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Experimental quantification of long distance dispersal potential of aquatic snails in the gut of migratory birds.

van Leeuwen CH, van der Velde G, van Lith B, Klaassen M - PLoS ONE (2012)

Bottom Line: One of the snail species tested was found to survive passage through the digestive tract of mallards as fully functional adults.This may be explained by a digestive trade-off in birds, which maximize their net energy intake rate rather than digestive efficiency, since higher efficiency comes with the cost of prolonged retention times and hence reduces food intake.The resulting lower digestive efficiency allows species like aquatic snails, and potentially other fully functional organisms without obvious dispersal adaptations, to be transported internally.

View Article: PubMed Central - PubMed

Affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology, NIOO-KNAW, Wageningen, The Netherlands. c.vanleeuwen@nioo.knaw.nl

ABSTRACT
Many plant seeds and invertebrates can survive passage through the digestive system of birds, which may lead to long distance dispersal (endozoochory) in case of prolonged retention by moving vectors. Endozoochorous dispersal by waterbirds has nowadays been documented for many aquatic plant seeds, algae and dormant life stages of aquatic invertebrates. Anecdotal information indicates that endozoochory is also possible for fully functional, active aquatic organisms, a phenomenon that we here address experimentally using aquatic snails. We fed four species of aquatic snails to mallards (Anas platyrhynchos), and monitored snail retrieval and survival over time. One of the snail species tested was found to survive passage through the digestive tract of mallards as fully functional adults. Hydrobia (Peringia) ulvae survived up to five hours in the digestive tract. This suggests a maximum potential transport distance of up to 300 km may be possible if these snails are taken by flying birds, although the actual dispersal distance greatly depends on additional factors such as the behavior of the vectors. We put forward that more organisms that acquired traits for survival in stochastic environments such as wetlands, but not specifically adapted for endozoochory, may be sufficiently equipped to successfully pass a bird's digestive system. This may be explained by a digestive trade-off in birds, which maximize their net energy intake rate rather than digestive efficiency, since higher efficiency comes with the cost of prolonged retention times and hence reduces food intake. The resulting lower digestive efficiency allows species like aquatic snails, and potentially other fully functional organisms without obvious dispersal adaptations, to be transported internally. Adopting this view, endozoochorous dispersal may be more common than up to now thought.

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Percentage of ingested snails retrieved viable (A), intact (B) or damaged (C) as a function of retention time.Data for the two experiments combined.
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pone-0032292-g001: Percentage of ingested snails retrieved viable (A), intact (B) or damaged (C) as a function of retention time.Data for the two experiments combined.

Mentions: Retrieval of viable snails and intact or damaged shells differed between snail species and changed with retention time (Table S2, Table S3, Fig. 1). Viable snails were retrieved up to five hours after feeding, but only for H. ulvae (Fig. 1A). Most viable snails of H. ulvae were retrieved in the first four hours after ingestion, and most intact shells of all snail species together between four and eight hours after ingestion (235 versus 366, respectively, Fig. 1B). Only 99 shells were retrieved between eight and 12 hours, and 26 shells between 12 and 24 hours after feeding (Fig. 1B). Birds with higher body mass excreted less intact snails, and this relation became more pronounced with increasing retention time (indicated by the negative interaction coefficient in a generalized mixed model, Table S3). Viable snails stayed alive for at least three months after retrieval.


Experimental quantification of long distance dispersal potential of aquatic snails in the gut of migratory birds.

van Leeuwen CH, van der Velde G, van Lith B, Klaassen M - PLoS ONE (2012)

Percentage of ingested snails retrieved viable (A), intact (B) or damaged (C) as a function of retention time.Data for the two experiments combined.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3293790&req=5

pone-0032292-g001: Percentage of ingested snails retrieved viable (A), intact (B) or damaged (C) as a function of retention time.Data for the two experiments combined.
Mentions: Retrieval of viable snails and intact or damaged shells differed between snail species and changed with retention time (Table S2, Table S3, Fig. 1). Viable snails were retrieved up to five hours after feeding, but only for H. ulvae (Fig. 1A). Most viable snails of H. ulvae were retrieved in the first four hours after ingestion, and most intact shells of all snail species together between four and eight hours after ingestion (235 versus 366, respectively, Fig. 1B). Only 99 shells were retrieved between eight and 12 hours, and 26 shells between 12 and 24 hours after feeding (Fig. 1B). Birds with higher body mass excreted less intact snails, and this relation became more pronounced with increasing retention time (indicated by the negative interaction coefficient in a generalized mixed model, Table S3). Viable snails stayed alive for at least three months after retrieval.

Bottom Line: One of the snail species tested was found to survive passage through the digestive tract of mallards as fully functional adults.This may be explained by a digestive trade-off in birds, which maximize their net energy intake rate rather than digestive efficiency, since higher efficiency comes with the cost of prolonged retention times and hence reduces food intake.The resulting lower digestive efficiency allows species like aquatic snails, and potentially other fully functional organisms without obvious dispersal adaptations, to be transported internally.

View Article: PubMed Central - PubMed

Affiliation: Department of Aquatic Ecology, Netherlands Institute of Ecology, NIOO-KNAW, Wageningen, The Netherlands. c.vanleeuwen@nioo.knaw.nl

ABSTRACT
Many plant seeds and invertebrates can survive passage through the digestive system of birds, which may lead to long distance dispersal (endozoochory) in case of prolonged retention by moving vectors. Endozoochorous dispersal by waterbirds has nowadays been documented for many aquatic plant seeds, algae and dormant life stages of aquatic invertebrates. Anecdotal information indicates that endozoochory is also possible for fully functional, active aquatic organisms, a phenomenon that we here address experimentally using aquatic snails. We fed four species of aquatic snails to mallards (Anas platyrhynchos), and monitored snail retrieval and survival over time. One of the snail species tested was found to survive passage through the digestive tract of mallards as fully functional adults. Hydrobia (Peringia) ulvae survived up to five hours in the digestive tract. This suggests a maximum potential transport distance of up to 300 km may be possible if these snails are taken by flying birds, although the actual dispersal distance greatly depends on additional factors such as the behavior of the vectors. We put forward that more organisms that acquired traits for survival in stochastic environments such as wetlands, but not specifically adapted for endozoochory, may be sufficiently equipped to successfully pass a bird's digestive system. This may be explained by a digestive trade-off in birds, which maximize their net energy intake rate rather than digestive efficiency, since higher efficiency comes with the cost of prolonged retention times and hence reduces food intake. The resulting lower digestive efficiency allows species like aquatic snails, and potentially other fully functional organisms without obvious dispersal adaptations, to be transported internally. Adopting this view, endozoochorous dispersal may be more common than up to now thought.

Show MeSH