cockroach possesses ventral nerve cord. Spiracles help in respiration. Phallomere is present in male cockroach. It helps in the transfer of spermatophore from male cockroach to female cockroach. Ocellus is a simple eye that occurs in insects and other invertebrates.

The two mandibles in the mouth part of cockroach bear teeth which cut and masticate the food into fine particles. Gizzard is a part of alimentary canal which is used for grinding the food as it bears six muscular folds covered by chitinous conical plates, the teeth. Malpighian tubules arise from the junction of mid-out and hind-gut. Orygen is transported by tracheae as no pigment is present in the blood. Nitrogenous excretory product is uric acid.

Immediately after hatching, the nymphs undergo first moulting or ecdysis and then 13 successive moults follow. As nymphal development proceeds, the wing pads arise, body increases in size, colouration becomes darker and ultimately the adult takes its form with fully developed wings and genitalia.

In male cockroach, from the side of the 9^th sternum, there arises a paired, small unjoined outgrowths called anal styles. These structures are sensitive to touch. These are absent in female cockroach. Nervous system is located ventrally. There are 100-150 Malpighian tubules. Grinding of food is carried out by gizzard.

Figure (C) shows the mandibles of a cockroach.

Collaterial glands are present in female cockroach as part of reproductive system. These glands are branched tubular glands opening independently on the dorsal side of the genital chamber. The secretion produced by these glands forms the oothecal case of ootheca.

Alimentary canal of cockroach is a long and somewhat coiled tube of uneven diameter. Crop is large, thin-walled, pear-shaped sac, which extends well up to the third or fourth abdominal segment. It is the largest part of foregut. Crop serves as a reservoir for storing food. The gizzard or proventriculus, marks the end of foregut. In the gizzard, the cuticular lining first forms 6 plates with teeth to grind the food, and then bears bristles to let only the well crushed food to pass on. Opening into the anterior end of midgut are 7 or 8 short, narrow, blindly ending hollow tubes, called enteric or hepatic caeca. These are internally lined by epithelium and secrete digestive enzymes. From the junction of midgut and hindgut arise 80 to 90 very narrow, thread-like, yellow-coloured blind tubules projecting freely into haemocoel. These are called Malpighian tubules and are excretory in function.

The mouth parts of cockroach are of biting and chewing type consisting of labrum (upper lip), a pair of mandibles, a pair of maxillae and a labium (lower lip). Within the oral cavity enclosed by the mouthparts, lies a median flexible lobe called hypopharynx (tongue).

In female cockroach, each ovary is formed of a group of eight ovarian tubules or ovarioles, containing a chain of developing ova

Hepatic caecae secrete digestive juice and Malpighian tubules help in removal of excretory products from haemolymph.

In male cockroach, the junction of vasa defferentia and the ejaculatory duct is surrounded by a characterstick mushroom gland; lying in the 6^th-7^th abdominal segments. Its secretion provides nourishment to the sperms and forms the innermost layer of spermatophore. Cockroach excretes uric acid, therefore it is uricotelic. Blood from sinuses enter 68
heart through ostia and is pumped anteriorly to sinuses again. In cockroach, excretion is done by Malpighian tubules. In addition, the fat body, neohrocytes and uricose glands also help in excretion.

'B' is seminal vesicle where the sperms are stored. Here, the sperms are glued together in the form of bundles called spermatophores which are discharged during copulation.

Smooth muscle - do not have striations and are spindle shaped
Cockroach - 10 pairs of spiracles
Earthworm - Alimentary canal consists of a sequence of pharynx → oesophagus → gizzard → stomach → intestine
Frog - Body divisible into two regions:  head and trunk

The development of Periplaneta americana is paurometabolous, i.e., there is development through nymphal stage.