Beyond Venom and Constriction: Bite Performance and Trophic Ecology in the Genus Drymarchon

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  Beyond Venom and Constriction: Bite Performance and Trophic Ecology in the Genus Drymarchon Abstract Snakes exhibit extreme cranial kinesis that facilitates ingestion of prey with large cross-sectional area, but this ability is widely predicted to reduce bite performance due to decreased structural rigidity. Consequently, most large-bodied snakes rely on envenomation or constriction to subdue prey prior to ingestion. Species within the genus Drymarchon represent a notable exception: these large, non-venomous, non-constricting snakes routinely consume a wide range of prey, including large and potentially dangerous vertebrates, using only simple seizing and pinioning behaviors. Here, we quantify bite performance in three species of Drymarchon ( D. corais, D. couperi, and D. melanurus ), examine morphological predictors of biting performance, compare biting pressure to constriction pressure in similarly sized snakes, and synthesize dietary records across the genus. Our results sh...

Polar bodies serve as a landmark for anteroposterior axis formation in spiders

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Polar bodies serve as a landmark for anteroposterior axis formation in spiders

Abstract

The early embryogenesis of many spiders involves the formation of a radially symmetric germ disc. While the cells of the rim of this germ disc develops into anterior structures, the center of the disc will form the posteriorly located segment addition zone of the embryo. Therefore, germ disc formation sets the anterior-posterior (AP) body axis of spider embryos. The early spider egg is a spherical structure with no apparent asymmetry. So far it is unclear if the placement of the germ disc is a predetermined or a stochastic process.
For this study, we have re-analyzed early spider embryogenesis and found a link between the position of the polar bodies and the formation of the germ disc. Using cell tracking and time-lapse recordings of live embryos injected with the live cell nuclear stain SPY555-DNA, we show that the germ disc forms opposite to the polar bodies. Our results suggest that germ disc formation in the common house spider Parasteatoda tepidariorum is not a stochastic but a pre-determined process. By analyzing germ disc formation in a basally branching cobweb spider and a curtain-web spider, we provide evidence that the initial process of germ disc placement might be conserved between araneomorph and mygalomorph spider species.
Wang, R., & Pechmann, M. (2025). Polar bodies serve as a landmark for anteroposterior axis formation in spiders. Developmental Biology. https://doi.org/10.1016/j.ydbio.2025.12.006