Ref ID : 767
John J. Gilbert; Defenses of males against cannibalism in the rotifer Asplanchna: size, shape, and failure to elicit tactile feeding responses. Ecology 58:1128-1135, 1977
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In Asplanchna, MM are considerably smaller than the FF. In A. sieboldi this sexual dimorphism may be further accentuated because the FF are trimorphic in size and shape. The intermediate-sized, cruciform, and especially the largest, campanulate morphs are cannibalistic. However, the MM are protected from these cannibalistic FF by 2 different types if mechanisms. They can fail to elicit contact feeding responses and they can have body sizes and body wall outgrowths sufficiently large to prevent attacking FF from capturing them. The degree to which each of these mechanisms is developed can vary greatly between clones or taxa, may be inversely related, and may be a function of the voracity and size of cannibalistic FF to which the MM are generally exposed. Campanulate FF from clone 12C1 readily attacked both FF from the smallest, saccate morph of their own clone and also MM from clone 10C6, but they rarely attacked MM of their own clone. Campanulate FF from clone 10C6 regularly attacked M clonemates, but cruciform FF from this clone responded more frequently to MM from clone 12C1 than to MM from their own clone. On a given diet, MM from clone 10C6 were about 1.5x larger and had more pronounced body wall outgrowths than those from clone 12C1. In both clones, the size of MM and mictic (M-producing) FF were influenced by the diet, being larger in population fed on the rotifer Brachionus calyciflorus than those fed on the ciliate Paramecium aurelia. It may be adaptive for MM to be as small and simply constructed as possible; they have only a rudimentary digestive system, and so energy for their production must come entirely from their mictic-F parents. Therefore, M size and body wall outgrowth development may represent a balance between production costs and ability to withstand cannibalism. Evolution of a mechanism preventing attack by cannibalistic FF may decrease the requirements for defensive structures and increase the efficiency of M production and hence subsequent resting egg production.