Adult female crickets,Gryllus texensis, maintain reproductive output after repeated immune challenges

Abstract

Both immunity and reproduction are thought to be energetically costly and therefore likely to make trade-offs with one another. To assess whether increasing immune system activity results in a decline in egg production, the immune system in the cricket Gryllus texensis is activated over a period of 12 days with regular injections of lipopolysaccharide (LPS) derived from Serratia marcescens , and the number of eggs laid during this time counted. Egg quality is also assessed by measuring total protein of eggs laid, fertilization and hatching success, and the weight of individual eggs laid after the series of injections. Indirect evidence suggests that LPS induces an immune response in G. texensis . However, the number of eggs produced is not affected. There is also no effect of repeated LPS injections on female weight, egg protein content, or fertilization and hatching success. Taken together, these results suggest that with food and water provided ad libitum , females can protect many aspects of fitness in the face of increased immune system activity. However, there is some evidence to suggest that large (100 g) doses of LPS lead to reduced female longevity, and also in egg weight that could affect offspring success. Although the possibility exists that the decline in lifespan and egg weight after high-dose injections reflects a trade-off between reproduction and immune investment, another possibility is that these doses yield nonspecific effects, or that the high-dose induces an overwhelming immune response that leads to self-damage.

Some like it hot: the effects of climate change on reproduction, immune function and disease resistance in the cricketGryllus texensis

“…These observations underscore the necessity of distinguishing between immune function activities and disease resistance (Adamo, 2004b;Adamo, 2009). At typical environmental temperatures, increased egg production does not suppress immune function (Shoemaker et al, 2006a); nor does a bacterial immune challenge result in a decline in egg output in G. texensis, at least in the short term (Shoemaker et al, 2006b;Shoemaker and Adamo, 2007). Similarly, implanting a nylon filament does not reduce egg laying in another female cricket, Acheta domesticus (Bascunan-Garcia et al, 2010), for 2weeks after the implant.…”

“…Female crickets store mature eggs in their lateral oviducts, and initially the increase in egg laying could have occurred by laying stored eggs (Shoemaker and Adamo, 2007). However, to maintain increased egg laying for 6days would require increased egg production (Shoemaker and Adamo, 2007). Therefore, the increase in egg output at 33°C appears to reflect increased reproductive effort.…”

“…These results also suggest that increases in egg laying due to increased temperature do not come at the expense of egg quality. Female crickets store mature eggs in their lateral oviducts, and initially the increase in egg laying could have occurred by laying stored eggs (Shoemaker and Adamo, 2007). However, to maintain increased egg laying for 6days would require increased egg production (Shoemaker and Adamo, 2007).…”

“…There is also evidence that immune system activation is costly in this cricket (Shoemaker and Adamo, 2007). Immune challenge usually reduces female reproduction in insects (Reaney and Knell, 2010 and references therein), however, under normal temperatures, there is little evidence for trade-offs between reproduction and immune function in female G. texensis (Shoemaker et al, 2006a;Shoemaker et al, 2006b;Shoemaker and Adamo, 2007). Therefore, it is possible to use this species to test whether such trade-offs are induced at higher temperatures.…”

The behavioural effects of predator-induced stress responses in the cricket (Gryllus texensis): the upside of the stress response

“…Such metabolic costs are not trivial for small animals. For females, the amount of lipid mobilized during a stress response ) is equivalent to 1.4% of the resources in an egg (see Shoemaker and Adamo, 2007). When resources are scarce, additional demands decrease reproduction in this species (Adamo and Lovett, 2011).…”