scholarly journals Carbon dioxide levels and ventilation in Acromyrmex nests: significance and evolution of architectural innovations in leaf-cutting ants

2021 ◽  
Vol 8 (11) ◽  
Author(s):  
Martin Bollazzi ◽  
Daniela Römer ◽  
Flavio Roces
Keyword(s):  
Soil Surface ◽  
Fungus Garden ◽  
Ant Colonies ◽  
Gas Exchanges ◽  
Selective Pressures ◽  
Leaf Cutting ◽  
Single Opening ◽  
Carbon Dioxide Levels ◽  
Nesting Habits ◽  
Ancestral Type

Leaf-cutting ant colonies largely differ in size, yet all consume O 2 and produce CO 2 in large amounts because of their underground fungus gardens. We have shown that in the Acromyrmex genus, three basic nest morphologies occur, and investigated the effects of architectural innovations on nest ventilation. We recognized (i) serial nests, similar to the ancestral type of the sister genus Trachymyrmex , with chambers excavated along a vertical tunnel connecting to the outside via a single opening, (ii) shallow nests, with one/few chambers extending shallowly with multiple connections to the outside, and (iii) thatched nests, with an above-ground fungus garden covered with plant material. Ventilation in shallow and thatched nests, but not in serial nests, occurred via wind-induced flows and thermal convection. CO 2 concentrations were below the values known to affect the respiration of the symbiotic fungus, indicating that shallow and thatched nests are not constrained by harmful CO 2 levels. Serial nests may be constrained depending on the soil CO 2 levels. We suggest that in Acromyrmex , selective pressures acting on temperature and humidity control led to nesting habits closer to or above the soil surface and to the evolution of architectural innovations that improved gas exchanges.

scholarly journals Ammonia Production by Streptomyces Symbionts of Acromyrmex Leaf-Cutting Ants Strongly Inhibits the Fungal Pathogen Escovopsis

2021 ◽  
Vol 9 (8) ◽  
pp. 1622
Author(s):  
Basanta Dhodary ◽  
Dieter Spiteller
Keyword(s):  
Fungal Pathogen ◽  
Closed Loop ◽  
Pathogenic Fungus ◽  
Ant Colonies ◽  
Strong Activity ◽  
Streptomyces Sp ◽  
Mutualistic Symbiosis ◽  
Leaf Cutting ◽  
Leucoagaricus Gongylophorus ◽  
Production Of Ammonia

Leaf-cutting ants live in mutualistic symbiosis with their garden fungus Leucoagaricus gongylophorus that can be attacked by the specialized pathogenic fungus Escovopsis. Actinomyces symbionts from Acromyrmex leaf-cutting ants contribute to protect L. gongylophorus against pathogens. The symbiont Streptomyces sp. Av25_4 exhibited strong activity against Escovopsis weberi in co-cultivation assays. Experiments physically separating E. weberi and Streptomyces sp. Av25_4 allowing only exchange of volatiles revealed that Streptomyces sp. Av25_4 produces a volatile antifungal. Volatile compounds from Streptomyces sp. Av25_4 were collected by closed loop stripping. Analysis by NMR revealed that Streptomyces sp. Av25_4 overproduces ammonia (up to 8 mM) which completely inhibited the growth of E. weberi due to its strong basic pH. Additionally, other symbionts from different Acromyrmex ants inhibited E. weberi by production of ammonia. The waste of ca. one third of Acomyrmex and Atta leaf-cutting ant colonies was strongly basic due to ammonia (up to ca. 8 mM) suggesting its role in nest hygiene. Not only complex and metabolically costly secondary metabolites, such as polyketides, but simple ammonia released by symbionts of leaf-cutting ants can contribute to control the growth of Escovopsis that is sensitive to ammonia in contrast to the garden fungus L. gongylophorus.

scholarly journals Mathematical Modelling on Avoidance-to- Acceptance Transition in Leaf Cutting Ant Colonies

2016 ◽  
Vol 9 (11) ◽  
Author(s):  
J. Amudhavel ◽  
C. Kodeeswari ◽  
S. Jarina ◽  
S. Jaiganesh ◽  
B. Bhuvaneswari
Keyword(s):  
Mathematical Modelling ◽  
Ant Colonies ◽  
Leaf Cutting

scholarly journals BIOLOGICAL CONTROL IN LEAF-CUTTING ANTS, Atta sexdens (HYMENOPTERA: FORMICIDAE), USING PATHOGENIC FUNGI

2021 ◽  
Vol 45 ◽  
Author(s):  
Tarcísio Marcos Macedo Mota Filho ◽  
Luis Eduardo Pontes Stefanelli ◽  
Roberto da Silva Camargo ◽  
Carlos Alberto Oliveira de Matos ◽  
Luiz Carlos Forti
Keyword(s):  
Biological Control ◽  
Chemical Control ◽  
Pathogenic Fungi ◽  
Behavioral Changes ◽  
The Other ◽  
Fungus Garden ◽  
Atta Sexdens ◽  
Main Method ◽  
New Methods ◽  
Leaf Cutting

ABSTRACT Chemical control using toxic baits containing the active ingredient sulfluramid at 0.3% (w/w) is the main method for controlling leaf-cutting ants of the genera Atta and Acromyrmex. However, since 2009, when sulfluramid was included in Annex B of the Stockholm Convention on Persistent Organic Pollutants, there has been an intense search for new methods that are efficient in controlling these insects. Among said new methods, biological control using pathogenic fungi has shown promising results in laboratory conditions. The objective of this study, given the context presented, was to assess the potential of the fungi Beauveria bassiana and Trichoderma harzianum in controlling Atta sexdens. Colonies of A. sexdens were exposed to the fungi by means of formulated baits provided in a foraging chamber, or of suspensions sprayed on the fungus garden, and had their behavioral changes recorded for 21 days. For both formulations, concentrations of 10 and 20% (w/w) of the fungi being studied were used. The results allowed concluding that baits containing 10 and 20% (w/w) of the fungi B. bassiana and T. harzianum were not efficient in controlling colonies of A sexdens. On the other hand, spraying suspensions of 20% (w/w) of B. bassiana and 10% and 20% (w/w) of T. harzianum was efficient and resulted in 100% mortality of the colonies 11, 9 and 7 days after application, respectively. These findings indicate that the fungi B. bassiana and T. harzianum are promising as agents for the control of A. sexdens colonies, when sprayed on the fungus garden, although there are still some challenges as to their use related to the development of technologies for the application of the pathogen.

scholarly journals Endophytic fungi reduce leaf-cutting ant damage to seedlings

2010 ◽  
Vol 7 (1) ◽  
pp. 30-32 ◽  
Author(s):  
L. S. Bittleston ◽  
F. Brockmann ◽  
W. Wcislo ◽  
S. A. Van Bael
Keyword(s):  
Leaf Area ◽  
Plant Communities ◽  
Endophytic Fungi ◽  
Cordia Alliodora ◽  
Neotropical Forests ◽  
Ant Colonies ◽  
Leaf Toughness ◽  
Leaf Tissues ◽  
Leaf Cutting ◽  
Atta Colombica

Our study examines how the mutualism between Atta colombica leaf-cutting ants and their cultivated fungus is influenced by the presence of diverse foliar endophytic fungi (endophytes) at high densities in tropical leaf tissues. We conducted laboratory choice trials in which ant colonies chose between Cordia alliodora seedlings with high ( E high ) or low ( E low ) densities of endophytes. The E high seedlings contained 5.5 times higher endophyte content and a greater diversity of fungal morphospecies than the E low treatment, and endophyte content was not correlated with leaf toughness or thickness. Leaf-cutting ants cut over 2.5 times the leaf area from E low relative to E high seedlings and had a tendency to recruit more ants to E low plants. Our findings suggest that leaf-cutting ants may incur costs from cutting and processing leaves with high endophyte loads, which could impact Neotropical forests by causing variable damage rates within plant communities.

Social Carrying and Defensive Behavior During Colony Emigration in the Leaf-cutting Ant Atta sexdens

Sociobiology ◽  
2017 ◽  
Vol 64 (4) ◽  
pp. 492
Author(s):  
Lohan Valadares ◽  
Fábio S. Nascimento
Keyword(s):  
Body Surface ◽  
Defensive Behavior ◽  
The Body ◽  
Fungus Garden ◽  
Atta Sexdens ◽  
Defensive Strategies ◽  
Laboratory Conditions ◽  
Nesting Site ◽  
Leaf Cutting ◽  
First Time

In this work, we describe for the first time and under laboratory conditions, the behaviors related to social carrying and defensive strategies during colony emigration in the leaf-cutting ant Atta sexdens. Once colonies were laid on a tray under suboptimal conditions, groups of workers aggregated all over the body surface of the queen and brood, with mandibles half open and legs widely open in a ‘entangle’ formation. Queens were the first caste to be reallocated, followed respectively by the transportation of brood, newly-emerged workers, and pieces of fungus garden to the new nesting site. Contrary to what have been reported to the Myrmicinae species, adult transport followed a stereotyped sequence of acts involving approach, seize and transportation of newly-emerged workers to new target areas. Our results suggest that, in front of rapid unfavorable changes, leaf-cutting ants are capable of reorganize the nest in order to protect their members and resources.

scholarly journals Optimality in a partitioned task performed by social insects

2008 ◽  
Vol 4 (6) ◽  
pp. 627-629 ◽  
Author(s):  
Martin Burd ◽  
Jerome J Howard
Keyword(s):  
Social Insects ◽  
Social Insect ◽  
Leaf Tissue ◽  
Leaf Fragment ◽  
Ant Colonies ◽  
Tissue Processing ◽  
Leaf Cutting ◽  
Laboratory Colonies ◽  
Atta Colombica ◽  
Behavioural Adaptations

Biologists have long been aware that adaptations should not be analysed in isolation from the function of the whole organism. Here, we address the equivalent issue at the scale of a social insect colony: the optimality of component behaviours in a partitioned sequence of tasks. In colonies of Atta colombica , a leaf-cutting ant, harvested leaf tissue is passed from foragers to nest workers that distribute, clean, shred and implant the tissue in fungal gardens. In four laboratory colonies of A. colombica , we found that the highest colony-wide rate of leaf tissue processing in the nest was achieved when leaf fragment sizes were suboptimal for individual delivery rate by foragers. Leaf-cutting ant colonies appear to compromise the efficiency of collecting leaf tissue in order to increase their ability to handle the material when it arrives in the nest. Such compromise reinforces the idea that behavioural adaptations, like adaptations in general, must be considered within the context of the larger entity of which they are a part.

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