Physiological costs during the first maternal care in the wolf spider Pardosa saltans (Araneae, Lycosidae)

Abstract

Many arachnids like other terrestrial arthropods, provide extensive maternal care. Few studies have quantified the underlying physiological costs of maternal care. We investigated how maternal care affects the free-moving wolf spider's (Pardosa saltans) energy requirements. We described in detail their basic reproduction biology (i.e. carrying cocoon and young) and we evaluated the variation in the females' energy reserves during maternal care. Our results show that mothers guard eggs until hatching and then guard their spiderlings for 27-30 more days. Laboratory observations indicated that spiderlings start leaving the maternal abdomen gradually 5-7days after hatching. Females carry an egg sac (cocoon) that can weigh up to 77% of their post-reproduction weight and carry young that weigh 87-100% of their body mass. Females lost weight over time despite regular food intake, while carrying cocoon and young; but their weights increased gradually during the dispersal of young. The contributions of proteins, glucose and triglycerides to maintain females' energy were calculated. Their energetic state varied during maternal care, in particular lipid levels declined, during the care of spiderlings when the females' predatory behaviour was inhibited. Our results show that the maternal care provided by P. saltans females is particularly costly physiologically, during the 30days following egg sac formation and development of spiderlings, even when food is available.

Keywords: Biochemical status; Energetic cost; Lycosid; Maternal investment; Spider.