Effects of substrate, ant and fungal species on plant fiber degradation in a fungus-gardening ant symbiosis

Alexandria M. DeMilto, Monte Rouquette, Ulrich G. Mueller, Katrin Kellner, Jon N. Seal

Research output: Contribution to journalArticle

Abstract

Fungus-gardening or attine ants have outsourced most of their digestive function to a symbiotic fungus. The ants feed their fungus – essentially an external digestive organ – a variety of substrates of botanical origin, including fresh and dried flowers, leaves and insect frass (processed leaves). Although plant tissues are rich in fibers (lignocelluloses, hemicelluloses, pectins and starches) and the symbiotic fungus possesses the genetic and enzymatic machinery to metabolize these compounds, the highly derived attines, the leaf-cutters (Atta and Acromyrmex), are known to produce fiber-rich waste. While leaf-cutting ants are important consumers of primary plant tissue, there have been fewer studies on physiological activity of fungi grown by closely related ant species in the genus Trachymyrmex, which generally grow related species of fungi, have smaller colonies and consume a wider variety of fungal substrates in addition to fresh leaves and flowers. In this study, we measured the cellulase activity of the fungus-gardening ants Atta texana, Trachymyrmex arizonensis and T. septentrionalis. We then quantified fiber consumption of the fungus-gardening ants Trachymyrmex septentrionalis and Trachymyrmex arizonensis by comparing the amounts and percentages present in their food and in fungus garden refuse during a controlled feeding experiment over the span of several months. Finally, we compared waste composition of T. arizonensis colonies growing different fungal strains, because this species is known to cultivate multiple strains of Leucoagaricus in its native range. The leaf-cutting ant A. texana was found to have lower cellulytic activity than T. arizonensis or T. septentrionalis. Total lignocellulose and hemicellulose amounts were significantly lower in refuse piles than in the substrates fed to the Trachymyrmex colonies, thus these fibers were consumed by the fungal symbionts of these ant species. Although lignocellulose utilization was similar in two distinct fungal species grown by T. arizonensis colonies, hemicellulose utilization was higher in T. arizonensis colonies growing a derived leaf-cutting ant fungal symbiont than when growing a native type of symbiont. The results of this study demonstrate that fiber digestion in fungus-gardening ants is an outcome of ant-fungal interaction.

Original languageEnglish (US)
Pages (from-to)301-308
Number of pages8
JournalJournal of Insect Physiology
Volume98
DOIs
StatePublished - Apr 1 2017

Fingerprint

Formicidae
Symbiosis
Ants
Fungi
fungus gardening
Trachymyrmex
fungi
leaves
Trachymyrmex septentrionalis
leaf-cutting ants
lignocellulose
hemicellulose
symbionts
Atta texana
plant tissues
flowers
Leucoagaricus
Acromyrmex
plant fibers
Atta

Keywords

  • Attini
  • Hemicellulose
  • Lignocellulose
  • Symbiosis
  • Trachymyrmex

ASJC Scopus subject areas

  • Physiology
  • Insect Science

Cite this

Effects of substrate, ant and fungal species on plant fiber degradation in a fungus-gardening ant symbiosis. / DeMilto, Alexandria M.; Rouquette, Monte; Mueller, Ulrich G.; Kellner, Katrin; Seal, Jon N.

In: Journal of Insect Physiology, Vol. 98, 01.04.2017, p. 301-308.

Research output: Contribution to journalArticle

DeMilto, Alexandria M.; Rouquette, Monte; Mueller, Ulrich G.; Kellner, Katrin; Seal, Jon N. / Effects of substrate, ant and fungal species on plant fiber degradation in a fungus-gardening ant symbiosis.

In: Journal of Insect Physiology, Vol. 98, 01.04.2017, p. 301-308.

Research output: Contribution to journalArticle

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