Sperm limitation erases fecundity advantages of large female size in an extremely size-dimorphic spider

Methods: We used adult females (n = 101) of Nephilingis cruentata, a spider where females are ~75× heavier than males (Kralj-Fišer et al., 2023). Individuals came from a laboratory population maintained at the Institute of Biology, ZRC SAZU (Ljubljana, Slovenia), which we established from wild-caught spiders collected in South Africa in 2015 and 2018 (permits OP 552/2015 and OP 3031/2020). We housed spiders individually in inverted transparent plastic cups (250 mL) with a cotton-plugged aperture for ventilation and water supply. Environmental conditions were standardized at 25 ± 2 °C under a 12:12 h light:dark photoperiod. We aimed to feed spiders ad libitum; juveniles received Drosophila spp. until the fourth moult, then blow flies until sexual maturity; adult females received three flies twice per week. Additional husbandry details follow (Kralj-Fišer et al., 2023) Once females reached sexual maturity (adulthood), we weighed them to the nearest 0.01 mg using a precision microbalance (KERN ABT-100-5NM), calibrated before each use, and mated each female once with a single male within three weeks. For mating, we transferred females to a 35 × 35 × 12 cm poly(methyl methacrylate) frame and allowed up to 7 days to build a web; we then introduced a male and left him until copulation occurred or for a maximum of 24 h. From 101 pairs, 88.1% copulated once (in one copulatory opening) and the remaining 12.9% copulated twice (in both copulatory openings). After mating, we monitored reproductive output five times per week. We collected egg-sacs within 48 h of oviposition, weighed, and then incubated them in ventilated 200 mL vials that were misted twice weekly until hatching. At hatching of the first egg-sac, we randomly selected 20 spiderlings and reared them to sexual maturity under the same conditions described above. We monitored females until their natural death. For each oviposition (egg-sac laying) we recorded the oviposition date, female mass after oviposition, and egg-sac mass and hatching success (viable vs. non‑viable). To quantify the probability of offspring reaching sexual maturity, thereafter offspring performance, we randomly selected 20 spiderlings from the first egg-sac at hatching and reared them to sexual maturity; we recorded the numbers reaching sexual maturity overall and by sex, i.e., daughters and sons. We also measured adult lifespan. Variables in dataset: variable description animal animal ID mass_ad0 body mass at maturity [g] N_copul number of copulations [1 / 2] date_mat date of mating date_egg date of oviposition (order 1-17) mass_egg mass of female after aviposition (order 1-17) [g] mass_ad mass of egg-sac (order 1-17) [g] adult lifespan time from reaching sexual maturity to natural death hatch hatching (order 1-17) [yes / no] eggs count of oviposited egg-sacs eggs_H count of viable egg-sacs oviposition period time from mating until last oviposition [days] viable oviposition period time from mating until last viable oviposition [days] post-oviposition period time from last oviposition until natural death [days] post-viable-oviposition period time from last viable oviposition until natural death [days] daughter number of daughters reaching sexual maturity from all together 20 hatchlings son number of sons reaching sexual maturity from all together 20 hatchlings offspring number of offspring reaching sexual maturity from all together 20 hatchlings