Invertebrate Zoology

In most of the invertebrates, the excretory structures are simple tubular forms whereas vertebrates have complex tubular organs called kidneys. Shark is a vertebrate and has kidneys as excretory structures.
Protonephridia or flame cells are the excretory structures in Platyhelminthes (Flatworms, e.g., Planaria), rotifers, some annelids and the cephalochordate Amphioxus. Protonephridia are primarily concerned with ionic and fluid volume regulation, i.e., osmoregulation.
Nephridia are the tubular excretory structures of earthworms and other annelids like Leech. Nephridia help to remove nitrogenous wastes and maintain a fluid and ionic balance.
Malpighian tubules are the excretory structures of most of the insects including cockroaches. Malpighian tubules help in the removal of nitrogenous wastes and osmoregulation.

Nephridial organs, or nephridia, are excretory structures that evolved in many invertebrates, including flatworms, nemerteans, rotifers, annelids, mollusks, and lancelets. Each nephridial organ consists of simple or branching tubes that typically open to the outside of the body through excretory pores, called nephridiopores. Two types of nephridial organs are protonephridia and metanephridia. The excretory system of insects and spiders consists of several hundred Malpighian tubules. Malpighian tubules are slender extensions of the gut wall. Their blind ends lie in the hemocoel (blood cavity) and are bathed in hemolymph. The mammalian urinary system consists of the kidneys, the urinary bladder, and associated ducts. Each kidney has more than 1 million functional units called nephrons. A nephron consists of a cuplike Bowmans capsule connected to a long, partially coiled renal tubule.
In option A typhlosole is an intestinal fold for absorption but contractile vacuole is meant for osmoregulation. In option C antennae of cockroach are sensory but clitellum of earth worm forms cocoon. In option D tube feet of starfish are meant for locomotion and not related to other structures mentioned which have a role in digestion of food.

'Green Gland' is one of the pair of excretory organs in each side of the head region of decapod crustaceans, emptying at the base of the antennae. Prawns have green glands for excretion.

Various animals of animal kingdom presents a variety of excretory structures. In most of the invertebrates, these structures are simple tubular forms. Protonephridia or flame cells are the excretory structures in Platyhelminthes (Flatworms, e.g., Planaria), rotifers, some annelids and the cephalochordate Amphioxus. Protonephridia are primarily concerned with ionic and fluid volume regulation, i.e., osmoregulation. Nephridia are the tubular excretory structures of earthworms and other annelids. Nephridia help to remove nitrogenous wastes and maintain a fluid and ionic balance. Malpighian tubules are the excretory structures of most of the insects including cockroaches. Malpighian tubules help in the removal of nitrogenous wastes and osmoregulation. Antennal glands or green glands perform the excretory function in crustaceans like prawns. Vertebrates have complex tubular organs called kidneys as primary excretory organ. Towards the centre of the inner concave surface of the kidney is a notch called hilum through which ureter, blood vessels and nerves enter. Inner to the hilum is a broad funnel shaped space called the renal pelvis with projections called calyces. The outer layer of kidney is a tough capsule. Inside the kidney, there are two zones, an outer cortex and an inner medulla. The medulla is divided into a few conical masses (medullary pyramids) projecting into the calyces (sing.: calyx). The cortex extends in between the medullary pyramids as renal columns called Columns of Bertini.

Green glands are excretory organs in crustaceans. The excretory organ in annelids is nephridia. The column of bertini is an extension of renal cortex between the renal pyramids.

Planarians are one of the types of flatworms belonging to the class Turbellaria. The excretory organs of planarians are flame cells. The flame cells work like a kidney and remove excretory wastes from the body.

In decapod crustaceans, the excretory organs are known as antennary glands or green glands. These glands are opaque-white, pea seed sized structures, enclosed in the coxa of each second antenna. These glands play an important role in the process of excretion.

Earthworms (annelids) have slightly more evolved excretory structures called nephridia. A pair of nephridia is present on each segment of the earthworm. Malpighian tubules are found lining the gut of some species of arthropods, such as the bee. They are usually found in pairs and the number of tubules varies with the species of insect.

Green glands are excretory organs of some arthropods like crustaceans. They are also called antennal glands because these glands are located near the base of larger antennae. Each gland has three parts end sac, labyrinth and bladder. The labyrinth is the proper excretory gland. Hence green glands help in excretion.

Green glands are excretory organs of some arthropods like crustaceans.  For example, prawns, crayfishes, lobsters etc. They are also called antennal glands because these glands are located near the base of larger antennae. Each gland has three parts end sac, labyrinth and bladder. The labyrinth is the proper excretory gland. Hence antennal gland functions as the excretory organ in prawn.

Earthworms (annelids) have slightly more evolved excretory structures called nephridia. A pair of nephridia is present on each segment of the earthworm. Excretion occurs through a pore called the nephridiopore. Malpighian tubules are found lining the gut of some species of arthropods, such as the bee. They are usually found in pairs and the number of tubules varies with the species of insect.

Green glands are excretory organs of crustaceans. For example, prawn. They are also called antennal glands because these glands are located near the base of larger antennae. Each gland has three parts end sac, labyrinth and bladder. The labyrinth is the proper excretory gland. Hence green glands help in excretion.