Background matching can reduce responsiveness of jumping spiders to stimuli in motion.

Motion and camouflage were previously considered to be mutually exclusive, as sudden movements can be easily detected. Background matching, for instance, is a well-known, effective camouflage strategy where the colour and pattern of a stationary animal match its surrounding background. However, background matching may lose its efficacy when the animal moves, as the boundaries of the animal become more defined against its background. Recent evidence shows otherwise, as camouflaged objects can be less detectable than uncamouflaged objects even while in motion. Here, we explored whether the detectability of computer-generated stimuli varies with the speed of motion, background (matching and unmatching) and size of stimuli in six species of jumping spiders (Araneae: Salticidae). Our results showed that, in general, the responsiveness of all six salticid species tested decreased with increasing stimulus speed regardless of whether the stimuli were conspicuous or camouflaged. Importantly, salticid responses to camouflaged stimuli were significantly lower compared with those to conspicuous stimuli. There were significant differences in motion detectability across species when the stimuli were conspicuous, suggesting differences in visual acuity in closely related species of jumping spiders. Furthermore, small stimuli elicited significantly lower responses than large stimuli across species and speeds. Our results thus suggest that background matching is effective even when stimuli are in motion, reducing the detectability of moving stimuli.

Phylogenetic placement and species delimitation of the crab spider genus Phrynarachne (Araneae: Thomisidae) from China.

Evolutionary biologists have long been fascinated by the striking resemblance to bird droppings of the sit-and-wait crab spiders of the genus Phrynarachne. In doing so, species of Phrynarachne have evolved not to avoid detection, but rather, to cause predators to misidentify them as inedible and/or inanimate bird droppings. However, the lack of a phylogeny for Phrynarachne impedes our understanding of the evolution of this trait in the genus. Here we explore species boundaries in species of Phrynarachne from China using single- and multi-locus species delimitation approaches based on 30 Phrynarachne samples. All species delimitation approaches supported six species of Phrynarachne in China. We further present the first phylogenetic analysis of the genus Phrynarachne and estimate divergence times using two mitochondrial and three nuclear genes. All of our phylogenetic analyses supported the monophyly of Phrynarachne in China, with the genus still included within the higher 'Thomisus group' based on our results. Our dating analyses place the crown age of Phrynarachne in China to the middle Miocene. Taken together, our study provides a time-calibrated phylogeny of the genus Phrynarachne in China for testing hypotheses regarding the evolution of the lineage and bird dropping masquerade.

Phylogenomic Analysis of Ultraconserved Elements Resolves the Evolutionary and Biogeographic History of Segmented Trapdoor Spiders.

The segmented trapdoor spiders (Liphistiidae) are the sole surviving family of the suborder Mesothelae, which forms the sister lineage to all other living spiders. Liphistiids have retained a number of plesiomorphic traits and their present-day distribution is limited to East and Southeast Asia. Studying this group has the potential to shed light on the deep evolutionary history of spiders, but the phylogeny and divergence times of the family have not been resolved with confidence. We performed phylogenomic and molecular dating analyses of 2765 ultraconserved element loci from 185 liphistiid taxa. Our analyses show that the crown group of Liphistiidae appeared in the mid-Cretaceous at 102 Ma (95% credibility interval 92-113 Ma), but it was not until the Neogene that much of the diversification within the family occurred in mainland Southeast and East Asia. This diversification was coincident with tectonic events such as the extension of the East Asian continental margin, as well as geological upheavals in Indochina induced by the collision between India and Asia. Our study highlights the important role of major tectonic events in shaping the evolutionary history, present-day diversity, and geographical distribution of mesothele and liphistiid spiders. [biogeography; concatenation; Liphistiidae; molecular dating; summary coalescent; UCEs.].

Fully automated leg tracking of Drosophila neurodegeneration models reveals distinct conserved movement signatures.

Some neurodegenerative diseases, like Parkinsons Disease (PD) and Spinocerebellar ataxia 3 (SCA3), are associated with distinct, altered gait and tremor movements that are reflective of the underlying disease etiology. Drosophila melanogaster models of neurodegeneration have illuminated our understanding of the molecular mechanisms of disease. However, it is unknown whether specific gait and tremor dysfunctions also occur in fly disease mutants. To answer this question, we developed a machine-learning image-analysis program, Feature Learning-based LImb segmentation and Tracking (FLLIT), that automatically tracks leg claw positions of freely moving flies recorded on high-speed video, producing a series of gait measurements. Notably, unlike other machine-learning methods, FLLIT generates its own training sets and does not require user-annotated images for learning. Using FLLIT, we carried out high-throughput and high-resolution analysis of gait and tremor features in Drosophila neurodegeneration mutants for the first time. We found that fly models of PD and SCA3 exhibited markedly different walking gait and tremor signatures, which recapitulated characteristics of the respective human diseases. Selective expression of mutant SCA3 in dopaminergic neurons led to a gait signature that more closely resembled those of PD flies. This suggests that the behavioral phenotype depends on the neurons affected rather than the specific nature of the mutation. Different mutations produced tremors in distinct leg pairs, indicating that different motor circuits were affected. Using this approach, fly models can be used to dissect the neurogenetic mechanisms that underlie movement disorders.

Global Diversification of Anelosimus Spiders Driven by Long-Distance Overwater Dispersal and Neogene Climate Oscillations.

Vicariance and dispersal events, combined with intricate global climatic history, have left an imprint on the spatiotemporal distribution and diversity of many organisms. Anelosimus cobweb spiders (Theridiidae), are organisms ranging in behavior from solitary to highly social, with a cosmopolitan distribution in temperate to tropical areas. Their evolutionary history and the discontinuous distribution of species richness suggest that 1) long-distance overwater dispersal and 2) climate change during the Neogene (23-2.6 Ma), may be major factors in explaining their distribution and diversification. Here, we test these hypotheses, and explicitly test if global Miocene/Pliocene climatic cooling in the last 8 Ma affected Anelosimus radiation in parallel in South America and Madagascar. To do so, we investigate the phylogeny and spatiotemporal biogeography of Anelosimus through a culmination of a 20-year comprehensive global sampling at the species level (69 species, including 84% of the known 75 species worldwide, represented by 268 individuals) using nucleotide data from seven loci (5.5 kb). Our results strongly support the monophyly of Anelosimus with an Oligocene ($\sim $30 Ma) South American origin. Major clades on other continents originate via multiple, long-distance dispersal events, of solitary or subsocial-but not social-lineages, from the Americas. These intercontinental dispersals were to Africa, Madagascar (twice), and SE Asia/Australasia. The early diversification of Anelosimus spiders coincides with a sudden thermal increase in the late Oligocene ($\sim $27-25 Ma), though no causal connection can be made. Our results, however, strongly support the hypothesis that global Neogene climatic cooling in the last 8 Ma drove Anelosimus radiation in parallel in South America and Madagascar, offering a rare empirical evidence for diversification of a socially diverse group driven by an interplay between long-distance dispersal and global Neogene climatic changes. [Cobweb spiders; diversification; global biogeography; long-distance dispersal; molecular phylogenetics; neogene climate changes; sociality; vicariance.].

Female spider aggression is associated with genetic underpinnings of the nervous system and immune response to pathogens.

Identifying the genetic architecture underlying phenotypic variation in natural populations and assessing the consequences of polymorphisms for individual fitness are fundamental goals in evolutionary and molecular ecology. Consistent between-individual differences in behaviour have been documented for a variety of taxa. Dissecting the genetic basis of such behavioural differences is however a challenging endeavour. The molecular underpinnings of natural variation in aggression remain elusive. Here, we used comparative gene expression (transcriptome analysis and RT-PCR), genetic association analysis and pharmacological experiments to gain insight into the genetic basis of aggression in wild-caught jumping spiders (Portia labiata). We show that spider aggression is associated with a putative viral infection response gene, BTB/POZ domain-containing protein 17 (BTBDH), in addition to a putative serotonin receptor 1A (5-HT1A) gene. Spider aggression varies with virus loads, and BTBDH is upregulated in docile spiders and exhibits a genetic variant associated with aggression. We also identify a putative serotonin receptor 5-HT1A gene upregulated in docile P. labiata. Individuals that have been treated with serotonin become less aggressive, but individuals treated with a nonselective serotonin receptor antagonist (methiothepin) also reduce aggression. Further, we identify the genetic variants in the 5-HT1A gene that are associated with individual variation in aggression. We therefore conclude that co-evolution of the immune and nervous systems may have shaped the between-individual variation in aggression in natural populations of jumping spiders.

Molecular species delimitation in the primitively segmented spider genus Heptathela endemic to Japanese islands.

Determining species boundaries forms an important foundation for biological research. However, the results of molecular species delimitation can vary with the data sets and methods that are used. Here we use a two-step approach to delimit species in the genus Heptathela, a group of primitively segmented trapdoor spiders that are endemic to Japanese islands. Morphological evidence suggests the existence of 19 species in the genus. We tested this initial species hypothesis by using six molecular species-delimitation methods to analyse 180 mitochondrial COI sequences of Heptathela sampled from across the known range of the genus. We then conducted a set of more focused analyses by sampling additional genetic markers from the subset of taxa that were inconsistently delimited by the single-locus analyses of mitochondrial DNA. Multilocus species delimitation was performed using two Bayesian approaches based on the multispecies coalescent. Our approach identified 20 putative species among the 180 sampled individuals of Heptathela. We suggest that our two-step approach provides an efficient strategy for delimiting species while minimizing costs and computational time.

High-lipid prey reduce juvenile survivorship and delay egg laying in a small linyphiid spider Hylyphantes graminicola.

Prey proteins and lipids greatly impact predator life-history traits. However, life-history plasticity offers predators the opportunity to tune the life-history traits in response to the limited macronutrients to allocate among traits. A fast-growing predator species with a strict maturation time may be more likely to consume nutritionally imbalanced prey. Here, we tested this hypothesis by examining the effect of the protein-to-lipid ratio in prey on a small sheet web-building spider, Hylyphantes graminicola, with a short life span, using adult Drosophila melanogaster as the prey. By manipulating the macronutrient content of the prey to generate three prey types with different protein-to-lipid ratios (i.e. high, intermediate and low), we demonstrated that the majority of the spiders that consumed only these flies could reach full maturity. However, juvenile spiders that consumed high-lipid (low protein-to-lipid ratio) flies had a higher rate of mortality than those consuming medium-protein and high-protein flies. The prey protein-to-lipid ratio had no significant effects on the developmental duration and size at maturity. Although the prey protein-to-lipid ratio had no significant influence on mating behaviour and female fecundity, females reared on high-lipid flies exhibited a significant delay in oviposition compared with those reared on high-protein flies. We conclude that high-lipid prey has negative effects on the survival and reproductive function of H. graminicola Our study thus provides clear evidence that low plasticity with fast development to a certain size means a high nutritional requirement for protein at a cost of lower survival and prolonged time to egg laying when prey have low protein-to-lipid content in H. graminicola.

Singapore's Anopheles sinensis Form A is susceptible to Plasmodium vivax isolates from the western Thailand-Myanmar border.

BACKGROUND: Singapore has been certified malaria-free by the World Health Organization since November 1982. However, sporadic autochthonous malaria outbreaks do occur. In one of the most recent outbreaks of vivax malaria, an entomological investigation identified Anopheles sinensis as the most probable vector. As metaphase karyotype studies divided An. sinensis into two forms, A and B, with different vector competence: the investigation of vector competence of An. sinensis found in Singapore was thus pursued using Plasmodium vivax field isolates from the Thailand-Myanmar border. METHODS: Adults and larvae An. sinensis were collected from Singapore from 14 different locations, using various trapping and collection methods between September 2013 and January 2016. Molecular identification of An. sinensis species were conducted by amplifying the ITS2 and CO1 region using PCR. Experimental infections of An. sinensis using blood from seven patients infected with P. vivax from the Thailand-Myanmar border were conducted with Anopheles cracens (An. dirus B) as control. RESULTS: Phylogenetic analysis showed that An. sinensis (F22, F2 and collected from outbreak areas) found in Singapore was entirely Form A, and closely related to An. sinensis Form A from Thailand. Artificial infection of these Singapore strain An. sinensis Form A resulted in the development of oocysts in four experiments, with the number of sporozoites produced by one An. sinensis ranging from 4301 to 14,538. CONCLUSIONS: Infection experiments showed that An. sinensis Form A from Singapore was susceptible to Thai-Myanmar P. vivax strain, suggesting a potential role as a malaria vector in Singapore.

Extant primitively segmented spiders have recently diversified from an ancient lineage.

Living fossils are lineages that have retained plesiomorphic traits through long time periods. It is expected that such lineages have both originated and diversified long ago. Such expectations have recently been challenged in some textbook examples of living fossils, notably in extant cycads and coelacanths. Using a phylogenetic approach, we tested the patterns of the origin and diversification of liphistiid spiders, a clade of spiders considered to be living fossils due to their retention of arachnid plesiomorphies and their exclusive grouping in Mesothelae, an ancient clade sister to all modern spiders. Facilitated by original sampling throughout their Asian range, we here provide the phylogenetic framework necessary for reconstructing liphistiid biogeographic history. All phylogenetic analyses support the monophyly of Liphistiidae and of eight genera. As the fossil evidence supports a Carboniferous Euramerican origin of Mesothelae, our dating analyses postulate a long eastward over-land dispersal towards the Asian origin of Liphistiidae during the Palaeogene (39-58 Ma). Contrary to expectations, diversification within extant liphistiid genera is relatively recent, in the Neogene and Late Palaeogene (4-24 Ma). While no over-water dispersal events are needed to explain their evolutionary history, the history of liphistiid spiders has the potential to play prominently in vicariant biogeographic studies.

The spectral transmission of non-salticid spider corneas.

Although many salticid spiders have been shown to have corneas that transmit ultraviolet (UV) light, whether the corneas of non-salticid spiders transmit UV has not been previously investigated. In this study, we determined the spectral corneal transmission properties of 38 species belonging to 13 non-salticid families. We used these data to estimate the T50 transmission cut-off value, the wavelength corresponding to 50% maximal transmission for each species. The corneas of almost all species from the families Deinopidae, Lycosidae, Oxyopidae, Pisauridae, Sparassidae and Thomisidae, all of which have been reported to rely to a substantial extent on vision, transmitted short wavelength light below 400 nm, ranging from 306 to 381 nm. However, species from the families Atypidae and Ctenizidae are not known to rely substantially on vision, and the corneas of these species tended to absorb light of wavelengths below 380 nm, which may not allow UV sensitivity in these spiders. Liphistiidae, the family widely regarded as most basal among spiders, is of particular interest. The species in this family are not known to make substantial use of vision, and yet we found that liphistiid corneas transmitted UV light with a low T50 value (359 nm). T50 values of non-salticid spider corneas also varied with light habitat. Species living in dim environments tended to have UV-opaque corneas, but species inhabiting open areas had UV-transmitting corneas. However, there was no evidence of corneal transmission properties being related to whether a species is diurnal or nocturnal.

Antipredator defences in motion: animals reduce predation risks by concealing or misleading motion signals.

Motion is a crucial part of the natural world, yet our understanding of how animals avoid predation whilst moving remains rather limited. Although several theories have been proposed for how antipredator defence may be facilitated during motion, there is often a lack of supporting empirical evidence, or conflicting findings. Furthermore, many studies have shown that motion often 'breaks' camouflage, as sudden movement can be detected even before an individual is recognised. Whilst some static camouflage strategies may conceal moving animals to a certain extent, more emphasis should be given to other modes of camouflage and related defences in the context of motion (e.g. flicker fusion camouflage, active motion camouflage, motion dazzle, and protean motion). Furthermore, when motion is involved, defence strategies are not necessarily limited to concealment. An animal can also rely on motion to mislead predators with regards to its trajectory, location, size, colour pattern, or even identity. In this review, we discuss the various underlying antipredator strategies and the mechanisms through which they may be linked to motion, conceptualising existing empirical and theoretical studies from two perspectives - concealing and misleading effects. We also highlight gaps in our understanding of these antipredator strategies, and suggest possible methodologies for experimental designs/test subjects (i.e. prey and/or predators) and future research directions.

Seven new species of the segmented spider genus Liphistius (Mesothelae, Liphistiidae) in Thailand and Myanmar.

Seven new species of the primitive segmented spider genus Liphistius are described and assigned to species groups based on characters of the male palp and vulva plate. The bristowei group includes L.dawei Sivayyapram & Warrit, sp. nov. (♂♀) from southeastern Myanmar, L.choosaki Sivayyapram & Warrit, sp. nov. (♀) from northwestern Thailand, and L.lansak Sivayyapram & Warrit, sp. nov. (♀) from western Thailand; the trang group (Complex A) contains L.kaengkhoi Sivayyapram & Warrit, sp. nov. (♂♀), L.hintung Sivayyapram & Warrit, sp. nov. (♂♀), L.buyphradi Sivayyapram & Warrit, sp. nov. (♂♀), and L.champakpheaw Sivayyapram & Warrit, sp. nov. (♂♀) from central Thailand.

Males armed with big weapons win fights at limited cost in ant-mimicking jumping spiders.

A core assumption of sexual selection theory is that sexually selected weapons, specialized morphological structures used directly in male contests, can improve an individual's reproductive success but only if the bearer can overcome associated costs, the negative effects on the bearer's fitness components. However, recent studies have shown that producing and wielding exaggerated weapons may not necessarily be costly. Rather, some traits can be selected for supporting, or compensating for, the expense of producing and wielding such exaggerated weapons. In the ant-mimicking jumping spider Myrmarachne gisti, exaggerated chelicerae are borne only by adult males and not females, showing sexual dimorphism and steep positive allometry with body size. Here, we determine the potential benefits of bearing exaggerated chelicerae during male contests and explore the potential for costs in terms of prey-capture efficiency and compensation between chelicera size and neighboring trait size. While males with longer chelicerae won most of their male-male contests, we found no significant differences in prey-capture efficiency between males and females regardless of whether prey was winged or flightless. Males' elongated chelicerae thus do not impede their efficiency at capturing prey. Furthermore, we found that the sizes of all neighboring traits are positively correlated with chelicera size, suggesting that these traits may be under correlational selection. Taken together, our findings suggest that M. gisti males armed with the exaggerated chelicerae that function as weapons win more fights at limited cost for performance in prey capture and compensate for neighboring structures.

Studies on South-east Asian fireflies: Abscondita, a new genus with details of life history, flashing patterns and behaviour of Abs. chinensis (L.) and Abs. terminalis (Olivier) (Coleoptera: Lampyridae: Luciolinae).

Abscondita, a new genus of fireflies from South-east Asia, is described from males and females of Abs. anceyi (Olivier 1883), Abs. cerata (Olivier 1911), Abs. chinensis (L. 1767), Abs. perplexa (Walker 1858), Abs. promelaena (Walker 1858) and Abs. terminalis (Olivier 1883), all transferred from Luciola Laporte. Both L. dubia Olivier 1903 and L. dejeani Gemminger 1870 are synonymised with Luciola perplexa (Walker), and L. aegrota Olivier 1891 and L. melaspis Bourgeois 1909 with L. promelaena Walker. Females are characterised by their bursa plates. Larvae are associated and described for Abs. anceyi (Olivier), Abs. chinensis (L.) and Abs. terminalis (Olivier). Taxonomic issues regarding the identification of species with very similar colouration of pale dorsum and black tipped elytra are addressed and in some cases resolved. A neotype for Luciola chinensis (L.) is erected and Luciola praeusta (Kiesenwetter 1874) is synonymised with L. chinensis (L.). Descriptions of life histories, biology and flashing patterns of populations of Abs. chinensis and Abs. terminalis from central China are included. A bs. terminalis is the first Asian firefly known to possess multiple flash trains where males are documented to display with repeating flash trains.

Three new species of the primitively segmented spider genus Songthela (Mesothelae, Liphistiidae, Heptathelinae) from Hunan Province, China.

Three new species of the primitively segmented spider genus Songthela Ono, 2000 are identified and described from Hunan Province, China, based on morphological characters of males and females: S.anhua Zhang & Xu, sp. nov. (♂♀), S.longhui Zhang & Xu, sp. nov. (♂♀), and S.zhongpo Zhang & Xu, sp. nov. (♂♀). All the new Songthela species belong to the multidentata-group according to male palp and female genital morphology.

Eyeless cave-dwelling Leptonetela spiders still rely on light.

Subterranean animals living in perpetual darkness may maintain photoresponse. However, the evolutionary processes behind the conflict between eye loss and maintenance of the photoresponse remain largely unknown. We used Leptonetela spiders to investigate the driving forces behind the maintenance of the photoresponse in cave-dwelling spiders. Our behavioral experiments showed that all eyeless/reduced-eyed cave-dwelling species retained photophobic response and that they had substantially decreased survival at cave entrances due to weak drought resistance. The transcriptomic analysis demonstrated that nearly all phototransduction pathway genes were present and that all tested phototransduction pathway genes were subjected to strong functional constraints in cave-dwelling species. Our results suggest that cave-dwelling eyeless spiders still use light and that light detection likely plays a role in avoiding the cave entrance habitat. This study confirms that some eyeless subterranean animals have retained their photosensitivity due to natural selection and provides a case of mismatch between phenotype and genotype or physiological function in a long-term evolutionary process.

A novel property of spider silk: chemical defence against ants.

Spider webs are made of silk, the properties of which ensure remarkable efficiency at capturing prey. However, remaining on, or near, the web exposes the resident spiders to many potential predators, such as ants. Surprisingly, ants are rarely reported foraging on the webs of orb-weaving spiders, despite the formidable capacity of ants to subdue prey and repel enemies, the diversity and abundance of orb-web spiders, and the nutritional value of the web and resident spider. We explain this paradox by reporting a novel property of the silk produced by the orb-web spider Nephila antipodiana (Walckenaer). These spiders deposit on the silk a pyrrolidine alkaloid (2-pyrrolidinone) that provides protection from ant invasion. Furthermore, the ontogenetic change in the production of 2-pyrrolidinone suggests that this compound represents an adaptive response to the threat of natural enemies, rather than a simple by-product of silk synthesis: while 2-pyrrolidinone occurs on the silk threads produced by adult and large juvenile spiders, it is absent on threads produced by small juvenile spiders, whose threads are sufficiently thin to be inaccessible to ants.

Spectral transmission of the principal-eye corneas of jumping spiders: implications for ultraviolet vision.

Ultraviolet (UV) vision plays an important role in interspecific and intraspecific communication in many animals. However, UV vision and its adaptive significance have been investigated in only approximately 1% of more than 5000 species of jumping spiders (Araneae: Salticidae), renowned for their unique, complex eyes that support exceptional spatial acuity and visually based behaviour. To appreciate the adaptive significance of UV vision, it is important to establish whether salticids can perceive UV and whether the perception of UV varies with ecological factors such as light environment. In this study, we measured the UV-transmission properties of the principal-eye corneas of 128 salticid species. We found that the corneas of all measured species were able to transmit UV light, making the perception of UV possible. Three classes of corneal spectral transmission curves were identified; the majority of species had a Class II curve with a less-steep slope and a gradual onset of the transmission cut-off; all the remaining species had a Class I curve with a very steep slope and a sharp cut-off except for one species that had a Class III curve with an intermediate step, which appeared as a shoulder on the descending part of the transmission curve. The T(50) cut-off transmission values (the wavelength at which 50% of the maximum transmission is reached) in salticid corneas vary with species and light habitat. The corneas of species inhabiting open bush had a higher relative transmission at short wavelengths in the UV than forest species. This is the first investigation of corneal transmission in spiders and suggests that UV perception is widespread in salticids.

Remote copulation: male adaptation to female cannibalism.

Sexual cannibalism by females and associated male behaviours may be driven by sexual conflict. One such male behaviour is the eunuch phenomenon in spiders, caused by total genital emasculation, which is a seemingly maladaptive behaviour. Here, we provide the first empirical testing of an adaptive hypothesis to explain this behaviour, the remote copulation, in a highly sexually cannibalistic orb-web spider Nephilengys malabarensis. We demonstrate that sperm transfer continues from the severed male organ into female genitals after the male has been detached from copula. Remote copulation increases the total amount of sperm transferred, and thus probably enhances paternity. We conclude that the mechanism may have evolved in response to sexual cannibalism and female-controlled short copulation duration.