Epigean communities of harvestmen (Opiliones) in Pannonian Basin floodplain forests: an interaction with environmental parameters

During the years 2015–2016, we studied the fauna of epigeon in eight similar habitats in Slovakia and Serbia. The study material of Opiliones was obtained by a pitfall trap method. We focused on the comparison of the incidence of harvestmen in floodplain forests and ecotones alongside the Danube River in Slovakia and along the Tisa and Begej River in Serbia. We examined their dependence on anthropogenic impact (frequency of visits), cover of vegetation layers (herbs, shrubs and trees), plant diversity of vegetation layers, area of forest stands, distance to the forest edge, circumference of forest stands, age of forest stands, thickness of litter layer and physico-chemical properties of soil and litter (pH, conductivity, P, N, C, H). Total epigeic activity of harvestman showed significant positive relationship with proportion of N in litter. Community equitability was positively related with species richness of plant communities in shrub layer and negatively related with H content of soil. We did not find any significant correlations between diversity of harvestman communities and measured environmental characteristics.     

Two new harvestmen species (Arachnida: Opiliones) from the Caucasus

Two new harvestmen species of the family Phalangiidae, Rilaena caucasica sp. n. and Rilaena silhavyi sp. n. are diagnosed, illustrated, and described from the Caucasus region. Comparative illustration of the related Rilaena anatolica (Roewer, 1956), R. atrolutea (Roewer, 1915) and R. kelbajarica Snegovaya &; Pkhakadze, 2014 Snegovaya, N. Y., &; Pkhakadze, V. D. (2014): New species of the genus Rilaena (Opiliones, Phalangiidae) from the mount Gyamish, Azerbaijan. Vestnik zoologii, 48, 313–318. doi: 10.2478/vzoo-2014-0037[Crossref] , [Google Scholar] are given.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:7B29FD94-45A2-4E32-A41E-3276E016410B     

Four new Laniatorean harvestmen (Arachnida: Opiliones) from mid-Cretaceous Burmese amber

Four new laniatorean harvestmen specimens (Arachnida: Opiliones: Laniatores) are described from the mid-Cretaceous (upper Albian–lower Cenomanian) Burmese amber of Northern Myanmar. One is placed as Insidiatores indet., but is not formally named as it is probably immature. Burmalomanius circularis n. gen. n. sp. and Petroburma tarsomeria n. gen. n. sp. represent the first fossil records of the extant families Podoctidae and Petrobunidae respectively. Finally, Mesodibunus tourinhoae n. gen. n. sp. belongs to Epedanidae, a family previously recorded from Burmese amber. These new records bring the total number of Burmese amber laniatorean species to ten, and the total number of fossil laniatoreans to fifteen. The new finds offer additional calibration points for the Laniatores tree of life and are consistent with the hypothesis that the modern Laniatores fauna of Southeast Asia may have had Gondwanan, as opposed to a Laurasian, origins.     

Influence of agricultural management form on the species structure of harvestman (Opiliones) communities

The paper is aimed at evaluation of the influence of two different agricultural management forms on harvestman (Opiliones) communities structure in relation to the optimization of land use on the model territory of Agricultural Cooperative (AC) Očová (Central Slovakia). The research was carried out using pitfall trapping through growing seasons from 2005 to 2007. Harvestmen were captured at four pairs of sites (8 sites in total). For each pair of sites the cultivation of the same crop with application of two different forms of agricultural management (conventional form and sustainable form with basic sustainable agro-environmental scheme) was characteristic. In total, 667 individuals of 8 species of the Phalangiidae family were captured during the research. The research results confirm the influence of management form on the structure of harvestman communities only partially. The obtained data indicate that the management form plays a significant role, especially in such agrocoenoses, in which the same crop is cultivated for several years (e.g., sites with alfalfa or permanent lawn), i.e., on the sites without ploughing or use of other similar agrotechnical measures. In these cases, the sites with the sustainable agro-environmental scheme showed higher diversity and equability of harvestman communities than the sites with the conventional form of agrotechnical management. Harvestman communities structure on sites with crop rotation and repeated ploughing was more influenced by additional factors than by the agricultural management form.     

Metabolic rates in harvestmen (Arachnida, Opiliones): the influence of running activity

Abstract. Metabolic rates of adult Lophopilio palpinalis (Herbst, 1799) (Arachnida, Opiliones, Phalangioidea) and Paranemastoma quadripunctatum (Perty, 1833) (Arachnida, Opiliones, Troguloidea) are measured during rest and activity. Carbon dioxide release during rest is continuous in both species. Mean values at 20 °C are 4.2 µL min⁻¹ g⁻¹ for the males of P. quadripunctatum, 4.1 µL min⁻¹ g⁻¹ for the males of L. palpinalis and 4.7 µL min⁻¹ g⁻¹ for the females of L. palpinalis, thus being significantly higher in the egg-producing females. In L. palpinalis, respiratory quotient at rest is 0.84. Spontaneous walking activity with speeds of 15–30 cm min⁻¹ raises the metabolic rate by up to three-fold in both species. Lophopilio palpinalis is made to undertake constant running on a treadmill with speeds of 60, 72 and 96 cm min⁻¹. Enforced activity causes the animals to raise their metabolic rates by up to five-fold above resting rates. Animals reach a steady state of CO₂ release on the treadmill and show a fast t_1/2 on-response, indicating aerobic exercise. The minimum cost of locomotion is determined to be 2.5 × 10⁻³ J cm⁻¹ g⁻¹, thus fitting the predicted values for terrestrial locomotion.     

Interspecific variation in the microanatomy of cosmetid harvestmen (Arachnida,Opiliones, Laniatores)

Scanning electron microscopy (SEM) is a useful tool for identifying interspecific variation in often overlooked structures that may represent useful sources for informative phylogenetic characters. In this study, we used SEM to compare the morphology of 12 cosmetid species from Central America, the Caribbean, and North America including multiple species for the genera Cynorta, Erginulus, and Paecilaema. To determine if microanatomical structures were unique to the cosmetid taxa under examination, we investigated the microanatomical structures of six additional species of gonyleptoidean harvestmen representing the families Agoristenidae, Cranaidae, Gonyleptidae, Manaosbiidae, and Stygnidae. Our results indicate that the shape of the ocularium (narrow, intermediate, or broad) did not vary within cosmetid genera, whereas the morphology of the rough pit glands on the eye mound varied considerably between species. Each cosmetid species had 10–20 rough pit glands on the ocularium whereas only the eye mounds of Avima intermedia (Agoristenidae) and Glysterus sp. (Gonyleptidae) had similar structures. With regards to the surface texture of the dorsal scutum, cosmetid harvestmen exhibited a rivulose‐microgranulate morphology (6 species), a microtuberculate‐rivulose‐microrgranulate morphology (4 species), or a microgranulate morphology (2 species). In contrast, each of the gonyleptoidean species exhibited a microgranulate pattern, with the exception of Stygnoplus clavotibialis, which had a rivulose‐microgranulate surface texture. For cosmetid harvestmen, we observed considerable interspecific variation in the shape and number of teeth on the fixed and moveable fingers of the male chelicerae. Similarly, we also observed interspecific variation in the distribution and shape of tubercles on the ventral and dorsal surfaces of the femur of the pedipalp. Overall, our results indicate that there are several microanatomical structures associated with the ocularium, dorsal scutum, male chelicera, and pedipalp that could represent informative phylogenetic characters in future taxonomic studies of cosmetid harvestmen. J. Morphol. 275:1386–1405, 2014. © 2014 Wiley Periodicals, Inc.     

Population genomics and geographical parthenogenesis in Japanese harvestmen (Opiliones,Sclerosomatidae, Leiobunum)

Naturally occurring population variation in reproductive mode presents an opportunity for researchers to test hypotheses regarding the evolution of sex. Asexual reproduction frequently assumes a geographical pattern, in which parthenogenesis‐dominated populations are more broadly dispersed than their sexual conspecifics. We evaluate the geographical distribution of genomic signatures associated with parthenogenesis using nuclear and mitochondrial DNA sequence data from two Japanese harvestman sister taxa, Leiobunum manubriatum and Leiobunum globosum. Asexual reproduction is putatively facultative in these species, and female‐biased localities are common in habitat margins. Past karyotypic and current cytometric work indicates L. globosum is entirely tetraploid, while L. manubriatum may be either diploid or tetraploid. We estimated species phylogeny, genetic differentiation, diversity, and mitonuclear discordance in females collected across the species range in order to identify range expansion toward marginal habitat, potential for hybrid origin, and persistence of asexual lineages. Our results point to northward expansion of a tetraploid ancestor of L. manubriatum and L. globosum, coupled with support for greater male gene flow in southern L. manubriatum localities. Specimens from localities in the Tohoku and Hokkaido regions were indistinct, particularly those of L. globosum, potentially due to little mitochondrial differentiation or haplotypic variation. Although L. manubriatum overlaps with L. globosum across its entire range, L. globosum was reconstructed as monophyletic with strong support using mtDNA, and marginal support with nuclear loci. Ultimately, we find evidence for continued sexual reproduction in both species and describe opportunities to clarify the rate and mechanism of parthenogenesis.     

Pitfall trap design affects the capture efficiency of harvestmen (Opiliones) and millipedes (Diplopoda)

Pitfall trapping is one of the standard methods used for the capture of ground‐active arthropod groups. Despite being frequently used, the standardization of this method is problematic due to the large range of combinations of the individual parameters of pitfall traps with varying efficacy under different environmental conditions. We evaluated the effects of the trap diameter, the fixing fluid, and their combination on the capture efficacy for harvestmen (Opiliones) and millipedes (Diplopoda). We used pitfall traps with three different diameters: 3 cm, 5 cm, and 12 cm, filled with three types of fixing fluids (saturated fluid of NaCl, 10:1 mixture of 70% ethanol and glycerol and 4% formaldehyde). Altogether, 90 traps representing nine combinations of trap diameters and fixing fluid were placed on a mown meadow in spring and autumn intervals for a total of 45 days. We sampled 1,488 individuals representing 11 harvestmen species and 881 individuals representing 11 millipede species. Large (d = 12 cm) and medium (5 cm) traps captured significantly more millipede species and individuals than the small‐sized traps (3 cm). The same effect was observed for harvestmen species richness, whereas the medium traps (d = 5 cm) captured the highest mean activity of harvestmen. By analyzing the differences in the body sizes of the studied arthropods in relation to the trap diameter and fluid, we found that larger traps, as well as traps filled with NaCl solution, captured larger harvestmen more frequently than the other trap types. Our results revealed that the combination of larger traps (d = 5 and 12 cm) and formaldehyde was most effective in the capture of both studied groups. However, the disadvantage of formaldehyde is its toxicity.     

Evolution of hyperflexible joints in sticky prey capture appendages of harvestmen (Arachnida,Opiliones)

The rigid leg segments of arthropods are flexibly connected by joints, which usually consist of two ball-and-bowl hinges, permitting a uniaxial pivoting up to 140°. Here, we report the occurrence of hyperflexible joints (range of movements?=?160–200°) in the pedipalps (second pair of appendages) of some harvestmen (Sabaconidae and Nemastomatidae), representing some of the most flexible leg joints among arthropods. Hyperflexion is achieved by a reduction of hinges and a strong constriction of the joint region. We demonstrate that hyperflexion occurs during prey capture and is used to clamp appendages of the prey, in addition to attachment by glue secreted by specialized setae. By means of high-speed video recordings, we found that in the Sabaconidae the tibiotarsal joint of the pedipalp can flex extremely rapidly (<5 ms), limiting prey escape. This is the fastest reported predatory strike in arachnids and caused both by leverage and a click mechanism. By comparative analysis of different related taxa, we retraced joint evolution and found that hyperflexion has independently evolved in Sabaconidae and Nemastomatidae, with totally different joint kinematics. We hypothesize that (rapid) hyperflexion evolved to enhance the efficiency of the pedipalp as a means of prey capture, because in springtails detachable scales limit the action of the sticky secretion of pedipalpal setae.     

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.     

Phylogeny of harvestmen family Gonyleptidae inferred from a multilocus approach (Arachnida: Opiliones)

Gonyleptidae is the second most diverse harvestmen family and the most studied in terms of morphology, behaviour, and ecology. Despite this, few phylogenetic studies have focused on gonyleptids, and those are based on a very limited number of taxa. We addressed this gap by constructing a phylogenetic hypothesis of the family using 101 taxa from all 16 gonyleptid subfamilies and four mitochondrial and nuclear loci (COI, 28S rRNA, 12S rRNA, and 16S rRNA). These were analysed under parsimony and likelihood optimality criteria (and using direct optimization for the former). Relationships among Gonyleptoidea and within each subfamily of Gonyleptidae were largely congruent between parsimony and maximum‐likelihood approaches. Taxonomic actions from our phylogeny include the following: Tricommatidae, new status, is restored as a family; Metasarcidae, new status, is recognized as a family and considered sister to the Cosmetidae; and Cranainae and Manaosbiinae are suggested as members of Gonyleptidae, restoring Roewer's concept of the family. Within Gonyleptidae, the “K92” group—composed of Sodreaninae, Caelopyginae, Hernandariinae, Progonyleptoidellinae, and Gonyleptinae—forms a clade, although the latter two subfamilies are not monophyletic. The genus Parampheres is here transferred to Caelopyginae, and “Multumbo” dimorphicus to Gonyleptinae. Gonyleptidae is characterized by the presence of a ventral process on the penis glans and a bifid apophysis on the male coxa IV. The long‐legged Mitobatinae can be considered monophyletic only if some short‐legged pachylines are included, or if we assume that elongate legs arose twice independently (in the true mitobatine genera and in Longiperna). Pachylinae, the most diverse gonyleptid subfamily, represents several distinct lineages. We further conclude that the traditional use of a small set of morphological characters in the systematics of Gonyleptidae is unable to explain the complex evolution of the family.     

Leg injuries and wound repair among cosmetid harvestmen (Arachnida,Opiliones, Laniatores)

Previous studies of leg injuries in harvestmen have focused on the fitness consequences for individuals that use autospasy (voluntary detachment of the leg) as a secondary defense mechanism. Leg damage among non‐autotomizing species of laniatorean harvestmen has not been investigated. Under laboratory conditions, we damaged femur IV of Cynorta marginalis and observed with scanning electron microscopy (SEM) the changes in these wounds over ten days. We also used SEM to examine leg damage from individuals of three species of cosmetid harvestmen that were collected in the field. On the basis of changes in the external surface of the hemolymph coagulum, we classified these wounds as fresh (coagulum forming), recent (coagulum with smooth surface), older (coagulum is scale‐like with visible cell fragments), and fully healed (scale replaced by new cuticle growth on the terminal stump). Our observations indicate that wound healing in harvestmen occurs in a manner comparable to that of other chelicerates. Leg injuries exhibited interspecific variation with respect to the overall frequency of leg wounds and the specific legs that were most commonly damaged. In addition, we measured walking and climbing speeds of adult C . marginalis and found that individuals with fresh injuries (lab‐induced) to femur IV walked at speeds significantly slower than uninjured adults or individuals collected from the field that had fully healed wounds to a single leg. J. Morphol. 278:73–88, 2017. ©© 2016 Wiley Periodicals,Inc.     

Autophagic activity in the midgut gland of the overwintering harvestmen Gyas annulatus (Phalangiidae,Opiliones)

Juvenile harvestmen Gyas annulatus overwinter in dormancy in hypogean habitats for 4–5 months. The ultrastructure of the autophagic structures in their midgut epithelium cells was studied by light microscopy, transmission electron microscopy (TEM) and immunofluorescence microscopy (IFM) during this non-feeding period. Before overwintering (November), autophagic structures were scarce. In the middle (January) and at the end of overwintering (March), phagophores, autophagosomes and autolysosomes were present in the cytoplasm of both the secretory and the digestive midgut epithelium cells, gradually increasing their abundance during overwintering. In addition, vacuolization of the cytoplasm intensified. Both processes are induced by starvation. Autophagic structures and cytoplasm vacuolization enable the reuse of the cell's own components required for the maintenance of vital processes during dormancy. While TEM is a much more convenient method for recognition of the autophagic structure types and their ultrastructure, IFM enables exact counting of these structures.     

The evolution of pedipalps and glandular hairs as predatory devices in harvestmen (Arachnida,Opiliones)

Pedipalps are the most versatile appendages of arachnids. They can be equipped with spines (Amblypygi), chelae (Scorpiones), or adhesive pads (Solifugae), all of which are modifications to grasp and handle fast‐moving prey. Harvestmen (Opiliones) show a high diversity of pedipalpal morphologies. Some are obviously related to prey capture, like the enlargement and heavy spination of Laniatores pedipalps. Many Dyspnoi, by contrast, exhibit thin, thread‐like pedipalps that are covered with complex glandular setae (clavate setae). These extrude viscoelastic glue that is used to immobilize prey items. Comparable setae (plumose setae) have previously been found in representatives of both Eupnoi and Dyspnoi, yet comprehensive data on their distribution are lacking. This study examined the distribution and ultrastructure of glandular setae in harvestmen and related them to pedipalpal morphology. Pedipalpal and setal characters were analysed in a phylogenetic framework. We found that glandular setae are synapomorphic for and widespread in the Palpatores clade (Eupnoi plus Dyspnoi). Their occurrence correlates with pedipalp morphology and feeding habit. Remnants of arthropod cuticular structures or secretions, frequently found attached to glandular setae, and behavioural observations, underlined the importance of the setae for capturing and securing prey. We hypothesize that glandular setae evolved as an adaptation to capture small and agile prey, which are hard to catch with a capture basket. Details of ultrastructure indicate that the setae are derived sensilla chaetica, with both a secretory and sensory function. Derived ultrastructural characters of the glandular setae, such as slit‐like channel openings and a globular arrangement of the microtrichia, may increase their effectiveness. The functional role of further pedipalpal modifications, such as apophyses, stalked and hyperbendable joints, and curved segments, as well as sexual dimorphism and ontogenetic polymorphism, are discussed. Some implications of the results obtained for the taxonomic treatment of Phalangiidae are also discussed. These results shed new light on the biology and evolutionary history of this fascinating group of arthropods.     

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.     

Changes in the midgut diverticula in the harvestmen Amilenus aurantiacus (Phalangiidae,Opiliones) during winter diapause

The harvestmen Amilenus aurantiacus overwinter in diapause in hypogean habitats. The midgut diverticula have been studied microscopically (light microscopy, TEM) and biochemically (energy-storing compounds: lipids and glycogen) to analyze changes during this programmed starvation period. Throughout the investigated period, the epithelium of the midgut diverticula is composed of secretory cells, digestive cells and adipocytes. Additionally, after the middle of overwintering, the excretory cells appear, and two assemblages of secretory cells are present: the SC1 secretory cells are characterized by electron-dense cytoplasm with numerous protein granules, and the SC2 cells by an electron-lucent cytoplasm with fewer protein granules. The autophagic activity is observed from the middle of overwintering, indicating its vital role in providing nutrients during this non-feeding period. Lipids and glycogen are present in the midgut diverticula cells, except in the excretory cells. Measurements of the lipid droplet diameters and the lipid quantities yielded quite comparable information on their consumption. Lipids are gradually spent in both sexes, more rapidly in females, owing to ripening of the ovaries. Glycogen rates decrease towards the middle, and increase just before the end of overwintering, indicating that individuals are preparing for the epigean active ecophase.     

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.