RESUMEN
There is a great amount of ecological information for terrestrial arthropods in several types of habitats, but few studies have focused on populations living in tidal freshwater wetlands. During a two-year field survey, we studied the temporal dynamics of the harvestman Discocyrtus prospicuus inhabiting a freshwater wetland exposed to predictable tides and unpredictable floods. We also explored the effects of temperature, precipitation, and tide level on the population dynamics and reproductive phenology. Our findings are markedly different from those reported in other harvestman species living in different habitats and also from conspecific populations living in the mainland. Adults, subadults, and juveniles remain active throughout the year, and a long breeding season was observed. However, the number of adults, subadults, juveniles, and egg clutches showed clear variations over the year without a consistent seasonal pattern. Contrary to the general pattern in harvestmen, no climatic variables were significant predictors of abundance fluctuations. We discuss the potential masking effect of unpredictable flood events, obscuring the relationship between abundance and abiotic factors. In addition, given that climatic conditions seem to favor harvestmen activity throughout the year, we also hypothesized that abundance variations could be driven mainly by biotic rather than by abiotic interactions.
Asunto(s)
Arácnidos/clasificación , Arácnidos/fisiología , Animales , Femenino , Agua Dulce , Masculino , Dinámica Poblacional , Reproducción/fisiología , Estaciones del Año , Temperatura , HumedalesRESUMEN
The troglomorphic harvestman Otilioleptes marcelae gen. nov., sp. nov. from the basaltic cave Doña Otilia, Payunia region, Mendoza Province, Argentina, is described. Its systematic affinities were studied through cladistic and Bayesian analyses that included representatives of Gonyleptoidea; it was determined to represent a new monotypic family, Otilioleptidae fam. nov., occupying a basal position within the clade Laminata. This species shows accentuated troglomorphic traits, typical for troglobitic harvestmen: elongated appendages, depigmentation, reduction of eyes and fading of scutal sulci. Additionally, it almost lacks sexual dimorphism, the distal portion of coxa IV is not completely fused to the stigmatic segment, and penis morphology is remarkably divergent with other Laminata; these features cannot be attributed to cave adaptation and may reflect early lineage divergence. Otilioleptes marcelae is the first troglobitic gonyleptoid known from a lava tube. The xeric environments around the cave (Patagonian ecoregion) and the paleoenvironmental history of the area suggest the relictual character of O. marcelae. Scattered evidence supports a long time evolutionary scenario and a presumable relationship with the Chilean opiliofauna (especially with genus Osornogyndes). A comparative overview of all known troglobitic gonyleptoids is provided. The urgent need to protect this new species and its unique cave environment is emphasized.
Asunto(s)
Arácnidos/anatomía & histología , Arácnidos/fisiología , Teorema de Bayes , Evolución Biológica , Ecosistema , Animales , Arácnidos/clasificación , Argentina , Cuevas , Filogenia , Árboles , Erupciones VolcánicasRESUMEN
Surazomus saturninoae sp. nov. is described from eastern Amazon. The male has a pentagonal flagellum, similar to those of three other species in the genus. These four species are herein gathered as the arboreus-group of Surazomus. We present a brief synopsis of chaetotaxy description in hubbardiines and several homology proposals for the flagellum of the species in the arboreus-group: the posterior lobes may be homologous to the lateral lobes of hubbardiine species with trilobed flagella; the setal brush with 4-5 setae on the posterior lobe may be composed of one Dl2 seta and enlarged lobular microsetae; the single, median posterior coupling pocket may be homologous to the pair of posterior pockets seen in other hubbardiines; the single, median anterior coupling pocket may be homologous to the pair of pockets on the anterior border of the flagellum seen in other hubbardiines. Based on the morphology of these pockets and the chelicerae within Surazomus, we discuss the anchoring mechanism during the mating march.
Asunto(s)
Arácnidos/clasificación , Arácnidos/fisiología , Flagelos/fisiología , Reproducción , Sensilos/fisiología , Distribución Animal , Estructuras Animales/anatomía & histología , Estructuras Animales/crecimiento & desarrollo , Animales , Arácnidos/anatomía & histología , Femenino , Masculino , Sensilos/anatomía & histologíaRESUMEN
Here, we describe a new species of Eusarcus and reconstruct the geographical evolution of its species group based on biogeographical event-based analysis. Eusarcus dandara sp. nov. has been recorded from Alagoas state, in northeastern Brazil, which represents an important range extension of the genus to the northern Atlantic Rainforest. We performed a cladistic morphological analysis based on new data and data from a previous systematic review of the genus to reconstruct the phylogenetic placement of the new species. This analysis resulted in six most parsimonious cladograms. We performed the biogeographical reconstruction using the Treefitter 1.3B1 algorithm for the clade of eight species that includes E. dandara sp. nov., and we tested the significance of the reconstructions. We found two alternative reconstructions depended on the differences in species relationships; both were significant (0.002 ≤ p ≤ 0.019). The phylogenetic placement of the new species is consistent with some expectations based on previous biogeographical studies of Atlantic Rainforest harvestmen. Reconstructions reveal the origin of the species group in the northeast region, in the Atlantic Rainforest plus interior and dry biomes, such as the Caatinga xeric shrubland and Cerrado savanna, with subsequent dispersal to the southeast region. Harvestmen are good models to study the historical biogeography of the Atlantic Rainforest, especially those species that are endemic, like most Eusarcus. We have demonstrated a complex history of the spatial evolution of the group and the importance of the adjacent drier biomes in the evolution of endemic organisms of the Atlantic Rainforest.
Asunto(s)
Arácnidos/anatomía & histología , Arácnidos/clasificación , Distribución Animal , Animales , Arácnidos/fisiología , Brasil , Especificidad de la EspecieRESUMEN
Two new species of troglobiotic Brazilian palpigrades are described: Eukoenenia jequitinhonha sp. n., found in Lapa do Córrego do Vieira cave (Caraí, Minas Gerais) and E. cavatica sp. n., found in Cazanga cave (Arcos, Minas Gerais). The importance of documenting the occurrence of troglobiotic species, even if they are represented by only a single specimen, is discussed.
Asunto(s)
Arácnidos/anatomía & histología , Arácnidos/clasificación , Distribución Animal , Animales , Arácnidos/fisiología , Brasil , Cuevas , Femenino , MasculinoRESUMEN
The expression of costly traits often depends on the amount of food available to the individuals. Chemical defenses are costly, thus their production should be condition-dependent. Here, we tested the hypothesis that an increase in food availability and an acetate-supplemented diet will increase the production of chemical defenses by the harvestman Magnispina neptunus, which releases alkylated benzoquinones biosynthesized using acetate as a precursor. We manipulated the diet of the individuals and created four experimental groups: well-fed with acetate, well-fed without acetate, poorly-fed with acetate, and poorly-fed without acetate. Well-fed individuals produced secretions with higher mass and concentration of benzoquinones than poorly-fed individuals, but we detected no significant effect of the acetate supplement. Thus, the production of benzoquinones is condition-dependent, and even short periods of dietary restriction may make individuals more vulnerable to predators, imposing fitness consequences to chemically-protected arthropods that biosynthesize their own defensive compounds.
Asunto(s)
Acetatos/metabolismo , Arácnidos/fisiología , Benzoquinonas/metabolismo , Alquilación , Animales , Dieta , Femenino , MasculinoRESUMEN
Animals often rely on events in their environment that provide information (i.e. experience) to alter their future decision-making in ways that are presumed to be beneficial. Such experience-based learning, however, does not always lead to adaptive decision-making. In this study, we use the omnivorous harvestman Heteromitobates discolor to explore the role of past diet on subsequent food choice and survival. We first tested whether a short-term homogeneous diet (rotten crickets, fresh crickets or dog food) influenced subsequent food choice (rotten cricket versus fresh cricket). We next examine the impact of diet on survival. We found that following experience with a homogeneous cricket diet, adult harvestmen displayed a learned preference for familiar food, regardless of whether it was rotten or fresh crickets; individuals experiencing dog food were equally likely to choose rotten versus fresh crickets. We additionally found that individuals that ate rotten crickets suffered shorter survival than those that ate fresh crickets. Together, our results suggest that the diet an individual experiences can lead to maladaptive food preferences-preferences that ultimately result in reduced longevity.
Asunto(s)
Arácnidos/fisiología , Animales , Conducta Animal , Toma de Decisiones , Conducta Alimentaria , Femenino , Preferencias Alimentarias , Gryllidae , Aprendizaje , MasculinoRESUMEN
The genus Charinus comprises eleven described species in Brazil. Herein we describe two new species, Charinus caatingae sp n. and Charinus iuiu sp n., from caves of the state of Bahia, Brazil. Charinus caatingae is threatened, requiring special attention to its conservation. Furthermore, we present an updated identification key and a table of characters for the genus in the country.
Asunto(s)
Arácnidos , Animales , Arácnidos/anatomía & histología , Arácnidos/clasificación , Arácnidos/fisiología , Brasil , Cuevas , Ecosistema , Femenino , MasculinoRESUMEN
Natural selection shapes prey-predator relationships and their behavioral adaptations, which seek to maximize capture success in the predator and avoidance in the prey. We tested the ability of adults of the scorpion Bothriurus bonariensis (Bothriuridae) to prey on synchronous and sympatric adults harvestmen of Acanthopachylus aculeatus, Discocyrtus prospicuus, Parampheres bimaculatus and Pachyloides thorellii (Gonyleptidae). In 72.5% of the cases B. bonariensis tried to prey on the harvestmen. The most successful captures occurred in the trials against A. aculeatus and D. prospicuus. In all the successful attacks the scorpions stung the prey between the chelicerae and consumed them, starting by the anterior portion of their bodies. The harvestmen used different defensive strategies such as fleeing before or after contact with the predator, exudating of chemical substances or staying still at the scorpion's touch. When scorpions contacted the chemical substances secreted by the harvestmen, they immediately rubbed the affected appendix against the substrate. However, exudating of chemical substances did not prevent, in any case, predation on the harvestmen. This is the first study showing the ability of scorpions to prey on different species of harvestmen, as well as the capture and defensive behaviors used by the predator and the prey.
Asunto(s)
Conducta Predatoria/fisiología , Escorpiones/fisiología , Animales , Arácnidos/química , Arácnidos/fisiología , Conducta Animal , Secreciones Corporales/metabolismo , Escorpiones/químicaRESUMEN
Female investment in large eggs increases the demand for fatty acids, which are allocated for yolk production. Since the biosynthetic pathway leading to fatty acids uses the same precursors used in the formation of polyketides, allocation trade-offs are expected to emerge. Therefore, egg production should constrain the investment in chemical defenses based on polyketides, such as benzoquinones. We tested this hypothesis using the harvestman Acutiosoma longipes, which produces large eggs and releases benzoquinones as chemical defense. We predicted that the amount of secretion released by ovigerous females (OFs) would be smaller than that of non-ovigerous females (NOF). We also conducted a series of bioassays in the field and in the laboratory to test whether egg production renders OFs more vulnerable to predation. OFs produce less secretion than NOFs, which is congruent with the hypothesis that egg production constrains the investment in chemical defenses. Results of the bioassays show that the secretion released by OFs is less effective in deterring potential predators (ants and spiders) than the secretion released by NOFs. In conclusion, females allocate resources to chemical defenses in a way that preserves a primary biological function related to reproduction. However, the trade-off between egg and secretion production makes OFs vulnerable to predators. We suggest that egg production is a critical moment in the life of harvestman females, representing perhaps the highest cost of reproduction in the group.
Asunto(s)
Arácnidos/fisiología , Benzoquinonas/metabolismo , Oviposición/fisiología , Animales , Hormigas , Femenino , ReproducciónRESUMEN
The fifth species of the genus Guerrobunus, Guerrobunus barralesi sp. nov. is described from specimens collected in Hidalgo, Mexico. This species represents the first eastern record from the country and unlike other species of the genus, is completely epigean. Guerrobunus barralesi sp. nov. is compared with the most similar species, Guerrobunus minutus, which also has well developed and pigmented eyes. Finally, external morphology, including male genitalia, taxonomy of the genus, and familial assignment into the family Phalangodidae are discussed.
Asunto(s)
Distribución Animal , Arácnidos/clasificación , Arácnidos/ultraestructura , Animales , Arácnidos/fisiología , Femenino , Masculino , México , Especificidad de la EspecieRESUMEN
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.
Asunto(s)
Arácnidos/fisiología , Animales , Arácnidos/anatomía & histología , Arácnidos/química , Femenino , Masculino , Feromonas/análisis , Glándulas Odoríferas/anatomía & histología , Glándulas Odoríferas/química , Glándulas Odoríferas/fisiologíaRESUMEN
In this paper we describe two new species of Phareicranaus Roewer, 1913: Phareicranaus rohei sp. nov. from the state of Amazonas, Brazil and Phareicranaus tizana sp. nov., from the state of Zulia, Venezuela. The number of known species of this genus increases to 47. We discuss and suggest the possible relationships of these species with their relatives and assign them into the clades proposed by Pinto-da-Rocha & Bonaldo (2011). Additionally, we conducted field observations at the type locality of Phareicranaus manauara (Pinto-da-Rocha, 1994), provide the first descriptions of maternal care and gregarious behavior, and discuss the occurrence of this behavior in the genus.
Asunto(s)
Arácnidos/anatomía & histología , Arácnidos/clasificación , Conducta Animal/fisiología , Conducta Materna/fisiología , Animales , Arácnidos/fisiología , Brasil , Femenino , Masculino , Especificidad de la Especie , VenezuelaRESUMEN
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.
Asunto(s)
Arácnidos/fisiología , Feromonas/fisiología , Glándulas Odoríferas/fisiología , Comunicación Animal , Animales , Conducta Animal/fisiología , Ambiente , Extremidades/anatomía & histología , Extremidades/fisiología , Femenino , Masculino , Glándulas Odoríferas/anatomía & histologíaRESUMEN
Although organisms of the order Schizomida are not widely distributed in caves throughout the world, they can, eventually, be abundant in certain regions, becoming a major faunal element in some caves. The majority of works on this order includes species descriptions, with rare references to behavioral aspects. As such, the present study describes the behavioral repertoire, and the activity and feeding periods of Rowlandius potiguar (Schizomida: Hubbardiidae) in the laboratory. The specimens were maintained in a terrarium, in an aphotic room, with temperature and humidity levels similar to the cave of origin. We used the focal-animal and ad libitum methods to describe behavior with qualitative and quantitative evaluations of behavioral acts. We witnessed nineteen behavioral acts, which is considered representative for observations in captivity. Two activity periods were observed: between 10 a.m. and 4 p.m. and between 10 p.m. and 4 a.m., characterizing an ultradian rhythm. In adaptive terms, this condition may be important for population maintenance in oligotrophic environments such as caverns. Necrophagy and cannibalism were also registered and could have been selected in the subterranean environment due to oligotrophy. The observation of rare and unprecedented behavior in this group, as well as the presence of rhythmicity in activity patterns, contribute to a better understanding of the ecological aspects of the species of this still little known Order.
Asunto(s)
Arácnidos/fisiología , Conducta Animal/fisiología , Ritmo Circadiano/fisiología , Conducta Alimentaria/fisiología , Adaptación Fisiológica , Animales , Brasil , Canibalismo , Cuevas , Oscuridad , Femenino , MasculinoRESUMEN
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.
Asunto(s)
Arácnidos/fisiología , Aprendizaje por Asociación/fisiología , Conducta Animal/fisiología , Conducta Exploratoria/fisiología , Animales , Señales (Psicología)RESUMEN
Most empirical and theoretical papers on prey-predator interactions are for animals with long-range detection, animals that can detect and react to predators long before these touch the prey. Heavy-bodied and chemically defended harvestmen (Arachnida, Opiliones) are an exception to this general pattern and rely on contact to detect arthropod predators. We examined the interactions between the Brazilian wandering spider Ctenus ornatus with harvestmen (Mischonyx cuspidatus) or control prey (Gryllus sp. and M. cuspidatus immature, both with soft integuments). Considering a prey-predator system in which fleeing from or reacting to a predator at a distance is not possible, we predicted both a high survival value of near-range defense mechanisms and that mortality would be higher in the absence of such defense mechanisms. We also expected the predator to behave differently when interacting with harvestmen or with a control prey without such defense mechanisms. Our results from laboratory experiments partially matched our predictions: First of all, histological sections showed that the integument of adult harvestmen is thicker than that of immature harvestmen and that of crickets. Adult harvestmen were less preyed upon than the control prey; the heavy armature increases the survival rate but the secretions from the scent glands do not. The predator did behave differently when attacking harvestmen compared to crickets. Despite the large size difference between predator and harvestmen, the protection provided by the armature allowed some of the harvestmen to survive encounters without pre-contact detection, thus greatly reducing the reliance on long-range detection to survive encounters with predators. Harvestmen call for theoretical and empirical work on prey-predator interactions that take into account the possibility that prey may not detect the predator before contact is established.
Asunto(s)
Arácnidos/anatomía & histología , Arácnidos/fisiología , Cadena Alimentaria , Animales , Arácnidos/crecimiento & desarrollo , Brasil , Gryllidae/fisiología , Conducta Predatoria , Glándulas Odoríferas/metabolismo , Arañas/fisiologíaRESUMEN
The presence of Gryne orensis (Sørensen) (Opiliones: Cosmetidae) in a Yungas locality (northwestern Argentina) is reported for the first time, providing new evidence for the Mesopotamian-Yungas disjunct pattern. Combining a total of 19 new Mesopotamian records with previous, reliable citations from the literature, a dataset of 45 points was used to model the potential distribution of the species, using the presence-only methods BIOCLIM and MAXENT. Models supported the existence of a distributional gap across the Semiarid Chaco. The imprecise literature record from "El Impenetrable", province of Chaco, is assigned to three tentative locations to evaluate if models are affected by their inclusion; in all cases, the disjunction was maintained. It was thereby estimated that the actual record might have originated in a site closer to the Humid Chaco and/or associated to streams. This paper also provides a statement of the bioclimatic profile and identification of major environmental constraints that define the range of G. orensis.
Asunto(s)
Distribución Animal , Arácnidos/fisiología , Animales , Arácnidos/clasificación , Argentina , Clima , Modelos BiológicosRESUMEN
Two new species of ricinuleids of the genus Pseudocellus are described from Mexico: Pseudocellus cruzlopezi sp. nov. from Oaxaca, and Pseudocellus monjarazi sp. nov. from Chiapas. Both species are described from adult males and females. The first species is epigean and edaphomorphic, whereas the second is cavernicolous and troglomorphic. The number of known species of the genus Pseudocellus increases to 25, and Mexican species to 16, indicating that Mexico has the highest diversity of ricinuleids in the world. An updated identification key to adult males of the 16 described species found in Mexico and southern USA is provided.
Asunto(s)
Arácnidos/clasificación , Arácnidos/ultraestructura , Distribución Animal , Animales , Arácnidos/fisiología , Femenino , Masculino , México , Especificidad de la EspecieRESUMEN
Exclusive paternal care is the rarest form of parental investment in nature and theory predicts that the maintenance of this behavior depends on the balance between costs and benefits to males. Our goal was to assess costs of paternal care in the harvestman Iporangaia pustulosa, for which the benefits of this behavior in terms of egg survival have already been demonstrated. We evaluated energetic costs and mortality risks associated to paternal egg-guarding in the field. We quantified foraging activity of males and estimated how their body condition is influenced by the duration of the caring period. Additionally, we conducted a one-year capture-mark-recapture study and estimated apparent survival probabilities of caring and non-caring males to assess potential survival costs of paternal care. Our results indicate that caring males forage less frequently than non-caring individuals (males and females) and that their body condition deteriorates over the course of the caring period. Thus, males willing to guard eggs may provide to females a fitness-enhancing gift of cost-free care of their offspring. Caring males, however, did not show lower survival probabilities when compared to both non-caring males and females. Reduction in mortality risks as a result of remaining stationary, combined with the benefits of improving egg survival, may have played an important and previously unsuspected role favoring the evolution of paternal care. Moreover, males exhibiting paternal care could also provide an honest signal of their quality as offspring defenders, and thus female preference for caring males could be responsible for maintaining the trait.