Malpighian tubules and Coxal Glands in Arachnids

Malpighian Tubules. Malpighian tubules remove nitrogenous wastes
(uric acid) from the hemocoel. Various ions are actively transported
across the outer membrane of the tubule. Water follows these ions
into the tubule and carries amino acids, sugars, and some nitrogenous
wastes along passively. Some water, ions, and organic compounds are
reabsorbed in the basal portion of the Malpighian tubules and the
hindgut; the rest are reabsorbed in the rectum. Uric acid moves into
the hindgut and is excreted in the feces.
Coxal Glands in Arachnids. ( a ) The gut and excretory systems of a
spider. The stercoral pocket is a diverticulum off the hindgut that stores
waste prior to waste elimination. ( b ) Coxal gland muscles attach to the
thin saccular fi ltration membrane. These muscles promote fi ltration and
fl uid fl ow (black arrows) by contracting and relaxing along the tubular
duct. Water and solutes are reabsorbed along the tubular duct.

1. Malpighian Tubules and Coxal Glands Noshaba munawar

2. Malpighian Tubules Insects have an excretory system made up of the gut and Malpighian tubules ( named after Marcello Malpighi, Italian anatomist, 1628–1694) attached to the gut ( figure 28.13) .

3. Conti………. Excretion involves the active transport of potassium ions into the tubules from the surrounding hemolymph A nd the osmotic movement of water that follows. Nitrogenous waste (uric acid) also enters the tubules. As fluid moves through the Malpighian tubules, some of the water and certain ions are recovered. . In cellular biology, active transport is the movement of molecules across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient

4. Conti………. All of the uric acid passes into the gut and out of the body in the feces. Because insects are capable of conserving water very effectively, the insect’s excretory system is a key adaptation contributing to these animals’ tremendous success on land

5. Coxal Glands Coxal (L. coxa , hip) glands are common among arachnids ( spiders,scorpions , ticks, mites). These spherical sacs resemble annelid nephridia ( figure 28.14) . Wastes are collected from the surrounding hemolymph of the hemocoel and discharged through pores on one to several pairs of appendages near the proximal segment(coxa ) of the leg. .

6. Conti………. Evidence suggests that the coxal glands may also function in the release of pheromones. Other arachnid species have Malpighian tubules instead of , or in addition to, the coxal glands . In some of these species, however , Malpighian tubules seem to function in silk production rather than in excretion