Predation by dragonfly larvae (Aeshna grandis) on larvae of the crayfish Astacus astacus - the significance of parental effort and access to hiding places in order to reduce predation on newly-hatched crayfish fry (Abstract)
Jonsson, A. (1989). Predation by dragonfly larvae (Aeshna grandis) on larvae of the crayfish Astacus astacus - the significance of parental effort and access to hiding places in order to reduce predation on newly-hatched crayfish fry (Abstract), in: De Pauw, N. et al. (Ed.) Aquaculture: a biotechnology in progress: volume 1. pp. 933 In: De Pauw, N. et al. (1989). Aquaculture: a biotechnology in progress: volume 1. European Aquaculture Society: Bredene. ISBN 90-71625-03-6. 1-592 pp., more |
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| Abstract | Larvae of the dragonfly Aeshna grandis prey on juvenile Astacus when given opportunity .In order to elucidate this, a series of microcosm experiments were performed under various conditions. During the first weeks following hatching, female crayfish adopt a "nursing" behaviour towards their offspring by offering shelters under their abdomens. In the presence of an active dragonfly, the larvae seek shelter under the female. But when given access to hiding places (bricks with holes) as well as to maternal protection, they prefer the hiding places. The mortality was highest when the larvae were totally unprotected and lowest when they had access only to hiding places. It was also indicated that the conclusive mortality was somewhat higher when the larvae had access to both maternal protection and hiding places, than when they only had access to bricks. It is possible that the parental effort of female crayfishes, towards juvenile Astacus fry after the first moult, is less important in order to prevent predation, than access to hiding places. This is also supported by the behaviour of the crayfish larvae. It is possible that their very clear preference for using hiding places instead of the mother as shelters, may have an evolutionary explanation, generated by selection. |
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