Arthropoda

Pincushion millipedes or bristly millipedes (Polyxenida) are common and widespread around the world, yet we still lack a proper understanding of the life of these elusive animals. This limit is even more expressed when looking at their extinct counterparts. Luckily, such fossils are usually preserved in amber, which has the potential to preserve unusual details. We investigated 44 new and 6 previously published fossils of Polyxenida, starting from the Cretaceous period (~100 mya) through the Eocene (~35 mya) and Oligocene/Miocene (~23 mya) to the present. As suggested by previous research, fossil bristly millipedes in the Cretaceous period shared the same lifestyle as their extant counterparts, including aggregation behaviour of both immatures and adults. In addition, we report newly observed behaviours for the fossils such as defecation, cohabitation between representatives of Polyxenidae and Synxenidae, and the possible role of frass and exuviae as defence. Altogether these findings improve our knowledge on the intricate life of bristly millipedes, revealing not only glimpses into their past but also clues and cues on their modern-day counterparts. Bristly millipedes are not just “simple” bark-dwellers; their communities and behaviours visibly testify to a rather complex lifestyle, which remained largely unchanged for 100 million years. Full article

Vector-borne diseases account for over 17% of reported infectious diseases worldwide and are associated with approximately 700,000 deaths annually. The main vectors include mosquitoes, moths, sand flies, black flies, and ticks. Ticks deserve special attention because they transmit a wide range of pathogens, including viruses of major medical importance, such as tick-borne encephalitis virus (Orthoflavivirus encephalitidis) and Crimean-Congo hemorrhagic fever virus (Orthonairovirus haemorrhagiae), as well as animal-borne pathogens, such as African swine fever virus (Asfivirus haemorrhagiae). Recent advances in next-generation sequencing have expanded the ability to detect and characterize tick-borne viruses, revealing increasing viral diversity. However, for many of these viruses, aspects such as pathogenic potential, main vectors, and natural hosts remain unclear. To address this gap, we conducted an integrative literature review using the PubMed, SciELO, BVSalud, and Patuá-IEC databases. We analyzed 336 articles addressing various species of tick-borne viruses. The Flaviviridae, Phenuiviridae, and Nairoviridae families were the most frequently identified among the viral agents detected. Furthermore, we identified that as-yet-unclassified viruses have been frequently detected in different tick species, which sparks significant interest in investigating their potential interactions and public health implications. Investigating viral agents in tick populations is crucial for understanding viral diversity and assessing potential public health risks, especially in the current context of climate change. Full article

The American lobster (Homarus americanus) is a non-native species to Europe, but is imported as live seafood and has been identified in European waters. These introductions threaten native populations of the European lobster (Homarus gammarus) via disease introduction, competition, direct predation, and genetic introgression. Differentiating the two species and their hybrids based solely on morphological criteria can be difficult and unreliable. This study presents a real-time PCR assay targeting the cytochrome c oxidase gene 1 (cox1) for rapid detection and identification of H. americanus and H. gammarus. We have also designed a conventional duplex PCR from a previously described nuclear marker (Hgam98), which was sequenced and revealed the presence of a specific H. americanus insert downstream from a variable number tandem repeat region. The combination of these assays resulted in the accurate identification of the two lobster species and F1 hybrid specimens. Full article

Scorpions are characterized by their venomous adaptations, including specialized stingers, and their ecological diversity. Some families, such as Buthidae, have medically significant species and their venoms possess a diverse array of chemicals. In Mexico, Centruroides suffusus and Centruroides vittatus coexist, with C. suffusus considered medically important due to its highly toxic venom. This study describes the metabolomic and microbiomic profiles of C. suffusus and C. vittatus. The metabolomic profiling (12 amino acids and 28 acylcarnitines) reveals significant differences between the two species, hinting at metabolic and ecological variations. Ornithine (ORN) and arginine (ARG) were the most abundant in C. vittatus, while tyrosine (TYR) was the most abundant amino acid molecule in C. suffusus. The microbiome analysis (by Next-Generation Sequencing of the 16S ribosomal gene) indicates similarities in gut bacteria composition between the two species (Phyla: Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, Proteobacteria and Tenericutes). Full article

A new troglobitic species of Dalodesmidae, Pleonaraius spelaeus n. sp., is described from Rolo Vergara Cave, Neuquén Province, Argentina. This species represents the fourth known troglobitic member of the family, the first troglobitic species of Dalodesmidae recorded in South America, and the first known troglobitic millipede from Argentina. Pleonaraius spelaeus n. sp. is distinguished from its congeners by the absence of cuticular pigmentation and a unique combination of gonopodal characters. Ecological notes, a key, and a distribution map of Pleonaraius species are also provided. Full article

Scorpions possess unique, ornate mid-ventral sensory organs called pectines. The pectines are used to process chemo- and mechanosensory information acquired from the ground as the animal walks, and they are implicated in a variety of behaviors including navigation and detection of mates and prey. Many previous researchers have investigated pecten function by cutting the organs from the animals (full ablation) and comparing their behaviors with those of intact scorpions. This drastic approach is likely to not only cause enormous stress to the ablated animals but also change their behavior. Here, we have developed a method for gently and reversibly impairing the pectines by partially covering them to prevent them from lowering to the ground. Specifically, we fabricated small rectangles of a commercially available lightly adhesive foil tape that we placed across the pectines and secured to the body wall with a thin strip of a more strongly adhesive lab tape. Using a repeated measures design, we monitored the animals’ locomotory activity overnight in small behavioral arenas under three conditions: unmodified (intact) control, pectines restrained, and sham control. We found that scorpions with their pectines restrained had a significant increase in both the distance and duration of movement when compared to unmodified and sham control animals. Our method allows for temporary, reversible compromise of pecten function and should be useful in fully understanding the role of pectines in behavior. Full article

Spiders and other arthropods can sometimes consume others of their kind, and this is most often associated with mating activity, whereby females cannibalize males during or after mating, or during mating attempts. Nonsexual cannibalism is less common but may be associated with food availability or territorial aggression. In the Southeastern United States, a non-native orb-weaving spider, Trichonephila clavata (the “jorō spider”), is expanding its range. Prior lab experiments indicated this species to be “shy” compared to other native spiders, based on behavioral reactions to stimuli. Here, we report descriptive observations and photo-documentation of nonsexual cannibalism by this species, including from anecdotal observations, plus findings from controlled pairings of spiders, both in the lab and in natural webs in the field. In the cases where cannibalism was witnessed, it involved one female biting and killing another, typically after a short fight. When two females of a similar size were placed together in a container (n = 25 trials), fights ensued 40% of the time. When females of different sizes were paired (n = 27 trials), fights happened 18% of the time, and the larger females were not always the aggressor. Across all the lab trials (n = 52), six bouts (9%) led to the direct killing of one female. In field trials where two females were placed on an empty web (n = 14 trials), we observed one fight (7%) where the aggressor ended up killing and wrapping the other spider in silk. Given that some of these instances happened away from any web, these observations imply that the aggression is not necessarily an act of territoriality. The intraspecific aggression could arise when females are provoked or stressed, which deserves more study. Full article

Seven new species of the genus Cherax from the western region of Western New Guinea, Indonesia, are described and illustrated. All new species—Cherax veritas n. sp. from the southeastern part of Misool Island of Raja Ampat Regency, Southwest Papua; Cherax arguni n. sp. and Cherax kaimana n. sp. from the northern part of Kaimana Regency, West Papua; Cherax nigli n. sp. from the southeastern part of Kaimana Regency, West Papua; Cherax bomberai n. sp. from the northeastern part of the Fakfak Regency, West Papua; Cherax farhadii n. sp. and Cherax doberai n. sp. from the Teluk Bintuni Regency, West Papua—belong to the northern group of Cherax. The new species are compared with their closest relatives, from which they can all be easily distinguished by morphological characters, such as the shape of the chelae, rostrum, body, and by their coloration. A molecular phylogeny based on a mitochondrial gene fragment, 16S, supports the morphology-based description of the seven new species, which can also be clearly distinguished by sequence differences. Full article

The nine-banded armadillo, Dasypus novemcinctus, is one of only two species of armadillo found in Mexico. Among the ectoparasites reported on this mammal are ticks of the genus Amblyomma. Between December 2022 and April 2024, 52 ticks of different developmental stages (females, males, and nymphs) were collected from five D. novemcinctus. All ticks were morphologically identified as A. auricularium. This study reports for the first time the presence of this tick species in the Municipality of Santiago Llano Grande, Oaxaca. Full article

A new genus of Ectinosomatidae is recorded in association with an Ascidia from a permanent submerged coral community in Barra Beach, Salvador City, Bahia State (Brazil). The new taxon belongs to a smaller group of genera in the family Ectinosomatidae based on the geniculate maxilla and the prehensile first swimming leg. This group is composed of Bradiellopsis, Chaulionyx, Halophytophilus, and Sigmatidium. The new genus differs from the others due to distinct aspects of the mandible gnathobasis, which features sharp processes on the pars incisiva and pars molaris followed by a short spinulated area and a serrulated seta; the presence of a two-segmented endopod of the first swimming leg, with the first endopodal segment longer than all exopodites combined; and a short, quadratic second endopodal segment with two strong curved claws. In addition, it differs from other genera due to the distinct armature of the first to fourth swimming legs and the presence of fused exopod and baseoendopod on the fifth swimming leg. Cruscollatus gen.nov. lives specifically within the digestive tract of Eudistoma vannamei Millar, 1977, an Ascidia species endemic to northeastern Brazil. This study reports the first documented association between a harpacticoid copepod of the family Ectinosomatidae (order Harpacticoida) and ascidian hosts (Ascidia). Full article

Although it has its advantages for the development of urban areas, road construction is among the greatest threats to biodiversity, due to fragmentation, habitat loss, and changes in landscape structure. This study investigated the effects of different traffic intensities on the understory spider assemblage in the Brazilian Atlantic Forest. Understory spiders were collected between 09:00 h–16:00 h using beating tray samples on roadside vegetation on roads with and without traffic. In total, 1616 spiders belonging to 24 families and 317 morphospecies were collected. The families Araneidae and Theridiidae were more abundant and showed a higher number of morphospecies on both roads. Understory spiders were classified into seven guilds. However, no significant differences were found in functional and taxonomic richness and abundance between the roads. These results indicate that understory spider assemblages showed no significant response to traffic intensity, suggesting potential resilience to this disturbance in the studied context. Additionally, the proximity between locations may result in the founder effect, with spiders migrating from the preserved site to the impacted site. Overall, this study indicates that traffic presence does not significantly impact the diversity and composition of understory spider assemblages in the studied region. Full article

The genus Troglorhopalurus (Scorpiones: Buthidae) is endemic to northeastern Brazil and comprises cave-dwelling species with limited distributions. Based on newly collected specimens, this study provides a description of a new cave-dwelling Troglorhopalurus species and the first detailed description of the male hemispermatophore of the genus. Troglorhopalurus iuiu n. sp. is diagnosed based on morphometric characters, distinct carapace granulation, and differences in the pedipalps and metasomal carinae and peg sensillae shape. The hemispermatophore of Troglorhopalurus is like other Centruroidinae species, with internal, external, and basal lobes. Additionally, we discuss the distribution and conservation status of Troglorhopalurus species. Troglorhopalurus lacrau distribution range is extended based on additional epigean and hypogean records. This species may be reassessed from data deficient to least concern. Based on the limited localities and declining habitat quality, we propose that T. iuiu n. sp. be considered endangered. This research underscores the importance of further sampling to explore species-specific variations and promote conservation efforts for these ecologically specialized scorpions. Full article

Here, we confirm the presence of two species of caridean shrimps for the first time in Brazil: Latreutes parvulus and Ambidexter cochensis. During active samplings conducted in December 2023, April 2024 and September 2024 on the rocky shore of Prainha da USP (Ubatuba municipality, São Paulo state, southeastern Brazil), we captured five ovigerous females of L. parvulus and fifteen individuals of A. cochensis (five males, three non-ovigerous females and seven ovigerous females). All the females of L. parvulus exhibited eyestalks with small, truncated processes separating the cornea from the stalk, a unique feature of this species. On the other hand, all specimens of A. cochensis exhibited a unique combination of characteristics: a rostrum with an apex bifid, a stylocerite bearing a lateral spinule and a transverse row of setae between the anterior pair of spines, and three longitudinal rows of setae on the telson. Also, males of A. cochensis had the tip of their appendix masculina armed with four simple apical setae and another two setae positioned below them. All analyzed shrimps had fully developed gametes in their reproductive systems, indicating breeding populations in this area. This is the first record of L. parvulus on the Atlantic coast of South America and a new meridional distribution limit for A. cochensis. Full article

The palaemonid shrimp genus Pseudopalaemon Sollaud, 1911, is endemic to South America, comprising seven freshwater and low salinity species. This study aimed to compile an overview of the genus, including an illustrated identification key for species and updated distributional data. Diagnostic morphological characters of the species were analyzed using specimens from several museums and other scientific collections. Current knowledge about the genus reveals significant knowledge gaps, particularly in species ecology. The data and insights from this study support future research and highlight a need for further studies on this group. Full article

Trilobites, as typical euarthropods, possess compound eyes. In 1901, Lindström was the first to describe them in detail; on the one hand, we reconsider his descriptions of the different modes of trilobite eyes; on the other hand, we expand this by compiling the observations that have been possible in recent years. There are two, perhaps three kinds of trilobite compound eyes. The first are the primordial holochroal eyes, which are actually apposition compound eyes, similar to those of many modern diurnal crustaceans and insects. The abathochroal eyes, often referred to as the second form, are probably a subtype of the holochroal eyes. Consequently, the second is the schizochroal eye of phacopid trilobites, which are hyper-compound eyes composed of numerous small compound eyes below each of the big lenses, which appear from outside as one big lateral eye each. Thirdly, one may call the maculae light-sensitive organs, but this is still uncertain. Comparing what are probably the oldest trilobite eyes described so far with other forms, it is possible to conclude that the sensory apparatus is much older than the fossil record of trilobite eyes and probably developed in Precambrian times. The refractive apparatus, however, was developed later and separately within the systematic groups. This explains why, for example, the mandibulates have a lens and a crystalline cone. Still, the chelicerate xiphosurans, such as horseshoe crabs or eurypterids, possess a lens cylinder with an index gradient but no crystalline cone. Furthermore, this can explain why the calcite character of trilobites is unique in the arthropod kingdom. An important discovery is the probably epidermal, lens-building cells encompassing a prospective lens of Schmidtiellus reetae Bergström 1973 from the early Lower Cambrian of Estonia. We reconsider the morphology of hypostome maculae and interpret them as a potential phylogenetic relict and a potential predecessor of all arthropod ommatidial compound eyes. It will be of great relevance for future research to understand the evolution of compound eyes and vision because we witness the emergence of the first lenses in the trilobite, if not the arthropod kingdom. Full article

Mastigoproctus Pocock, 1894, is the most speciose genus in the thelyphonid subfamily Mastigoproctinae Speijer, 1933, with eighteen described species distributed from the Southern United States to Colombia and Venezuela. Ten of these species occur in Mexico. In the present contribution, Mastigoproctus spinifemoratus, sp. nov., is described based on an adult male and two juveniles from Eastern Nuevo León and Southwestern Tamaulipas, Mexico. It differs from five other species of Mastigoproctus, in which spiniform tubercles are present on the retrolateral surface of the pedipalp femur, in the ventrally directed epistome of the carapace, and the absence of an accessory spine on the prodorsal margin of the pedipalp trochanter. The new species raises the number of Mastigoproctus species to nineteen and the number in Mexico to eleven. Full article

Rock shrimps (Sicyonia dorsalis and Sicyonia typica) are commonly caught as bycatch during shrimp trawling along the Brazilian coast, but are not commercially exploited due to their small size and hard carapace. This study evaluated their spatio-temporal distribution, size classes, and sex ratio near the Almada River Estuary, Ilhéus, Bahia, Northeastern Brazil, and tested correlations between environmental factors and species abundance. Samples were collected monthly using double-rig trawl nets in the estuary and along transects at depths of 5–35 m. Bottom water and sediment samples were obtained for analyses of environmental factors. In total, 5336 individuals of S. dorsalis and 303 individuals of S. typica were collected. No individuals were recorded in the estuary. Both species were significantly more abundant between 25 and 35 m, where fine sediment with high levels of organic matter occurred. Considering the temporal variation, their abundance decreased during the rainy season, coinciding with increased river flow. Organic matter content, salinity, and water transparency were the primary environmental factors influencing abundance. Females were generally larger and predominant compared to males, likely due to life cycle dynamics. Despite being congeneric and sympatric, the species exhibited distinct population patterns, possibly to avoid niche overlap and competition. Full article

Two new species of the genus Cherax are described and illustrated. Cherax rayko n. sp., endemic to the Bian River drainage basin in the Muting District, in the northern part of the Merauke Regency, South Papua, Indonesia, is described, figured, and compared with its closest relatives, Cherax alyciae, Lukhaup, Eprilurahman & von Rintelen, 2018, and Cherax peknyi Lukhaup & Herbert, 2008. The new species may be easily distinguished from both by the shape of the rostrum, the shape of the chelae, the shape of the scaphocerite, and the coloration. Cherax phing n. sp., endemic to the Kali Ombak River drainage basin in the western part of the Kepala Burung (Vogelkop) Peninsula, Southwest Papua, Indonesia, is described, figured, and compared with its closest relatives, Cherax pulcher Lukhaup, 2015a, Cherax boesemani Lukhaup & Pekny, 2008, Cherax wagenknechtae Lukhaup and Eprilurahman, 2022, and Cherax gherardii Patoka, Bláha & Kouba, 2015. The new species may be easily distinguished from the latter species by the shape of the chelae, rostrum, and body and by the coloration. A molecular phylogeny based on a mitochondrial gene fragment, 16S, supports the morphology-based description of the two new species, which can also be clearly distinguished by sequence differences. Full article

Parasitoidism strongly influences the structure of the spiders’ populations, and it can be affected by environmental factors such as those caused by anthropogenic actions. We studied the prevalence of parasitoids in egg sacs and the proportion of eggs parasitized in each egg sac of two synanthropic spider species, one native to the American continent (Parasteatoda tepidariorum) and another recently introduced to the Americas (Latrodectus geometricus). We conducted the study at two scales, along an urban gradient (from highly urbanized to rural sites) and in the vegetation surrounding each sampling site (microscale). We expected to find a larger prevalence of parasitoids in the most urbanized sites and around sampling sites with more vegetation. However, we saw more parasitized egg sacs at the intermediate urbanized site for both species, and the vegetation surrounding the sampling sites did not affect the number of parasitized egg sacs. Therefore, conditions in the site with intermediate urban development favored parasitoids. We also found more parasitized egg sacs in P. tepidariorum than in L. geometricus, which is likely a consequence of native parasites not being adapted to a new host. The proportion of eggs parasitized was similar for both species in all sites, which may be related to the behavior (e.g., searching behavior) and number of spider eggs a female parasitoid can parasitize. Full article