Residual vitellus and energetic state of wolf spiderlings Pardosa saltans after emergence from egg-sac until first predation

Abstract

The aim of this study was to evaluate energetic source used by juveniles of a terrestrial oviparous invertebrate during the earliest periods of their life. Growth, behavioural activities and energy contents of Pardosa saltans spiderlings' residual vitellus were monitored during 8 days after their emergence from their egg-sac until they disperse autonomously. The life-cycle of juvenile after emergence can be divided into three periods: a gregarious while juveniles are aggregated on their mother, dismounting off their mother's back and dispersion. We present the first biochemical study of residual vitellus and energy expenditure during these three periods. At emergence, the mean weight of juveniles was 0.59 mg and energy stock from residual vitellus averaged 51 cal/g wet mass. During gregarious period, the weight of the juveniles aggregated on their mother did not vary significantly and juveniles utilized only 1 cal/day from their residual vitellus. During the period from dismounting until their first exogenous feed, juveniles lost weight and used 30 % of their residual vitellus stock. Proteins from the residual vitellus contributed principally to their energy expenditure during this period: 1.5 µg protein/day. Juveniles' first exogenous feeding was observed 7-8 days after emergence, when 70 % of residual vitellus energy had been utilized. Juveniles dispersed after eating, reconstituting an energy stock comparable to that observed at emergence from egg-sac (50 cal/g wet mass). This new energy stock contains mainly lipids unlike the energy stock from the residual vitellus.

The effects of prey lipid on female mating and reproduction of a wolf spider

“…It seldom happens that the field-collected female spiders were deficient in protein ( Wilder 2011 ; Wilder et al 2013 ). In addition, proteins play an important role in promoting the growth of juvenile spiders ( Jensen et al 2011b ; Wilder 2011 ; Laino et al 2020 ), but adult spiders might not grow much in size and what an adult spider has to reserve may be lipids to meet the needs of metabolism and reproduction ( Jensen et al 2010 ; Wilder and Rypstra 2010 ; Romero et al 2018 ; Trabalon et al 2018 ), especially for a female spider that has a far higher input in reproduction than a male ( Lease and Wolf 2011 ; Wilder 2011 ). Thus, it can be inferred that P. milvina also benefits from the lipids in the high-quality diet to accelerate egg production.…”

“…For example, Wilder and Schneider (2017) found that juvenile offspring of female spiders Argiope bruennichi supplemented with essential amino acids survived longer than those with fatty acids. Meanwhile, protein contributed principally to the energy expenditure of juvenile wolf spiders Pardosa saltans during the period between dismounting off their mother’s back until their first exogenous feed ( Laino et al 2020 ). On the contrary, Anderson (1978) examined the energy content (positive correlation with lipid content) of eggs of 12 spider species from 6 families and found no correlation between energy content per unit egg mass and size of the female parent, egg size, or clutch size.…”

“…In terms of reproduction, Wen et al (2020) demonstrated that female H. graminicola fed fruit flies with high lipid throughout their life cycle substantially delayed their egg-laying but not fecundity . However, a number of biochemical analyses on several spider species during the reproductive stage indicated that lipids play an important role in reproduction ( Salomon et al 2008 ; Blamires 2011 ; Romero et al 2018 ; Laino 2020 ).…”