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
, 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.
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.
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.
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.
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.
•Riparian animals should benefit of actually using rivers.•We have tested predictions of a semi aquatic habit in a harvestman (Arachnida).•H. discolor swim by rowing and walking, and moves onto the ...water when disturbed.•Strictly terrestrial species did not swim or moved onto the water.•H. discolor can survive 6 h under water, as did a strictly terrestrial species.
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.
Pedipalps in laniatorid harvestmen are usually cylindrical and raptorial, but species in Cosmetidae are exceptional in that adults, but not immature, have pedipalps flattened as a spoon. These have ...never been addressed with a functional approach. We have investigated possible roles of the pedipalps in Cosmetidae in exploration, social interactions and defence. Concerning exploration, we would expect the individuals to tap the substrate with the pedipalps, as species in the suborders Eupnoi and Dyspnoi do, but this was not observed. In social interactions, pedipalps could be used for holding females during mating or to fight other males but we could not relate the spoon-shape with any of the behaviours observed. For defence, we hypothesised that the pedipalp of adults would act as a barrier preventing the potentially noxious secretion from contacting the mouth when the individual performs 'leg-dabbing'. This is typical in adult cosmetids but not in other laniatorids. Because immature cosmetids have cylindrical pedipalps, we predicted that they would not perform 'leg-dabbing'. However, immature also performed leg-dabbing and the secretion did contact the mouth. We also found no evidence of pedipalps being used for digging, drinking or self-grooming. Although we have made progress, the question remains open.
Preliminary observations suggested that the Neotropical harvestman Jussara sp. (Sclerosomatidae, Eupnoi) had a patchy distribution and a marked seasonality, comparable to species in the Northern ...hemisphere. This would be an unusual pattern, since conditions of temperature and humidity are very different between tropical and temperate environments. Using a mark-recapture method, we investigated the phenology, habitat use and individual movement of Jussara sp. in a tropical rainforest in southern Brazil. We found a very marked seasonality in the population of adults, with a positive correlation between temperature, humidity and number of adults found. Adults were found only in the wet and warm months and significantly preferred the plant Psycothria suterella (Rubiaceae) as a resting substrate, spending the days motionless on its leaves, often in groups. The same individuals were found for a maximum of three months after their first capture, 30 m from their original site of capture. At night, the harvestmen would descend from the plants, forage and interact with conspecifics on the leaf litter. In this first long term behavioral study with a representative of the suborder Eupnoi in Brazil, we provide quantitative evidence that, despite the milder climate, Neotropical harvestmen may show a seasonality similar to the seasonality shown by related species in temperate regions.
Preliminary observations suggested that the Neotropical harvestman Jussara sp. (Sclerosomatidae, Eupnoi) had a patchy distribution and a marked seasonality, comparable to species in the Northern ...hemisphere. This would be an unusual pattern, since conditions of temperature and humidity are very different between tropical and temperate environments. Using a mark-recapture method, we investigated the phenology, habitat use and individual movement of Jussara sp. in a tropical rainforest in southern Brazil. We found a very marked seasonality in the population of adults, with a positive correlation between temperature, humidity and number of adults found. Adults were found only in the wet and warm months and significantly preferred the plant Psycothria suterella (Rubiaceae) as a resting substrate, spending the days motionless on its leaves, often in groups. The same individuals were found for a maximum of three months after their first capture, 30 m from their original site of capture. At night, the harvestmen would descend from the plants, forage and interact with conspecifics on the leaf litter. In this first long term behavioral study with a representative of the suborder Eupnoi in Brazil, we provide quantitative evidence that, despite the milder climate, Neotropical harvestmen may show a seasonality similar to the seasonality shown by related species in temperate regions.
Harvestmen (Arachnida, Opiliones) are arachnids that rely on chemicals for communication and are particularly dependent on high humidity. The harvestman Jussara spec. (Sclerosomatidae) clearly ...prefers to rest on the stem and leaves of Psychotria suterella Muell. Arg. (Rubiaceae), a plant having a complex architecture of overlapping branches. So far, few studies have focused on understanding how harvestmen find their host plant and the benefits associated with the selected plant. Here, we investigated cues harvestmen may exploit to find P. suterella and the potential benefits for harvestmen of this interaction. To address how harvestmen find the plant, we tested two non‐exclusive hypotheses: harvestmen use chemicals from conspecifics, and/or harvestmen use chemicals from plants. For the first hypothesis, we assessed the number of harvestmen choosing P. suterella with or without chemicals of Jussara spec. on the main stem. We did not find evidence that Jussara spec. uses chemicals from conspecifics to select P. suterella, at least in isolation, without any mechanical stimuli such as stem texture or size. For the second hypothesis, we tested harvestman behavior exposed to volatiles from P. suterella, a non‐preferred host plant – Impatiens walleriana Hook.f. (Balsaminaceae) – and a blank treatment, both in a triangular arena and in a Y‐tube olfactometer. We also found no evidence that the harvestmen use plant volatiles to find it. We also tested two non‐exclusive hypotheses regarding the benefits of selecting P. suterella for harvestmen. The first hypothesis is that P. suterella offers a higher humidity than other plants in the micro‐environment surrounding the leaves because of a high leaf transpiration rate. Harvestmen could benefit from this because they rest with the body in contact with the leaf or at less than 5 mm from it. We did not find evidence that leaf transpiration rate is important for Jussara spec., as P. suterella did not present high rates compared to other local species. The second hypothesis is that the leaves of P. suterella provide a better shadow than other plants, acting as a sun shade due to its complex architecture with overlapping leaves. We measured light passage through the leaves of P. suterella and three other local species and found that less light passes through the leaves of P. suterella, which therefore provides darker shadow. This potentially provides a favorable micro‐climate for harvestmen, which might help to explain the micro‐habitat preference of Jussara spec.
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.
A interação envolvendo artrópodes e plantas é uma das mais antigas e importantes interações ecológicas da natureza. As estratégias adotadas pelos artrópodes para reconhecer a sua planta hospedeira ...são bastante variáveis e pistas químicas desempenham um papel importante nessa relação. Opiliões (Arachnida, Opiliones) são altamente dependentes de quimiorrecepção para encontrar recursos e são particularmente dependentes de umidade. O opilião Jussara sp. possui uma clara preferencia por repousar em Psychotria suterella (Rubiacea), uma planta com uma arquitetura foliar complexa com folhas sobrepostas. Nada se sabe sobre como o opilião chega a ela ou quais as vantagens que ela proporciona ao opilião. Neste trabalho verificamos quais pistas são utilizadas pelo opilião para encontrar P. suterella e ainda quais os possíveis benefícios para o opilião nessa interação. Para verificação de como o opilião encontra a planta, partimos de duas hipóteses não excludentes: 1 - pistas de co-específicos são utilizadas; 2 - pistas químicas provenientes da planta são utilizadas. Para a primeira hipótese, montamos um experimento em campo com um grupo de plantas de P. suterella contendo químicos de Jussara sp. e um grupo sem químicos de Jussara sp. no caule principal e comparamos como os tratamentos afetaram o número de opiliões nas plantas de cada grupo. Para a hipótese da utilização de químicos da planta, realizamos dois experimentos visando verificar a preferência do opilião pelos voláteis de P. suterella. No primeiro utilizamos extratos de químicos voláteis de P. suterella e de mais dois controles em uma arena triangular com os 3 estímulos oferecidos simultâneamente. No segundo experimento utilizamos a própria planta P. suterella, pareada com uma planta controle ou um controle branco em um olfatômetro em Y. Para verificar os benefícios da associação também partimos de duas hipóteses não exludentes relacionadas a possíveis diferenças microclimáticas geradas por P. suterella em relação às demais plantas do local: 1- as folhas de P. suterella oferecem maior umidade do que outras plantas; 2 - as folhas de P. suterella fornecem um microambiente mais sombreado do que o de outras plantas. Para primeira hipótese, quantificamos o fluxo de transpiração foliar de P. suterella e mais 3 espécies de plantas do habitat do opilião. Já para segunda hipótese, quantificamos o bloqueio à passagem de luz através das folhas em P. suterella e das mesmas 3 espécies do teste anterior. Não obtivemos evidências claras de que os opiliões Jussara sp. utilizem químicos de co-específicos para selecionar P. suterella. Pistas químicas olfativas não parecem ser utilizadas de forma isolada para atrair Jussara sp., mas nossos resultados sugerem que talvez em combinação com outras plantas o odor possa ser utilizado. Em relação aos benefícios fornecidos por P. suterella, nós não encontramos evidências de que a transpiração foliar seja importante na interação. Contudo, o maior bloqueio de passagem de luz através da folha em comparação às demais espécies aliado a arquitetura foliar de P. suterella pode gerar microclimas benéficos para os opiliões que geralmente são altamente sensíveis a umidade
Interactions between arthropods and plants are among the oldest and important ecological interactions in nature. Strategies adopted by arthropods to recognize its host plant are very variable and volatiles often mediate the encounter between both parts. Harvestmen (Arachnida, Opiliones) are arachnids highly dependent on chemicals to find resources and particularly dependent on high humidity. The harvestman Jussara sp. clearly prefers to rest on Psychotria suterella (Rubiacea), a plant with a complex architecture with overlapping leaves. We know nothing about how the harvestmen find the plant or the advantages that such plant offers to the harvestmen. In this paper we investigate the cues used to find P. suterella by these harvestmen and how the harvestman benefits from this interaction. To test how the harvestman finds the plant, we raised two non-excludent hypotheses: 1 - conspecific chemicals are used; 2 - plant chemicals are used. For the first hypothesis, we conducted a field experiment with a group of P. suterella with chemicals of Jussara sp. and another without chemicals of of Jussara sp. on the main stem and compared how that affected the number of harvestmen on them. To test the importance of plant chemicals, we conducted two experiments to test the use of volatiles of P. suterella. We first used volatile extracts of P. suterella and two other plants in a triangular arena with the three stimuli offered simultaneously. In the second experiment, we used actual individuals of P. suterella paired with either a control plant of a white control in a Y maze. To investigate how Jussara sp. benefits by choosing P. suterella, we raised two non-excludent hypotheses related to microclimatic conditions potentially offered by P. suterella in comparison to other plants of the area: 1 - The leaves of P. suterella offer higher humidity than those of other plants; 2 - The leaves of P. suterella provide a better shadow that that of other plants. For the first hypothesis, we quantified the transpiration rate of the leaves of four local species including P. suterella. For the second hypothesis, we quantified how much light passes through the leaves of these four species. We did not find clear evidences that Jussara sp. uses conspecific chemicals to select P. suterella. Plant volatiles do not seem to be used at least isolated to attract Jussara sp., but our results suggest that maybe in combination with other plants such volatiles may be used. As for the benefits provided by P. suterella, we did not find evidence that the transpiration rate is important. However, the leaves of P. suterella do provide better shadows in comparison with the other plants, which in combination with the complex architecture with overlapping leaves may provide better microclimatic conditions to these very humidity sensitive animals
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