Cockroach Excretion: Malpighian Tubules and Uricotelism
Biology · Structural Organisation in Animals · NEET
The cockroach removes its nitrogenous waste using 100-150 yellow, thread-like Malpighian tubules found at the junction of the midgut and hindgut. It throws out the waste as uric acid, so the cockroach is uricotelic. Memory hook: "1 to 5 tubules make Uric acid" - about 100-150 tubules, and the waste is Uric acid (Uricotelic).
The cockroach gut has two rings of tubules. Gastric caeca (6-8) sit at the foregut-midgut junction and help digestion. Malpighian tubules (100-150, yellow) sit at the midgut-hindgut junction and remove uric acid. NEET swaps these two, so fix the junctions in your memory.
Your doubts, answered
Where exactly are the Malpighian tubules found in a cockroach?
They lie as a ring of 100-150 yellow, thin, thread-like tubules at the junction of the midgut and hindgut. NEET loves this exact spot. Do not mix it with the gastric (hepatic) caeca, which are 6-8 blind tubules at the junction of the foregut and midgut. Two different rings, two different junctions.
Is the cockroach uricotelic, ureotelic or ammonotelic?
The cockroach is uricotelic only. Being a land insect, it must save water, so it changes its nitrogen waste into uric acid, which is the least toxic and almost insoluble form. It does not make urea (like mammals) or ammonia (like many aquatic animals).
What is the difference between Malpighian tubules and gastric caeca?
Malpighian tubules do EXCRETION (remove uric acid) and sit at the midgut-hindgut junction. Gastric caeca do DIGESTION (secrete digestive juice) and sit at the foregut-midgut junction. Both are ring-like tubules, which is why NEET swaps them in match-the-column questions to trap you.
What do uricose glands, nephrocytes and the fat body do?
These are the accessory (helper) excretory structures. Uricose glands store uric acid, nephrocytes pick up and store waste from the haemolymph (blood), and part of the fat body acts as a 'storage kidney' that collects urates. The Malpighian tubules are still the MAIN excretory organ.
Why does the cockroach not excrete urea or ammonia?
Ammonia needs a lot of water to flush out and urea needs a moderate amount. A land insect cannot afford to lose that water. Uric acid needs almost no water because it is nearly insoluble, so it is thrown out as a semi-solid paste. This water saving is why terrestrial insects are uricotelic.
⚠️ The NEET trap ✗ Malpighian tubules lie at the junction of the foregut and midgut (like the gastric caeca). ✓ Malpighian tubules lie at the junction of the MIDGUT and HINDGUT. The 6-8 gastric (hepatic) caeca are the ones at the foregut-midgut junction. 🧠 Excretion happens AFTER digestion, so the excretory tubules sit LATER in the gut - at the midgut-hindgut junction. Digestion helpers (caeca) sit EARLIER at the foregut-midgut junction.
Real NEET questions
NEET 2023
The Cockroach is:
A · Ureotelic only
B · Ureotelic and Uricotelic
C · Ammonotelic only
D · Uricotelic only ✓
Solution: The cockroach is a land insect that saves water, so it excretes nitrogen waste as the least toxic, almost insoluble form - uric acid. Such animals are uricotelic. Excretion is done by 100-150 Malpighian tubules at the midgut-hindgut junction, helped by uricose glands, nephrocytes and the fat body. It does not make urea or ammonia, so it is uricotelic only.
NEET 2023
In cockroach, excretion is brought about by
A. Phallic gland
B. Uricose gland
C. Nephrocytes
D. Fat body
E. Collaterial glands
Choose the correct answer from the options given below:
A · A and E only
B · A, B and E only
C · B, C and D only ✓
D · B and D only
Solution: The main excretory organs are the Malpighian tubules. Accessory excretion is done by uricose glands (store uric acid), nephrocytes (store waste from haemolymph) and the fat body ('storage kidney' for urates) - so B, C and D. The phallic gland (male) and collaterial glands (female, secrete ootheca) are reproductive, not excretory.
NEET 2024
Match List I with List II.
List I
A. Structures used for storing food
B. Ring of 6-8 blind tubules at junction of foregut and midgut
C. Ring of 100-150 yellow filaments at junction of midgut and hindgut
D. Structures used for grinding food
List II
I. Gizzard
II. Gastric Caeca
III. Malpighian tubules
IV. Crop
A · A-I, B-II, C-III, D-IV
B · A-IV, B-III, C-II, D-I
C · A-III, B-II, C-IV, D-I
D · A-IV, B-II, C-III, D-I ✓
Solution: Crop (IV) stores food; gastric caeca (II) are 6-8 blind tubules at the foregut-midgut junction; Malpighian tubules (III) are 100-150 yellow filaments at the midgut-hindgut junction and remove uric acid; gizzard (I) grinds food. So A-IV, B-II, C-III, D-I.
Solved Structural Organisation in Animals NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
How many Malpighian tubules are present in a cockroach?
About 100-150 Malpighian tubules, arranged as a ring. They are yellow and thread-like.
What colour are the Malpighian tubules of a cockroach?
They are yellow and thin, filament-like (thread-like) structures.
What is the excretory product of the cockroach?
Uric acid. The cockroach is uricotelic, meaning uric acid is its main nitrogenous waste.
What is the main excretory organ of the cockroach?
The Malpighian tubules are the main (principal) excretory organs. Uricose glands, nephrocytes and the fat body give extra help.
Is this cockroach excretion topic in the NEET syllabus?
Cockroach details were trimmed from the core syllabus, but NEET still asked cockroach excretion questions in 2023 and 2024. So learn the Malpighian tubule location, the number 100-150, and the word uricotelic.
