Reproductive biology of the neotropical harvestman (Goniosoma longipes) (Arachnida, Opiliones: Gonyleptidae): mating and oviposition behaviour, brood mortality, and parental care

Abstract

Goniosoma longipes is a neotropical cavernicolous harvestman that exhibits parental care. Reproductive activity in G. longipes is more intense during the wet season. Mating lasts up to 3 min, and the whole oviposition process may take over 5 h. During oviposition the female may be reinseminated once or twice by the mating male. Females oviposit 60–210 eggs on the cave wall and guard egg batches for nearly 2 months, until the 1st-instar nymphs disperse. Four main factors can affect egg survival in G. longipes: dehydration, fungal attack, cannibalism, and interspecific predation. Frequency of fungal attack on egg batches was greater in the wet season and more intense near the river inside the study cave. Although egg-guarding by females failed to prevent fungal attack on eggs in G. longipes, the choice of a suitable oviposition site by the gravid female can reduce fungal attack within the cave habitat of this species. Guarding females successfully repel conspecific egg predators, but unguarded eggs are frequently consumed by adult and juvenile G. longipes, as well as cave crickets Strinatia sp. Field experiments in which females were removed from egg batches demonstrated that egg-guarding by the mother has an anti-predator role in G. longipes, with a significant positive effect on egg survival. Male G. longipes actively patrol their egg-guarding mates, and take over brood care for up to 2 weeks if the latter are experimentally removed. The degree to which male assistance can play a relevant role in parental care is still unclear for this species. Damage to the brood is regarded as a major force favouring the evolution of parental care in harvestman species. This field study provides the first experimental demonstration that egg-guarding by females affords protection against egg predation in a harvestman species.