What are crustacea?
Crustacea, like all other arthropods, have a segmented body and a hard exoskeleton.
However, they are distinguishable by their segmented appendages, unique nauplius larvae stage, and five-segmented head (1). |
Respiration in Crustacea
Crustaceans are arthropods too. Like insects, they rely on diffusion for gas exchange. Unlike insects, they respire using a system commonly known as gills, rather than trachae, in order to absorb oxygen from water. To the right, a set of gills from a crayfish is pictured. Thin layers of tissue form flaps in between which water can filter through. Blood (or other fluid) moves through the gills due to the constantly- circulating circulatory system (2).
The exchange of dissolved oxygen in water for CO2 in the bloodstream of crustaceans occurs in the gills, and in some certain species, such as crayfish, crustacean gills gain and lose surface area based on the locomotion of the organism. In crayfish, movement of the legs triggers movement of the anterior gills, allowing for greater absorption of oxygen while the individual is moving (3). |
Both pictures above are views of the gill tissue of a crayfish through a microscope.
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Evolution of crustaceaCrustacea were not widespread until the Cretaceous era, which is also when the first fossils were dated of crabs and lobsters.
The respiratory system and crustacea as a whole likely evolved rapidly after selective pressure was applied by the crustacea's predator at the time, the bony fish. The current respiratory system of crustacea is advantageous due to its adaptability to aquatic environments, and its ability to absorb large amounts of oxygen from water (4). |
Sources:
(1) "Crayfish Anatomy." Crayfish Anatomy. N.p., n.d. Web. 16 June 2016.
(2) "Crustaceans." Crustaceans. Marine Education Society of Australasia, n.d. Web. 16 June 2016.
(3) Meyer, John R. "RESPIRATORY SYSTEM." Respiratory System. North Carolina State University, 1 Nov. 2006. Web. 16 June 2016.
(4) Maas, Andreas. "Early Crustacean Evolution and the Appearance of Epipodites and Gills." © Museum Für Tierkunde Dresden, EISSN 1864-8312, 25.8.2009 Early Crustacean Evolution and the Appearance of Epipodites and Gills (2009): n. pag. 2009. Web. 16 June 2016.
(1) "Crayfish Anatomy." Crayfish Anatomy. N.p., n.d. Web. 16 June 2016.
(2) "Crustaceans." Crustaceans. Marine Education Society of Australasia, n.d. Web. 16 June 2016.
(3) Meyer, John R. "RESPIRATORY SYSTEM." Respiratory System. North Carolina State University, 1 Nov. 2006. Web. 16 June 2016.
(4) Maas, Andreas. "Early Crustacean Evolution and the Appearance of Epipodites and Gills." © Museum Für Tierkunde Dresden, EISSN 1864-8312, 25.8.2009 Early Crustacean Evolution and the Appearance of Epipodites and Gills (2009): n. pag. 2009. Web. 16 June 2016.