The effects of artificial light at night on spider brains.

Artificial light at night (ALAN) is an increasingly pervasive pollutant that alters animal behaviour and physiology, with cascading impacts on development and survival. Recent evidence links exposure to ALAN with neural damage, potentially due to its action on melatonin synthesis, a powerful antioxidant. However, these data are scarce and taxonomically limited. Here, we used micro-CT to test the effects of short-term ALAN exposure on brain volumes in the Australian garden orb-weaving spider (Hortophora biapicata), a species commonly found in urban areas and, specifically, around street lights. We found that short-term ALAN exposure was linked to reductions in the volumes of brain structures in the primary eye visual pathway, potentially as a consequence of oxidative stress or plastic shifts in neural investment. Although the effects of ALAN were subtle, they provided new insights into potential mechanisms underpinning the behavioural and physiological impacts of ALAN in this important urban predator.

Comparative anatomy of the spinneret musculature in cribellate and ecribellate spiders (Araneae).

Silk production is a prominent characteristic of spiders. The silk is extruded through spigots located on the spinnerets, which are single- to multimembered paired appendages at the end of the abdomen. Most extant spiders have three pairs of spinnerets, and in between either a cribellum (spinning plate) or a colulus (defunct vestigial organ), dividing these spiders into cribellate and ecribellate species. Previous research has shown that cribellate and ecribellate spiders differ not only in the composition of their spinning apparatus but also in the movements of their spinnerets during silk spinning. The objective of this study was to determine whether the differences in spinneret movements are solely due to variations in spinneret shape or whether they are based on differences in muscular anatomy. This was accomplished by analyzing microcomputed tomography scans of the posterior abdomen of each three cribellate and ecribellate species. It was found that the number of muscles did not generally differ between cribellate and ecribellate species, but varied considerably between the species within each of these two groups. Muscle thickness, particularly of the posterior median spinneret, varied slightly between groups, with cribellate spiders exhibiting more robust muscles, possibly to aid in the combing process during cribellar thread production. Interestingly, the vestigial colulus still possesses muscles, that can be homologized with those of the cribellum. This exploration into spinneret anatomy using microcomputed tomography data reveals that despite being small appendages, the spider spinnerets are equipped with a complex musculature that enables them to perform fine-scaled maneuvers to construct different fiber-based materials.

Biodiversity of orb-web spiders (family: araneidae) of buner valley, Pakistan / Biodiversidade de aranhas construtoras de teia (família: araneidae) do vale buner, Paquistão

The present research was carried out to explore the spider fauna of Buner valley with taxonomic study from February 2018 to January 2019. For this purpose samples were collected, four times at each month from 4 tehsils: Daggar, Gagra, Mandan and Totalai. Two methods were used, hand picking and sweep net for collection of samples. During day and night, three habitats, arid area, agriculture land and building area were search for collection. A total of 534 samples of spider were collected from four sampling sites, in which 379 were belonging to family Araniedae. After confirmation, the identified species were belonging to 8 genera (Neoscona, Argiope, Cyclosa, Araneus, Cyrtophora, Larinia, Erivoxia and Poltys) and 19 species. 18 of them were identified to specie level while a single specie to its generic level. The genus Neoscona was the dominant genus 26.31% having 5 species while the genus Argiope 21.05% is the second dominant having 4 species followed by Cyclosa 15.78% having 3 species followed by Cyrtophora and Araneus 10.52% having two species both. The Poltys and Larinia 5.26% are the rarest genera represent single-single specie both. Statistical analysis show that specie richness (D) = 5.77, Simpson index (1-D) = 0.87, Shannon index (H) = 2.33. Diversity of spiders was evenly distributed and calculated Evenness value was H/InS = 0.5408. There is also few atypical species and Fisher alpha estimate high value (Fisher α) = 4.42. Chao-1 estimated we have reported 22 species.

A presente pesquisa foi realizada para explorar a fauna de aranhas do vale Buner, em um estudo taxonômico realizado de fevereiro de 2018 a janeiro de 2019. Para esse fim, foram coletadas amostras, quatro vezes por mês, a partir de 4 subdistritos: Daggar, Gagra, Mandan e Totalai. Foram utilizados dois métodos, coleta manual e rede de varredura, para a obtenção das amostras. Durante o dia e a noite, foram pesquisados três habitats: área árida, área agrícola e área de construção. Foram coletadas 534 amostras de aranha em quatro locais de amostragem, sendo que 379 pertenciam à família Araneidae. Após a confirmação, as espécies identificadas pertenciam a 8 gêneros (Neoscona, Argiope, Cyclosa, Araneus, Cyrtophora, Larinia, Erivoxia e Poltys) e a 19 espécies (18 delas foram identificados em seu nível de espécie, enquanto uma única foi identificada em seu nível genérico). O gênero Neoscona foi dominante (26,31%), com 5 espécies, seguido pelos gêneros Argiope (21,05%), com 4 espécies, Cyclosa (15,78%), com 3 espécies, e Cyrtophora e Araneus (10,52%), com 2 espécies. Poltys e Larinia (5,26%) são os gêneros mais raros, representando a mesma espécie. A análise estatística mostrou que a riqueza de espécies (D) foi de 5,77, o índice de Simpson (1-D) foi de 0,87 e o índice de Shannon (H) foi de 2,33. A diversidade de aranhas foi distribuída uniformemente, e o valor calculado da uniformidade foi H / InS = 0,5408. Também existem poucas espécies atípicas, e o alfa de Fisher (Fisher α) estimou o valor de 4,42. Já Chao-1 estimou 22 espécies.

Biodiversity of orb-web spiders (family: araneidae) of buner valley, Pakistan

Abstract The present research was carried out to explore the spider fauna of Buner valley with taxonomic study from February 2018 to January 2019. For this purpose samples were collected, four times at each month from 4 tehsils: Daggar, Gagra, Mandan and Totalai. Two methods were used, hand picking and sweep net for collection of samples. During day and night, three habitats, arid area, agriculture land and building area were search for collection. A total of 534 samples of spider were collected from four sampling sites, in which 379 were belonging to family Araniedae. After confirmation, the identified species were belonging to 8 genera (Neoscona, Argiope, Cyclosa, Araneus, Cyrtophora, Larinia, Erivoxia and Poltys) and 19 species. 18 of them were identified to specie level while a single specie to its generic level. The genus Neoscona was the dominant genus 26.31% having 5 species while the genus Argiope 21.05% is the second dominant having 4 species followed by Cyclosa 15.78% having 3 species followed by Cyrtophora and Araneus 10.52% having two species both. The Poltys and Larinia 5.26% are the rarest genera represent single-single specie both. Statistical analysis show that specie richness (D) = 5.77, Simpson index (1-D) = 0.87, Shannon index (H) = 2.33. Diversity of spiders was evenly distributed and calculated Evenness value was H/InS = 0.5408. There is also few atypical species and Fisher alpha estimate high value (Fisher ) = 4.42. Chao-1 estimated we have reported 22 species.

Resumo A presente pesquisa foi realizada para explorar a fauna de aranhas do vale Buner, em um estudo taxonômico realizado de fevereiro de 2018 a janeiro de 2019. Para esse fim, foram coletadas amostras, quatro vezes por mês, a partir de 4 subdistritos: Daggar, Gagra, Mandan e Totalai. Foram utilizados dois métodos, coleta manual e rede de varredura, para a obtenção das amostras. Durante o dia e a noite, foram pesquisados três habitats: área árida, área agrícola e área de construção. Foram coletadas 534 amostras de aranha em quatro locais de amostragem, sendo que 379 pertenciam à família Araneidae. Após a confirmação, as espécies identificadas pertenciam a 8 gêneros (Neoscona, Argiope, Cyclosa, Araneus, Cyrtophora, Larinia, Erivoxia e Poltys) e a 19 espécies (18 delas foram identificados em seu nível de espécie, enquanto uma única foi identificada em seu nível genérico). O gênero Neoscona foi dominante (26,31%), com 5 espécies, seguido pelos gêneros Argiope (21,05%), com 4 espécies, Cyclosa (15,78%), com 3 espécies, e Cyrtophora e Araneus (10,52%), com 2 espécies. Poltys e Larinia (5,26%) são os gêneros mais raros, representando a mesma espécie. A análise estatística mostrou que a riqueza de espécies (D) foi de 5,77, o índice de Simpson (1-D) foi de 0,87 e o índice de Shannon (H) foi de 2,33. A diversidade de aranhas foi distribuída uniformemente, e o valor calculado da uniformidade foi H / InS = 0,5408. Também existem poucas espécies atípicas, e o alfa de Fisher (Fisher ) estimou o valor de 4,42. Já Chao-1 estimou 22 espécies.

Biodiversity of orb-web spiders (family: araneidae) of buner valley, Pakistan / Biodiversidade de aranhas construtoras de teia (família: araneidae) do vale buner, Paquistão

The present research was carried out to explore the spider fauna of Buner valley with taxonomic study from February 2018 to January 2019. For this purpose samples were collected, four times at each month from 4 tehsils: Daggar, Gagra, Mandan and Totalai. Two methods were used, hand picking and sweep net for collection of samples. During day and night, three habitats, arid area, agriculture land and building area were search for collection. A total of 534 samples of spider were collected from four sampling sites, in which 379 were belonging to family Araniedae. After confirmation, the identified species were belonging to 8 genera (Neoscona, Argiope, Cyclosa, Araneus, Cyrtophora, Larinia, Erivoxia and Poltys) and 19 species. 18 of them were identified to specie level while a single specie to its generic level. The genus Neoscona was the dominant genus 26.31% having 5 species while the genus Argiope 21.05% is the second dominant having 4 species followed by Cyclosa 15.78% having 3 species followed by Cyrtophora and Araneus 10.52% having two species both. The Poltys and Larinia 5.26% are the rarest genera represent single-single specie both. Statistical analysis show that specie richness (D) = 5.77, Simpson index (1-D) = 0.87, Shannon index (H) = 2.33. Diversity of spiders was evenly distributed and calculated Evenness value was H/InS = 0.5408. There is also few atypical species and Fisher alpha estimate high value (Fisher α) = 4.42. Chao-1 estimated we have reported 22 species.

A presente pesquisa foi realizada para explorar a fauna de aranhas do vale Buner, em um estudo taxonômico realizado de fevereiro de 2018 a janeiro de 2019. Para esse fim, foram coletadas amostras, quatro vezes por mês, a partir de 4 subdistritos: Daggar, Gagra, Mandan e Totalai. Foram utilizados dois métodos, coleta manual e rede de varredura, para a obtenção das amostras. Durante o dia e a noite, foram pesquisados três habitats: área árida, área agrícola e área de construção. Foram coletadas 534 amostras de aranha em quatro locais de amostragem, sendo que 379 pertenciam à família Araneidae. Após a confirmação, as espécies identificadas pertenciam a 8 gêneros (Neoscona, Argiope, Cyclosa, Araneus, Cyrtophora, Larinia, Erivoxia e Poltys) e a 19 espécies (18 delas foram identificados em seu nível de espécie, enquanto uma única foi identificada em seu nível genérico). O gênero Neoscona foi dominante (26,31%), com 5 espécies, seguido pelos gêneros Argiope (21,05%), com 4 espécies, Cyclosa (15,78%), com 3 espécies, e Cyrtophora e Araneus (10,52%), com 2 espécies. Poltys e Larinia (5,26%) são os gêneros mais raros, representando a mesma espécie. A análise estatística mostrou que a riqueza de espécies (D) foi de 5,77, o índice de Simpson (1-D) foi de 0,87 e o índice de Shannon (H) foi de 2,33. A diversidade de aranhas foi distribuída uniformemente, e o valor calculado da uniformidade foi H / InS = 0,5408. Também existem poucas espécies atípicas, e o alfa de Fisher (Fisher α) estimou o valor de 4,42. Já Chao-1 estimou 22 espécies.

Shaped by the Sun: the effect of exposure to sunlight on the evolution of spider bodies.

Body temperature can strongly influence fitness. Some Sun-exposed ectotherms thermoregulate by adjusting body posture according to the Sun's position. In these species, body elongation should reduce the risk of heat stress by allowing the exposure of a smaller body area to sunlight. Therefore, selection should favour more elongated bodies in Sun-exposed than in Sun-protected species. Diurnal orb-web spider species that sit on their webs are more likely to be Sun-exposed, on average, than nocturnal or diurnal shelter-building species. We measured the body elongation of orb-web spiders (Araneae, Araneidae) across 1024 species and classified them as Sun-protected or exposed based on the literature. We found that Sun-exposed species evolved more elongate bodies than Sun-protected ones. Further, we built a model combining traditional heat transfer models with models of thermoregulatory postures in orb-web spiders and meteorological data. The model indicates that body elongation in large orb-web spiders decreases the risk of high body temperatures. Overall, our results suggest that Sun exposure influenced the evolution of body shapes of orb-web spiders.

Insights into the gut bacterial communities of spider from wild with no evidence of phylosymbiosis.

In the present study, an effort has been made to elucidate the gut bacterial diversity of twelve species of the family Araneidae under three subfamilies collected from 5 states of India along with their predicted metabolic role in functional metabolism. Further, we also compared the host species phylogeny based on partial cytochrome c oxidase subunit I (COI) sequences with the gut bacteria composition dendrogram to decipher the phylosymbiotic relationships. Analysis revealed the presence of 22 bacterial phyla, 145 families, and 364 genera in the gut, with Proteobacteria, Firmicutes, Actinobacteria, and Deinococcus-Thermus as the highest abundant phyla. Moreover, phylum Bacteriodetes was dominated only in Cyclosa mulmeinensis and Chlamydiae in Neoscona bengalensis. At the genus level, Bacillus, Acinetobacter, Cutibacterium, Pseudomonas, and Staphylococcus were the most dominant genera. Furthermore, the genus Prevotella was observed only in Cyclosa mulmeinensis, and endosymbiont Wolbachia only in Eriovixia laglaizei. The differential abundance analysis (DeSeq2) revealed the 19 significant ASVs represented by the genera like Acinetobacter, Vagoccoccus, Prevotella, Staphylococcus, Curvibacter, Corynebacterium, Paracoccus, Streptococcus, Microbacterium, and Pseudocitrobacter. The inter- and intra-subfamilies comparison based on diversity indices (alpha and beta diversity) revealed that the subfamily Araneinae have high richness and diversity than Argiopinae and Gasteracanthinae. The phylosymbiotic analysis revealed that there is no congruence between the gut bacteria composition dendrogram with their host phylogeny.

The complete mitochondrial genome of Trichonephila clavipes (Araneae: Araneidae).

Trichonephila clavipes (Linnaeus, 1767) is known as a golden silk orb-weaver and belongs to the family Araneidae. T. clavipes is one of the few spider species whose genome has been reported and model organism for a molecular biology. Here, we present the complete mitochondrial genome sequence (mtDNA) of T. clavipes. The sequence was obtained using a long-read Nanopore technology and corrected with an Illumina technology. The circular genome is 14,902 bp in length, and the AT content was 77.21%. The T. clavipes mitochondrial genome contains 13 protein-coding genes (PCGs), 22 tRNA genes, and 2 rRNA genes. The majority of PCGs were found on the heavy strain.

Morphological Analysis Reveals a Compartmentalized Duct in the Venom Apparatus of the Wasp Spider (Argiope bruennichi).

Spiders are one of the most successful groups of venomous animals, but surprisingly few species have been examined in sufficient detail to determine the structure of their venom systems. To learn more about the venom system of the family Araneidae (orb-weavers), we selected the wasp spider (Argiope bruennichi) and examined the general structure and morphology of the venom apparatus by light microscopy. This revealed morphological features broadly similar to those reported in the small number of other spiders subject to similar investigations. However, detailed evaluation of the venom duct revealed the presence of four structurally distinct compartments. We propose that these subunits facilitate the expression and secretion of venom components, as previously reported for similar substructures in pit vipers and cone snails.

On a new synonymy in the spider genus Nephila Leach, 1815 (Araneidae, Nephilinae) from India with supplementary notes on colour polymorphism in the genus.

The golden orb-weaving spider genus Nephila Leach, 1815 currently has four representatives in India: Nephila dirangensis Biswas Biswas, 2006, Nephila kuhlii (Doleschall, 1859), Nephila pilipes (Fabricius, 1793) and Nephila robusta Tikader, 1962 (World Spider Catalog 2020). While N. kuhlii has its type locality in Java (Doleschall 1859) and that of N. pilipes in Australasia (Fabricius 1781), N. dirangensis and N. robusta are both confined to India (World Spider Catalog 2020). Tikader (1962) described the species N. robusta based on a single female specimen collected in West Bengal. The original genitalic illustrations of this species, however, show close resemblance to that of N. pilipes, indicating its possible synonymy with the latter. To confirm the novelty of N. robusta, we examined its type specimen and the result is presented below. Additionally, we discuss the occurrence of colour morphs in the Indian populations of N. pilipes.

A new species of Acrotaphus Townes (Hymenoptera: Ichneumonidae: Pimplinae) from the Brazilian Amazon, with notes on its host spider behavioral modification.

Some Ichneumonidae wasps, including the genus Acrotaphus Townes, 1960 (Ephialtini: Pimplinae), induce behavioral modification in their spider hosts. Acrotaphus is a New World parasitoid wasp genus with 26 described species. This genus belongs to the Polysphincta genus group, which are ectoparasitoids of spiders of the Araneidae. In this study, we describe a new species (Acrotaphus wagnerianae sp. n.) found in the Brazilian Amazon. In addition, we discuss for the first time the behavioral modification of spiders of the Wagneriana genus (Araneidae) by wasps of the Polysphincta genus group.

Sex differences in spiders: from phenotype to genomics.

Sexual reproduction is pervasive in animals and has led to the evolution of sexual dimorphism. In most animals, males and females show marked differences in primary and secondary sexual traits. The formation of sex-specific organs and eventually sex-specific behaviors is defined during the development of an organism. Sex determination processes have been extensively studied in a few well-established model organisms. While some key molecular regulators are conserved across animals, the initiation of sex determination is highly diverse. To reveal the mechanisms underlying the development of sexual dimorphism and to identify the evolutionary forces driving the evolution of different sexes, sex determination mechanisms must thus be studied in detail in many different animal species beyond the typical model systems. In this perspective article, we argue that spiders represent an excellent group of animals in which to study sex determination mechanisms. We show that spiders are sexually dimorphic in various morphological, behavioral, and life history traits. The availability of an increasing number of genomic and transcriptomic resources and functional tools provides a great starting point to scrutinize the extensive sexual dimorphism present in spiders on a mechanistic level. We provide an overview of the current knowledge of sex determination in spiders and propose approaches to reveal the molecular and genetic underpinnings of sexual dimorphism in these exciting animals.

Monophyly, Taxon Sampling, and the Nature of Ranks in the Classification of Orb-Weaving Spiders (Araneae: Araneoidea).

We address some of the taxonomic and classification changes proposed by Kuntner et al. (2019) in a comparative study on the evolution of sexual size dimorphism in nephiline spiders. Their proposal to recircumscribe araneids and to rank the subfamily Nephilinae as a family is fundamentally flawed as it renders the family Araneidae paraphyletic. We discuss the importance of monophyly, outgroup selection, and taxon sampling, the subjectivity of ranks, and the implications of the age of origin criterion to assign categorical ranks in biological classifications. We explore the outcome of applying the approach of Kuntner et al. (2019) to the classification of spiders with emphasis on the ecribellate orb-weavers (Araneoidea) using a recently published dated phylogeny. We discuss the implications of including the putative sister group of Nephilinae (the sexually dimorphic genus Paraplectanoides) and the putative sister group of Araneidae (the miniature, monomorphic family Theridiosomatidae). We propose continuation of the phylogenetic classification put forth by Dimitrov et al. (2017), and we formally rank Nephilinae and Phonognathinae as subfamilies of Araneidae. Our classification better reflects the understanding of the phylogenetic placement and evolutionary history of nephilines and phonognathines while maintaining the diagnosability of Nephilinae. It also fulfills the fundamental requirement that taxa must be monophyletic, and thus avoids the paraphyly of Araneidae implied by Kuntner et al. (2019).

Prey and predators perceive orb-web spider conspicuousness differently: evaluating alternative hypotheses for color polymorphism evolution.

Color polymorphisms have been traditionally attributed to apostatic selection. The perception of color depends on the visual system of the observer. Theoretical models predict that differently perceived degrees of conspicuousness by two predator and prey species may cause the evolution of polymorphisms in the presence of anti-apostatic and apostatic selection. The spider Gasteracantha cancriformis (Araneidae) possesses several conspicuous color morphs. In orb-web spiders, the prey attraction hypothesis states that conspicuous colors are prey lures that increase spider foraging success via flower mimicry. Therefore, polymorphism could be maintained if each morph attracted a different prey species (multiple prey hypothesis) and each spider mimicked a different flower color (flower mimicry hypothesis). Conspicuous colors could be a warning signal to predators because of the spider's hard abdomen and spines. Multiple predators could perceive morphs differently and exert different degrees of selective pressures (multiple predator hypothesis). We explored these 3 hypotheses using reflectance data and color vision modeling to estimate the chromatic and achromatic contrast of G. cancriformis morphs as perceived by several potential prey and predator taxa. Our results revealed that individual taxa perceive the conspicuousness of morphs differently. Therefore, the multiple prey hypothesis and, in part, the multiple predator hypothesis may explain the evolution of color polymorphism in G. cancriformis, even in the presence of anti-apostatic selection. The flower mimicry hypothesis received support by color metrics, but not by color vision models. Other parameters not evaluated by color vision models could also affect the perception of morphs and influence morph survival and polymorphism stability.

The complete mitochondrial genome of Argiope ocula (Araneae: Araneidae) and its phylogeny.

The complete mitochondrial genome of Argiope ocula (GenBank accession number MN331657) is a circular molecule of 14,079 bp in length, comprising of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), two ribosomal RNA genes, and a control region. Ten intergenic spacer regions and 19 reading frame overlaps were found in the mitogenome of A. ocula. Ten tRNAs (trnD, trnF, trnK, trnR, trnT, trnW, trnE, trnG, trnL1 , and trnM) lacked the TΨC arm stem, whereas three tRNAs (trnA, trnS1 , and trnS2 ) lost the dihydrouracil (DHU) arm. Phylogenetic analysis suggested that A. ocula had the closest evolutionary relationship with A. perforata.

The complete mitochondrial genome of an orb-weaver spider Araneus angulatus (Araneae: Araneidae).

The complete mitochondrial genome of an orb-weaver spider Araneus angulatus is 14,205 bp in length and contains 13 protein-coding genes, 2 ribosomal RNAs, 22 transfer RNAs, and a control region. The A + T content of the major strand is 75.4%. Nine of the protein-coding genes are initiated by typical ATN codons, one gene (COI) starts with TTA and other three genes (ND6, COII, and COIII) begin with TTG. The truncated stop codon (T) occurs in ND3, ND4L, and ND6, whereas the rest ten genes end with the canonical stop codon (TAA and TAG). Fifteen tRNAs lack the potential to form the typically cloverleaf-shaped secondary structure. The control region is 649 bp in length and contains a long tandem repeat region. The result of phylogenetic analysis shows that the relationship of A. angulatus was close to the species in the same family Araneidae.

Phonognatha vicitra Sherriffs, 1928-a taxonomic misidentification of the orb-weaving spider Acusilas coccineus Simon, 1895 (Araneae, Araneidae).

The species described as Phonognatha vicitra Sherriffs, 1928 is the only representative of the genus Phonognatha Simon, 1894 in India (World Spider Catalog 2018). The type locality of this species was a coffee estate named Charlotte estate/division, which is located adjacent to the Cauvery River in the Siddapura/ Sidapur village in the Kodagu (Coorg) district of the southwest Indian state of Karnataka (Sherriffs 1928). The species is still known from its original description, which is based on seven female specimens, and its male genitalia remained unveiled. For redescribing this species, we had visited the Charlotte estate/division and collected topotype materials of P. vicitra. However, while examining the materials, we found that the specimens from the Charlotte estate/division indeed belong to the South East Asian orb-weaving spider genus Acusilas Simon, 1895, indicating that Sherriffs misplaced his species in Phonognatha. In the present paper, we propose to transfer P. vicitra to Acusilas and synonymise it with Acusilas coccineus Simon, 1895.

Fitness implications of sex-specific catch-up growth in Nephila senegalensis, a spider with extreme reversed SSD.

BACKGROUND: Animal growth is often constrained by unfavourable conditions and divergences from optimal body size can be detrimental to an individual's fitness, particularly in species with determinate growth and a narrow time-frame for life-time reproduction. Growth restriction in early juvenile stages can later be compensated by means of plastic developmental responses, such as adaptive catch-up growth (the compensation of growth deficits through delayed development). Although sex differences regarding the mode and degree of growth compensation have been coherently predicted from sex-specific fitness payoffs, inconsistent results imply a need for further research. We used the African Nephila senegalensis, representing an extreme case of female-biased sexual size dimorphism (SSD), to study fitness implications of sex-specific growth compensation. We predicted effective catch-up growth in early food-restricted females to result in full compensation of growth deficits and a life-time fecundity (LTF) equivalent to unrestricted females. Based on a stronger trade-off between size-related benefits and costs of a delayed maturation, we expected less effective catch-up growth in males. METHODS: We tracked the development of over one thousand spiders in different feeding treatments, e.g., comprising a fixed period of early low feeding conditions followed by unrestricted feeding conditions, permanent unrestricted feeding conditions, or permanent low feeding conditions as a control. In a second experimental section, we assessed female fitness by measuring LTF in a subset of females. In addition, we tested whether compensatory development affected the reproductive lifespan in both sexes and analysed genotype-by-treatment interactions as a potential cause of variation in life-history traits. RESULTS: Both sexes delayed maturation to counteract early growth restriction, but only females achieved full compensation of adult body size. Female catch-up growth resulted in equivalent LTF compared to unrestricted females. We found significant interactions between experimental treatments and sex as well as between treatments and family lineage, suggesting that family-specific responses contribute to the unusually large variation of life-history traits in Nephila spiders. Our feeding treatments had no effect on the reproductive lifespan in either sex. DISCUSSION: Our findings are in line with predictions of life-history theory and corroborate strong fecundity selection to result in full female growth compensation. Males showed incomplete growth compensation despite a delayed development, indicating relaxed selection on large size and a stronger trade-off between late maturation and size-related benefits. We suggest that moderate catch-up growth in males is still adaptive as a 'bet-hedging' strategy to disperse unavoidable costs between life-history traits affected by early growth restriction (the duration of development and adult size).

Two new species of orb-weaving spiders of the genus Larinia (Araneae, Araneidae) in meridional Brazil.

The araneid genus Larinia Simon currently includes 56 species, eleven of them with New World distribution (World Spider Catalog, 2016). North American species of the genus were revised first time by Levi (1975) and South American species by Harrod et al. (1991). According to these authors there are four species known from subtropical South America (Larinia bivittata Keyserling 1885; L. montecarlo (Levi, 1988); L. t-notata (Tullgren, 1905); L. tucuman Harrod, Levi & Leibensperger, 1991) and also four species known from tropical South America (L. ambo Harrod, Levi & Leibensperger, 1991; L. directa (Hentz, 1847); L. lampa Harrod, Levi & Leibensperger, 1991; L. neblina Harrod, Levi & Leibensperger, 1991). According to Buckup et al. (2010) a total of 209 species of Araneidae are recorded for state of Rio Grande do Sul, including the three species L. bivittata, L. montecarlo and L. t-notata.

Eavesdropping on cooperative communication within an ant-butterfly mutualism.

Signalling is necessary for the maintenance of interspecific mutualisms but is vulnerable to exploitation by eavesdropping. While eavesdropping of intraspecific signals has been studied extensively, such exploitation of interspecific signals has not been widely documented. The juvenile stages of the Australian lycaenid butterfly, Jalmenus evagoras, form an obligate association with several species of attendant ants, including Iridomyrmex mayri. Ants protect the caterpillars and pupae, and in return are rewarded with nutritious secretions. Female and male adult butterflies use ants as signals for oviposition and mate searching, respectively. Our experiments reveal that two natural enemies of J. evagoras, araneid spiders and braconid parasitoid wasps, exploit ant signals as cues for increasing their foraging and oviposition success, respectively. Intriguingly, selection through eavesdropping is unlikely to modify the ant signal.