Female fecundity and offspring survival are not increased through sexual cannibalism in the spider Larinioides sclopetarius.

Many hypotheses explaining the evolution and maintenance of sexual cannibalism incorporate the nutritional aspect of the consumption of males. Most studies have focused on a fecundity advantage through consumption of a male; however, recent studies have raised the intriguing possibility that consumption of a male may also affect offspring quality. In particular, recent studies suggest prolonged survival for offspring from sexually cannibalistic females. Here, we measured the protein and lipid content of males compared to insect prey (crickets), quantified female nutrient intake of both prey types and finally assessed how sexual cannibalism affects female fecundity and spiderling quality in the orb-web spider Larinioides sclopetarius. We found no evidence that sexual cannibalism increased fecundity when compared to a female control group fed a cricket. Contrary to previous studies, spiderlings from females fed a male showed reduced survival under food deprivation compared to spiderlings from the control group. Offspring from females fed a male also tended to begin web construction sooner. The low lipid content of males compared to crickets may have reduced offspring survival duration. Whether additional proteins obtained through consumption of a male translate to enhanced silk production in offspring requires further investigation.

Comparative analysis of the macronutrient content of Central European ants (Formicidae): implications for ant-eating predators.

Prey nutrient quality determines predator performance. Polyphagous predators can address nutritional challenges by targeting prey with specific nutrient composition, but prey-specialised predators (e.g., ant-eaters), must obtain all nutrients from limited array of prey. Analysis of published data on prey specificity of European ant-eating spiders showed that some feed only on one ant genus, while others feed on several genera. Spiders feeding on several ant genera can possibly balance nutrient intake by selecting different ant prey. But monophagous species must extract all prey from a single prey species and can only vary nutrient intake by feeding on specific body parts. Most ant-eating spider species are catching Formica, Lasius and Messor ants, suggesting that these are most profitable ant species. We evaluated the nutritional content of a variety of 16 Central European ant species belonging to 11 genera and four subfamilies. We found that the nutritional composition, namely the amount of carbon, nitrogen and lipids, of European ants is heterogeneous. The largest variation in the amount of carbon and lipids was among ant subfamilies and species, while the largest variation in nitrogen was among ant genera. The largest amount of carbon and nitrogen was typical for Myrmicinae and the largest amount of lipids were typical for Formicinae. Within ants, the relative amounts of lipids were significantly higher in the gaster while the contents of carbon and nitrogen were highest in foreparts. Ant species did not cluster in the ordination space according to their taxonomic relationship or trophic strategy.

Maternal protein restriction before pregnancy reduces offspring early body mass and affects glucose metabolism in C57BL/6JBom mice.

Dietary protein restriction in pregnant females reduces offspring birth weight and increases the risk of developing obesity, type 2 diabetes and cardiovascular disease. Despite these grave consequences, few studies have addressed the effects of preconceptional maternal malnutrition. Here we investigate how a preconceptional low-protein (LP) diet affects offspring body mass and insulin-regulated glucose metabolism. Ten-week-old female mice (C57BL/6JBom) received either an LP or isocaloric control diet (8% and 22% crude protein, respectively) for 10 weeks before conception, but were thereafter fed standard laboratory chow (22.5% crude protein) during pregnancy, lactation and offspring growth. When the offspring were 10 weeks old, they were subjected to an intraperitoneal glucose tolerance test (GTT), and sacrificed after a 5-day recovery period to determine visceral organ mass. Body mass of LP male offspring was significantly lower at weaning compared with controls. A similar, nonsignificant, tendency was observed for LP female offspring. These differences in body mass disappeared within 1 week after weaning, a consequence of catch-up growth in LP offspring. GTTs of 10-week-old offspring revealed enhanced insulin sensitivity in LP offspring of both sexes. No differences were found in body mass, food intake or absolute size of visceral organs of adult offspring. Our results indicate that maternal protein restriction imposed before pregnancy produces effects similar to postconceptional malnutrition, namely, low birth weight, catch-up growth and enhanced insulin sensitivity at young adulthood. This could imply an increased risk of offspring developing lifestyle-acquired diseases during adulthood.

Maternal preconceptional nutrition leads to variable fat deposition and gut dimensions of adult offspring mice (C57BL/6JBom).

BACKGROUND: Maternal nutrition during pregnancy or lactation may affect the chance of offspring becoming obese as adults, but little is known regarding the possible role of maternal nutrition before conception. In this study, we investigate how variable protein and carbohydrate content of the diet consumed before pregnancy affects fat deposition and gut dimensions of offspring mice. METHODS: Eight-week-old female mice (C57BL/6JBom) were fed isocaloric low protein (8.4% protein; LP), standard protein (21.5% protein; ST) or high protein (44.2% protein; HP) diets. After 8 weeks of feeding, females were mated and fed a standard laboratory chow diet (22.5% protein) throughout periods of mating, gestation, lactation and weaning. Offspring mice were fed the same standard diet up to 46 days of age. Then offspring were killed and measures of dissected fat deposits and of the digestive system were taken. RESULTS: Fat deposition of the offspring was significantly affected by preconceptional maternal nutrition and the effects differed between sexes. Male offspring deposited most fat when mothers were fed the LP diet, whereas female offspring deposited most fat when mothers were fed the ST diet. The mass and length of the digestive organs were affected by preconceptional maternal nutrition. Total gut from pyloric sphincter to anus was significantly shorter and dry mass was heavier in mice whose mothers were fed LP diets compared with offspring of mothers fed ST diets or HP diets. There was no significant effect of maternal nutrition on dry mass of the stomach or ceca. CONCLUSION: Our study shows that preconceptional nutrition can have important influence on several body features of offspring in mice, including body composition and dimensions of the digestive system.

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

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.