Under the hood: Phylogenomics of hooded tick spiders (Arachnida, Ricinulei) uncovers discordance between morphology and molecules.

Ricinulei or hooded tick-spiders are a cryptic and ancient group of arachnids. The order consists of around 100 highly endemic extant species restricted to the Afrotropics and the Neotropics along with 22 fossil species. Their antiquity and low vagility make them an excellent group with which to interrogate biogeographic questions. To date, only four molecular analyses have been conducted on the group and they failed to resolve the relationships of the main lineages and even recovering the non-monophyly of the three genera. These studies were limited to a few Sanger loci or phylogenomic analyses with at most seven ingroup samples. To increase phylogenetic resolution in this little-understood and poorly studied group, we present the most comprehensive phylogenomic study of Ricinulei to date leveraging the Arachnida ultra-conserved element probe set. With a data set of 473 loci across 96 ingroup samples, analyses resolved a monophyletic Neotropical clade consisting of four main lineages. Two of them correspond to the current genera Cryptocellus and Pseudocellus while topology testing revealed one lineage to likely be a phylogenetic reconstruction artefact. The fourth lineage, restricted to Northwestern, Andean South America, is consistent with the Cryptocellus magnus group, likely corresponding to the historical genus Heteroricinoides. Since we did not sample the type species for this old genus, we do not formally re-erect Heteroricinoides but our data suggest the need for a thorough morphological re-examination of Neotropical Ricinulei.

Geometric regularity in webs of non-orb-weaving spiders.

Geometric regularity of spider webs has been intensively studied in orb-weaving spiders, although it is not exclusive of orb weavers. Here, we document the geometrically regular, repetitive elements in the webs of the non-orb-weaving groups Leptonetidae and Telemidae for the first time. Similar to orb weavers, we found areas with regularly spaced parallel lines in the webs of Calileptoneta helferi, Sulcia sp., and cf. Pinelema sp. Furthermore, we provide a detailed account of the regular webs of Ochyrocera (Ochyroceratidae). The sections of the web with regularly disposed parallel lines are built as U-shaped modules reminiscent of orb webs. It has been suggested that the regularly spaced parallel lines in the webs of Ochyroceratidae and Psilodercidae may be produced in a single sweep of their posterior lateral spinnerets, which have regularly spaced aciniform gland spigots, perhaps involving expansion of the spinnerets. To test this hypothesis, we compared the spacing between parallel lines with the spacing between spigots, searched for expansible membranes in the spinnerets, and examined the junctions of regularly spaced lines. The distance between parallel lines was 10-20 times the distance between spigots, and we found no expansible membranes, and the intersection of parallel lines are cemented, which opposes the single sweep hypothesis. Furthermore, we found cues of viscid silk in the parallel lines of the psilodercid Althepus and broadened piriform gland spigots that may be responsible of its production. Finally, we evaluated the presence or absence of geometrically regular web elements across the spider tree of life. We found reports of regular webs in 31 spider families, including 20 families that are not orb weavers and hypothesize that the two basic aspects of regularity (parallel lines spaced at regular intervals, and radial lines spaced at regular angles) probably appeared many times in the evolution of spiders.

Different environment, different reproductive strategies? Unexpected field observations in the harvestmen Discocyrtus prospicuus (Laniatores: Gonyleptidae).

The evolution of reproductive strategies depends on the relative balance between current benefits and future costs. Geographic variation in demographic and ecological factors has the potential to affect reproductive strategies by altering this optimal cost-benefit balance. Here, we studied a population of the harvestmen Discocyrtus prospicuus inhabiting an environment never studied before in this context: a tidal freshwater wetland. We made monthly observations of male-female interactions and their association with egg clutches during a two-year field survey. Our results do not match the expected pattern for this species, consisting of males deserting females immediately after copulation, and females laying isolated eggs and abandoning them after oviposition. Conversely, we show for the first-time pairs D. prospicuus, formed by a female and a male, resting together before and after oviposition. Females of this wetland population lay the eggs in small clutches and some of the clutches had eggs in more than one stage of development. Also, we found many females alone over or near the egg clutch in the typical resting position. These findings markedly widen the behavioral specter previously reported for this species and set the stage for future research to determine the causes of these variations.

On the problematic placement of the fossil arthropod Devonopilio hutchinsoni in Opiliones (Arachnida).

Harvestmen (Arachnida: Opiliones) were among the earliest terrestrial arthropods but their unmineralized exoskeletons are scarce and often fragmentary as fossils (Palencia et al. 2019). Consequently, the discovery and interpretations of fossil harvestmen from the early Palaeozoic can have disproportionate effects on the understanding of evolution in Opiliones. Recently, Devonopilio hutchinsoni Tihelka, Tian Cai, 2020, was described as a new fossil harvestman from the well-known Rhynie chert deposits of Scotland, an important source of information on freshwater and terrestrial ecosystems of the early Devonian (Tihelka et al. 2020). This species would be one of the earliest records of harvestmen. The description was based on a single slide showing fragments of arthropod cuticle, which Tihelka et al. interpreted as a harvestmen penis and unspecified associated body parts. As specialists on harvestman morphology and systematics, we were intrigued by these conclusions. However, based on the material presented by Tihelka et al. we find no compelling evidence supporting the proposal that the specimen is a harvestman.

Redescription of Promecostethus unifalculatus, the only known harvestman from Crozet Islands (Opiliones: Triaenonychidae).

Promecostethus unifalculatus Enderlein, 1909, is the only representative of the order Opiliones from the Crozet Islands. The species belongs to the family Triaenonychidae and is biogeographically interesting because it is a candidate for transoceanic dispersal, a very rare event in this ancient family. Despite this significance, P. unifalculatus is taxonomically still poorly known, and a redescription of this species using modern taxonomic standards is urgently needed. Here we redescribe the species, offer the first description and illustrations of the male genitalia and provide a full exomorphological survey of the species using scanning electron microscopy. Furthermore, we provide an emended diagnosis for the genus Promecostethus and discuss its relationship with some morphologically similar genera.

Rectifying the identities of the males of two Micrathena species (Araneae: Araneidae), with report of the first case of intersexuality in the genus.

Despite extensive taxonomic work on the Neotropical fauna of the spider genus Micrathena Sundevall, for 27 out of 117 (23%) species only the female morphology has been described, and some of the previously hypothesized male-female matches have been proven erroneous. This work provides new insight about sex matching in two species: Micrathena ruschii (Mello-Leitão, 1945) and Micrathena lata Chickering, 1960. For Micrathena ruschii, the male previously hypothesized to belong to this species was collected with females in Itatiaia; we here present morphologically different males, also collected with females, in Macaé, both in Rio de Janeiro, Brazil. Through a DNA barcoding approach, we present molecular evidence indicating conspecificity of M. ruschii females with the males collected in Macaé, proving the male from Itatiaia to be a misidentification. Therefore, a description of the correct male of Micrathena ruschii is herein provided. The male previously identified as M. ruschii probably represents an undescribed species but is not named here due to scarcity of material. We also describe for the first time the male of Micrathena lata based on one specimen collected in Misiones, Argentina. This male specimen belongs to the militaris species group, where M. lata is the only species from the Atlantic Forest previously only known by females. In addition, we detect an intersexual specimen of Micrathena ruschii, revealing the first case of intersexuality for the genus.

Three new species of Ochyrocera (Araneae, Ochyroceratidae) from Southeastern Brazil.

Three new species of the six-eyed  haplogyne and ecribellate spiders from the genus Ochyrocera Simon, 1891 are illustrated and described based on males and females from southeastern Brazil: Ochyrocera tinocoi new species (Sooretama, Espírito Santo state), Ochyrocera garayae new species (Linhares and Sooretama, Espírito Santo state) and Ochyrocera itatinga new species (Rio de Janeiro city, Rio de Janeiro state). The new species expand the distribution range of Ochyrocera in Brazil and increase to 50 the total number of species described, from which hitherto 33 species occur in South America, acknowledging the high diversity of the genus for the region.

Molecular phylogeny and revision of the false violin spiders (Araneae: Drymusidae) of Africa

The family Drymusidae includes 16 cryptic spiders that build irregular webs in dark places. The family is distributed in South Africa, the Neotropical and Andean regions. Here, we use a molecular approach to infer the relationships of Drymusidae using three mitochondrial (COI, 16S, 12S) and three nuclear (H3, 28S, 18S) markers. Our preferred analyses support Drymusidae and its American and African clades, which emerge as sister groups. Our analyses suggest a Gondwanan distribution of Drymusidae and a Westward radiation of Izithunzi gen. nov. within South Africa, but both hypotheses remain to be thoroughly tested. We describe Izithunzi gen. nov. for the African species. All previous African species are redescribed and new combinations are proposed: Izithunzi capense (Simon) comb. nov., Izithunzi productum (Purcell) comb. nov. and Izithunzi silvicola (Purcell) comb. nov. Two new species are described: Izithunzi lina sp. nov. (known from both sexes) and Izithunzi zondii sp. nov. (known only from females). The male of I. productum (Purcell) comb. nov. is also described for the first time. We consider Loxosceles valida Lawrence, 1964, a junior synonym of I. capense (Simon) comb. nov. (new synonymy). We also provide a dichotomous key for Izithunzi gen. nov. species.

Molecular phylogeny and revision of the false violin spiders (Araneae: Drymusidae) of Africa

The family Drymusidae includes 16 cryptic spiders that build irregular webs in dark places. The family is distributed in South Africa, the Neotropical and Andean regions. Here, we use a molecular approach to infer the relationships of Drymusidae using three mitochondrial (COI, 16S, 12S) and three nuclear (H3, 28S, 18S) markers. Our preferred analyses support Drymusidae and its American and African clades, which emerge as sister groups. Our analyses suggest a Gondwanan distribution of Drymusidae and a Westward radiation of Izithunzi gen. nov. within South Africa, but both hypotheses remain to be thoroughly tested. We describe Izithunzi gen. nov. for the African species. All previous African species are redescribed and new combinations are proposed: Izithunzi capense (Simon) comb. nov., Izithunzi productum (Purcell) comb. nov. and Izithunzi silvicola (Purcell) comb. nov. Two new species are described: Izithunzi lina sp. nov. (known from both sexes) and Izithunzi zondii sp. nov. (known only from females). The male of I. productum (Purcell) comb. nov. is also described for the first time. We consider Loxosceles valida Lawrence, 1964, a junior synonym of I. capense (Simon) comb. nov. (new synonymy). We also provide a dichotomous key for Izithunzi gen. nov. species.

Light from dark: A relictual troglobite reveals a broader ancestral distribution for kimulid harvestmen (Opiliones: Laniatores: Kimulidae) in South America.

A new troglobitic harvestman, Relictopiolus galadriel gen. nov et sp. nov., is described from Olhos d'Água cave, Itacarambi, Minas Gerais State, Brazil. Morphological characters, including male genitalia and exomorphology, suggest that this species belongs to the family Kimulidae, and it appears to share the greatest similarities with Tegipiolus pachypus. Bayesian inference analyses of a molecular dataset strongly support the inclusion of this species in Kimulidae and confirm the hypothesized sister-group relationship between R. galadriel and T. pachypus. A time calibrated phylogeny indicates that these sister-taxa diverged from a common ancestor approximately 40 Mya, during the Paleogene. The current range of Kimulidae illustrates a remarkable disjunct distribution, and leads us to hypothesize that the ancestral distribution of Kimulidae was once much more widespread across eastern Brazil. This may be attributed to the Eocene radiation associated with the warming (and humidifying) events in the Cenozoic when the best conditions for evergreen tropical vegetation in South America were established and followed by the extinction of kimulid epigean populations together with the retraction of rain forests during the Oligocene to Miocene cooling. The discovery of this relictual troglobite indicates that the Olhos d'Água cave was a stable refugium for this ancient lineage of kimulids and acted as a "museum" of biodiversity. Our findings, considered collectively with the diverse troglofauna of the Olhos d'Água cave, highlight it as one of the most important hotspots of troglobite diversity and endemism in the Neotropics. Given the ecological stresses on this habitat, the cavernicolous fauna are at risk of extinction and we emphasize the urgent need for appropriate conservation actions. Finally, we propose the transfer of Acanthominua, Euminua, Euminuoides and Pseudominua from Kimulidae to Zalmoxidae, resulting in two new synonymies and 13 new combinations.

Morphological tricks and blessed genitalia: rectifying the family placement of Fijicolana tuberculata (Opiliones: Laniatores: Zalmoxidae).

The type specimens of Fijicolana tuberculata Roewer, 1963 were re-examined and the male genital morphology is illustrated and described for the first time. Despite the presence of several morphological features that are typical of Samoidae, such as the presence of scopulae on legs III and IV, genital morphology unambiguously indicates that this species belongs to the Zalmoxidae rather than to the Samoidae. Fijicolana Roewer, 1963 is newly synonymized with Zalmoxis Sørensen, 1886. However, the newly implied combination is preoccupied by Z. tuberculatus Goodnight & Goodnight, 1948 thus the replacement name Zalmoxis roeweri nom. nov. is proposed to avoid secondary homonymy. The definition of Z. roeweri nom. nov. is amended, and the morphology of this species is compared with other representatives of Zalmoxidae and Samoidae. We conclude that the presence of scopulae alone is not a sufficiently diagnostic characteristic for Samoidae and, therefore, correctly placing taxa into families within Samooidea + Zalmoxoidea requires additional morphological evidence (e.g. genital morphology). In light of this result, we point out that the "scopulated" Australasian samoids Badessania metatarsalis Roewer, 1949, Sawaiellus berlandi Roewer, 1949 and Parasamoa gressitti Goodnight & Goodnight, 1957 require re-examination in order to detect potential errors in their family placement.

Spider diversity (Arachnida: Araneae) in Atlantic Forest areas at Pedra Branca State Park, Rio de Janeiro, Brazil.

BACKGROUND: There has never been any published work about the diversity of spiders in the city of Rio de Janeiro using analytical tools to measure diversity. The only available records for spider communities in nearby areas indicate 308 species in the National Park of Tijuca and 159 species in Marapendi Municipal Park. These numbers are based on a rapid survey and on an one-year survey respectively. NEW INFORMATION: This study provides a more thorough understanding of how the spider species are distributed at Pedra Branca State Park. We report a total of 14,626 spider specimens recorded from this park, representing 49 families and 373 species or morphospecies, including at least 73 undescribed species. Also, the distribution range of 45 species was expanded, and species accumulation curves estimate that there is a minimum of 388 (Bootstrap) and a maximum of 468 species (Jackknife2) for the sampled areas. These estimates indicates that the spider diversity may be higher than observed.

World Checklist of Opiliones species (Arachnida). Part 2: Laniatores - Samooidea, Zalmoxoidea and Grassatoresincertae sedis.

Including more than 6500 species, Opiliones is the third most diverse order of Arachnida, after the megadiverse Acari and Araneae. This database is part 2 of 12 of a project containing an intended worldwide checklist of species and subspecies of Opiliones, and it includes the members of the suborder Laniatores, infraorder Grassatores of the superfamilies Samooidea and Zalmoxoidea plus the genera currently not allocated to any family (i.e. Grassatores incertae sedis). In this Part 2, a total of 556 species and subspecies are listed.

A companion to Part 2 of the World Checklist of Opiliones species (Arachnida): Laniatores - Samooidea, Zalmoxoidea and Grassatores incertae sedis.

BACKGROUND: A series of databases is being prepared to list the valid species of Opiliones worldwide. This paper containing nomenclatural acts is meant to accompany Part 2, which includes the members of the infraorder Grassatores of the superfamilies Samooidea and Zalmoxoidea plus the Grassatores currently not allocated to any family (i.e. Grassatores incertae sedis). NEW INFORMATION: The following 32 taxonomic changes are proposed here: (1-3) The Afrotropical genera Hovanoceros Lawrence, 1959, Malgaceros Lawrence, 1959 and Tetebius Roewer, 1949 (all currently in Samoidae) are all newly transferred to Biantidae. (4-5) Microminua soerenseni Soares & Soares, 1954, from Brazil is newly transferred to Tibangara (Gonyleptoidea: Cryptogeobiidae), newly combined as Tibangara soerenseni new comb., new familial allocation for the species. (6-7) The new genus Llaguenia Gen. nov is erected for the South American species Zamora peruviana Roewer, 1956, newly combined as Llaguenia peruviana new comb., and newly placed in Gonyleptoidea: Cranaidae (Prostygninae). (8) Bebedoura Roewer, 1949, known from a single Brazilian species, is transferred from Tricommatinae to Grassatores incertae sedis. (9) Microconomma Roewer, 1915, known from a single Cameroonian species, is transferred from Samoidae to Grassatores incertae sedis. (10) Stygnomimus Roewer, 1927, with two Indomalayan species and hitherto included in the Stygnommatidae, is here formally considered Grassatores incertae sedis. (11) Bichito González-Sponga, 1998, known from a single Venezuelan species, originally described in Phalangodidae: Phalangodinae, and currently in Grassatores incertae sedis is transferred to Samoidae. (12) The Neotropical genus Microminua Sørensen, 1932, currently with two species, is newly transferred from Kimulidae to Samoidae. (13-14) Cornigera González-Sponga, 1987 (currently in Samoidae), is newly considered a junior subjective synonym of Microminua, and its single species is combined under Microminua as Microminua flava (González-Sponga, 1987) new comb. (15) Niquitaia González-Sponga, 1999 (originally in Phalangodidae: Phalangodinae, currently in Zalmoxidae), monotypic from Venezuela, is newly transferred to Samoidae. (16) Heteroscotolemon Roewer, 1912 originally described in Phalangodidae: Phalangodinae, and currently in Grassatores incertae sedis is transferred to Zalmoxidae. (17) While the Australasian genus Zalmoxista Roewer, 1949 is currently in Samoidae and some of its former species have been transferred to Zalmoxis Sørensen, 1886, Zalmoxista americana Roewer, 1952 from Peru, is here newly transferred to Zalmoxidae into Minuides Sørensen, 1932, forming the combination Minuides americanus (Roewer, 1952) new comb. (specific name inflected to match the masculine gender). (18) Neobabrius Roewer, 1949 (currently in Phalangodidae), monotypic from Indonesia, is newly transferred to Zalmoxidae. (19) While Crosbyella Roewer, 1927, belongs to Phalangodidae, Crosbyella roraima Goodnight & Goodnight, 1943 (originally Phalangodinae, but currently Zalmoxidae without generic assignment) is here transferred to Soledadiella González-Sponga, 1987, as Soledadiella roraima new comb. (Zalmoxoidea: Zalmoxidae). (20) Zalmoxissus Roewer, 1949 is newly synonymized with Zalmoxis Sørensen, 1886 (Zalmoxidae). (21) The original spelling Zalmoxis sorenseni Simon, 1892 is restored from the unjustified emendation soerenseni. (22) The Neotropical genus Phalangodella Roewer, 1912 (originally in Phalangodidae: Tricommatinae, but currently in Grassatores incertae sedis) is newly transferred to Zalmoxoidea incertae sedis and (23-26) four other genera are newly synonymized with it: Phalangodella Roewer, 1912 = Exlineia Mello-Leitão, 1942 = Langodinus Mello-Leitão, 1949 = Cochirapha Roewer, 1949 = Phalpuna Roewer, 1949, generating the following new combinations (27-32): Phalangodella fulvescens (Mello-Leitão, 1943) new comb., Phalangodella milagroi (Mello-Leitão, 1942) new comb., Phalangodella rhinoceros (Mello-Leitão, 1945) new comb., Phalangodella flavipes (Mello-Leitão, 1949) new comb., Phalangodella rugipes (Roewer, 1949) new comb. and Phalangodella urarmata (Roewer, 1949) new comb.

First Harvestman Record for the Juan Fernández Archipelago, Chile, with Morphological Notes on Acropsopilio chilensis (Opiliones: Caddidae: Acroposopilioninae).

Acropsopilio chilensis Silvestri, 1904 (Eupnoi: Caddidae: Acropsopilioninae), is recorded for Robinson Crusoe Island, Chile. This is the first harvestman species recorded for the Juan Fernández Archipelago and also the first extra-continental record for this species. During the comparison with continental co-specific specimens, some previously unknown, remarkable morphological characteristics were discovered, among them: the absence of ovipositor seminal receptacles and tracheal system, small and probably imperforate spiracles and the presence of a subdistal spiny structure, maybe a stylus, in the major branch of the penis. 

Sexually dimorphic tegumental gland openings in Laniatores (Arachnida, Opiliones), with new data on 23 species.

Sexually dimorphic glands often release sexual pheromones both in vertebrates and invertebrates. Species of Laniatores (Arachnida, Opiliones) seem to depend on chemical communication but few studies have addressed this topic. In this study, we review the literature for the Phalangida and present new data for 23 species of Laniatores. In 16 taxa, we found previously undescribed sexually dimorphic glandular openings on the femur, patella, metatarsus, and tarsus of legs I and metatarsus of legs III and IV. For the other species, we provide scanning electron micrographs of previously undescribed sexually dimorphic setae and pegs located on swollen regions of the legs. We also list additional species in which males have swollen regions on the legs, including the tibia, metatarsus, and tarsus of legs I, trochanter and tibia of legs II, femur, metatarsus, and tarsus of legs III, and metatarsus and tarsus of legs IV. The function and biological role of the secretions released by these glands are discussed.