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...

Food availability influences adult body mass variability and reproductive traits in a spider

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Food availability influences adult body mass variability and reproductive traits in a spider

Abstract

All animals require food to survive, grow, reproduce, and thus optimize fitness in nature. Food availability can profoundly affect demographic parameters such as longevity and fecundity. Here, we compared reproductive parameters in the false widow spider, Steatoda grossa (Araneae, Theridiidae), when the availability and size of prey (the house cricket, Acheta domesticus) were manipulated. Adult mated female spiders that were fed weekly (constant prey treatment) produced more progeny during their lifetime than females fed every 3 weeks (intermittent prey treatment). Furthermore, the monitoring of fecundity schedules showed that over the first 10 egg sacs, the mean number of neonate spiderlings per egg sac was around 40% higher in constantly fed than intermittently fed spiders. Time intervals between egg sac productions were generally higher when prey availability was lower. Some females lost more than 50% of their body mass after the production of the first egg sac, although reproductive investment tended to decrease thereafter. The amount of prey offered to females significantly affected mass gain between reproductive events, but fewer progeny were produced by females per egg sac, as well as cumulatively over the first three egg sacs, when they were only fed small prey. Starved females that had not produced egg sacs in several months exhibited total reproductive recovery when fed. Our results demonstrate the importance of prey attributes on S. grossa reproduction. Furthermore, females invest remarkably large amounts of resources during each reproductive cycle and over the course of a lifetime.

Dong, Y., Gols, R. & Harvey, J.A. Food availability influences adult body mass variability and reproductive traits in a spider. Oecologia 207, 179 (2025). https://doi.org/10.1007/s00442-025-05818-w