5.3 The excretory system of the adult honey bee and the substances excreted Flashcards
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Functions of the excretory system
- Filtration of substances from the haemolymph
- Reabsorption from the excretory system into the haemolymph of useful substances which would otherwise be lost
- Active secretion of substances (grabbing them from the haemolymph and passing them into the system)
- Complete removal of the end product to the outside of the bee’s body
5 waste products that are excreted
- Pollen husks
- Pollen fat globules
- Exhausted epithilial cells
- Nitrogenous waste
- Water
What is the role of the Malpighian tubules in honey bees?
Excretion of nitrogenous substances is carried out by the Malpighian tubules, of which there are around 100 in the abdomen.
What is the structure of a Malpighian tubule?
Each tube is built of a single layer of cells attached to a thin basement membrane, with muscle fibres and tracheoles supplying oxygen.
How do Malpighian tubules connect to the digestive system?
The open ends of the tubes link into the digestive system just above the pyloric valve leading to the small intestine.
How are substances filtered in the Malpighian tubules?
Substances in the haemolymph are filtered through the wall of a Malpighian tubule at its upper end, passing through gaps and cells.
Is the filtration process in Malpighian tubules selective?
The process is passive and does not discriminate between waste and useful substances.
What happens to water and minerals during excretion?
Some water, minerals, and salts are re-absorbed back into the haemolymph to maintain balance.
Can the same substances be filtered and reabsorbed?
Yes, it is common for the same substances to be filtered out and reabsorbed based on need and balance.
How are other substances secreted in the Malpighian tubules?
Other substances are actively secreted by the cells, pulled in and passing into the lumen of each tubule.
Where does absorption and reabsorption occur in the Malpighian tubules?
Absorption and reabsorption occur in the lower (proximal) end of the tubule.
What happens to waste material after passing through the tubules?
Waste material passes into the Ventriculus, through the small intestine and rectum, before leaving the body via the anus.
What occurs while waste passes through the intestine and rectum?
More water may be absorbed from the gut contents.
What is the simplest nitrogenous waste product in honey bees?
Ammonia is the simplest waste product but is toxic and requires lots of water to remove.
In what form is nitrogenous waste typically excreted by honey bees?
The normal form of nitrogenous waste excreted is uric acid, along with various salts and harmful substances.
