Review of Hemolymph

Hemolymph receives nutrients from the gut and water and ions from the rectum in the last part of the alimentary canal. Hemolymph supplies water to the organs and tissues, and water consumed in honey and nectar can enter the hemolymph through the alimentary canal. Hemolymph is a reservoir for water for the body. The water of hemolymph holds about twenty percent of the body water of the bee, but its percentage varies. In larvae, hemolymph may contain up to fifty percent of the larva's body water. Hemolymph distributes nutrients, ions and hormones to muscles and organs surrounding the hemocoel and transports cells of the immune system to where they are needed. Numerous hemocytes or blood cells float in the hemolymph. These cells resemble the white blood cells of vertebrates and are of several kinds. Hemolymph distributes digested molecules that are absorbed from the alimentary canal. Hemolymph receives the breakdown products of metabolism that are later removed by the excretory organs, the Malphigian tubules. Hemolymph also transports carbon dioxide to be eliminated through the respiratory system and cuticle and as bicarbonate with the feces.

Regulation of the volume and compositon of hemolymph as well as changes in its hydrostatic pressure occur during times of increased and decreased hydration, to provide a stable cellular environment and a continuous supply of nutrients and energy to active areas and muscles of the body. Volumes of hemolymph can rise and fall without endangering circulation that can occur in mammals and other vertebrates. Good data on the relative amounts of fluid in insects at different stages and under different conditions are rare, and much of what we have is quite old.

Chapter seven

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