The largest fossil of the segmented spider Parvithele muelleri Wunderlich, 2017 (Mesothelae: Parvithelidae) from Cretaceous Burmese amber

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  The largest fossil of the segmented spider Parvithele muelleri Wunderlich, 2017 (Mesothelae: Parvithelidae) from Cretaceous Burmese amber Abstract A new specimen of the fossil spider Parvithele muelleri Wunderlich, 2017 (Araneae: Mesothelae) is described from the mid-Cretaceous (ca. 99 Ma) Burmese amber of Myanmar. Like the original holotype, the new specimen is a mature male, which clearly preserves a series of tibial macrospines, similar to the condition in the extant genus Liphistius Schiødte, 1849. Given that the single extant mesothele family, Liphistiidae, is predicted to have radiated ca. 39–58 million years ago, the occurrence of somewhat modern-looking male pedipalp spination in older fossil mesotheles is of considerable interest. The new specimen also shows spinnerets in a relatively posterior position, although variability observed in extant species suggests that this trait may be of limited systematic value. Of particular note is the presence of a large and well-dev...

Adoption behavior and physiological stress responses following offspring loss in Pardosa lugubris spider

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By Fritz Geller-Grimm - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1501346

Adoption behavior and physiological stress responses following offspring loss in Pardosa lugubris spider

Abstract

Parental care increases offspring survival and thus contributes to the reproductive success of a species. However, offspring loss may induce behavioral and physiological stress responses in parents. By examining stress markers—heat shock proteins and reactive oxygen species—alongside behavioral observations, we analyzed the stress responses in Pardosa lugubris females following the removal of their egg sacs or juveniles. Stress markers were measured in both females and juveniles. Behavioral trials were conducted to assess maternal responses to egg sac loss: unfertilized females, females adopting foreign egg sacs, and females given a choice between their own and a foreign sac. The results indicate that fertilized females tend to adopt egg sacs after offspring loss, even when the sac is not their own. Offspring removal induced measurable stress responses in both mothers and juveniles, which decreased over time. These findings highlight how offspring loss affects maternal behavior and stress physiology in Pardosa lugubris, offering insight into the mechanisms underlying parental investment and resilience in invertebrates.

Sawadro, M., Czerwonka, A., Łozowski, B., Glenszczyk, M., Porc, W., & Babczyńska, A. (2025). Adoption behavior and physiological stress responses following offspring loss in Pardosa lugubris spider. Scientific Reports. https://doi.org/10.1038/s41598-025-30418-2