Question

Consider the following four statements (i) - (iv) and select the correct option stating which ones are true (T) and which ones are false (F). (i) In male cockroach genital pouch or chamber lies at the hind end of abdomen bounded dorsally by \(9^{\text {th }}\) and \(10^{\text {th }}\) terga and ventrally by the \(9^{\text {th }}\) sternum. (ii) In cockroach the haemolymph is composed of colourless plasma and haemocytes. (iii) In female cockroach each ovary is formed of a group of ten ovarian tubules or ovarioles, containing a chain of developing ova. (iv) In cockroach the nymph grows by moulting about 6-13 times to reach the adult form.

Short answer

All statements (i), (ii), (iii), and (iv) are True.

Step-by-step solution

Verify Statement (i)

To verify the accuracy of statement (i), refer to texts or scholarly articles about the cockroach's anatomy. The male cockroach's genital pouch is indeed located at the hind end of its abdomen, bounded dorsally by the 9th and 10th terga, and ventrally by the 9th sternum. Therefore, the statement (i) is True.

Verify Statement (ii)

To confirm statement (ii), return to authoritative sources on cockroach physiology. In the cockroach, haemolymph is indeed composed of colorless plasma and haemocytes (the invertebrate equivalent of blood cells). Thus, statement (ii) is True.

Verify Statement (iii)

For validating statement (iii), consult entomology resources to understand the structure of the female cockroach's reproductive system. Each ovary in the female cockroach is made up of a group of ovarian tubules or ovarioles. Moreover, each ovariole does contain a chain of developing ova. Consequently, statement (iii) is True.

Verify Statement (iv)

To evaluate statement (iv), research the life cycle of cockroaches. The nymph stage in cockroaches does involve multiple moultings before reaching adulthood. The typical number of moultings ranges from 6 to 13 times, depending on the species and environmental conditions. Therefore, statement (iv) is True.

Key concepts

Cockroach Genital Pouch

Cockroaches exhibit distinctive sexual dimorphism, meaning males and females have different anatomical structures, especially in their reproductive systems. One particularly interesting feature is the male cockroach's genital pouch. This reproductive compartment is situated at the hind end of the abdomen, precisely bounded by the 9th and 10th terga on top and the 9th sternum below.

This internal chamber serves as a critical area for reproductive activities, housing various structures such as the testes, seminal vesicles, and ejaculatory duct. The male uses this pouch during mating to transfer sperm to the female. To ensure students fully grasp this concept, it is helpful to provide diagrams or 3D models that detail the location and components of the genital pouch. Understanding its role in cockroach reproduction can make learning about insect physiology more interesting and memorable.

Cockroach Haemolymph

The hemolymph in cockroaches, akin to blood in vertebrates, plays an integral role in their physiology. It is comprised of colorless plasma and haemocytes, which are comparable to white blood cells. The haemolymph circulates within the cockroach's open circulatory system, filling body cavities and providing nutrients, hormones, and immune cells to tissues.

To elaborate, haemocytes fend off infections and assist in wound healing. Movement and general activity help circulate the haemolymph since cockroaches lack the more complex circulatory system found in higher animals. A deep dive into the functions of haemolymph can significantly enhance a student's understanding of how nvertebrates, such as cockroaches, maintain internal stability despite their lack of a closed circulatory system.

Cockroach Ovarian Tubules

In female cockroaches, the ovaries are vital reproductive organs, each composed of bundles of ovarian tubules, each known as an ovariole. A typical female cockroach has about ten of these tubules on each side, making up the entire ovary. Within these tubules, a fascinating process unfolds: the development of the ova, or egg cells.

Each ovariole acts as an assembly line for eggs, starting from rudimentary germ cells at the anterior end, developing into mature oocytes ready for fertilization at the posterior end. The development pattern of these ova is an impressive display of the cockroach's reproductive prowess. By examining the structure of the ovarian tubules, students can better appreciate the complexities involved in insect reproduction.

Cockroach Nymph Moulting

Cockroach nymphs go through a phase called moulting, where they periodically shed their exoskeleton to grow. This process, also known as ecdysis, involves the nymph expanding its body and splitting the old exoskeleton, allowing the larger, soft new exoskeleton beneath to expand. Post-moulting, this new layer hardens to form the new durable outer shell.

This moulting can occur numerous times, typically between 6 and 13 instances, throughout the nymph's life before it matures into an adult cockroach. Each successive molt allows the nymph to increase in size until it reaches full adulthood. Observing a nymph undergo moulting can provide students with a visceral understanding of growth and development in insects and the importance of exoskeletons in invertebrate biology.