After another required practical we researched more into organ systems. As we had recently been studying the gas exchange process of fish I decided to research into two very interesting and extraordinary fish.
Lungfish:
The lungfish is the only fish which has two respiratory systems: gills and lungs. This adaptation allows the lungfish to survive when its water habitat dried ups due to seasonal drought. The lungfish has the presence of a single dorsal lung, used to replace the oxygen supply through the gills. During times of excessive activity, drought, or high temperatures, which will cause water to become deoxygenated, the lungfish can rise to the surface and swallow air into its lung. Air breathing is more frequent when the fish has periods of greater activity at night as it uses its lung as a supplementary organ of respiration. The lungs of the lungfish are connected to the larynx and pharynx without a trachea. While other species of fish can breathe air using gas bladders, they are usually simple sacs, devoid of any complex structure. In contrast, the lungs of a lungfish are divided into multiple smaller air sacs, maximising the surface area available for gas exchange.
Broadnose Seven-gill Shark:
The Broadnose Seven-gill shark is easily distinguished by its seven gills as opposed to 5 like most other sharks. Along with the Sharpnose Seven-gill shark these species are more closely related to ancient sharks of the Jurassic period. In most other fish species, the gills are covered by the operculum, which acts as a lid over the gill. However, sharks do not have this covering. There is a modified slit, called the spiracle, which lies immediately behind the eye on the shark’s head. The spiracle assists in the process of taking water into the shark’s mouth where is it forced over and out of the gills as the shark moves forward. When at rest the shark actively pumps water over its gills, a process aided by gill rakers. These rakers are perpendicular to the gill arches and they direct the water over the full length of the filaments allowing gas exchange to occur.
References:
JoOrmisher/AQA AS/A-Level Practical Biology/2017/Oxfordshire/HodderEducation/For 2015 Specification/34
ShmoopEditorialTeam/2008/Biology Animal Respiration-Shoop Biology/https://www.shmoop.com/animal-movement/animal-respiration.html/09.03.18
AmeliaMeyer/2013/SharksInfo.com/https://www.sharksinfo.com/respiration.html/09.03.18
WikipediaContributors/2018/Wikipedia/https://en.wikipedia.org/wiki/Broadnose_sevengill_shark/09.03.18
Wikipedia Contributors/2018/Wikipedia/https://en.wikipedia.org/wiki/Lungfish#Lungs/09.03.18
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