Final answer:
The Loop of Henle is the structure usually not found in marine teleosts. These fish have evolved different mechanisms to regulate their fluid and electrolyte balance due to living in a hypertonic environment.
Step-by-step explanation:
The structure that is usually not found in marine teleosts is the Loop of Henle. Marine teleost fish have developed highly efficient kidneys that differ from those of humans and other mammals. These fish live in a hypertonic environment where the water salinity is higher than their body fluids, leading to a constant loss of water by osmosis. To conserve water, marine teleosts have a shorter loop of Henle or this structure is absent altogether, which means they have a reduced ability to concentrate urine compared to mammals. They rely on other mechanisms, such as drinking seawater and actively excreting salt through their gills, to balance fluid and electrolyte levels.
It's worth noting that inside the nephron - the functional unit of the kidney - the Bowman's capsule surrounds the glomerulus, and the distal convoluted tubule is the part of the renal tubule most distant from the glomerulus. Water recovery or disposal fine tuning occurs in the collecting ducts.