Microbiomes and Specific Symbionts of Social Spiders: Compositional Patterns in Host Species, Populations, and Nests

Abstract

Social spiders have remarkably low species-wide genetic diversities, potentially increasing the relative importance of microbial symbionts for host fitness. Here we explore the bacterial microbiomes of three species of social Stegodyphus (S. dumicola, S. mimosarum, and S. sarasinorum), within and between populations, using 16S rRNA gene amplicon sequencing. The microbiomes of the three spider species were distinct but shared similarities in membership and structure. This included low overall diversity (Shannon index 0.5-1.7), strong dominance of single symbionts in individual spiders (McNaughton's dominance index 0.68-0.93), and a core microbiome (>50% prevalence) consisting of 5-7 specific symbionts. The most abundant and prevalent symbionts were classified as Chlamydiales, Borrelia, and Mycoplasma, all representing novel, presumably Stegodyphus-specific lineages. Borrelia-and Mycoplasma-like symbionts were localized by fluorescence in situ hybridization (FISH) in the spider midgut. The microbiomes of individual spiders were highly similar within nests but often very different between nests from the same population, with only the microbiome of S. sarasinorum consistently reflecting host population structure. The weak population pattern in microbiome composition renders microbiome-facilitated local adaptation unlikely. However, the retention of specific symbionts across populations and species may indicate a recurrent acquisition from environmental vectors or an essential symbiotic contribution to spider phenotype.

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

“…The gut microbiome plays important roles in several spider traits, and recent studies have shown that spiders are hosts to many types of endosymbionts (Zhang et al, 2018b). Furthermore, it has been established that spiders on the same web are characterized by a very similar microbial richness, whereas differences in the microbial compositions are more pronounced among spiders on different webs (Busck et al, 2020). Kumar et al (2020) found that the gut microbiota in the Oxyopidae and Thomisidae spider families not only metabolize fatty acids and sugars but are also involved in the synthesis of vitamins.…”

An antimicrobial Staphylococcus sciuri with broad temperature and salt spectrum isolated from the surface of the African social spider, Stegodyphus dumicola

“…Isolation In total ve distinct morphotypes appeared on plates after 2-3 days, with milky-white, circular colonies as the dominant type. Cells of these colonies were Gram-positive cocci, 0.7 to 1.2 µm in diameter, non-motile and non-sporeforming, and occurred singly or in pairs; their partial 16S rRNA gene sequence represented an ASV found in 35% of all sequenced spiders of a previous study (Busck et al, 2020). was 100% identical to S. sciuri.…”

“…In a previous study, 16S rRNA gene amplicon sequencing of three social spider species revealed that the spider microbiomes were dominated by a few speci c endosymbionts but amplicon sequence variants (ASVs) indicative of spider surface microbes were also detected (Busck et al, 2020). We therefore aimed at isolating and characterizing putative symbiotic bacteria from the surface of social spiders.…”

“…We therefore aimed at isolating and characterizing putative symbiotic bacteria from the surface of social spiders. One isolate, i1, had 100% 16S rRNA gene sequence identity to an ASV found in 35% of all spiders, mostly with low relative abundance (< 1%) but occasionally as high as 48%, and classi ed as Staphylococcus (Busck et al, 2020). Their broad distribution and sometimes high abundance in Stegodyphus spiders may indicate a (facultative) symbiotic relationship.…”

Antimicrobial Compounds in the Volatilome of Social Spider Communities

“…The nest microbiomes of S. dumicola were shown to differ significantly between different sampling sites, even though there is a core microbiome on genus level ( Nazipi et al, 2021 ). A study investigating the spider microbiome of S. dumicola (endo- and exosymbionts) showed significant differences even between spiders from different nests from the same sampling site ( Busck et al, 2020 ). Therefore, differences of the nest and spider microbiomes between the different geographic sites might contribute to the differences between the volatilomes found in the present study.…”