Tuesday, July 26, 2011

Water Transport in Cicidella viridis

Female Cicidella viridis
While many leafhoppers are rather drab in appearance, there are some that aim to dazzle. One of the most colouful found in Ireland is Cicidella viridis. Its yellow head and yellow and green protonum give way to strking wings, a wonderful turquoise in females, but a lot darker (often a blue-purple) in males. They feed on a variety of grasses, sedges and rushes by by inserting two pairs of feeding stylets (modified mandibles and maxillae) into the host plant tissue, injecting saliva, and ingesting fluid (1). This feeding method, common to all Auchenorrhyncha (Cicadas, Spittlebugs, Leafhoppers, Treehoppers, and Planthoppers) presents a particular problem. When sap is ingested, a large volume of excess water is also taken in, which presents a raft of osmotic issues. C. viridis posses an organ called a filter chamber to combat this problem. This rapidly transfers excess water from the initial midgut to the terminal midgut down a transepithelial osmotic gradient (2). The membrane of the filter chamber is composed of a protein known as P25, a member of a family of protieins (MIP) that are permeated by water but not any associated solutes.

References:
  1. Dietrich, 2009 in Encyclopedia of Insects (Second Edition) pp. 56-64
  2. Beuron et al., 1995. The Journal of Biological Chemistry 270 pp. 17414-17422

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