The purpose of the malpighian tubule is to absorb and excrete the metabolic wastes that make up urine in arthropods. They actively absorb water, dissolved substances and waste from the surrounding body fluids to be released as solid nitrogen-based compounds.
The malpighian tubules absorb urea and amino acids very easily, but ions such as potassium and sodium are actively pumped in through their membranes. The tubules carry these wastes to the rectum, where water and ions are reabsorbed and the urea is mixed with feces to be excreted through the anus. Various species have specialized purposes for the malpighian tubules beyond these basic functions. New Zealand glow worms have modified tubules that generate light to attract prey to their sticky trap lines, which they dangle from cave ceilings. Other insects that eat toxic plants have special mechanisms to quickly excrete any toxins through the tubules.
Malpighian tubules are slender tubes with walls composed of a single layer of cells. Most are highly convoluted and bathed in hemolymph, the arthropod equivalent of blood and lymph fluid, for much of their length. They are reinforced with proteins and have structures to help push any wastes along. Most arthropods have muscles that move the tubules around, although some species lack these muscles and others lack tubules altogether.Learn More
Pelvic fins can serve multiple purposes depending on the species of fish, like sharks use them for balance when swimming and on males they are part of the sexual organs, but fish like the O'opu in Hawaii use them to navigate up stream and stick to rocks in fast-moving water. Almost all fish have some sort of pelvic fin along their stomach.Full Answer >
Nephridia, the plural of nephridium, is a unit of the excretory system in many primitive invertebrates that is responsible for expelling the metabolic wastes of the organism. When this structure evolved it allowed for the specialization of tissues within the excretory system and eliminated the need for all of an organism's cells to be involved in the process of excreting waste by being in contact with water.Full Answer >
The proximal convoluted tubules, or PCTs, are part of a system of absorption and reabsorption as well as secretion from within the kidneys. Specifically, PCTs are part of a complex system that reabsorbs most of the water and ions from the urinary space back into the body, which is a process called tubular reabsorption.Full Answer >
The habitats of arthropods range from the polar regions, to urban areas (including parks, gardens and buildings), temperate and coniferous forests, tropical forests and rain forests, and deserts and semi-deserts. Arthropods are also found in open habitats, such as savannas, grassland and scrubland.Full Answer >