Biogeographical variation in the harvestman Mitopus morio (Opiliones, Arachnida)

The taxonomic status of three forms of the harvestman Mitopus morio in Britain have been examined. These have been identified by previous workers as a small, upland M, morio cinerascens , a larger, lowland M. morio morio , and a northern M. morio borealis. In this paper, the delimitation of trinomials has been found to be inappropriate for M. morio. since all three forms have been shown to lie at different points on a continuum of phenotypic variation within the species M. morio. It is suggested that this phenotypic variation is mediated by the variation in temperature regimes between different localities.     

Population ecology ofGoniosoma spelaeum, a cavernicolous harvestman from south-eastern Brazil (Arachnida: Opiliones: Gonyleptidae)

Goniosoma spelaeum (Mello-Leitão) is a widespread trogloxene harvestman in caves of the Ribeira Valley in São Paulo State. It inhabits walls and ceilings near cave entrances. Populations inhabiting six selected caves of the region were analysed during this study. Mark-recapture techniques were used to estimate population sizes. Populations vary from tens to hundreds of individuals in each cave, and vary throughout the year. Barra Bonita cave had the largest population and was used to identify other ecological features of the species. These harvestmen show a high degree of philopartry, and recapture rate was high. They remain motionless inside the caves during the day, leaving them after dark to forage, and return just after dawn. They always feed outside the caves and do not carry food into the caves. Soft-bodied insects were the main food observed in the field. In the laboratory, they accepted plant and animal items and industrial foods. Their main predators are the spider Ctenus fasciatus , the heteropteran Zelurus travassosi , and the marsupial Philander opossum , and their main parasites are dipteran larvae (probably Phoridae).     

Chemical and behavioral defenses of the neotropical harvestman Camarana flavipalpi (Arachnida: Opiliones)

The defensive secretion of the harvestman Camarana flavipalpi (Gonyleptidae) was chemically characterized, revealing the presence of a single, highly volatile component (2-methyl-5-ethyl-phenol). Individuals do not frequently use chemical defenses and rely mainly on thanatosis as defense. Two types of emission of secretions were recorded: a globule at the gland opening without liquid displacement and liquid displacement along the lateral margins of the dorsal scute with accumulation of fluid at the lateroposterior area of the body. The anterior opening of the ozopore is covered by an integumentary dome that faces the laterodorsal area of the scute. The lateral channel is well defined near the opening of the ozopore and along the lateral margin of the dorsal scute as rows of small granules. The ozopore morphology of C. flavipalpi is similar to closely related species and simplified when compared with other species that promptly release chemical secretions.     

Costs and benefits of freezing behaviour in the harvestman Eumesosoma roeweri (Arachnida, Opiliones)

Animals present an enormous variety of behavioural defensive mechanisms, which increase their survival, but often at a cost. Several animal taxa reduce their chances of being detected and/or recognized as prey items by freezing (remaining completely motionless) in the presence of a predator. We studied costs and benefits of freezing in immature Eumesosoma roeweri (Opiliones, Sclerosomatidae). Preliminary observations showed that these individuals often freeze in the presence of the syntopic predatory spider Schizocosa ocreata (Araneae, Lycosidae). We verified that harvestmen paired with predators spent more time freezing than when alone or when paired with a conspecific. Then, we determined that predator chemical cues alone did not elicit freezing behaviour. Next, we examined predator behaviour towards moving/non-moving prey and found that spiders attacked moving prey significantly more, suggesting an advantage of freezing in the presence of a predator. Finally, as measure of the foraging costs of freezing, we found that individuals paired with a predator for 2 h gained significantly less weight than individuals paired with a conspecific or left alone. Taken together, our results suggest that freezing may protect E. roeweri harvestmen from predatory attacks by wolf spiders, but at the cost of reduced food and/or water intake.     

Skeletomuscular anatomy of the harvestman Leiobunum aldrichi (Weed, 1893) (Arachnida: Opiliones: Palpatores) and its evolutionary significance

Skeletal muscles of the North American harvestman Leiobunum aldrichi are exhaustively surveyed and compared with other chelicerates to clarify the evolutionary morphology and phylogenetic relationships of arachnids. Representatives of 104 muscle groups are described and illustrated, and their possible functions are proposed. Comparisons of the feeding apparatus of L. aldrichi with that of other opilions, especially Sim (Cyphophthalmi) and Acromares (Laniatores), and two scorpion genera ( Centruroides, Pandinus ) indicate that the pharyngeal apparatus in L. aldrichi is derived and that its ability to accommodate large food particles is a secondary rather than primitive condition. Comparisons reveal several possible synapomorphies between Opiliones and Scorpiones suggesting that these orders may be sister groups. Apparently unique synapomorphies include an extrinsic cheliceral muscle that arises from the carapace and inserts on the second cheliceral article (deutomerite); an epistome divided into distal and proximal parts by a transverse sulcus; pharyngeal dilator muscles supported by a peripharyngeal skeleton formed by one dorsomedial and two ventrolateral epistomal processes, the latter also with muscular attachments to the endosternite; a specialized preoral chamber (stomodieca) derived from extensions (coxapophyses) of the coxae of the pedipalp and first two leg pairs; internal processes associated with the coxapophyses that serve, in part, as an attachment for muscles operating the coxa-trochanter joints, and lateral endosternal suspensor muscles that insert on the arthrodial membrane between the leg coxae. These are the first observations providing explicit support for an Opiliones-Scorpiones clade.     

Grazing history influences biodiversity: a case study on ground-dwelling arachnids (Arachnida: Araneae, Opiliones) in the Natural Park of Alpi Marittime (NW Italy)

Alpine pastures are typical examples of “high nature value farmlands”, representing important habitats harbouring unique biological communities. Disturbance induced by overgrazing influences significantly ecosystem processes, in which invertebrates play a major role. To develop new models of sustainable management of pastures, more knowledge is needed of the animal communities, essential to the ecological functioning of pasture ecosystems. The apparent poor ecological state of several pastures in the Natural Regional Park of Alpi Marittime (NW-Italy) lead us to evaluate the influence of grazing history on biodiversity, using spider and harvestmen assemblages as key groups. Four different pastoral types characterized by four different grazing histories were identified using the Daget-Poissonet method. Spiders and harvestmen were collected by means of pitfall traps. Arachnid assemblages were characterized in terms of composition, abundance, species richness, richness of endemic species and taxonomic relatedness. Generalized linear mixed models (GLMM) were used to test differences among assemblages occurring in each pastoral type. Furthermore, we tested differences in terms of plant communities (species richness and percentage of zoogenic species). Specificity and fidelity of every spider and harvestmen species within pastoral types were explored by the IndVal (Indicator Value) procedure. Fifty-eight species of spiders and seven species of harvestmen were collected (2,304 individuals). Pastoral types related to intensive grazing were characterized by the dominance of diurnal wanderer spiders (namely Lycosidae) while, conversely, nocturnal wanderers (mainly Gnaphosidae) were more abundant in extensive pastoral types. Results show that both species richness and spider abundance were higher in abandoned areas of extensive grazing, while endemic assemblages were richer in extensive grazed areas, which also hosted the most diverse plant community. Furthermore, most of the indicator species of spiders of this type were endemic, characterized by more demanding ecological requirements.     

Screening pigment granule formation in Eumesosoma roeweri (Arachnida: Opiliones)

A unique pathway that utilizes endoplasmic reticulum (ER) networks is proposed for screening pigment granule formation in the retina of adult Eumesosoma roeweri. Smooth endoplasmic reticulum (SER) functions to transport pigment particles to the formative site. Each site is composed of concentric, interconnected rings of SER that are filled with dense-cored, spherical pigment particles. Formation of the screening pigment granule begins by the release of particles from the innermost rings of carrier SER. Continued release followed by fusion and condensation of the pigment particles results in the formation of a mature pigment granule.     

Chemical sex recognition in the harvestman <Emphasis Type="Italic">Discocyrtus prospicuus</Emphasis> (Arachnida: Opiliones)

Several arachnid species use chemicals to detect sexual partners. In harvestmen, there are evidences that chemicals may play a role in intraspecific communication. Using the behavior of Discocyrtus prospicuus (Holmberg 1876), whose males expose the penis to females before they engage in mating posture, we tested if males detect females by contact chemoreception (chemicals left on the substrate) and if males detect females by olfaction. First, we exposed males to three experimental groups, where males had to choose between two substrates: female chemicals/blank control; male chemicals/blank control; female/male chemicals. Then, we gave males access to volatiles of males, females, and control simultaneously. We predicted that males would expose the penis when approaching volatiles and chemicals deposited on the substrate by females. We also tested if males spent more time close to the source of female volatiles and on the substrate with female chemicals and if males tapped the substrate with female chemicals for more time than the others. Finally, we put males and females together to observe if males would expose the penis upon touching the female’s cuticle. Most of our predictions were not supported, though males did tap for more time when exposed to female cues instead of male cues and exposed the penis in 70% of the observations when interacting with the female but only after touching her. Our data does not support olfaction as a way to detect females and corroborate the idea that contact chemicals, either on the substrate or on female’s cuticle, play an important role in the detection and recognition of the opposite sex. This is the first evidence in harvestmen that males may react differently to female/male chemicals.     

Fissiphalliidae, a new family of South American laniatorean harvestmen (Arachnida: Opiliones)

Fissiphalliidae, a new family of the Opiliones suborder Laniatores, is described in the superfamily Gonyleptoidea, based on a new genus (Fissiphallius n. gen.) und 3 new species (F. sturmi n. sp., F. spinulatus n. sp., F. sympatricus n. sp.) from Colombia. Most emphasized are the male genitalic characters, unique in Opiliones: A honzontally split truncus which results in a long movable (glans) and an immovable finger (distal part of the truncus). Both hide the extremely long stylus with the seminal opening at its end. In an expanded state, the movable finger is bent dorsally by an erectile vesicle. It is shown that male genitalic characters in Opiliones display clear functional and constructional traits on the family level. Those characters, if used appropriately, will demonstrate that several families in gonyleptoid Laniatores are polyphyletic and should be divided into several taxa of the family level.     

A divergent Cardinium found in daddy long-legs (Arachnida: Opiliones)

Recent studies indicate that a newly described bacterial endosymbiont, Cardinium, is widespread in arthropods and induces different reproductive manipulations in hosts. In this study, we used a portion of the 16S rRNA gene of the Cardinium to screen 16 Opilionid species from the suborder Palptores. We found the incidence of Cardinium in these Opiliones was significantly higher than in other pooled arthropods (31.2% versus 7.2%, P = 0.007). Phylogenetic analyses using maximum parsimony (MP) and Bayesian analysis revealed two distinct clades in Opiliones. One is a divergent monophyletic clade with strong support that has so far not been found in other arthropods, and a second one contains Cardinium both from Opiliones and other arthropods. There is not complete concordance of the Cardinium strains with host phylogeny, suggesting some horizontal movement of the bacteria among Opiliones. Although the divergence in the sequenced 16S rRNA region between the Cardinium infecting Opiliones and Cardinium from other arthropods is greater than among Cardinium found in other arthropods, all are monophyletic with respect to the outgroup bacteria (endosymbionts of Acanthamoeba). Based on high pairwise genetic distances, deep branch, and a distinct phylogenetic grouping, we conclude that some Opiliones harbor a newly discovered Cardinium clade.     

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.     

Hidden Mediterranean diversity: Assessing species taxa by molecular phylogeny within the opilionid family Trogulidae (Arachnida,Opiliones)

This is the first comprehensive study to evaluate the relationships between the western palearctic harvestman families Dicranolasmatidae, Trogulidae and Nemastomatidae with focus on the phylogeny and systematics of Trogulidae, using combined sequence data of the nuclear 28S rRNA and the mitochondrial cytochrome b gene. Bayesian analysis and Maximum parsimony do not reliably resolve Dicranolasma as distinct family but place it on a similar phylogenetic level as several lineages of Trogulidae. Nemastomatidae and Trogulidae turned out to be monophyletic, as did genera Anelasmocephalus and Trogulus within the Trogulidae. The genera Calathocratus, Platybessobius and Trogulocratus each appeared para or polyphyletic, respectively and are synonymized with Calathocratus. The monotypic genus Kofiniotis is well supported. We show molecular data to be in general concordance with taxa characterized by morphology. Molecular data are especially useful to calibrate morphological characters for systematic purposes within homogeneous taxa. In the majority of closely related valid species we show the lowest level of genetic distance to be not lower than 5%. By this threshold in terms of traditionally accepted species the estimated number of species turns out to be 1.5–2.4 times higher than previously believed. With respect to European fauna cryptic diversity in Trogulidae is obviously extraordinarily high and hitherto largely underestimated.     

Variation of plant diversity in a temperate unmanaged forest in northern Spain: behind the environmental and spatial explanation

The persistence of seedlings in the forest understorey is of major importance for the maintenance and regeneration of canopy trees in several forested ecosystems. In the present study, we examine the small-scale spatial pattern of a mixed beech and oak seedling–sapling bank in two areas of an unmanaged temperate deciduous forest with different environmental conditions. We used environmental, biotic and spatial variables to establish the main factors that explain the spatial pattern of these seedling–sapling banks at different scales. The stand structure in both areas was similar, but while in plot A beech dominated the canopy, plot B was dominated by oaks. In both areas, established beech individuals showed a clear reverse J-shaped distribution, whereas established oaks showed a unimodal distribution with only a few young individuals. Seedlings of beech and oak were distributed in aggregates, whereas beech saplings had a random distribution. At broader scales, the abundance of seedlings and saplings is affected by the environment as well as by inter-species competition, while at finer scales the spatial pattern is mainly influenced by stochastic processes, probably related to seed predation and establishment. The structure of the seedling–sapling bank indicates an advantage of beech over oak as far as regeneration is concerned. Beech seedlings and saplings tolerate the stress induced by the canopy and the understorey and persist for many years, while oak seedlings decline in a few years. Therefore, if current conditions persist, after canopy opening beech seedlings and saplings can grow rapidly into the canopy and the stands will move towards beech dominance.     

A new highly specialized cave harvestman from Brazil and the first blind species of the genus: Iandumoema smeagol sp. n. (Arachnida,Opiliones, Gonyleptidae)

A new species of troglobitic harvestman, Iandumoemasmeagolsp. n., is described from Toca do Geraldo, Monjolos municipality, Minas Gerais state, Brazil. Iandumoemasmeagolsp. n. is distinguished from the other two species of the genus by four exclusive characteristics – dorsal scutum areas with conspicuous tubercles, enlarged retrolateral spiniform tubercle on the distal third of femur IV, eyes absent and the penial ventral process slender and of approximately the same length of the stylus. The species is the most highly modified in the genus and its distribution is restricted only to caves in that particular area of Minas Gerais state. The type locality is not inside a legally protected area, and there are anthropogenic impacts in its surroundings. Therefore, Iandumoemasmeagolsp. n. is vulnerable and it must be considered in future conservation projects.     

Maternal care, defensive behavior, and sociality in neotropical Goniosoma harvestmen (Arachnida, Opiliones)

Summary: Goniosoma includes large and conspicuous species of harvestmen that occur exclusively in the Brazilian Atlantic forest. This paper reports on the parental activities, defensive behavior, and gregariousness of five species of Goniosoma, and also summarizes the published biological data for the genus. The behavioral patterns within the genus are discussed and a hypothesis for the emergence of gregariousness in the group is presented. Several Goniosoma live inside caves, mainly as trogloxenes. Although species of the genus comprise only 5% of the harvestmen fauna in Brazil, they account for 20.6% of all harvestmen species recorded in Brazilian caves. In addition to several morphological and physiological features that may favor the occupation of caves, species of Goniosoma also present subsocial behavior, which may confer a special advantage in this particular environment. Female protection is crucial for egg survival since predators may consume entire batches in a single night. Most species of Goniosoma form dense diurnal aggregations ranging from three to 200 individuals (mainly subadults and adults of both sexes). In a hypothetical scenario for the evolution of sociality in the Goniosoma, physiological constraints acting on individual harvestmen would lead to a behavioral response for the selection of sites with appropriate microclimatic conditions. The lack of cannibalism among adults and subadults may favor tolerance towards conspecifics, and may represent a pre-adaptation to gregariousness. The derived functions of gregarious behavior may include strengthening of the defensive signal through the collective release of a repugnant secretion, the dilution effect, and promptness in fleeing a predator attack as a consequence of the additional alarm role of scent gland secretions. These defensive functions may overcome the costs of group living and may be responsible for the maintenance of gregariousness in Goniosoma.