Zool 250
Best Annotated Bibliography 2005
Submitted by Lee Axford


Turner V.L.G., S.M. Lynch, L. Paterson, J.L. Leon-Cortes and J.P. Thorpe. 2003. Aggression as a function of genetic relatedness in the sea anemone Actinia equina (Anthozoa: Actiniaria). Marine Ecology Progress Series 247: 85-92.

Sea anemones can sense genetic relatedness through chemical stimuli. Sensing an individual that has different glycoprotein genes may result in acts of aggression. Is the level of genetic relatedness in Actinia equina indicative of the degree of aggression (number of acrorhagial peels) displayed and what would be the advantages of acting aggressively?

Acrorhagi (structures lined with dense concentrations of nematocysts) are used by A. equina during territorial wars and other acts of aggression. An acrorhagial peel is a strip acrorhagial tissue that is applied to the column of the opposing anemone which causes localized necrosis of the column. This is how A. equina and other anemones fight.

In order to create genetically identical clones of A. equina, 17 individuals of the spp. were collected and sectioned vertically into 2 equal halves, producing 2 smaller but normal anemones. Other species of Actinia and species from other anemone genera were collected. Aggressive displays were counted. A. equina showed no aggressive responses to clonemates. Acrorhagial peeling was very common among non-clonemates of A. equina. Intraspecific competition was higher than interspecific competition.

Turner concludes that the increased incidence of intraspecific acrorhagial peels were due to competition for space and food among non-self individuals (individuals that were not clonemates). Nematocysts in the acrorhagi are very efficient structures for aggression and defense. The level of genetic relatedness indeed plays a role in the degree of aggression. Using nematocysts in aggression is advantageous in that it is an efficient way to ward off potential competition for resources.

(250 words)


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(posted March 19, 2009)