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Lomanius annae sp. nov. is described from southern Vietnam. The species is characterized by the greatly developed dorso-basal process on cheliceral hand of males and by the partial effacement of all mesotergal grooves. The genus Lomanius contains four generic synonyms and currently comprises eight valid species distributed in China, Java, peninsular Malaysia, the Philippines, and Taiwan. The new species displays a general morphology similar to the former genus Paralomanius, with a combination of sexually dimorphic interocular mound (which is very large and strongly leaned back in males) and pedipalpus (which is extremely elongate in males). This morphological suite of features is herein called facies reclinobunoides. The replacement name Metibalonius triceratops nom. nov. is proposed for Trispinibunus abnormis Roewer, 1915, which is a junior secondary homonym of Ibalonius abnormis Strand, 1911. Finally, numerous morphological structures found in Podoctidae are recognized and named: (1) the cheliceral comb, present on cheliceral fingers, (2) the chained tubercular ridges, present on dorsal scutum and (3) several others related to the ocular region. The distribution of these two structures among podoctid species is not fully known, but both are absent in the former Ibaloniinae. We suggest that both structures may be useful to define supra-generic groups in the clade composed of the former Podoctinae and Erecananinae.

When there is a temporal trade-off between mating effort and parental care, theoretical models predict that intense sexual selection on males leads to reduced paternal care. Thus, high-quality males should invest more in mating effort because they have higher chances of acquiring mates, whereas low-quality males should bias their investment towards parental care. Once paternal care has evolved, offspring value should also influence males' decisions to invest in offspring attendance. Here, we performed a manipulation under field conditions to investigate the factors that influence male allocation in either mating effort or parental care. We predicted that facultative paternal care in the harem-holding harvestman Serracutisoma proximum would be negatively influenced by male attractiveness and positively influenced by offspring value. We found that attractive males were less likely to engage in egg attendance and that the higher the perceived paternity, the higher the caring frequency. Finally, egg mortality was not related to caring frequency by males, but predation pressure was much lower than that recorded in previous studies with the same population. Thus, the benefits of facultative male care may be conditional to temporal variation in the intensity of egg predation. In conclusion, males adjust their investment in either territory defence or egg attendance according to their recent mating history and perceived paternity. Our findings suggest that exclusive paternal care can evolve from facultative paternal care only if the trade-off between mating effort and parental care is circumvented., (© 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.)

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.

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.

Strong sexual selection may lead small males or males in poor condition to adopt alternative reproductive tactics (ARTs) as a way to avoid the risk of being completely excluded from the mating pool. ARTs, sometimes accompanying morphological dimorphism among males, are taxonomically widespread, especially common in arthropods. Here we review the current knowledge on ARTs and male dimorphism in a diverse but relatively overlooked group of arachnids, the order Opiliones, popularly known as harvestmen or daddy long-legs. We begin with a summary of harvestman mating systems, followed by a review of the two lines of evidence for the presence of ARTs in the group: (1) morphological data from natural populations and museum collections; and (2) behavioral information from field studies. Despite receiving less attention than spiders, scorpions and insects, our review shows that harvestmen are an exciting group of organisms that are potentially great models for sexual selection studies focused on ARTs. We also suggest that investigating the proximate mechanisms underlying male dimorphism in the order would be especially important. New research on ARTs and male dimorphism will have implications for our understanding of the evolution of mating systems, sperm competition, and polyandry. This article is part of a Special Issue entitled: Neotropical Behaviour., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Secondary sexual traits increase male fitness, but may be maladaptive in females, generating intralocus sexual conflict that is ameliorated through sexual dimorphism. Sexual selection on males may also lead some males to avoid expenditure on secondary sexual traits and achieve copulations using alternative reproductive tactics (ARTs). Secondary sexual traits can increase or decrease fitness in males, depending on which ART they employ, generating intralocus tactical conflict that can be ameliorated through male dimorphism. Due to the evolutionary forces acting against intralocus sexual and tactical conflicts, male dimorphism could coevolve with sexual dimorphism, a hypothesis that we tested by investigating these dimorphisms across 48 harvestman species. Using three independently derived phylogenies, we consistently found that the evolution of sexual dimorphism was correlated with that of male dimorphism, and suggest that the major force behind this relationship is the similarity between selection against intralocus sexual conflict and selection against intralocus tactical conflict. We also found that transitions in male dimorphism were more likely in the presence of sexual dimorphism, indicating that if a sexually selected trait arises on an autosome and is expressed in both sexes, its suppression in females probably evolves earlier than its suppression in small males that adopt ARTs., (© 2014 The Author(s). Evolution © 2014 The Society for the Study of Evolution.)

Arthropods produce a great variety of natural compounds, many of which have unexplored biosynthesis. Among the armored harvestmen (Arachnida: Opiliones) of the suborder Laniatores, the defensive gland exudates contain vinyl ketones and other constituents of supposed polyketide origin. We have studied the biosynthesis of 1-hepten-3-one in the Neotropical harvestman Iporangaia pustulosa by feeding individuals with ¹³C-labeled precursors, demonstrating its mixed acetate/propionate origin. ¹³C NMR spectroscopy showed an unusual labeling pattern suggesting different propionate sources for starting and extender units. Our analysis also indicates the presence of methylmalonyl-CoA mutase, converting acetate into propionyl-CoA via succinyl-CoA, together with other C₃ unit routes. This is the first biosynthetic study of alkyl vinyl ketones in arthropods. Our results shed light on the origin and diversification of chemical compounds in a major arthropod group.

Four species of gonyleptid harvestmen, Acanthogonyleptes pulcher, Gonyleptes saprophilus (Gonyleptinae), Sodreana barbiellini, and Sodreana leprevosti (Sodreaninae), were examined by GC-MS and ¹³H NMR. All of these species release vinyl ketones, and three of them produce the corresponding pyranyl ketones, which are presumed hetero-Diels-Alder (HDA) dimers. The vinyl ketones 5-methyl-1-hexen-3-one, rac-4-methyl-1-hexen-3-one, and (S)-4-methyl-1-hexen-3-one were synthesized. Natural 4-methyl-1-hexen-3-one is present as a single stereoisomer and has the R-configuration. Vinyl ketone dimers (HDA dimers) were also observed in the scent gland exudate and characterized by HRMS, ¹³C NMR, and ¹H NMR chemical shifts of the pyranyl moiety.

Benzoquinones are usually present in arthropod defence exudates. Here, we describe the chemical profiles of 12 harvestman species belonging to the neotropical family Gonyleptidae. Nine of the studied species produced benzoquinones, while three produced alkyl phenols. Two benzoquinones and one phenol exhibited biological activity against bacteria and fungi. We also studied the biosynthesis of 2-ethyl-1,4-benzoquinone by feeding Magnispina neptunus individuals with ¹³C-labelled precursors; the benzoquinones were biosynthesised through a polyketide pathway using acetate and propionate building blocks.

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.

The defensive secretions of five neotropical species of harvestmen (Opiliones: Gonyleptidae) from the Brazilian Atlantic Forest were analyzed and chemically characterized by GC-MS and NMR methods. Three of the species, Cobania picea, Roweria virescens, and Serracutisoma proximum, secrete a mixture of 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone. The secretions produced by the other two species, Iporangaia pustulosa and Neosadocus maximus, contain 1-hepten-3-one, 5-methyl-1-hexen-3-one, and 1-(6-butyl-3,4-dihydro-2H-pyran-2-yl)pentanone (1) as major components, as well as 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone as minor constituents. The dihydropyran 1-(6-butyl-3,4-dihydro-2H-pyran-2-yl)pentanone (1) is a new natural product, composed of two 1-hepten-3-one subunits formally linked in a hetero-Diels-Alder reaction. The natural product was proven to be racemic, and its biogenetic origin is discussed.

The evolution of sexually dimorphic traits has been the focus of much theoretical work, but empirical approaches to this topic have not been equally prolific. Males of the neotropical family Gonyleptidae usually present a strong fourth pair of legs armed with spines, but their functional significance is unknown. We investigated the putative functions of the leg armature in the harvestman Neosadocus maximus. Being a non-visual species, the spines on male legs can only be perceived by females through physical contact. Thus, we could expect females to touch the armature on the legs of their mates if they were to evaluate it. However, we found no support for this hypothesis. We did show that (1) leg armature is used as a weapon in contests between males and (2) spines and associated sensilla are sexually dimorphic structures involved in "nipping behavior", during which a winner emerged in most fights. Finally, we demonstrate that five body structures directly involved in male-male fights show positive allometry in males, presenting slopes higher than 1, whereas the same structures show either no or negative allometry in the case of females. In conclusion, leg armature in male harvestmen is clearly used as a device in intrasexual contests.

1. Few studies have experimentally quantified the costs and benefits of female egg-guarding behaviour in arthropods under field conditions. Moreover, there is also a lack of studies assessing separately the survival and fecundity costs associated with this behavioural trait. 2. Here we employ field experimental manipulations and capture-mark-recapture methods to identify and quantify the costs and benefits of egg-guarding behaviour for females of the harvestman Acutisoma proximum Mello-Leitão, a maternal species from south-eastern Brazil. 3. In a female removal experiment that lasted 14 days, eggs left unattended under natural conditions survived 75.6% less than guarded eggs, revealing the importance of female presence preventing egg predation. 4. By monitoring females' reproductive success for 2 years, we show that females experimentally prevented from guarding their eggs produced new clutches more frequently and had mean lifetime fecundity 18% higher than that of control guarding females. 5. Regarding survival, our capture-mark-recapture study does not show any difference between the survival rates of females prevented from caring and that of control guarding females. 6. We found that experimentally females prevented from guarding their eggs have a greater probability to produce another clutch (0.41) than females that cared for the offspring (0.34), regardless of their probability of surviving long enough to do that. 7. Our approach isolates the ecological costs of egg-guarding that would affect survival, such as increased risk of predation, and suggests that maternal egg-guarding also constrains fecundity through physiological costs of egg production. 8. Weighting costs and benefits of egg-guarding we demonstrate that the female's decision to desert would imply an average reduction of 73.3% in their lifetime fitness. Despite the verified fecundity costs of egg-guarding, this behaviour increases female fitness due to the crucial importance of female presence aimed to prevent egg predation.

We describe herein the sperm morphology of the harvestman Iporangaia pustulosa. Adult males were dissected, the reproductive tract was schematized and the seminal vesicle was processed by light, transmission and scanning electron microscopy. The male reproductive tract is composed of a tubular testis, two deferent ducts, a seminal vesicle, a propulsive organ and a penis, similar to that observed in other Opiliones. The spermatozoa from the seminal vesicle are oval, aflagellate and immotile, presenting a nucleus surrounding an invagination of the cytoplasm, as well as a complex acrosome and projections on the cell surface. In the testis, spermatozoa are devoid of projections. In the seminal vesicle, they gradually acquire the projections with tufts adhering to it. Consequently, spermatozoa in various distinct stages of projection development can be found in the seminal vesicle. We believe that these projections (1) could help transport sperm along the male and perhaps female reproductive tracts; (2) are used to anchor the spermatozoa inside the female spermatheca in order to avoid mechanical displacement by the genitalia of other males and (3) may play a role in oocyte recognition. We propose that the evolution of aflagellarity in Opiliones is related to the unique morphology of the female reproductive tract. Since eggs are fertilized on the tip of the ovipositor just prior to being laid, there is no advantage favoring sperm mobility. Additionally, female sperm receptacles are small and males that produced small spermatozoa would have a higher chance of fertilizing more eggs.

Two alkylated 1,4-benzoquinones were identified from the defensive secretion produced by the neotropical harvestman Goniosoma longipes (Gonyleptidae). They were characterized as 2,3-dimethyl-1,4-benzoquinone and 2-ethyl-3-methyl-1,4-benzoquinone. We tested the effectiveness of these benzoquinone secretions against several predator types, including invertebrates and vertebrates. Different predators were exposed to the harvestmen's gland secretion or to distilled water in laboratory bioassays. Our results indicate that secretions containing the 1,4-benzoquinones released by G. longipes can be an effective defense against predation, and that the effectiveness of the secretion is dependent on the predator type. The scent gland secretion repelled seven ant species, two species of large wandering spiders, and one frog species, but was not an effective defense against an opossum. Our study also demonstrates that the scent gland secretion of G. longipes can work as a chemical shield preventing the approach of three large predatory ants for at least 10 min. The chemical shield may protect the harvestman against successive attacks of the same ant worker and also allow the harvestman to flee before massive ant recruitment. Our data support the suggestion that chemical defenses may increase survival with some but not all potential predators. This variation in defense effectiveness may result from many interacting factors, including the attack strategy, size, learning ability, and physiology of the predators, as well as the chemical nature of the defensive compounds, type of emission, and amount of effluent released by the prey.

Most harvestmen are nocturnal, nonacoustical, and nonvisual arthropods. They have a pair of exocrine glands on the cephalothorax that produce defensive volatile secretions. We investigated in the field the possible alarm effect of these secretions in the gregarious harvestman Goniosoma aff. proximum. A cotton swab soaked with the species' own exudate (treatment), or with water (control), was held 1-2 cm from the center of harvestmen aggregations. The results showed that the gland secretion elicits an alarm response in Goniosoma: whereas 73.3% of the aggregations dispersed after being stimulated with the gland exudate, only 3.3% responded to the water control. Respondent groups are larger than nonrespondent groups, and the time of reaction to the secretion was inversely related to group size. This is the first demonstration of a chemically-mediated alarm effect in harvestmen. The alarm response in gregarious harvestmen has possibly evolved as a by-product of a primarily defensive reaction in the context of predator avoidance. The discovery of this novel function of scent-gland secretion is meaningful in view of the widespread occurrence of gregarious habit among species of the order Opiliones.

Egg attendance is the most common and phylogenetically widespread form of post-ovipositional care among ectotherms. The main benefit of egg attendance is to enhance offspring survival by preventing or attenuating attacks from natural enemies. In arachnids, there are few experimental studies on the benefits of egg attendance, and they pertain to species living in few types of habitats, mainly forests. To understand how the benefits of egg attendance vary in large geographical scales, we need to include species from poorly explored habitats, such as caves. Here, we describe a case of maternal egg attendance in an exclusive cave-dwelling harvestman, Phalangodus briareos. Using a parent removal experiment, we also assessed the benefits of egg attendance. We found that egg attendance improves egg survival because unattended clutches were almost entirely consumed by conspecifics and crickets. When females were maintained on their clutches, egg survival was always high, regardless of female body size. There was a positive effect of clutch size on egg predation, which was higher during nighttime. We suggest that larger clutches emit more chemical cues, attracting more predators in the cave habitat. Finally, we argue that the benefits of egg protection should be higher inside caves when compared to external habitats because food is scarce inside caves and the fauna consists mainly of predators and detritivores. [ABSTRACT FROM AUTHOR]