Habituation to a predatory stimulus in a harvester (Arachnida, Opiliones).

Several studies have investigated habituation in a defensive context, but few have addressed responses to dangerous stimuli. In such cases, animals should not habituate since this could cost their lives. Here we have stimulated individuals of the harvester Mischonyx squalidus with a predatory stimulus (squeezing with tweezers) in repeated trials within and between days, and measured the occurrence and magnitude of nipping, a defensive behavior. Contrary to our expectations, they did habituate to this stimulus. The probability and magnitude of response declined over trials during each of three days of testing in a typical habituation pattern. During the trials we also observed other defensive behaviors. We discuss our results mainly considering alternative defensive responses. Our data show that we lack information on (1) the role played by the ambiguity of stimuli, (2) the role played by subsequent stimuli and (3) the importance of the array of defensive behaviors of a species in understanding habituation. Although ubiquitous across animals and therefore expected, habituation is described for the first time in the order Opiliones.

Experimental approach to the dislodging effect and the mortality of a pesticide in the yellow scorpion Tityus serrulatus.

Accidents with scorpions are a problem in several regions of the world. In Brazil, the number of accidents is sometimes higher than 160k/year, and the responsible for most accidents and deaths is the yellow scorpion Tityus serrulatus. Unfortunately, there are few publications testing the effectiveness of most of the products for chemical control of scorpions. Using the pesticide Bifentol, we tested: I-the effect of the pesticide on the mortality of T. serrulatus, II-whether the scorpion avoids areas with pesticide and, III-whether it leaves the shelter if pesticide is applied. In the first experiment, we applied pesticide or water on the dorsal region of the scorpion or substrate according to treatment. For five days we noted whether the scorpion slide (dead) or clung to the substrate (alive) after turning the arena vertically to left and right. After five days, no pesticide-treated scorpions were alive while all water-treated scorpions were. In the second experiment, we placed two shelters, applied pesticide and/or water inside the shelter. We then released a scorpion on the opposite side. We scored latency to enter one of the shelters and the choice made by the scorpions. We did not find differences in latency or in the choice made. In the third experiment, we applied the pesticide or water to the shelter where the scorpion was being maintained, and, on the following day, we recorded whether the scorpion had left the shelter. None of the scorpions left the shelters and only one died. Thus, we obtained evidence that a pesticide can kill scorpions, but we did not find a dislodging effect.

Morphology of the arthrodial membrane gland in a Neotropical harvester (Arachnida: Opiliones)

We describe a gland in the arthrodial membrane of the coxa-trochanter articulation in the fourth pair of legs in the Neotropical harvester Mischonyx squalidus Bertkau, 1880. Externally the glandular area has a rough appearance with pores on its surface, with folds of the arthrodial membrane. Internally, its secretory cells have spherical secretory vesicles, smooth endoplasmic reticulum, mitochondria and ducts that exit from the cells and cross the arthrodial membrane. Histochemical tests indicate the presence of proteins and neutral glycoproteins. The function of the gland might be to produce lubricating products that allow better movement of the coxa-trochanter region.

Voracity, reaction to stings, and survival of domestic hens when feeding on the yellow scorpion (Tityus serrulatus).

BACKGROUND: Scorpionism is a worldwide problem that has already made thousands of victims, and multi-disciplinary approaches for controlling their populations are to be more successful. Hens are often mentioned as tools for controlling scorpions; however, systematic/experimental behavioral studies are not available. Moreover, there is no systematic information on the effect of scorpion venoms on hens. Using the venomous yellow scorpion Tityus serrulatus, the present study aimed to clarify the following aspects: (1) voracity of hens, (2) how hens react when stung, (3) the effect of scorpion stings on hen behavior during attacks, and (4) hen survivorship after feeding on scorpions. METHODS: We attracted hens with corn powder, offered them scorpions and then recorded the hen-scorpion interaction. To test the effects of the sting we manually removed the scorpion's telson. RESULTS: We found that some hens ate up to six scorpions within minutes. By means of an ethogram and drawings, we showed that they exhibited several aversive behaviors when capturing scorpions. Removal of the scorpion telson stopped the aversive reactions, which was not observed in the control group. Finally, hens did not exhibit atypical behaviors after 1, 7 and 30 days and were all alive after 30 days. CONCLUSION: This is the first empirical and video recorded study providing evidence that hens are clearly affected by scorpion venom but do not die. Therefore, they may have potential to be used in biological control of these arthropods.

Voracity, reaction to stings, and survival of domestic hens when feeding on the yellow scorpion (Tityus serrulatus)

Abstract Background: Scorpionism is a worldwide problem that has already made thousands of victims, and multi-disciplinary approaches for controlling their populations are to be more successful. Hens are often mentioned as tools for controlling scorpions; however, systematic/experimental behavioral studies are not available. Moreover, there is no systematic information on the effect of scorpion venoms on hens. Using the venomous yellow scorpion Tityus serrulatus, the present study aimed to clarify the following aspects: (1) voracity of hens, (2) how hens react when stung, (3) the effect of scorpion stings on hen behavior during attacks, and (4) hen survivorship after feeding on scorpions. Methods: We attracted hens with corn powder, offered them scorpions and then recorded the hen-scorpion interaction. To test the effects of the sting we manually removed the scorpions telson. Results: We found that some hens ate up to six scorpions within minutes. By means of an ethogram and drawings, we showed that they exhibited several aversive behaviors when capturing scorpions. Removal of the scorpion telson stopped the aversive reactions, which was not observed in the control group. Finally, hens did not exhibit atypical behaviors after 1, 7 and 30 days and were all alive after 30 days. Conclusion: This is the first empirical and video recorded study providing evidence that hens are clearly affected by scorpion venom but do not die. Therefore, they may have potential to be used in biological control of these arthropods.

Voracity, reaction to stings, and survival of domestic hens when feeding on the yellow scorpion (Tityus serrulatus)

Scorpionism is a worldwide problem that has already made thousands of victims, and multi-disciplinary approaches for controlling their populations are to be more successful. Hens are often mentioned as tools for controlling scorpions; however, systematic/experimental behavioral studies are not available. Moreover, there is no systematic information on the effect of scorpion venoms on hens. Using the venomous yellow scorpion Tityus serrulatus, the present study aimed to clarify the following aspects: (1) voracity of hens, (2) how hens react when stung, (3) the effect of scorpion stings on hen behavior during attacks, and (4) hen survivorship after feeding on scorpions. Methods: We attracted hens with corn powder, offered them scorpions and then recorded the hen-scorpion interaction. To test the effects of the sting we manually removed the scorpion's telson. Results: We found that some hens ate up to six scorpions within minutes. By means of an ethogram and drawings, we showed that they exhibited several aversive behaviors when capturing scorpions. Removal of the scorpion telson stopped the aversive reactions, which was not observed in the control group. Finally, hens did not exhibit atypical behaviors after 1, 7 and 30 days and were all alive after 30 days. Conclusion: This is the first empirical and video recorded study providing evidence that hens are clearly affected by scorpion venom but do not die. Therefore, they may have potential to be used in biological control of these arthropods.(AU)

Do predators react differently to dangerous and larger prey? The case of a mygalomorph generalist spider preying upon insects.

Prey morphology and size are known to influence a predator's decision to attack and consume particular prey; however, studies that evaluate both traits simultaneously are uncommon. Here, we first described the trophic niche in the mygalomorph spider Paratropis sp. These spiders have a narrow trophic niche and feed mainly on sympatric species such as larvae of lepidopterans and of beetles such as carabids, passalids and scarabeids. Second, we evaluated the effect of prey taxon and size on acceptance and immobilization duration, and built an ethogram of the predator's behaviors. For each prey taxa, we offered large (approximately same size than the spider) and small larvae (approximately half of the size of the spider) of the aforementioned prey. We classified carabid beetle larvae as the most dangerous prey because of their sharp mandibles and predatory habits, followed by scarabeid larvae; lepidopteran and passalids larvae were considered to be non-dangerous prey. We did not find a significant effect of prey taxon or size on spiders' acceptance. Prey size did not affect the time invested on each behavioral category, but prey taxon did. Moreover, although spiders used a similar strategy for capturing prey, they spent more time biting carabid larvae than other prey. Our results suggest that, at least in our study area, prey that are dangerous or the predator's size do not seem to affect Paratropis sp. acceptance per se, but can cause the predator to change the time budget allocated to each behavior.

Protein Components of the Arthrodial Membrane Gland in a Neotropical Harvestman (Arachnida, Opiliones).

The content of arthrodial membrane glands in arthropods has seldom been studied. Here, we have analyzed the proteins of the arthrodial membrane gland of the trochanter-coxa articulation of the fourth pair of legs in the harvestman Mischonyx cuspidatus via reverse-phase high-performance liquid chromatography (RP-HPLC), polyacrylamide gel electrophoresis (PAGE), and nanoscale liquid chromatography coupled to mass spectrometry (nLC-MS/MS) analysis. Most of the fractions studied are hydrophobic, being proteins with molecular weights of ∼28, 62, and ∼198 kDa. These proteins seem to be homologous to proteins involved in product secretion, cytoskeleton, protein binding, cellular metabolism, and antimicrobial action among others. Lubricant function is also possible based on the literature. We were able to identify 147 proteins in the inner region, 91 proteins from the outer dorsal region, and 36 proteins from the outer ventral region. Some proteins are present only in one of these regions and some are shared by one or more regions. Our work provides, to the best of our knowledge, the first proteome characterization of the content of an arthrodial membrane gland in arachnids. Dataset Identifier: ftp://massive.ucsd.edu/MSV000087195/.

Protein components of the arthrodial membrane gland in a Neotropical Harvestman (Arachnida, Opiliones)

The content of arthrodial membrane glands in arthropods has seldom been studied. Here, we have analyzed the proteins of the arthrodial membrane gland of the trochanter–coxa articulation of the fourth pair of legs in the harvestman Mischonyx cuspidatus via reverse-phase high-performance liquid chromatography (RP-HPLC), polyacrylamide gel electrophoresis (PAGE), and nanoscale liquid chromatography coupled to mass spectrometry (nLC-MS/MS) analysis. Most of the fractions studied are hydrophobic, being proteins with molecular weights of ∼28, 62, and ∼198 kDa. These proteins seem to be homologous to proteins involved in product secretion, cytoskeleton, protein binding, cellular metabolism, and antimicrobial action among others. Lubricant function is also possible based on the literature. We were able to identify 147 proteins in the inner region, 91 proteins from the outer dorsal region, and 36 proteins from the outer ventral region. Some proteins are present only in one of these regions and some are shared by one or more regions. Our work provides, to the best of our knowledge, the first proteome characterization of the content of an arthrodial membrane gland in arachnids. Dataset Identifier: ftp://massive.ucsd.edu/MSV000087195/.

Water locomotion and survival under water in a riparian harvestman (Opiliones, Arachnida).

Animals that live by rivers may benefit from being able to cross them, but behavioral adaptations are needed. Additionally, being able to remain submerged is also important if the animal moves under water. Here we asked whether the harvestman Heteromitobates discolor (Opiliones), that lives by rivers, (a) can propel itself across the water surface, (b) moves onto the water if disturbed and (c) can survive for long periods when submerged. Heteromitobates discolor exhibited two gaits on water, whereas a strictly terrestrial species was not able to propel itself. When experimentally submitted to simulated predator attack on a rock on the river, H. discolor walked onto the water, while a strictly terrestrial species did not. Finally, it was able to survive for 6 h under water, presumably due to the conspicuous air film that formed around its body, which was also observed in a strictly terrestrial species. Altogether, these observations suggest that the aquatic environment is not a barrier for regular activity and can be used as an extension of the terrestrial environment for H. discolor.

The Scent Glands of the Neotropical Harvestman Discocyrtus pectnifemur: Morphology, Behavior and Chemistry.

Harvestmen have a pair of scent glands that open through ozopores. The literature suggests a link between the morphology of the ozopore area and the emission of a defensive secretion. A previous study on a species that aggregates in open areas, where individuals are probably more easily spotted by predators, showed that this defensive secretion causes conspecifics to flee. However, it is unknown whether this behavior occurs in species that aggregate in sheltered areas, where prey are harder to find. Herein, we describe the morphology of the ozopore area, the mode of emission of the defensive secretion, and its chemical composition in the harvestman Discocyrtus pectinifemur. We also tested if the defensive secretion is used as an alarm pheromone. We found that D. pectinifemur releases the defensive secretion in different ways, one of them being as a jet. Emission as a jet contrasts with that known for all congeners previously studied, and is in accord with the expected morphology of the ozopore. We found that the defensive secretion of D. pectinifemur does not function as an alarm pheromone. The composition of the defensive secretion, a mixture of quinones, is congruent with those already described for the clade that includes Discocyrtus. Our results support the link between the morphology of the scent glands area and the emission behavior of the defensive secretion, and they suggest that the alarm pheromone function in harvestmen may be dependent on ecological factors.

Foraging, oviposition sites and notes on the natural history of the harvestman Heteromitobates discolor (Opiliones, Gonyleptidae) / Forrageamento, sítios de oviposição e notas sobre a história natural do opilião Heteromitobates discolor (Opiliones, Gonyleptidae)

The lack of data on the natural history often hampers phylogenetic studies on the evolution of behavior. Herein we provide quantitative field data on foraging and oviposition sites of a Neotropical harvestman belonging to a subfamily with a published phylogeny, Goniosomatinae. Heteromitobates discolor rests during the day on granitic boulders on rivers, laying eggs in sheltered and darker areas. The female guard the eggs and aggressively respond to approaching conspecific females. In the absence of the female, ants, conspecifics and reduviids may predate the eggs. Egg-guarding females are known not to leave the clutch, but males and non-guarding females may leave the granitic boulders and forage on the vegetation at night, close to the river margins and with no difference in the sites explored between males and females. The general features described in H. discolor are similar to what has been reported for other species in this subfamily, suggesting an evolutionary conservatism within the group.

A falta de dados de história natural por vezes dificulta estudos filogenéticos sobre a evolução do comportamento. Nesse estudo nós fornecemos dados quantitativos de campo sobre forrageamento e sítios de oviposição de um opilião Neotropical pertencente a uma subfamília com uma filogenia publicada, Goniosomatinae. Heteromitobates discolor passa o dia em rochedos graníticos em rios, onde deposita os ovos em áreas abrigadas e escuras. A fêmea cuida dos ovos e responde agressivamente a fêmeas co-específicas que se aproximam. Na ausência de fêmeas, formigas, co-específicos e percevejos reduvídeos podem predar os ovos. Fêmeas que guardam ovos não deixam as desovas, mas machos e fêmeas sem ovos deixam os rochedos graníticos e forrageiam sobre a vegetação è noite, próximos è margem do rio e sem diferença nos sítios explorados entre os machos e as fêmeas. As características gerais descritas em H. discolor são similares ao que tem sido reportado para outras espécies nesta subfamília, sugerindo um conservadorismo evolutivo dentro do grupo.

Neotropical harvestmen (Arachnida, Opiliones) use sexually dimorphic glands to spread chemicals in the environment.

Sexually dimorphic glands have convergently appeared in animals and are often responsible for the production of pheromones. In the suborder Laniatores of the order Opiliones (Arachnida), glands of such type are widespread, but there is not a single paper on how they are used. Using Scanning Electron Microscopy and a behavioral approach, we describe glandular openings and how these glands are used, in the harvestmen Gryne perlata and Gryne coccinelloides (Cosmetidae). Males of these two species have glandular openings on the metatarsi of legs I and on the metatarsi IV. Males were shown rubbing the glands of the metatarsi I against their other legs, whereas glands on the metatarsi IV are gently touched on the substrate or rubbed either against other legs, or against the substrate. Not all behaviors were seen in both species.

Associative learning in a harvestman (Arachnida, Opiliones).

Associative learning has been demonstrated in many species of invertebrates, but has not been studied in arachnids, except for some spiders and a whip-spider. Herein, we tested the ability of a Neotropical harvestman, Discocyrtus invalidus (Arachnida, Opiliones) to associate a shelter with a chemical stimulus. We used an arena with a white light at the top and two openings on the floor, one giving access to a dark shelter and the other one closed with a mesh. Filter paper with different chemicals (mate or green tea) surrounded both openings. A harvestman (n=37) was released in the arena and its behavior recorded. The procedure was repeated for 14 consecutive days with each individual. We found that harvestmen got faster at finding the refuge, became less exploratory and tended to move toward the open shelter as the days passed. We conclude that the animals learned to associate the chemical stimulus with the shelter.