|MadSci Network: Zoology|
Hi Steve, Cockroaches and shrimp are distantly related to each other, but it is doubtful that is the reason for the common names ‘land shrimp’ and ‘sea roach’. Cockroaches and shrimp are both members of the phylum Arthropoda and share some common characteristics, including segmented bodies and legs, and a hard outer skeleton. However cockroaches and shrimp belong to two different lineages: the Hexapoda (which includes the insects) and the Crustacea (shimp and crabs, but also barnacles and water fleas) respectively. While it is not known for certain when the Hexapoda diverged from the Crustacea, the emergence of land dwelling hexapods is thought to have occurred during the Silurian period (between 416 and 444 million years ago). It is often hard to tell how common names originated, but they usually refer to physical and behavioral resemblances rather than to whether or not organisms are evolutionarily related. The animals usually known as ‘sea roaches’ are the isopods in the genus Ligia. These crustaceans have a flattened body with long antenna that looks vaguely roach-like and share with roaches the habit of congregating in large numbers (usually under beach debris) and fleeing quickly when their shelter is exposed. It is probably from these traits that the common name ‘sea roach’ is derived. I’m less familiar with the term ‘land shrimp’ referring to cockroaches… in the part of the world I come from, ‘land shrimp’ refers to terrestrial amphipods… small laterally flattened crustaceans that, while not true shrimp, are somewhat related to isopods. In this case, physical resemblance between amphipods and true shrimp explain the common name. The one time I have heard the name ‘land shrimp’ referring to a cockroach is to the use of some large tropical cockroaches in food, where they are cooked in much the same way (and used in many of the same dishes) as shrimp. I personally cannot attest to whether these roaches actually do taste like shrimp, but if you are curious there are several cook books available. Hope that helps, Dr. T. Clarke References and other readings: 1. Tree of Life webpage on arthropod relationships: http://tolweb.org/tree? group=arthropoda - a good general description of how different arthropod groups are related to each other. 2. Regier, J.C. and Shultz, J.W. 1997 Molecular phylogeny of the major arthropod groups indicates polyphyly of crustaceans and a new hypothesis for the origin of hexapods. Molecular Biology and Evolution 14: 902 – 913 - Very technical, but presents evidence from comparison of genes that show the relationship between the Hexapoda and the Crustacea relative to other arthropods. 3. Engel, M.S. and Grimaldi, D.A. 2004. New light shed on the oldest insect. Nature 427: 627 – 630 - Description of the oldest insect, discussing their possible origins in the Silurian period. 4. A short descriptive web page on the Ligia exotica, the sea roach: http://www2.bishopmuseum.org/HBS/invertguide/species/ligia_exotica.htm 5. Entertaining with Insects by Taylor, R.L. and Carter, J.B. 1976. (although I believe it has been recently reprinted) - There are several other books available on cooking insects, but this is the only work from which I have personally tried a few recipes, and it’s the book that ‘started it all’ as far as bug cuisine.
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