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

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.