Sexual Cannibalism in Spiders

Theory 4: Female Choice

Mechanism:

A female selects her mate based on the male’s signals (i.e. body size). Her decision as to if and when to eat her partner (also related to SSD) influences her fertilization and that male’s reproductive fitness. In the more aggresive species, such as the fishing spider Dolomedes and Argiope (below), females may attack their mates during courtship, prior to copulation. This pre-copulatory timing of cannibalism is favorable to the female choice model, while it rules out the hypothesis of male complicity.

Orb-web spider Argiope keyserlingi.

Image courtesy of emblatame, Flickr.com

Adaptive Value:

In timing her cannibalism, the female choice model has adaptive value in its paternal control. Male traits that are favorabale, leading to prolonged copulation and greater fitness, are selected for in the female's delay of cannibalization. Offspring are of greater fitness, and the fertilizing male gains reproductive benefit.

Ontogeny:

Elgar et. al. 2000

A. keyserlingi are polyandrous and sexually cannibalistic. The body size of the females mate is a deciding factor in whether he will be cannibalized post coppulation. In support of Birkhead & Moller's (1998) criteria for female cryptic choice, the timing of cannibalization, and duration of copulation, is unambigously a female choice, and in direct effect to the fertilized offspring. Also, the decision in timing is based upon the male character of body size (Elgar et. al. 2000).