how do spiders breath?
how do the book lung & air tubes work in the spider? I need to know as much as possible, my science teacher is really hard on us!!!
how do the book lung & air tubes work in the spider? I need to know as much as possible, my science teacher is really hard on us!!!
Comments
Book lungs consist of stacks of between 10 and 80 flattened hollow discs. These are bathed in haemolymph (the spider's equivalent of blood), and the shape of the book lung maximises the surface area at which gaseous exchange can occur. Air enters a hole in the spider's abdomen called a spiracle and diffuses into the book lungs. Since the spider's heart is continually pumping deoxygenated haemolymph through the book lungs, the concentration of oxygen in the air in the book lungs is
always higher than in the haemolymph, and therefore oxygen will move from the air into the haemolymph down an oxygen gradient. The oxygenated haemolymph is then pumped to the organs where it delivers its oxygen.
Tracheae consist of a system of branching tubes, which extend from the spiracles to deliver oxygen directly to the organs. It is generally assumed that there has beena gradual evolutionary change from book lungs to tracheae, possibly in response to the need to conserve water, since a great deal can be lost across the large surface area of the book lung. Although doubts have been raised about whether tracheae could evolve directly from book lungs, the book lungs of some spiders have a small
number of greatly elongated chambers, and these have been interpreted as an evolutionary intermediate in the evolution of tracheae from book lungs.
Respiration
Most spiders breathe through organs called 'Book Lungs'. These are generally situated centrally towards the anterior ventral surface of the opisthosoma. In the primitive spiders such as the Mesothelae there are two pairs of book lungs, however in more modern spiders one of these pairs has become modified into a pair of tubular tracheae which branch out throughout the whole body. In a few families the second pair of book lungs has also been modified or lost. Scientists agree that the book lung system is older system and that tracheae developed later. The tracheae lie posterior to the book lungs and open to the external world just anterior of the spinnerets, often through a single opening called a stigma. The development of the tracheae is quite varied between different spider families. Usually there are two sets of tubes called the lateral and median tubes. Tracheae can be very complicated and highly branched or simple and unbranched. Two main types of tracheae are recognised, tubular tracheae and sieve tracheae. Book lungs consist of an atrium or space into which numerous layers of membrane bound tissue extend. Haemolymph flows through these thin layers of tissue and gaseous exchange occurs across the membrane. The overall effect is of a series of sheets of tissue with air spaces between each sheet. This arrangement means that there is a large surface area here, up to 70cm2 in large tarantulas, across which gaseous exchange can occur. There is considerable variety exhibited by different spider families within this basic pattern.
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