3 research outputs found
Polymorphisms in predator induced defences of coexisting Daphnia pulex and D. longispina
A comparison of juvenile predator-avoidance polymorphisms of Daphnia pulex and D. longispina
in a shallow water body of Northern Italy is reported. The presence of the Chaoborus larvae
resulted in juvenile adaptive predator-avoidance cyclomorphosis in both species. The frequency of
induced morphotypes was higher in the small-sized D. longispina than in the large-sized D. pulex. Relative
tail-spine size was higher in D. longispina than in D. pulex. D. longispina displayed much more responsiveness
to Chaoborus than D. pulex. Both species showed at least 6 different defensive morphotypes that
were classified according to the neckteeth number, the neckteeth position and the thickness of occipital
epithelia under neckteeth. The frequencies of different morphotypes varied significantly between species.
The developmental responses of Daphnia to the presence of predators are regulated at various levels,
according to specific timelines of kairomone sensitive phases and developmental frame of defense trait
formation. Variation of a specific timeline might be linked to flexibility in developmental responses of
Daphnia to Chaoborus and seasonal variation in the frequencies of various morphotypes. Cyclomorphosis
should not only be due to changes in environmental factors that directly affects risk, but also to ones that
act as proxy signaling changes in predation risk