Gustatory adaptation affects sexual maturation in male German cockroaches, Blattella germanica

Abstract

Adaptations to hazardous environmental factors are essential for survival, although they may be maladaptive in conditions where the hazard is absent. In German cockroach (Blattella germanica L.) populations, glucose aversion has evolved rapidly in response to glucose-containing insecticidal baits, but little is known about the consequences of this behaviour in the absence of bait. In the present study, glucose-averse (GA) and wild-type (WT) male German cockroaches are restricted to a range of nutritionally defined diets containing either glucose or fructose as the sole carbohydrate source, and time to first expression of courtship is measured by stimulating the male antennae daily with isolated antennae from receptive, 6-day-old females. Glucose-averse males that are restricted to glucose-containing diets mature their courtship responses significantly later than GA males restricted to fructose-containing diets, whereas there is no difference in maturation of courtship responses between GA males restricted to fructose-containing diets and WT males restricted to diets containing either sugar type. Glucose-averse males furthermore respond later to GA female antennae than to WT female antennae, all from 6-day-old females. This suggests that GA females are less sexually stimulating, and the results are also consistent with earlier findings showing that GA females contain less developed oocytes than WT females at this age. These findings demonstrate that an adaptive gustatory mutation conferring protection from a toxin may have comparatively detrimental effects under conditions where the toxin has vanished, both by delaying female sexual maturation and signalling and by delaying male sexual maturation and courtship under conditions where glucose is a major energy source.

Diet quality affects bait performance in German cockroaches (Dictyoptera: Blattellidae)

“…These results add to a growing body of evidence that evolutionary shifts in diet breadth of cockroaches 20,29,30,38,39 may have downstream effects on life history characteristics such as sexual maturation 40 and courtship. 41 We suggest that glucose-averse cockroaches have evolved lower carbohydrate needs, an adaptation that may facilitate the persistence of glucose aversion in German cockroach populations in the absence of selection with glucose-containing baits.…”

Persistence of a sugar-rejecting cockroach genotype under various dietary regimes

“…In addition, we showed that newly eclosed adult GA females matured their oöcytes at a slower rate than WT females on the same laboratory diet, delaying the attainment of sexual receptivity42. Furthermore, in two recent studies we found that GA males had significantly smaller body mass than WT males developing on the same standard laboratory diet4344. Smaller body mass is often a disadvantage in sexual selection due to lower performance under male-male competition and female choice45.…”

“…In addition, delayed sexual maturation in male GA cockroaches that only had access to glucose-containing food43 may have influenced mating success of these males and given WT males a mating advantage from the start of the experiment. On glucose-free diets, GA and WT males reach sexual maturity at the same age43, and differences in male sexual maturation are therefore not likely to explain the changes in population structure.…”

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“…Beberapa laporan terkait resistensi perilaku pada kecoak Jerman adalah adanya perilaku glucose aversion/bait version (Silverman & Bieman, 1993), ditemukan 12% starin yang terdeteksi menghindari glukosa dari 41 strain yang diujikan di Malaysia (Lee & Soo, 2002), adanya reaksi menghindari glukosa dan fruktosa serta adaptasi gustatori kecoak Jerman pada populasi kecoak Jerman yang heterogen (Jensen et al, 2016;Jensen et al, 2017;Wang et al, 2004) Di Indonesia juga dilaporkan adanya potensi perkembangan perilaku glucose aversion/bait aversion pada beberapa strain kecoak Jerman (Ambarningrum et al, 2019).…”

“…Berdasarkan uji ketertarikan Kecoak Jerman terhadap fagostimulan berbeda, didapat hasil seperti tertera dalam tabel 1. (Jensen et al, 2016). Adanya sifat omnivora ini didorong dari kebutuhan nutrisi kecoak Jerman akan karbohidrat, lemak, dan protein yang tergolong tinggi, sehingga keempat fagostimulan diatas, dapat dijadikan sebagai bahan umpan (Lauprasert et al, 2006).…”