A further new species for the genus Ananteris Thorell, 1891 (Scorpiones: Ananteridae) from a poorly prospected region of Brazilian Amazonia

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  A further new species for the genus Ananteris Thorell, 1891 (Scorpiones: Ananteridae) from a poorly prospected region of Brazilian Amazonia Abstract  A new species of the genus Ananteris Thorell, 1891 is described from the region which today defines the ‘Reserva Biológica do Río Trombetas’ in the state of Pará, Brazil. The collection of the unique specimen, presently study, took place previously to the definition of this reserve, in a joint field trip with a team of the Instituto Brasileiro de Desenvolvimento Florestal (IBDF). Ananteris antoni sp. n. is described based on one female specimen collected in a zone of dense humid forest, under death log. With this new description, the number of Ananteris species known for the scorpion fauna of Brazil is now raised to 33. Lourenço W. R., 2026. – A further new species for the genus Ananteris Thorell, 1891 (Scorpiones: Ananteridae) from a poorly prospected region of Brazilian Amazonia. Faunitaxys, 14(63): 1 – 5.  https://doi.o...

The role of male body size in mating success and male–male competition in a false widow spider

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The role of male body size in mating success and male–male competition in a false widow spider

In many animals, body size is correlated with reproductive success. Selection sometimes generates striking differences in body size between males and females (i.e. sexual size dimorphism, SSD). SSD is common in spiders (Araneae) and is typically explained by selection for larger, more fecund females and rapidly maturing, and consequently smaller, males. Within a species males and females also often vary in body size. In the false widow spider, Steatoda grossa, females are larger than males and males trade body size for rapid development and early maturation. Moreover, males vary considerably in body size, suggesting that under certain conditions there may be advantages to large size. Here, we tested the role of male body size on mating success under noncompetitive and competitive mating conditions (i.e. male–male competition) in S. grossa. We found that body size did not influence mating success or copulation duration under noncompetitive conditions, but that larger males were more successful at obtaining access to females under competitive mating conditions. Additionally, we found that total copulation duration was significantly lower when a rival male was present. Our results show a large male advantage under male–male competition, which we suggest may contribute to the high variation in male body size observed in S. grossa. We further suggest that the reduced copulation duration observed under competitive mating conditions may have potential ramifications for male and female reproductive success and we discuss how patterns of selection acting on male body size might limit the extent of SSD in this species.

Yuting Dong, Jeffrey A. Harvey, Robin Steegh, Rieta Gols, Melissah Rowe, The role of male body size in mating success and male–male competition in a false widow spider, Animal Behaviour, Volume 206, 2023, Pages 53-59, ISSN 0003-3472, 
https://doi.org/10.1016/j.anbehav.2023.09.011.