The excretory systems in invertebrates exhibit a wide range of structural diversity depending on their evolutionary history, complexity, and habitat. This diversity has led to confusion regarding which structures exist in which groups and their specific roles. This article evaluates the four given statements about invertebrate excretion to clarify which are true.

Statement Analysis

Statement A: Flame Cells Are Found in Molluscs and Jellyfish

Flame cells, also known as protonephridia, are specialized excretory structures found in flatworms (Platyhelminthes) and some related invertebrates. They consist of ciliated cells that aid the filtration and excretion of wastes. However:

• Flame cells are not found in molluscs or jellyfish (Cnidarians).

• Molluscs have nephridia (metanephridia) or similar excretory organs, and jellyfish mainly use diffusion through their body surfaces for excretion.

• Therefore, statement A is incorrect.vedantu+2

Statement B: Nephridia and Malpighian Tubules Convert Ammonia to Urea for Water Conservation

This statement is incorrect:

• Nephridia are excretory tubules found in annelids and some other invertebrates; they filter body fluids and excrete nitrogenous wastes, primarily ammonia or urea but do not convert ammonia to urea as a specific function.

• Malpighian tubules, found in insects and terrestrial arthropods, primarily excrete uric acid, not urea.

• Conversion of ammonia to urea occurs mainly in vertebrates (ureotelic animals), not as a primary specific function of these invertebrate excretory structures.byjus+2

Statement C: Green Glands Are Found in Flatworm and Help in Excreta Elimination

Incorrect:

• Green glands, also called antennal or maxillary glands, are present in crustaceans (such as crabs and lobsters) and are involved in osmoregulation and excretion.

• They are not found in flatworms.

• Flatworms use protonephridia (flame cells) for excretion.britannica+2

Statement D: Excretory Canals in Nematodes Carry Waste Materials to Excretory Pores in the Body Wall

This statement is correct:

• Nematodes (roundworms) have a unique excretory system consisting of excretory canals or ducts.

• These canals collect wastes and empties them through pores on the body wall, facilitating nitrogenous waste elimination.bio.libretexts+1

Correct Answer

Among the given options:

• Only statement D is correct.

• Thus, none of the options presenting only C or combinations involving C fit.

• Since the question format limits choices, the correct choice is (4) B and D, understanding that B is not fully accurate but D is correct and the better choice among the provided answers.

If strict correctness is necessary, only D is valid, but given the exam-style options, (4) is the most reasonable.

Summary Table

Conclusion

The only accurate statement related to invertebrate excretion among those given is that excretory canals in nematodes carry waste to pores on the body wall. Flame cells are exclusive to flatworms and related invertebrates; nephridia and Malpighian tubules have specific roles but are not primarily responsible for ammonia to urea conversion; and green glands are restricted to crustaceans, not flatworms.

Most appropriate answer: (4) B and D