Two new arthropod toxins purified from the venom of the Mexican scorpion Centruroides nigrescens

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  Two new arthropod toxins purified from the venom of the Mexican scorpion Centruroides nigrescens Abstract The venom of the slender black scorpion Centruroides nigrescens , from the State of Guerrero México, was fractionated by Sephadex G–50 gel filtration, followed by carboxymethyl cellulose ion separation and high–performance liquid chromatography, permitting to obtain two new peptides toxic to arthropods. The estimate LD 50 of the soluble venom for the insect Acheta domesticus was 11.1 μg/g body weight, and for the arthropod Armadillidium vulgare was 61.1 μg body weight . The amino acid sequence of toxin Cnige1 (toxic to A. domesticus and A. vulgare ) contains 65 amino acids, with a molecular mass of 7273.37 mass units, whereas toxin Cnige2, toxic to A. domesticus , contains 68 amino acids, with a molecular mass of 7548.81 units. Both peptides are well packed, containing 8 cysteines, which in the native venoms are forming 4 disulfide bridges each. The amino acid sequences f...

Hypothesis-driven biogeography to estimate rates and dates when fossil evidence is scarce: a case study using an ancient, Holarctic genus of spider (Araneae, Antrodiaetidae, Antrodiaetus)

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Hypothesis-driven biogeography to estimate rates and dates when fossil evidence is scarce: a case study using an ancient, Holarctic genus of spider (Araneae, Antrodiaetidae, Antrodiaetus)

Abstract

Understanding when lineages diverged is a common inquiry within the field of biogeography and often requires a rate of evolution and a means to calibrate the phylogeny to absolute time. While fossil evidence is the most common means regarding calibration, estimated molecular rates specific to the group in question are not as widespread. Furthermore, geological events can also be employed to calibrate a phylogeny, especially when lineages have a poor fossil record. In this paper, the effectiveness of employing biogeographic hypotheses to overcome a depauperate fossil record is tested in a group of spiders whose evolution is strongly affected by abiotic forces. Using a known biogeographic break, the fit of two competing biogeographic hypotheses (Ancient Vicariance vs. Inland Dispersal) is tested as calibration points for estimating an evolutionary rate and dates elsewhere across the tree. An optimized dataset of ultraconserved element (UCE) phylogenomic loci, which have been shown to be highly informative in mygalomorph spider systematics (i.e., tarantulas and trapdoor spiders), is employed. Hypothesis testing strongly supports Ancient Vicariance over Inland Dispersal, and phylogenetic inferences recover topological patterns predicted by Ancient Vicariance. Significantly, subsequent modeling proposes a novel estimate of ancient vicariance older than that of any other system observed across this biogeographic break. Finally, the modeling proposes divergence estimates among other Antrodiaetus species that correlate with previous hypotheses. This research broadens knowledge of mygalomorph evolutionary rates, answers questions about the evolutionary history of a relatively old lineage of folding-door spiders, Antrodiaetus (Antrodiaetidae, Mygalomorphae), and proposes a novel hypothesis for divergence times in the Pacific Northwest.

Ciaccio E, Hamilton CA (2026) Hypothesis-driven biogeography to estimate rates and dates when fossil evidence is scarce: a case study using an ancient, Holarctic genus of spider (Araneae, Antrodiaetidae, Antrodiaetus). Frontiers of Biogeography 19: e182722. https://doi.org/10.21425/fob.19.182722