Diversity and Function of Wolf Spider Gut Microbiota Revealed by Shotgun Metagenomics

Wolf spiders (Lycosidae) are crucial component of integrated pest management programs and the characteristics of their gut microbiota are known to play important roles in improving fitness and survival of the host. However, there are only few studies of the gut microbiota among closely related species of wolf spider. Whether wolf spiders gut microbiota vary with habitats remains unknown. Here, we used shotgun metagenomic sequencing to compare the gut microbiota of two wolf spider species, Pardosa agraria and P. laura from farmland and woodland ecosystems, respectively. The results show that the gut microbiota of Pardosa spiders is similar in richness and abundance. Approximately 27.3% of the gut microbiota of P. agraria comprises Proteobacteria, and approximately 34.5% of the gut microbiota of P. laura comprises Firmicutes. We assembled microbial genomes and found that the gut microbiota of P. laura are enriched in genes for carbohydrate metabolism. In contrast, those of P. agraria showed a higher proportion of genes encoding acetyltransferase, an enzyme involved in resistance to antibiotics. We reconstructed three high-quality and species-level microbial genomes: Vulcaniibacterium thermophilum, Anoxybacillus flavithermus and an unknown bacterium belonging to the family Simkaniaceae. Our results contribute to an understanding of the diversity and function of gut microbiota in closely related spiders.

Modest sexual size dimorphism and allometric growth: a study based on growth and gonad development in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae)

ABSTRACT Sexual size dimorphism (SSD) is a notable phenomenon in terrestrial animals, and it is correlated with unusual morphological traits. To date, the underlying sex-specific growth strategies throughout the ontogenetic stage of spiders are poorly understood. Here, we comprehensively investigated how the growth trajectories and gonad development shaped SSD in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae). We also hypothesized the potential growth allometry among the carapace, abdomen, and gonads of spiders in both sexes. By measuring the size of the carapace and abdomen, investigating developmental duration and growth rate, describing the gonadal sections, and calculating the area of gonads at all instars from hatching to maturity, we demonstrated that SSD results from sex-specific growth strategies. Our results indicated that the growth and developmental differences between both sexes appeared at early life stages, and there was allometric growth in the carapace, abdomen, and gonads between males and females.

Genomic Identification and Functional Analysis of JHAMTs in the Pond Wolf Spider, Pardosa pseudoannulata

Juvenile hormone (JH) plays a critical role in many physiological activities of Arthropoda. Juvenile hormone acid methyltransferase (JHAMT) is involved in the last steps of JH biosynthesis as an important rate-limiting enzyme. In recent studies, an increasing number of JHAMTs were identified in arthropods, but no JHAMT was reported in spiders. Herein, eight JHAMTs were identified in the pond wolf spider, Pardosa pseudoannulata, all containing the well conserved S-adenosyl-L-methionine binding motif. JHAMT-1 and the other seven JHAMTs were located at chromosome 13 and chromosome 1, respectively. Multiple alignment and phylogenetic analysis showed that JHAMT-1 was grouped together with insect JHAMTs independently and shared high similarities with insect JHAMTs compared to the other seven JHAMTs. In addition, JHAMT-1, JHAMT-2, and JHAMT-3 were highly expressed in the abdomen of spiderlings and could respond to the stimulation of exogenous farnesoic acid. Meanwhile, knockdown of these three JHAMTs caused the overweight and accelerated molting of spiderlings. These results demonstrated the cooperation of multi-JHAMTs in spider development and provided a new evolutionary perspective of the expansion of JHAMT in Arachnida.

Phylogenomic Variation at the Population-Species Interface and Assessment of Gigantism in a Model Wolf Spider Genus (Lycosidae, Schizocosa)

Animal body size has important evolutionary implications. The wolf spider genus Schizocosa Chamberlin, 1904 has developed as a model for studies on courtship, with visual and vibratory signals receiving attention; however, body size has never been carefully evaluated. Although species of Schizocosa can be distinguished from their close relatives by differences in genitalic structures, male ornamentation, and behavior, some species are morphologically similar, making diagnosis, and identification difficult. Evaluation of species boundaries using genetic data across Schizocosa is limited. The similar species S. maxima Dondale & Redner, 1978 and S. mccooki (Montgomery, 1904) are separated predominantly on the basis of size differences, with S. maxima being larger. We evaluate the evolution of size in these two Schizocosa species distributed in western North America, where gigantism of S. maxima is hypothesized to occur, particularly in California. We sampled subgenomic data (RADseq) and inferred the phylogeny of S. mccooki, S. maxima, and relatives. We apply a variational autoencoder machine learning approach to visualize population structuring within widespread S. mccooki and evaluate size within the context of a comparative phylogenetic framework to test the hypotheses related to genetic clustering of populations and gigantism. Our data show S. mccooki populations are not genealogically exclusive with respect to S. maxima. Likewise, S. maxima individuals are not recovered as a lineage and do not form an isolated genetic cluster, suggesting that the observed differences in size cannot be used to accurately delimit species. The cause of gigantism in S. maxima remains unexplained, but provides a framework for future studies of size variation and speciation.