Arthropoda

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).

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.

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.