Symbiotic relations are present in the nature and can contribute to the success of the organisms involved. Endophytic fungi live within the leaf tissues without causing any harm to the host plant, and some of them can...Symbiotic relations are present in the nature and can contribute to the success of the organisms involved. Endophytic fungi live within the leaf tissues without causing any harm to the host plant, and some of them can be a defense mechanism against the attack by the leaf-cutting ants. Ants of the genus <em>Atta</em> are known as leaf-cutting ants and have an obligatory association with the fungus <em>Leucoagaricus gongylophorus</em>, cutting pieces of leaves and bringing them back to the colony to the fungus. The present study aimed to find out the endophytic fungi community of an attractive plant (<em>Acalypha wilkesiana</em>) and a less attractive plant (<em>Colocasia esculenta</em>) to the ants <em>Atta sexdens</em>. We found out that the communities are different in quantity and in composition and 73% of the isolated fungi were from <em>A. wilkesiana</em>, which has fungi known as attractive to leaf-cutting ants, such as genus<em> Colletotrichum</em>, <em>Pestalotiopsis</em>, <em>Phomopsis </em>and <em>Xylaria</em>. On the other hand, in <em>C. esculenta</em>, there was found the genus<em> Fusarium</em>, known to be reject by the leaf-cutting ants, and less fungal diversity than in the attractive plant <em>A. wilkesiana</em>. Therefore, our data suggest that attractivity or repelence of a plant to the leaf-cutting ants could be related to presence or ausence of determinated fungi more than the quantity of fungi present in a leaf.展开更多
The fungus-growing ants （Tribe Attini） are a New World group of〉 200 species, all obligate symbionts with a fungus they use for food. Four attine taxa are known to be social parasites of other attines. Acromyrmex ...The fungus-growing ants （Tribe Attini） are a New World group of〉 200 species, all obligate symbionts with a fungus they use for food. Four attine taxa are known to be social parasites of other attines. Acromyrmex （ Pseudoatta） argentina argentina and Acromyrmex （Pseudoatta） argentina platensis （parasites of Acromyrmex lundi）, and Acromyrmex sp. （a parasite of Acromyrmex rugosus） produce no worker caste. In contrast, the recently discovered Acromyrmex insinuator （a parasite of Acromyrmex echinatior） does produce workers. Here, we describe a new species, Acromyrmex ameliae, a social parasite of Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus brunneus in Minas Gerais, Brasil. Like A. insinuator, it produces workers and appears to be closely related to its hosts. Similar social parasites may be fairly common in the fungus-growing ants, but overlooked due to the close resemblance between parasite and host workers.展开更多
In the natural world,leaf-cutting ants cause vibrations through their mutual scraping of file-scraper organs.In this study,we designed a Biomimetic Ultrasonic Exciter(BUE)that imitates leaf-cutting ants.The operating ...In the natural world,leaf-cutting ants cause vibrations through their mutual scraping of file-scraper organs.In this study,we designed a Biomimetic Ultrasonic Exciter(BUE)that imitates leaf-cutting ants.The operating characteristics of the BUE were studied through experimental testing and finite element simulations.The results showed that the BUE could generate stable ultrasonic vibrations,and that the excitation frequency only needed to be half the Output Frequency(OF).This frequency-doubling phenomenon was conducive to achieving BUE miniaturization.To further explore the phenomenon of frequency-doubling vibration output,this study designed scrapers of five different sizes,conducted excitation and first-order natural frequency measurement tests,and the corresponding finite element simulations.It was found that each scraper could operate in frequency-doubling mode,but the operating frequency and natural mode frequencies did not correspond with one another.To further explicate experimental and simulation results,a two-degrees-of-freedom vibration model was developed.It was evident that the contact relationship between the dentate disc and scraper introduced strong nonlinear factors into the system,accounting for the frequency-doubling phenomenon and the difference between the BUE’s operating and mode frequencies.The BUE could be expected to facilitate the production of high-power micro-ultrasonic generators and has potential application value in the fields of mechanical processing,industrial production,and medical health.展开更多
The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study th...The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study the physical influence factors： filter paper with paraffin, filter paper without paraffin and polyester film. To study the chemical factors, some fragments were impregnated with organic extract of orange albedo, others were soaked with soybean oil and for the remaining ones nothing was applied. The fonowing parameters were evaluated： （i） attractiveness of substrate for transport and number of loading workers per treatment; （ii） foraged material incorporation; （iii） rejection by numbers of fragments deposited in the garbage or beside the fungus garden. All the polyester film fragments carried out to the fungus garden were subsequently rejected. We verified that chemical factors of the substrate were more quickly detected by the workers, whereas physical factors were used as a criterion in the decision-making to reject or accept the substrate collected.展开更多
文摘Symbiotic relations are present in the nature and can contribute to the success of the organisms involved. Endophytic fungi live within the leaf tissues without causing any harm to the host plant, and some of them can be a defense mechanism against the attack by the leaf-cutting ants. Ants of the genus <em>Atta</em> are known as leaf-cutting ants and have an obligatory association with the fungus <em>Leucoagaricus gongylophorus</em>, cutting pieces of leaves and bringing them back to the colony to the fungus. The present study aimed to find out the endophytic fungi community of an attractive plant (<em>Acalypha wilkesiana</em>) and a less attractive plant (<em>Colocasia esculenta</em>) to the ants <em>Atta sexdens</em>. We found out that the communities are different in quantity and in composition and 73% of the isolated fungi were from <em>A. wilkesiana</em>, which has fungi known as attractive to leaf-cutting ants, such as genus<em> Colletotrichum</em>, <em>Pestalotiopsis</em>, <em>Phomopsis </em>and <em>Xylaria</em>. On the other hand, in <em>C. esculenta</em>, there was found the genus<em> Fusarium</em>, known to be reject by the leaf-cutting ants, and less fungal diversity than in the attractive plant <em>A. wilkesiana</em>. Therefore, our data suggest that attractivity or repelence of a plant to the leaf-cutting ants could be related to presence or ausence of determinated fungi more than the quantity of fungi present in a leaf.
文摘The fungus-growing ants （Tribe Attini） are a New World group of〉 200 species, all obligate symbionts with a fungus they use for food. Four attine taxa are known to be social parasites of other attines. Acromyrmex （ Pseudoatta） argentina argentina and Acromyrmex （Pseudoatta） argentina platensis （parasites of Acromyrmex lundi）, and Acromyrmex sp. （a parasite of Acromyrmex rugosus） produce no worker caste. In contrast, the recently discovered Acromyrmex insinuator （a parasite of Acromyrmex echinatior） does produce workers. Here, we describe a new species, Acromyrmex ameliae, a social parasite of Acromyrmex subterraneus subterraneus and Acromyrmex subterraneus brunneus in Minas Gerais, Brasil. Like A. insinuator, it produces workers and appears to be closely related to its hosts. Similar social parasites may be fairly common in the fungus-growing ants, but overlooked due to the close resemblance between parasite and host workers.
基金supported by the National Natural Science Foundation of China(grant nos.91960203,51975035)。
文摘In the natural world,leaf-cutting ants cause vibrations through their mutual scraping of file-scraper organs.In this study,we designed a Biomimetic Ultrasonic Exciter(BUE)that imitates leaf-cutting ants.The operating characteristics of the BUE were studied through experimental testing and finite element simulations.The results showed that the BUE could generate stable ultrasonic vibrations,and that the excitation frequency only needed to be half the Output Frequency(OF).This frequency-doubling phenomenon was conducive to achieving BUE miniaturization.To further explore the phenomenon of frequency-doubling vibration output,this study designed scrapers of five different sizes,conducted excitation and first-order natural frequency measurement tests,and the corresponding finite element simulations.It was found that each scraper could operate in frequency-doubling mode,but the operating frequency and natural mode frequencies did not correspond with one another.To further explicate experimental and simulation results,a two-degrees-of-freedom vibration model was developed.It was evident that the contact relationship between the dentate disc and scraper introduced strong nonlinear factors into the system,accounting for the frequency-doubling phenomenon and the difference between the BUE’s operating and mode frequencies.The BUE could be expected to facilitate the production of high-power micro-ultrasonic generators and has potential application value in the fields of mechanical processing,industrial production,and medical health.
文摘The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study the physical influence factors： filter paper with paraffin, filter paper without paraffin and polyester film. To study the chemical factors, some fragments were impregnated with organic extract of orange albedo, others were soaked with soybean oil and for the remaining ones nothing was applied. The fonowing parameters were evaluated： （i） attractiveness of substrate for transport and number of loading workers per treatment; （ii） foraged material incorporation; （iii） rejection by numbers of fragments deposited in the garbage or beside the fungus garden. All the polyester film fragments carried out to the fungus garden were subsequently rejected. We verified that chemical factors of the substrate were more quickly detected by the workers, whereas physical factors were used as a criterion in the decision-making to reject or accept the substrate collected.
