Dietary and prey-capture adaptations by which Zodarion germanicum, an ant-eating spider (Araneae: Zodariidae), specialises on the Formicinae

Abstract

There has been considerable recent interest in the biology of spiders that specialise on ants as prey, but previous studies have tended to envisage the level of adaptation as being to ants as a group. In this paper, we provide evidence that Zodarion germanicum is a spider that has dietary and venom adaptations by which it targets a particular subset of ants, the subfamily Formicinae. We reared spiders from first instar in the laboratory on three different diets: formicine ants only, myrmicine ants only and mixed (both formicine and myrmicine ants). Fitness-related life-history parameters were determined, and we found that the spiders on the formicine-only diet lived longer and grew at a faster rate. Lipid, carbon and nitrogen compositions of ants were analysed, but we found no evidence of formicines differing from myrmicines in macro-nutrient content. This suggests that effects on longevity and growth depended on more specific nutrients or on compounds the prey uses for defence. We investigated how efficient Z. germanicum was at paralysing different ants and our findings suggest that the spider's venom is especially effective against formicines. Taken together, our findings suggest that Z. germanicum has evolved specialisation at the level of targeting a particular ant subfamily, the Formicinae.

Spiders (Araneae) of Hůrka u Hranic National Nature Reserve (Moravia, Czech Republic)

“…Occurrence of this species is closely associated with ants (Pekár et al, 2008). Occurrence of this species was already published from the region by Majkus (1988) from the Obora NM.…”

Eating chemically defended prey: alkaloid metabolism in an invasive ladybird predator of other ladybirds (Coleoptera: Coccinellidae)

“…High metabolic specificity might be expected to lead to strong genetic trade-offs in the tolerance of different prey defensive chemicals, leading to a higher degree of prey specialisation. The limited evidence relating to prey chemistrybased trade-offs in invertebrate predators is mixed (Albuquerque et al, 1997;Sadeghi and Gilbert, 1999;Pekár et al, 2008), and in aphidophagous ladybirds such trade-offs have been suggested to be of limited importance compared with trade-offs related to prey capture, notably body size (Sloggett, 2008a, Sloggett, 2008b. Clearly additional work is required to link metabolic tolerance and the role of trade-offs in predators.…”

Innate prey preference overridden by familiarisation with detrimental prey in a specialised myrmecophagous predator

“…The optimal prey was assumed to achieve the highest fitness, while detrimental prey was assumed to achieve the lowest fitness. In our previous study, in which we reared myrmecophagous spider specialist on different diets (Pekár et al 2008;Pekár and Toft 2009), we revealed that spiders achieved very low fitness (measured as survival, rate of development and body size) on alternative prey (Drosophila melanogaster Meigen flies), high fitness on ants form the alternative subfamily and the highest fitness on ants from the subfamily they specialise on. Thus, here, we used D. melanogaster flies as a representative of the detrimental prey and Messor structor Latreille (Formicidae: Myrmicinae) ants as representatives of optimal prey.…”

“…Alternative prey has been shown to have negative effects on their fitness (e.g. Hauge et al 1998;Pekár et al 2008). Thus, specialists have adapted to recognise a narrow range of cues (Dukas and Kamil 2001;Powell and Wright 1991).…”

“…Such preference should be irreversible so that familiarisation with alternative prey encountered on the way is unlikely. Otherwise, olfactory familiarisation with abundant alternative prey could bias innate preference and lead to lowered fitness as has been shown for a few specialised predators reared on alternative prey (Pekár et al 2008;Li and Jackson 1997).…”