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 biology of a koinobiont parasitoid of leaf-cutting ant larvae, <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Szelenyiopria talitae<span ...The biology of a koinobiont parasitoid of leaf-cutting ant larvae, <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Szelenyiopria talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> (Hymenoptera: Diapriidae), was studied from naturally infested <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Acromyrmex subterraneus<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> (Hymenoptera: Formicidae) nests. Nests were collected in the field from the Atlantic rainforest biome in the state of Rio de Janeiro. A total of fifty-three nests were collected from 2015 to 2018. Parasitized nests were only found during the months of September and October. Approximately 22% of the nests collected over a four-year period were found to have been parasitized by <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i>. The mean within-nest parasitism rate was<span "=""> 66.3%. This diapriid displayed both solitary (14%) and gregarious parasitism (86%), with up to a maximum of 12 parasitoids developing within a single host. Gregarious parasitism with two (29%) or three (21%) <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i></span><i></i> per host was most frequently observed. There was a positive correlation between the number of parasitoids per host and host size (dry weight), indicating that <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> females oviposited a higher number of eggs in larger hosts. There was also a negative correlation between <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S.</i> <i>talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> pharate adult size and the number of parasitoids per host, which could have been caused by sibling competition for limited host resources. The high levels of parasitism seen here had a debilitating effect on the colonies. <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Acromyrmex subterraneus<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> is a serious pest in Brazil, and these studies lay the foundation for understanding the impact of <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> on ant populations.展开更多
The ultrasonic scalpel has a number of excellent properties; however, its use in in vivo surgery is limited since the scalpel is not flexible enough. Changing the mechanism of ultrasonic vibration can allow the ultras...The ultrasonic scalpel has a number of excellent properties; however, its use in in vivo surgery is limited since the scalpel is not flexible enough. Changing the mechanism of ultrasonic vibration can allow the ultrasonic scalpel to bend. This paper reveals the mecha- nism of vibration generation of leaf-cutting ants, which is based on the microstructural and mechanical properties of special organs that produce the vibrations. Mierostructural characteristics of cross-sections of the vibratory organ of Atta cephalotes were observed using scanning electron microscopy. It was found that the scraper perfectly matches the file plate dorsoventrally; however, the file teeth cannot catch the scraper. An exploration of the kinematics of the file-scraper device was subsequently carried out to reveal a face-to-face contact mode, facilitating a gentler engagement process. For the first time, the mechanism of vibration generation of leaf-cutting ants was inves- tigated using a laser micrometer and high-speed camera. Results reveal the file-scraper device significantly amplifies the input frequency by 125 times, and magnification depends mainly on the tooth spacing and speed of engagement. Finally, nanoindentation tests were performed on file and scraper samples. The results show that they have similar mechanical properties, which greatly reduces friction and wear. This paper may provide theoretical guidance for the develooment of bionic vibration generators.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
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 biology of a koinobiont parasitoid of leaf-cutting ant larvae, <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Szelenyiopria talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> (Hymenoptera: Diapriidae), was studied from naturally infested <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Acromyrmex subterraneus<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> (Hymenoptera: Formicidae) nests. Nests were collected in the field from the Atlantic rainforest biome in the state of Rio de Janeiro. A total of fifty-three nests were collected from 2015 to 2018. Parasitized nests were only found during the months of September and October. Approximately 22% of the nests collected over a four-year period were found to have been parasitized by <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i>. The mean within-nest parasitism rate was<span "=""> 66.3%. This diapriid displayed both solitary (14%) and gregarious parasitism (86%), with up to a maximum of 12 parasitoids developing within a single host. Gregarious parasitism with two (29%) or three (21%) <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i></span><i></i> per host was most frequently observed. There was a positive correlation between the number of parasitoids per host and host size (dry weight), indicating that <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> females oviposited a higher number of eggs in larger hosts. There was also a negative correlation between <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S.</i> <i>talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> pharate adult size and the number of parasitoids per host, which could have been caused by sibling competition for limited host resources. The high levels of parasitism seen here had a debilitating effect on the colonies. <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>Acromyrmex subterraneus<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> is a serious pest in Brazil, and these studies lay the foundation for understanding the impact of <span style="color:#4D5156;background-color:#FFFFFF;"><i></i></span><i><i>S. talitae<span style="color:#4D5156;background-color:#FFFFFF;"></span></i></i> on ant populations.
基金The authors would like to thank the financial support from the National Natural Science Foundation of China （Nos. 51475029 and 51475031）.
文摘The ultrasonic scalpel has a number of excellent properties; however, its use in in vivo surgery is limited since the scalpel is not flexible enough. Changing the mechanism of ultrasonic vibration can allow the ultrasonic scalpel to bend. This paper reveals the mecha- nism of vibration generation of leaf-cutting ants, which is based on the microstructural and mechanical properties of special organs that produce the vibrations. Mierostructural characteristics of cross-sections of the vibratory organ of Atta cephalotes were observed using scanning electron microscopy. It was found that the scraper perfectly matches the file plate dorsoventrally; however, the file teeth cannot catch the scraper. An exploration of the kinematics of the file-scraper device was subsequently carried out to reveal a face-to-face contact mode, facilitating a gentler engagement process. For the first time, the mechanism of vibration generation of leaf-cutting ants was inves- tigated using a laser micrometer and high-speed camera. Results reveal the file-scraper device significantly amplifies the input frequency by 125 times, and magnification depends mainly on the tooth spacing and speed of engagement. Finally, nanoindentation tests were performed on file and scraper samples. The results show that they have similar mechanical properties, which greatly reduces friction and wear. This paper may provide theoretical guidance for the develooment of bionic vibration generators.
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.
