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Sequential Subterranean Transport of Excavated Sand and Foraged Seeds in Nests of the Harvester Ant, Pogonomyrmex badius.

Tschinkel WR, Rink WJ, Kwapich CL - PLoS ONE (2015)

Bottom Line: Upward transport of excavated sand is carried out in stages, probably by different groups of ants, through deposition, re-transport, incorporation into the nest walls and floors and remobilization from these.This results in considerable mixing of sand from different depths, as indicated in the multiple sand colors even within single sand pellets brought to the surface.The upward and downward transport is an example of task-partitioning in a series-parallel organization of work carried out by a highly redundant work force in which each worker usually completes only part of a multi-step process.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America.

ABSTRACT
During their approximately annual nest relocations, Florida harvester ants (Pogonomyrmex badius) excavate large and architecturally-distinct subterranean nests. Aspects of this process were studied by planting a harvester ant colony in the field in a soil column composed of layers of 12 different colors of sand. Quantifying the colors of excavated sand dumped on the surface by the ants revealed the progress of nest deepening to 2 m and enlargement to 8 L in volume. Most of the excavation was completed within about 2 weeks, but the nest was doubled in volume after a winter lull. After 7 months, we excavated the nest and mapped its structure, revealing colored sand deposited in non-host colored layers, especially in the upper 30 to 40 cm of the nest. In all, about 2.5% of the excavated sediment was deposited below ground, a fact of importance to sediment dating by optically-stimulated luminescence (OSL). Upward transport of excavated sand is carried out in stages, probably by different groups of ants, through deposition, re-transport, incorporation into the nest walls and floors and remobilization from these. This results in considerable mixing of sand from different depths, as indicated in the multiple sand colors even within single sand pellets brought to the surface. Just as sand is transported upward by stages, incoming seeds are transported downward to seed chambers. Foragers collect seeds and deposit them only in the topmost nest chambers from which a separate group of workers rapidly transports them downward in increments detectable as a "wave" of seeds that eventually ends in the seed chambers, 20 to 80 cm below the surface. The upward and downward transport is an example of task-partitioning in a series-parallel organization of work carried out by a highly redundant work force in which each worker usually completes only part of a multi-step process.

No MeSH data available.


Related in: MedlinePlus

Sample images from the pink sand experiment.A. Pink sand pellets and grains on the surface disc. B. Heavy deposition and backfill of pink sand in a chamber at 2 cm depth, just below the surface. Chamber outlines shown by the black line. C. Scattered grains and light deposition in a deeper chamber. Chamber outline shown by black line. Circles are magnified vignettes from the indicated location, showing scattered grains of pink sand or light deposition. D. Chamber in which the pink sand was injected.
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pone.0139922.g015: Sample images from the pink sand experiment.A. Pink sand pellets and grains on the surface disc. B. Heavy deposition and backfill of pink sand in a chamber at 2 cm depth, just below the surface. Chamber outlines shown by the black line. C. Scattered grains and light deposition in a deeper chamber. Chamber outline shown by black line. Circles are magnified vignettes from the indicated location, showing scattered grains of pink sand or light deposition. D. Chamber in which the pink sand was injected.

Mentions: The deposition observed in the layer cake dig was created between October 2011 and May 2012, and it is not possible to determine when or how rapidly it was created. Is deposition a constant and continuous part of nest excavation, or does it occur in particular phases of this process? To address this question, pink fluorescent sand was placed into a 30 to 50 cm deep nest chamber from a lateral pit. One to three days later, the nest disc was checked for pink sand pellets, and the nest excavated chamber by chamber to check for deposits of pink sand or pellets of pink sand. Pink sand was visible in the nest disc in 6 of the 7 nests (Fig 15A), and excavation showed that of 42 chambers in the 7 nests, 27 contained scattered to many grains of pink sand (e.g. Fig 15B and 15C), one was backfilled with pink sand, one contained intact pellets and 8 had no evidence of pink sand. The backfilled chamber was an uppermost one, and pink-free chambers were mostly of intermediate depths. Fig 15D shows the chamber into which the pink sand was emplaced. This experiment showed that "contamination" of nest levels by sediment excavated from below is an integral part of excavation in which some fraction of the transported sand is dropped and picked up more than once before reaching the surface.


Sequential Subterranean Transport of Excavated Sand and Foraged Seeds in Nests of the Harvester Ant, Pogonomyrmex badius.

Tschinkel WR, Rink WJ, Kwapich CL - PLoS ONE (2015)

Sample images from the pink sand experiment.A. Pink sand pellets and grains on the surface disc. B. Heavy deposition and backfill of pink sand in a chamber at 2 cm depth, just below the surface. Chamber outlines shown by the black line. C. Scattered grains and light deposition in a deeper chamber. Chamber outline shown by black line. Circles are magnified vignettes from the indicated location, showing scattered grains of pink sand or light deposition. D. Chamber in which the pink sand was injected.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4624972&req=5

pone.0139922.g015: Sample images from the pink sand experiment.A. Pink sand pellets and grains on the surface disc. B. Heavy deposition and backfill of pink sand in a chamber at 2 cm depth, just below the surface. Chamber outlines shown by the black line. C. Scattered grains and light deposition in a deeper chamber. Chamber outline shown by black line. Circles are magnified vignettes from the indicated location, showing scattered grains of pink sand or light deposition. D. Chamber in which the pink sand was injected.
Mentions: The deposition observed in the layer cake dig was created between October 2011 and May 2012, and it is not possible to determine when or how rapidly it was created. Is deposition a constant and continuous part of nest excavation, or does it occur in particular phases of this process? To address this question, pink fluorescent sand was placed into a 30 to 50 cm deep nest chamber from a lateral pit. One to three days later, the nest disc was checked for pink sand pellets, and the nest excavated chamber by chamber to check for deposits of pink sand or pellets of pink sand. Pink sand was visible in the nest disc in 6 of the 7 nests (Fig 15A), and excavation showed that of 42 chambers in the 7 nests, 27 contained scattered to many grains of pink sand (e.g. Fig 15B and 15C), one was backfilled with pink sand, one contained intact pellets and 8 had no evidence of pink sand. The backfilled chamber was an uppermost one, and pink-free chambers were mostly of intermediate depths. Fig 15D shows the chamber into which the pink sand was emplaced. This experiment showed that "contamination" of nest levels by sediment excavated from below is an integral part of excavation in which some fraction of the transported sand is dropped and picked up more than once before reaching the surface.

Bottom Line: Upward transport of excavated sand is carried out in stages, probably by different groups of ants, through deposition, re-transport, incorporation into the nest walls and floors and remobilization from these.This results in considerable mixing of sand from different depths, as indicated in the multiple sand colors even within single sand pellets brought to the surface.The upward and downward transport is an example of task-partitioning in a series-parallel organization of work carried out by a highly redundant work force in which each worker usually completes only part of a multi-step process.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Science, Florida State University, Tallahassee, Florida, United States of America.

ABSTRACT
During their approximately annual nest relocations, Florida harvester ants (Pogonomyrmex badius) excavate large and architecturally-distinct subterranean nests. Aspects of this process were studied by planting a harvester ant colony in the field in a soil column composed of layers of 12 different colors of sand. Quantifying the colors of excavated sand dumped on the surface by the ants revealed the progress of nest deepening to 2 m and enlargement to 8 L in volume. Most of the excavation was completed within about 2 weeks, but the nest was doubled in volume after a winter lull. After 7 months, we excavated the nest and mapped its structure, revealing colored sand deposited in non-host colored layers, especially in the upper 30 to 40 cm of the nest. In all, about 2.5% of the excavated sediment was deposited below ground, a fact of importance to sediment dating by optically-stimulated luminescence (OSL). Upward transport of excavated sand is carried out in stages, probably by different groups of ants, through deposition, re-transport, incorporation into the nest walls and floors and remobilization from these. This results in considerable mixing of sand from different depths, as indicated in the multiple sand colors even within single sand pellets brought to the surface. Just as sand is transported upward by stages, incoming seeds are transported downward to seed chambers. Foragers collect seeds and deposit them only in the topmost nest chambers from which a separate group of workers rapidly transports them downward in increments detectable as a "wave" of seeds that eventually ends in the seed chambers, 20 to 80 cm below the surface. The upward and downward transport is an example of task-partitioning in a series-parallel organization of work carried out by a highly redundant work force in which each worker usually completes only part of a multi-step process.

No MeSH data available.


Related in: MedlinePlus