Life-history of the parthenogenetic oonopid spider, Triaeris stenaspis (Araneae: Oonopidae)

Abstract

Abstract. Selected life-history traits of an oonopid spider, Triaeris stenaspis Simon, which has been introduced into greenhouses in Europe, were investigated. Spiders were reared in the laboratory under constant physical and dietary conditions, and followed from egg to death. The spiders passed through 3 juvenile instars, each lasting approximately a month. The adult stage lasted on average 6 months, which is 54% of the entire life cycle. The mortality in each juvenile instar was similar. Five morphological characters were recorded for each instar, which provided a reliable means of identifying the developmental stages. All spiders developed into females and although kept isolated they laid fertile eggs, which indicates thelytokous parthenogenesis. Eggs were always enclosed in a disc-shaped egg-sac, each containing 2 eggs. Total fecundity was on average 27 eggs and rate of laying eggs decreased with age. Fecundity was positively correlated with adult longevity. Fertility was rather low, approximately 59%. It was negatively correlated with fecundity but not related to longevity. Low fertility appears to be the only cost of parthenogenetic reproduction. There was considerable genotypic variation in all traits studied compared to that in sexually reproducing spiders. There were no apparent maternal effects on all the traits studied. Using molecular methods proved that parthenogenesis in T. stenaspis is not induced by the endosymbiotic bacteria,

Got Males?: The Enigmatic Goblin Spider GenusTriaeris(Araneae, Oonopidae)

“…Within a few years, additional specimens were found in the greenhouses of the Muséum National d'Histoire Naturelle in Paris (Simon, 1896), and also in greenhouses in Ireland (Jackson, 1909; O. P. -Cambridge, 1909). Today, numerous greenhouse populations of the species appear to be well established in various European countries, including Finland (Koponen, 1997) and Germany (Kielhorn, 2008), and a population found in Brno, Czech Republic, has been shown to be parthenogenetic (Korenko et al, 2009). It is possible that all the populations of the species are parthenogenetic, as no males appear ever to have been taken together with any of the 1,600 female specimens recorded below.…”

Ecology of Arachnida alien to Europe

“…There was a considerable genotypic variation found in life history traits (fecundity, fertility, longevity), comparable with traits found in sexually reproducing spider species (Korenko et al 2009b). A single cost of parthenogenesis was recognised, i.e., low fertility amounting to 60%.…”

“…Later, thelytokous parthenogenesis was proved in this species as all laboratory reared spiders developed into females and these, although kept isolated, laid fertile eggs (Korenko et al 2009b). It is not known whether T. stenaspis is parthenogenetic also in its native range, in the Caribbean, as the male of this species has not been found yet (Platnick 2011), but as females of T. stenaspis possess fully developed copulatory organs (Korenko et al 2007), this indicates that parthenogenesis might be only a recent apomorphy of populations expanding outside their native range.…”

“…Eggs are laid in pairs. The lifetime fecundity of females is on average 27 eggs (Korenko et al 2009b).…”

The Goblin Spider Genus Heteroonops (Araneae, Oonopidae), With Notes on Oonops

“…There are a few widespread, pantropical species of oonopids, and at least in the case of Triaeris stenaspis Simon (1891), also initially described from St. Vincent, and for which only females are known, parthenogenesis has now been demonstrated in the laboratory (Korenko et al, 2009). However, other pantropical oonopids, such as the three species treated by Platnick and Dupérré (2009), have normal sex ratios and have apparently attained their widespread distributions at least partly because of synanthropic habits, not because they are parthenogenetic.…”