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Abstract BackgroundSexual-size dimorphism (SSD) is replete among animals, but while the selective pressures that drive the evolution of SSD have been well studied, the developmental mechanisms upon which these pressures act are poorly understood. Ours and others’ research has shown that SSD inD. melanogasterreflects elevated levels of nutritional plasticity in females versus males, such that SSD increases with dietary intake and body size, a phenomenon called sex-specific plasticity (SSP). Additional data indicate that while body size in both sexes responds to variation in protein level, only female body size is sensitive to variation in carbohydrate level. Here, we explore whether these difference in sensitivity at the morphological level are reflected by differences in how the insulin/IGF-signaling (IIS) and TOR-signaling pathways respond to changes in carbohydrates and proteins in females versus males, using a nutritional geometry approach. ResultsThe IIS-regulated transcripts of4E-BPandInRmost strongly correlated with body size in females and males, respectively, but neither responded to carbohydrate level and so could not explain the sex-specific response to body size to dietary carbohydrate. Transcripts regulated by TOR-signaling did, however, respond to dietary carbohydrate in a sex-specific manner. In females, expression ofdILP5positively correlated with body size, while expression ofdILP2,3and8,was elevated on diets with a low concentration of both carbohydrate and protein. In contrast, we detected lower levels of dILP2 and 5 protein in the brains of females fed on low concentration diets. We could not detect any effect of diet ondILPexpression in males. ConclusionAlthough females and males show sex-specific transcriptional responses to changes in protein and carbohydrate, the patterns of expression do not support a simple model of the regulation of body-size SSP by either insulin- or TOR-signaling. The data also indicate a complex relationship between carbohydrate and protein level,dILPexpression and dILP peptide levels in the brain. In general, diet quality and sex both affect the transcriptional response to changes in diet quantity, and so should be considered in future studies that explore the effect of nutrition on body size.
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This content will become publicly available on December 1, 2026
The Effects of Diet on the Expression of Male Dimorphic Colouration and Weaponry in a Species of Neotropical Katydid
ABSTRACT Male alternative reproductive tactics are taxonomically widespread, with many species showing males with distinctly different phenotypic characters such as body size or weaponry. Several mechanisms can drive the expression of these male morphs, including genetic polymorphism or environmental interactions during development. In insects, multiple male morphs are common in several orders, including Coleoptera, Odonata, and Hymenoptera, but are rare in Orthoptera. This study establishes the presence of two male phenotypic morphs in the bush cricketSatizabalus jorgevargasi, a species in which the males display mandibular weaponry, and tests the effects of diet on the expression of male dimorphic characters. Male nymphs were raised under standard conditions until adulthood, whereupon morphological measurements were taken. Males raised under standard conditions showed two male phenotypes on the basis of head size and body colouration—a major morph with larger heads and more colouration, and a smaller and duller minor morph. A second group of male nymphs were housed individually and fed either a high‐protein diet or a high‐carbohydrate diet. Body weight and pronotum length were measured on a weekly basis as the nymphs developed, and once the males had matured, morphological and bioacoustic characters were measured. Diet had a significant impact on these male dimorphic characters, with protein‐fed males having significantly larger heads and mandibles. Additionally, males reared on the high‐protein diet had significantly more regions with colour when compared to carbohydrate‐fed males. Our data parallel that seen in other invertebrate groups, where higher levels of protein during maturation are key to the production of larger male morphs.
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- Award ID(s):
- 1937815
- PAR ID:
- 10657816
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 15
- Issue:
- 12
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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