Think and creat 3 independent questions from the reading. At least 1 of the questions must be a "higher-level" question that demonstrates in depth thinking and reasoning. A good format for these types

Original Article

Change in sex pheromone expression by

nutritional shift in male cockroaches

Kim Jensen, a,b,c Melanie Shearman, a James Rapkin, a Matthew R. Carey, a

Clarissa M. House, a,d and John Hunt a,d

aCentre for Ecology and Conservation, College of Life and Environmental Sciences, University of

Exeter, Tremough Campus, Penryn TR10 9FE, UK, bDepartment of Chemistry and Bioscience, Section

for Biology and Environmental Science, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg,

Denmark, cDepartment of Bioscience, Terrestrial Ecology, Aarhus University, Vejlsøvej 25, 8600

Silkeborg, Denmark, and dSchool of Science and Health, Western Sydney University, Locked Bag 1797,

Penrith, NSW 2751, Australia

Received 27 December 2016; revised 24 April 2017; editorial decision 26 July 2017; accepted 5 September 2017; Advance Access publication 12 September 2017.

Environmental conditions during sexual maturation impact sexual signal expression, but little is known about how individual histories

of changing environmental conditions affect the intensity of male sexual advertisement. We investigated the effects of shifting dietary

nutrient composition (protein vs. carbohydrates) in male Nauphoeta cinerea cockroaches on consumption, final lipid reserves, and sex

pheromone levels subsequent to completing sexual maturation on a specific diet, at high and low concentration of dietary nutrients.

Consumption, lipid reserves, and sex pheromone levels were highly affected by dietary nutrient composition with higher values on car -

bohydrate-biased diet, and males had significantly higher and lower levels of consumption, lipid reserves, and sex pheromones when

shifted to a carbohydrate-biased and a protein-biased diet, respectively, compared with males maintained on either initial diet through -

out the experiment. Males shifted to a carbohydrate-biased diet at high nutrient concentration fully recouped their sex pheromone

levels, attaining levels that were not significantly lower than those in males maintained on carbohydrate-biased diet at high nutrient

concentration throughout the experiment. Our study shows that male sexual display in N. cinerea is plastic and highly affected by pres -

ent as well as previous dietary conditions. Signaling of adaptive quality through male sex pheromones can therefore vary dynamically

within the early adult life of a male in response to the nutritional composition of food that is available to ingest. This contrasts morpho -

logical sexual traits in arthropods that are affected during development and are fixed at adulthood.

Key words : condition dependence, lipid reserves, Nauphoeta cinerea , nutrient balance, nutritional history, sexual signaling.

INTRODUCTION

The handicap theory of sexual selection predicts that male sexual

traits are costly to produce and maintain and therefore serve as reli -

able signals of male genetic quality ( Andersson 1994 ; Johnstone

1995b ; Hunt et al. 2004b ; Andersson and Simmons 2006 ).

According to this model, the magnitude of sexual trait expression

reflects the portion of resources that the male has been able to

allocate toward sexual investment, above and beyond that which is

needed to maintain his basic vital requirements ( Rowe and Houle

1996 ; Tomkins et al. 2004 ). For species that have to actively search

their environment for resources, these signals should express a com -

bination of how good the male is at locating resources, his com -

petitive abilities for accessing the resource, and how physiologically

efficient he is at utilizing ingested nutrients for basic requirements

thereby enabling a larger allocation to sexual display. In nature,

opportunistically foraging omnivores rarely live under constant

environmental conditions, yet studies investigating the effects of

condition on male sexual display have all been conducted under

constant conditions. Furthermore, most studies have manipulated

condition at the juvenile stage and measured performance in the

adults ( Rantala et al. 2003 ; Hunt et al. 2004a ; Ming and Lewis

2010 ; Weddle et al. 2012 ). In contrast, the effect of condition on

the plasticity of male sexual displays after reaching sexual matu -

rity has been little investigated. More specifically, it has not been

investigated how the history of shifting nutritional conditions on

reaching adulthood may affect the condition-dependent expression

of male sexual traits.

The quantity of male sex pheromones has been shown to influ -

ence male attractiveness to females in a range of arthropod species

(Johansson and Jones 2007 ; Ruther et al. 2009 ; Kelly et al. 2012 ;

Steiger and Stökl 2014 ; Ingleby 2015 ), and the expression of sex Address correspondence to J. Hunt. E-mail: [email protected] .

Behavioral Ecology (2017), 28(6), 1393–1401. doi:10.1093/beheco/arx120

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The Author 2017. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology.

The o cial journal of the

ISBE

International Society for Behavioral Ecology

Behavioral

Ecology

Edito s choice Behavioral Ecology

pheromones is found to be highly affected by nutritional conditions

during development and sexual maturation (e.g., ; Rantala et al.

2003 ; Ming and Lewis 2010 ; Weddle et al. 2012 ; Ingleby et al.

2013 ). For example, starved male beetles ( Tenebrio molitor ) produce

significantly lower levels of sex pheromones than fed individuals

(Rantala et al. 2003 ), and male Tribolium castaneum that develop on

diluted diets have lower sex pheromone levels than males develop -

ing on undiluted diets which causes lower attractiveness to females

(Ming and Lewis 2010 ). Furthermore, male decorated crickets

(Gryllodes sigillatus ) that consume a diet of higher nutritional quality

as a nymph show enhanced cuticular hydrocarbon (CHC) expres -

sion as adults ( Weddle et al. 2012 ), and in Drosophila simulans , both

larval diet and temperature during sexual maturation significantly

affected CHC expression in mature adults ( Ingleby et al. 2013 ).

Male lipid reserves often correlate with female preference and male

mating success ( Otronen 1995 ; Cotton et al. 2004 ; Tomkins et al.

2004 ), and lipids as well as dietary carbohydrates are fundamen -

tal components in the synthesis of sex pheromones in arthropods

(Chase et al. 1990 ; Schal et al. 1991 ; Foster and Anderson 2015 ).

However, very little is known about the exact nutrient(s) responsi -

ble for the observed effects of diet on sex pheromone expression.

Furthermore, the extent to which male sex pheromone expression

is a plastic trait that may change according to shifting nutritional

conditions after sexual maturation has not, to our knowledge, been

investigated.

Omnivorous animals are often found to regulate protein intake

more tightly than carbohydrate and lipid intake ( Sørensen et

al. 2008 ; Jensen et al. 2013 ). This includes a limited willingness

to ingest protein (P) in excess of requirements due to deleterious

effects of excessive P consumption. Cockroaches in particular tend

not to over-ingest P relative to their requirements ( Raubenheimer

and Jones 2006 ; Jensen et al. 2015 ), which is most likely linked to

a limited ability to excrete nitrogenous waste products as a conse -

quence of adaptation to low nitrogen availability ( Cochran 1985 ;

Mullins 2015 ). In the ovoviviparous cockroach Nauphoeta cinerea ,

the male sex pheromone blend consists of 3 major components:

2-methylthiazolidine (2MET), 4-ethyl-2-methoxyphenol (4E2M),

and 3-hydroxy-2-butanone (3H2B) ( Sréng 1990 ). Males with

increased amounts of all 3 components are more attractive to

females both at a distance and on contact ( Moore 1997 ; Moore and

Moore 1999 ). Expression of the 3 sex pheromones is affected by

temperature and food availability during sexual maturation ( Clark

et al. 1997 ), and more recent experiments have shown that nutrient

concentration and the specific balance of dietary P to carbohydrate

lipid reserves and sex pheromone expression ( South et al. 2011 ;

Bunning et al. 2016 ), as well as the attractiveness of male N. cinerea

to females. In particular, each of these male traits were shown to

increase with C intake but not P intake, being maximized at a P:C

ratio of 1:8 ( South et al. 2011 ; Bunning et al. 2016 ). These studies,

however, did not examine the effects of shifting male dietary nutri -

ent composition subsequent to sexual maturation.

In this study, we varied the specific nutritional history of newly

eclosed adult male N. cinerea in a factorial design of good (G;

C-biased) and bad (B; P-biased) dietary nutrient concentration in a

10-day temporal sequence (G →G, B →G, G →B, or B →B) at high

and low total macronutrient concentration. We measured the intake

of diet (and therefore nutrients) by males, as well as the degree of

lipid deposition and sex pheromone expression using gas chroma -

tography-mass spectrometry (GC-MS). Based on our previous work

showing that lipid deposition ( South et al. 2011 ) and pheromone

expression ( South et al. 2011 ; Bunning et al. 2016 ) are maximized

at a high intake of C and low intake of P, we predict that both

traits will be increased on a G diet and reduced on a B diet. If

pheromone expression and lipid deposition are flexible and able

to respond rapidly to changes in the nutritional environment, we

predict that the expression of these traits will depend critically on

the order that G and B diets are consumed. We predict, however,

that the ability of males to recoup lipid reserves and pheromone

expression (relative to males on the G →G diet) is greater on diets

with high than on diets with low nutrient concentration. This will

be reflected as a significant interaction between nutritional history

and nutrient concentration on dietary consumption, lipid reserves,

and pheromone expression.

METHODS

Animals and housing

Individual N. cinerea were obtained from our mass culture consisting

of more than 200 000 cockroaches distributed across 10 plastic con -

tainers (50 cm × 35 cm × 30 cm), which are kept in an incubator at

28 ± 1 °C and a 14L:10D regime. The culture was maintained by

providing a cupful of pelleted rodent chow (Rat and Mouse No.1

Maintenance, Special Diet Services, Essex, UK) containing approx -

imately 12.92% digestible protein, 49.02% digestible carbohydrate,

2.47% digestible lipid, and 17.05% fiber, and 2 cotton-plugged

water tubes (3-cm diameter, 15-cm long) weekly to each container.

Individuals were transferred across containers at regular intervals

to maintain the culture as one large, genetically mixed population.

We established an isolated culture of male final instar nymphs from

the mass colony and provided ad libitum rat chow and water. Males

were allocated randomly to experimental treatments on their day

of eclosion to adulthood (see below). During the experiment, male

cockroaches were housed individually in transparent plastic con -

tainers (17 cm × 12 cm × 6 cm). The experiment was performed in

a constant temperature room at 28 ± 1 °C with a 14L:10D regime

similar to conditions in the mass colony.

Artificial diets

We produced 4 artificial diets differing in quality by varying the

dietary P:C ratio and total macronutrient concentration ( Table 1 ),

following the protocols of Simpson and Abisgold (1985) and Dadd

(1961) . These diets are identical to diets 2, 4, 22, and 24 in South

et al. (2011) and Bunning et al. (2015 , 2016 ). Diets with a good

nutritional balance contained a P:C ratio of 1:8, and diets with

a bad nutritional balance contained a P:C ratio of 5:1 ( Table 1 ).

Protein plus carbohydrate constituted 84% of diet dry mass at high

nutrient concentration and 36% of diet dry mass at low nutrient

concentration. High and low dietary macronutrient concentrations

were created by adding different ratios of crystalline α-cellulose

(Table 1 ), which functioned as a bulking agent. Because protein and

carbohydrate contain equal amounts of metabolizable energy ( FAO

2003 ; Buchholz and Schoeller 2004 ; Simpson and Raubenheimer

2012 ), the diets were isocaloric within each macronutrient concen -

tration. All diets in addition contained equal amounts of choles -

terol, linoleic acid, ascorbic acid, salt mixture, and vitamin mixture

(Table 1 ).

Experimental design

We used a 2-way factorial design to examine the effects of nutri -

tional history and total nutrient concentration on diet, nutrient and

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Jensen et al. • Sex pheromone expression and nutritional history

energy consumption, as well as on subsequent lipid reserves and sex

pheromone expression. Within each dietary nutrient concentration

(high and low), male cockroaches were allocated at random to 1

of 4 nutritional history regimes ( n = 30 males per regime, total n

= 240 males). Half of the cockroaches within each level of nutri -

ent concentration were provided with diet of either good (G; P:C

= 1:8) or bad (B; P:C = 5:1) nutrient composition for the first 10

days posteclosion: this represents the period of sexual maturation

in male N. cinerea . For each level of nutrient concentration, the diet

was then shifted to the opposite diet for half of the cockroaches

while the other half continued receiving the same diet for a further

10 days posteclosion. Within each total nutrient concentration, this

produced the following 4 nutritional history regimes: good nutrient

composition for all 20 days posteclosion (G →G), bad nutrient com -

position for 10 days then good nutrient composition for 10 days

posteclosion (B →G), good nutrient composition for 10 days then

bad nutrient composition for 10 days posteclosion (G →B), or bad

nutrient composition for all 20 days posteclosion (B →B). On day

20 posteclosion the cockroaches were killed by freezing at −80 °C.

Fresh diet and water was provided in ad libitum amounts every

5 days during the experiment. Diet was provided as a powder in

feeding platforms created by gluing an upturned plastic lid (1.6-cm

diameter, 1.0-cm deep) to the center of an inverted petri dish lid

(5.5-cm diameter, 0.5-cm deep). Water was provided in an upturned

plastic lid (2.0-cm diameter, 1.0-cm deep) glued to the center of a

petri dish bottom (5.4-cm diameter, 1.0-cm deep).

Measuring diet, nutrient, and energy

consumption

The dry mass of diet in each feeding platform was weighed before

and after each feeding period using an electronic balance (Ohaus

Explorer Professional, model EP214C). Before weighing, diets

were dried in a drying oven (Binder model FD 115, Tuttlingen,

Germany) at 30 °C for 48 h. Any feces were removed with a pair

of forceps before drying. Diet consumption was calculated as the

difference in diet dry mass before and after feeding. P and C intake

was calculated by multiplying dry mass consumption with the pro -

portion of each nutrient in the ingested diet. Energy intake was

calculated as the sum of energy ingested from each macronutrient

group, calculated as 16.7 J per mg of P and C eaten ( FAO 2003 ;

Buchholz and Schoeller 2004 ).

Measuring sex pheromones

To measure male sex pheromone expression, the sternum was dis -

sected from each male cockroach and blotted on tissue paper to

remove any lipid. The sternum was then completely submerged in

400 μL of HPLC grade dichloromethane containing an internal

standard ([E,Z]-4–7-tridecadienyl acetate) at 10 ng/ μL in a 1-mL

conical vial, and allowed to soak at room temperature for 2 h, after

which the sternum was removed. Using an autosampler (Agilent

7683B), 2 μL of the sample extract was injected into a DB-Wax

column (30 m × 0.25 mm × 0.25 μm film thickness) housed in an

Agilent 7890 GC coupled with an Agilent 5975 mass spectrometer

with helium as carrier gas. The inlet temperature was set at 200 °C

and the injection was in pulsed split less mode. After injection, the

column was held at 50 °C for 1.5 min before the temperature was

raised at a rate of 10 °C/min to 250 °C, with a final hold time of

2 min. The MS transfer line was set at 240 °C. The mass spectrom -

eter was operated in selected ion mode to limit the output to the

target compounds (2MET, 4E2M, and 3H2B), with analysis limited

to ions 45, 88, 103, 79, 107, 137, and 152. Samples were quantified

against a multilevel calibration curve that we prepared using solu -

tions containing the 3 target compounds at known concentrations.

Analytical grade (99% pure) 3H2B was purchased from Sigma–

Aldrich (St. Louis, MO), 4E2M was purchased from Pfaltz and

Bauer (Waterbury, CT), and 2MT was purchased from Endeavor

Specialty Chemicals (Daventry, UK).

Measuring lipid reserves

After removing the sternum for pheromone analysis, each cock -

roach was cut along the ventral side and dried at 60 °C for 48 h,

after which dry mass was weighed with an electronic balance. Lipids

were extracted by placing the dry cockroach in a sealed glass vial

containing 20 mL of a 2:1 solution of dichloromethane:methanol

and rotating the vial at 100 rpm for 48 h on an orbital shaker

(IKA-Werke, KS501 digital). Cockroaches were then removed from

Table 1

Ingredient compositions of the 4 artificial diets

Nutrient composition (nutrient concentration)

Ingredients (per 100 g) Good (high) Bad (high) Good (low) Bad (low)

Carbohydrate (g) a 74.67 14.00 32.00 6.00 Sucrose (g) 37.33 7.00 16.00 3.00 Dextrin (g) 37.33 7.00 16.00 3.00 Protein (g) b 9.33 70.00 4.00 30.00 Casein (g) 5.60 42.00 2.40 18.00 Peptone (g) 1.87 14.00 0.80 6.00 Albumin (g) 1.87 14.00 0.80 6.00 α-cellulose (g) 12.00 12.00 60.00 60.00 Cholesterol (g) 0.55 0.55 0.55 0.55 Linoleic acid (mL) 0.55 0.55 0.55 0.55 Ascorbic acid (g) 0.28 0.28 0.28 0.28 Salt mixture (g) c 2.50 2.50 2.50 2.50 Vitamin mixture (g) d 0.18 0.18 0.18 0.18

aIncludes sucrose and dextrin.bIncludes casein, peptone and albumin.cWesson’s salt mixture.dIncludes choline chloride (70.38%), meso-inositol (14.08%), nicotinic acid (5.63%), calcium pantothenate (2.82%), folic acid (1.41%), p-aminobenzoic acid (1.41%), pyridoxine (1.41%), riboflavin (1.41%), thiamine (1.41%), and biotin (0.06%). All percentages are mass based.

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Behavioral Ecology

the solution and their lean dry masses were weighed after drying

at 60 °C for 48 h. Lipid content was calculated by subtracting lean

dry mass from total dry mass and expressed as a percentage of the

initial dry mass of the cockroach (before lipid extraction) to control

for variation in the body size of males.

Statistical analysis

The data were analyzed in a 2-factor design with nutritional his -

tory regime and diet nutrient concentration as factors. Total diet

consumption, P intake, C intake, and energy intake were analyzed

using multivariate analysis of variance (Manova) with nutritional his -

tory, diet nutrient concentration, and their interaction as fixed effects.

This Manova was followed by univariate analysis of variance (Anova)

to determine which trait(s) contributed to any overall multivariate

effects and Fisher LSD post hoc analysis (at α = 0.05) was used to

determine which specific treatments differed significantly. Lipid

reserves (expressed as a percentage of initial dry body mass) and

the expression of 3H2B, 2MT, and 4E2M were analyzed using the

same Manova procedure followed by post hoc analyses. Within each

treatment, we determined if diet consumption differed significantly

between the 2 feeding periods using a paired t-test (at α = 0.05).

RESULTS

Diet, nutrient, and energy consumption

Nutritional history and diet nutrient concentration both signifi -

cantly affected the consumption of diet, specific nutrients (P and

C), and energy, and there was also a significant interaction between

these main effects ( Table 2 ). On average, males consumed more

diet when provided with the carbohydrate-biased diet (G) than

when provided with the protein-biased diet (B) irrespective of the

nutrient concentration of the diet ( Figure 1a ). Furthermore, males

provided with only G diet consumed significantly more diet, whear -

eas males provided only with B diet consumed significantly less diet

over the experiment than males with shifting diets at both nutrient

concentrations ( Figure 1a ). At both nutrient concentrations, males

shifted to a G diet after restriction to a B diet significantly increased

consumption in the second feeding period relative to the first,

approaching but not reaching the total consumption of males pro -

vided exclusively with the G diet ( Figure 1a ). Conversely, at both

nutrient concentrations, males shifted to the B diet after restriction

to G diet significantly reduced their diet consumption in the second

feeding period and thus approached (but again did not fully reach)

the low overall dietary consumption of males exclusively restricted

to B diet ( Figure 1a ).

Because much more G than B diet was consumed, there was a

high resemblance between total dietary consumption and C intake

(Figure 1b ) but no resemblance with P intake ( Figure 1c ). As the

diets were isocaloric within nutrient concentrations, energy intake

also resembled total nutrient consumption but with an obvious

lower energy intake on the diets with low nutrient concentration

(Figure 1d ). For diet consumption, C intake and energy intake, the

significant interaction term between nutritional history and nutri -

ent concentration occurs because the observed reduction in con -

sumption across the G →G, B →G, G →B, and B →B nutritional

history treatments was greater on diets with high than diets with

low nutrient concentration ( Figure 1a ,b,d). In the case of P intake,

the interaction between nutritional history and nutrient concentra -

tion occurs because the mean intake of P in the different nutri -

tional history treatments was highly affected by dietary nutrient

concentration ( Figure 1c ).

Lipid reserves and sex pheromone expression

We found highly significant effects of nutritional history and

dietary nutrient concentration, as well as the interaction between

these main effects, on the amount of lipid reserves ( Figure 2a ) and

on the expression of the three sex pheromones 3H2B ( Figure 2b ),

2MT ( Figure 2c ), and 4E2M ( Figure 2d ) (Table 3 ). At both nutri -

ent concentrations, lipid reserves, and quantities of 3H2B, 2MT,

and 4E2M were highest when males exclusively consumed the G

diet and lowest when males exclusively consumed the B diet ( Figure

Table 2

Manova and univariate Anova tests examining the effects of nutritional history of dietary nutrient composition (good →good, bad →good, good →bad, or bad →bad), dietary nutrient concentration (high or low), and their interaction on total diet consumption, carbohydrate (C) intake, protein (P) intake, and energy intake in the male Nauphoeta cinerea at 20 days posteclosion

Model term

Manova

Pillai’s trace F df P

Nutritional history 0.962 36.527 9696 0.0001 Nutrient concentration 0.912 795.857 3230 0.0001 History × concentration 0.770 26.691 9696 0.0001

Univariate Anova

Trait F df P

Nutritional history Consumption 83.345 3232 0.0001 C intake 181.633 3232 0.0001 P intake 59.995 3232 0.0001 Energy intake 74.115 3232 0.0001 Nutrient concentration Consumption 10.973 1232 0.0011 C intake 356.818 1232 0.0001 P intake 169.452 1232 0.0001 Energy intake 392.676 1232 0.0001 History × concentration Consumption 3.126 3232 0.0266 C intake 42.094 3232 0.0001 P intake 15.919 3232 0.0001 Energy intake 21.931 3232 0.0001

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Jensen et al. • Sex pheromone expression and nutritional history

Figure 1 Individual consumption (mean ± SE) of (a) diet, (b) carbohydrate, (c) protein, and (d) metabolizable energy by male Nauphoeta cinerea over 20 days posteclosion, according to nutritional history regime and dietary nutrient concentration. Calculations of ingested amounts of energy are based on a general metabolizable energetic value of 16.7 J per mg for both carbohydrate and protein ( FAO 2003 ; Buchholz and Schoeller 2004 ). Gray columns show intake on dietary treatments with high total nutrient concentration (84%), and white columns show intake from dietary treatments with low total nutrient concentration (36%). Different letters indicate significant differences (Fisher LSD test, P < 0.05). The sequence of G and B shows the sequential 10 day access to a diet with good (G; P:C = 1:8) or a bad (B; P:C = 5:1) nutrient composition. In (a), the second 10-day feeding period is stacked on top of the first, and error bars are for total consumption. The presence and location of the asterisk within each treatment indicates significantly larger consumption within the given feeding period than in the alternate feeding period (paired t-tests, P < 0.05).

(a)

(b)

(c)

(d)

3H2B ( g)

2MT ( g)

4E2M ( g)

D E

A A

C C C

A A

C C CD

A A

D C

Lipid reserves (%)

D D

High Low

Nutritional history

Figure 2 Individual (mean ± SE) (a) lipid reserves as a percentage of body dry mass, and amounts of the 3 sex pheromones (b) 3-hydroxy-2-butanone (3H2B), (c) 2-methylthiazolidine (2MT), and (d) 4-ethyl-2-methoxyphenol (4E2M) in the pheromone glands of male Nauphoeta cinerea at 20 days posteclosion, according to nutritional history and dietary nutrient concentration. Gray columns represent dietary treatments with high total nutrient concentration (84%), and white columns show dietary treatments with low total nutrient concentration (36%). Different letters indicate significant differences (Fisher LSD test, P < 0.05). The sequence of G and B shows the sequential 10 day access to a diet with either a good (G; P:C = 1:8) or a bad (B; P:C = 5:1) nutrient composition.

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Behavioral Ecology

2a–d ). As demonstrated by the significant interaction term between

nutritional history and nutrient concentration ( Table 3 ), the mag -

nitude of lipid reserves and pheromone levels relative to the G →G

and B →B treatments differed with nutrient concentration. At both

low and high nutrient concentration, lipid reserves, and pheromone

levels of males in the G →B treatment were significantly greater

than in males in the B →B treatment but significantly lower than

in males in the G →G treatment ( Figure 2a–d ). A similar pattern

for lipid reserves and pheromone levels was shown for males in the

B→G treatment when diets were of low nutrient concentration

(Figure 2a–d ). However, when diets in this treatment were of high

nutrient concentration, males had attained pheromone expression

at the same level as those which had exclusively consumed the G

diet ( Figure 2a–d ). Collectively, this demonstrates that males receiv -

ing a nutritionally imbalanced diet during sexual maturation are

able to partially restore their lipid reserves and fully restore phero -

mone levels when shifted to a G diet, but only if the nutrient con -

centration of this diet is high ( Figure 2a–d ).

DISCUSSION

Changes in nutritional conditions during an individual’s feed -

ing history has been studied in relation to a number of key life-

history traits, including growth ( Metcalfe and Monaghan 2001 ;

Jespersen and Toft 2003 ; Raubenheimer and Jones 2006 ), longev -

ity ( Zajitschek et al. 2009 ), and female reproduction ( Barrett et al.

2009 ), but nutritional changes during adult life has not before

been studied in relation to male sexual signaling intensity. While

it is well known that male sexual signaling is affected by nutritional

conditions during development and sexual maturation ( Hunt et al.

2004a ; South et al. 2011 ; Weddle et al. 2012 ), all knowledge to

date is based on studies giving constant nutritional conditions dur -

ing these key periods. Consequently, very little is known about how

changes in the nutritional environment during adult life affect the

expression of male sexual signals. This is important given that most

organisms are likely to experience fluctuating nutritional conditions

during their lifetime ( Simpson and Raubenheimer 2012 ), which

may continuously affect the development and expression of sexual

signals.

We found that sex pheromone expression in adult male N. cinerea

responded to shifts in dietary nutrient composition and correlated

strongly with total consumption, C and energy intake, as well as

body lipid reserves, all of which were inhibited when males were

restricted to a protein-biased (B) diet. Thus, a male’s feeding his -

tory, and the consequences for total energy intake, are essential

for the maintenance of lipid reserves and sex pheromone expres -

sion in male N. cinerea . This suggests that sex pheromones in this

species are energetically costly to produce and depend on a high

and preferably stable intake of C and energy for maximal expres -

sion. Lipid reserves and sex pheromone expression were generally

affected by both the feeding period during and subsequent to sexual

maturation, showing that sex pheromones in N. cinerea are flexible

and respond to the nutritional environment. When given a G diet

of high nutrient concentration after a period of restriction to a

nutritionally imbalanced (B) diet during sexual maturation, males

were able to replenish lipid reserves and boost sex pheromone pro -

duction to maximal levels. This conclusively shows that poor nutri -

tional conditions during sexual maturation will not necessarily have

a detrimental effect on male attractiveness in this species, as long

as males are able to gain nutrients that were previously deficient.

Conversely, our work also illustrates that good nutritional condi -

tions during sexual maturation do not guarantee that male sexual

signals will remain maximized, especially if the future diet is defi -

cient in key nutrients.

Our study agrees with the recent claim that exact measures of

lipid reserves are often good predictors of current body condition

and potential fitness ( Wilder et al. 2015 ). While the effects of nutri -

ent intake on pheromone expression are well documented in male

N. cinerea (South et al. 2011 ; Bunning et al. 2016 ), as well as on the

chemical signals of other insect species (e.g., Fedina et al. 2012 ;

Weddle et al. 2012 ; Rapkin et al. 2017 ), our results are novel in

showing that sexual signaling in N. cinerea is plastic and accurately

reflects recent nutrient-specific foraging history. Sexual signaling

intensity in male N. cinerea correlates with the nutritional resources

(C and energy) they have recently consumed and with their current

body condition (lipid reserves). This contrasts the scenario associ -

ated with sexually selected morphological traits in holometabolous

insects, which are fixed at eclosion and therefore cannot change

after reaching the adult stage (reviewed by Toubiana and Khila

2016 ).

The reliance of pheromone production in N. cinerea on the cur -

rent nutritional environment suggests that chemical signaling in this

species may have evolved under fluctuating nutritional conditions

where it is important to adjust the cost of sexual signaling to pre -

serve energy when conditions are poor and increase signaling inten -

sity when conditions are good. A similar strategy has already been

documented in female N. cinerea , which invest less in reproduction

and save resources under poor nutritional conditions, and thereby

increase their probability of surviving until nutritional conditions

improve ( Barrett et al. 2008 ). In contrast to males, however, this

strategy in females is not determined by the diet consumed as an

adult but rather is fixed by the diet consumed as a juvenile ( Barrett

Table 3

Manova and univariate Anova tests examining the effects of nutritional history of dietary nutrient composition (good →good, bad →good, good →bad, or bad →bad), dietary nutrient concentration (high or low), and their interaction on lipid reserves (%) and the expression of the three sex pheromones 3-hydroxy-2-butanone (3H2B), 2-methylthiazolidine (2MT), and 4-ethyl-2-methoxyphenol (4E2M) in the male Nauphoeta cinerea at 20 days posteclosion

Model term

Manova

Pillai’s trace F df P

Nutritional history 0.911 25.172 12 693 0.0001 Nutrient concentration 0.625 95.353 4229 0.0001 History × concentration 0.298 6.364 12 693 0.0001

Trait

Univariate Anova

F df P

Nutritional history Lipid reserves 74.721 3232 0.0001 3H2B 106.887 3232 0.0001 2MT 73.216 3232 0.0001 4E2M 155.800 3232 0.0001 Nutrient concentration Lipid reserves 130.271 1232 0.0001 3H2B 81.009 1232 0.0001 2MT 74.730 1232 0.0001 4E2M 202.413 1232 0.0001 History × concentration Lipid reserves 10.478 3232 0.0001 3H2B 10.746 3232 0.0001 2MT 3.883 3232 0.010 4E2M 4.231 3232 0.006

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Jensen et al. • Sex pheromone expression and nutritional history

et al. 2009 ). Similar albeit far more complex effects of shifting the

nutritional quality of the diet between the juvenile and adult life

stage have been shown for the amount of time spent calling in male

black field crickets, Teleogryllus commodus (Zajitschek et al. 2009 ).

The plastic effect of recent nutritional history on pheromone

expression in male N. cinerea raises the question: what information

about male quality do pheromone levels signal to potential mates? It

is well established that males producing high quantities of all 3 com -

ponents of the sex pheromone are more attractive to females ( Moore

and Moore 1999 ), and that females mating to these preferred males

live longer ( Moore et al. 2003 ), produce sons that are more attractive

(Moore 1990 , 1997 ), and have a shorter development time ( Moore

1994 ; but see Moore et al. 2003 ). Our current experiment suggests

that male pheromones signal the foraging success and body condition

of a male and thereby his level of adaptation to the environment and

his ability to pass resources to females and offspring. Clearly, more

work is needed before we will fully understand how male nutrition

influences female reproduction and offspring performance.

The male N. cinerea did not appear to be able to build lipid

reserves from ingested P, even though P contains similar amounts of

metabolizable energy as C per unit dry mass ( FAO 2003 ; Buchholz

and Schoeller 2004 ). This conforms with our previous work on

lipid deposition in male N. cinerea (South et al. 2011 ), as well as with

recent work on Blattella ger manica (Ko et al. 2016 ), and supports find -

ings in Periplaneta americana which indicate that the gluconeogenic

pathway is little functional in cockroaches ( Sevala and Steele 1989 ).

It has been argued that cultured male and female N. cinerea , con -

trary to other omnivorous insects such as crickets ( Maklakov et al.

2008 ; Harrison et al. 2014 ), do not require dietary P for the expres -

sion of reproductive traits because they have full nitrogen stores

from excess P consumed during earlier life stages, which they can

use to resynthezise P when P is limited in the diet ( Bunning et al.

2016 ). It would therefore be interesting to deprive male N. cinerea

of P during development and determine if this influences the P

requirement for sex pheromone expression as adults and the ability

to store energy from P as lipids while the nitrogen is deposited in

uric acid stores.

While our work demonstrates a correlation between nutrient

intake and pheromone production in N. cinerea , we currently do

not know the mechanistic basis of this relationship. However, sex

pheromone production in a range of cockroach species (e.g., Bell

and Bath 1978 ; Woodhead and Stay 1989 ; Smith and Schal 1990 ;

Schal et al. 1991 ), including male N. cinerea (Sréng et al. 1999 ; Kou

et al. 2008 ), is stimulated by the biosynthesis of juvenile hormone,

and starvation or nutrient deficiencies are known to significantly

lower rates of juvenile hormone biosynthesis in a number of cock -

roach species ( Weaver and Pratt 1981 ; Woodhead and Stay 1989 ;

Aclé et al. 1990 ; Chase et al. 1990 ; Schal and Smith 1990 ; Schal

et al. 1991 , 1993 ; Young et al. 1999 ).

Fatty acids are the most typical pheromone precursors in cock -

roaches and other insects ( Schal 1991 , 1994 ; Juárez et al. 1992 ; Gu

et al. 1995 ; Tillman et al. 1999 ), and the precursors needed for sex

pheromone biosynthesis could therefore be expected to be supplied

from the lipid stores or directly from feeding. However, the fatty

acid pathway is unlikely for the production of the 3 pheromones

produced by male N. cinerea and only 1 (3H2B) of the 3 phero -

mone components could in theory be synthesized from carbohy -

drate through pyruvate, while the other 2 components (2MT and

4E2M) are phenolics and cannot be synthesized from lipids or car -

bohydrate. Instead, these would need to be sequestered from other

components, for example amino acids, as it is unlikely that N. cinerea

can make phenolic rings de novo. Carbohydrate intake and lipid

stores thus support the energetic requirements for pheromone syn -

thesis but do not directly provide the precursors for these constitu -

ents. The precursors may come from other constituents in the diet,

however, maybe through symbiotic interactions with gut microor -

ganisms ( Schauer et al. 2014 ; Pérez-Cobas et al. 2015 ; Tinker and

Ottesen 2016 ).

In conclusion, our study shows that sex pheromone expres -

sion in male N. cinerea is highly plastic, being heavily influenced

by nutrient concentration and recent nutritional history. After

restriction to P-biased (B) diet during sexual maturation, males

were able to fully recoup lipid reserves and pheromone levels if

given a C-biased diet that had a high nutrient concentration, but

not when the diet was of low nutrient concentration. Our study

therefore adds to the growing literature documenting the specific

nutrients responsible for the condition-dependent expression of

male chemical signals (e.g., South et al. 2011 ; Fedina et al. 2012 ;

Bunning et al. 2016 ; Rapkin et al. 2017 ). More importantly, how -

ever, our work demonstrates the inherent flexibility that can exist

in condition dependent chemical signals due to their reliance on

feeding and nutrition. Although compensatory feeding for specific

nutrients and its subsequent effects on traits such as growth is well

documented in animals ( Metcalfe and Monaghan 2001 ; Jespersen

and Toft 2003 ; Raubenheimer and Jones 2006 ), most studies have

focused on juvenile life stages. Our work shows that nutritionally

determined consumption can have equally important compensa -

tory effects on the expression of phenotypic traits during adult -

hood and represents a potent mechanism that enables animals to

counteract the effects of poor nutritional conditions experienced

in the past. This is likely to have important consequences for the

functioning of sexual selection in N. cinerea . A central assumption

of handicap models of sexual selection is that only high quality

males are able to afford the high costs associated with producing

and/or maintaining elaborate sexual traits ( Johnstone et al. 2009 ).

Consequently, it is argued that exaggerated sexual traits reliably

signal male quality in female mate choice ( Johnstone 1995a ) and

male–male competition ( Johnstone et al. 2009 ). The ability of

male N. cinerea to rapidly adjust their pheromone expression with

changes in the nutritional environment is likely to compromise the

reliability of this sexual trait as a signal of male quality. Exactly

how this will influence the outcome of sexual selection, however,

is complex and theoretical models suggest that it will depend on a

variety of factors, including the degree of heterogeneity that exists

in the nutritional environment ( Higginson and Reader 2009 ), the

extent to which males disperse between environments ( Kokko and

Heubel 2008 ), and the degree to which pheromone expression

is influenced by the interaction between male genotype and the

nutritional environment ( Kokko and Heubel 2008 ; Higginson and

Reader 2009 ). More work is clearly needed before we can assess

the full impact that the plastic response of male pheromones to

shifts in the nutritional environment will have on the operation of

sexual selection in N. cinerea .

FUNDING

This study was supported by grants awarded to J.H. from Natural

Environment Research Council (NE/G00949X/1), a University

Royal Society Fellowship and a Royal Society Equipment Fund

grant. J.R. was funded by NERC studentship (awarded to J.H.)

and C.M.H. was funded by a Leverhulme Trust Early Career

Fellowship.

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Behavioral Ecology

Conflict of Interest: The authors declare no conflict of interest.

Data accessibility: Analyses reported in this article can be reproduced using the data provided by Jensen et al. (2017) .

Handling editor: Dan Papaj

REFERENCES

Aclé D, Brookes VJ, Pratt GE, Feyereisen R. 1990. Activity of the corpora allata of adult female Leucophaea maderae : effects of mating and feeding. Arch Insect Biochem Physiol. 14:121–129.Andersson M. 1994. Sexual selection. Princeton (NJ): Princeton University Press.Andersson M, Simmons LW. 2006. Sexual selection and mate choice. Trends Ecol Evol. 21:296–302.Barrett EL, Hunt J, Moore AJ, Moore PJ. 2009. Separate and combined effects of nutrition during juvenile and sexual development on female life-history trajectories: the thrifty phenotype in a cockroach. Proc Biol Sci. 276:3257–3264.Barrett EL, Preziosi RF, Moore AJ, Moore PJ. 2008. Effects of mating delay and nutritional signals on resource recycling in a cyclically breeding cock - roach. J Insect Physiol. 54:25–31.Bell WJ, Bath RH. 1978. Quantitative effect of juvenile hormone on repro - duction in the cockroach Byrotria fumigate . J Insect Physiol. 16:2303–2313. Buchholz AC, Schoeller DA. 2004. Is a calorie a calorie? Am J Clin Nutr. 79:899S–906S.Bunning H, Bassett L, Clowser C, Rapkin J, Jensen K, House CM, Archer CR, Hunt J. 2016. Dietary choice for a balanced nutrient intake increases the mean and reduces the variance in the reproductive performance of male and female cockroaches. Ecol Evol. 6:4711–4730.Bunning H, Rapkin J, Belcher L, Archer CR, Jensen K, Hunt J. 2015. Protein and carbohydrate intake influence sperm number and fertility in male cockroaches, but not sperm viability. Proc Biol Sci. 282:20142144.Chase J, Jurenka RA, Schal C, Halarnkar PP, Blomquist GJ. 1990. Biosynthesis of methyl branched hydrocarbons: precursors to female contact sex pheromone of the German cockroach Blattella ger manica (L.) (Orthoptera, Blattellidae). Insect Biochem. 20:149–156.Clark DC, DeBano SJ, Moore AJ. 1997. The influence of environmental quality on sexual selection in Nauphoeta cinerea (Dictyoptera: Blaberidae). Behav Ecol. 8:46–53.Cochran DG. 1985. Nitrogen excretion in cockroaches. Annu Rev Entomol. 30:29–49.Cotton S, Fowler K, Pomiankowski A. 2004. Do sexual ornaments dem - onstrate heightened condition-dependent expression as predicted by the handicap hypothesis? Proc Biol Sci. 271:771–783.Dadd RH. 1961. The nutritional requirements of locusts—IV. Requirements for vitamins of the B complex. J Insect Physiol. 6:1–12.FAO. 2003. Food energy—methods of analysis and conversion factors. Rome (Italy): Food and Agriculture Organization of the United Nations.Fedina TY, Kuo TH, Dreisewerd K, Dierick HA, Yew JY, Pletcher SD. 2012. Dietary effects on cuticular hydrocarbons and sexual attractiveness in Drosophila . PLoS One. 7:e49799. Foster SP, Anderson KG. 2015. Sex pheromones in mate assessment: analy - sis of nutrient cost of sex pheromone production by females of the moth Heliothis virescens . J Exp Biol. 218:1252–1258. Gu X, Quilici D, Juarez P, Blomquist GJ, Schal C. 1995. Biosynthesis of hydrocarbons and contact sex pheromone and their transport by lipo - phorin in females of the German cockroach ( Blattella ger manica ). J Insect Physiol. 41:257–267.Harrison SJ, Raubenheimer D, Simpson SJ, Godin J-GJ, Bertram SM. 2014. Towards a synthesis of frameworks in nutritional ecology: inter - acting effects of protein, carbohydrate and phosphorus on field cricket fitness. Proc Biol Sci. 281:20140539.Higginson AD, Reader T. 2009. Environmental heterogeneity, genotype-by-environment interactions and the reliability of sexual traits as indicators of mate quality. Proc Biol Sci. 276:1153–1159.Hunt J, Brooks R, Jennions MD, Smith MJ, Bentsen CL, Bussière LF. 2004a. High-quality male field crickets invest heavily in sexual display but die young. Nature. 432:1024–1027.

Hunt J, Bussière LF, Jennions MD, Brooks R. 2004b. What is genetic qual - ity? Trends Ecol Evol. 19:329–333.Ingleby FC. 2015. Insect cuticular hydrocarbons as dynamic traits in sexual communication. Insects. 6:732–742.Ingleby FC, Hosken DJ, Flowers K, Hawkes MF, Lane SM, Rapkin J, Dworkin I, Hunt J. 2013. Genotype-by-environment interactions for cuticular hydrocarbon expression in Drosophila simulans . J Evol Biol. 26:94–107.Jensen K, Engelke S, Simpson SJ, Mayntz D, Hunt J. 2013. Balancing of specific nutrients and subsequent growth and body composition in the slug Arion lusitanicus . Physiol Behav. 122:84–92. Jensen K, Schal C, Silverman J. 2015. Adaptive contraction of diet breadth affects sexual maturation and specific nutrient consumption in an extreme generalist omnivore. J Evol Biol. 28:906–916.Jensen K, Shearman M, Rapkin J, Carey M, House C, Hunt J. 2017. Data from: change in sex pheromone expression by nutritional shift in male cockroaches. Behavioral Ecology. 28:1393–1401.Jespersen LB, Toft S. 2003. Compensatory growth following early nutritional stress in the wolf spider Pardosa prativaga . Funct Ecol. 17:737–746.Johansson BG, Jones TM. 2007. The role of chemical communication in mate choice. Biol Rev Camb Philos Soc. 82:265–289.Johnstone RA. 1995a. Honest advertisement of multiple qualities using multiple signals. J Theor Biol. 177:87–94.Johnstone RA. 1995b. Sexual selection, honest advertisement and the handicap principle: reviewing the evidence. Biol Rev Camb Philos Soc. 70:1–65.Johnstone RA, Rands SA, Evans MR. 2009. Sexual selection and condi - tion-dependence. J Evol Biol. 22:2387–2394.Juárez P, Chase J, Blomquist GJ. 1992. A microsomal fatty acid synthetase from the integument of Blattella ger manica synthesizes methyl-branched fatty acids, precursors to hydrocarbon and contact sex pheromone. Arch Biochem Biophys. 293:333–341.Kelly CA, Norbutus AJ, Lagalante AF, Iyengar VK. 2012. Male courtship pheromones as indicators of genetic quality in an arctiid moth ( Utetheisa ornatrix ). Behav Ecol. 23:1009–1014. Ko AE, Schal C, Silverman J. 2016. Diet quality affects bait performance in German cockroaches (Dictyoptera: Blattellidae). Pest Manag Sci. 72:1826–1836.Kokko H, Heubel K. 2008. Condition-dependence, genotype-by-environ - ment interactions and the lek paradox. Genetica. 134:55–62.Kou R, Chang HW, Huang ZY, Yang RL. 2008. Pheromone, juvenile hor - mone, and social status in the male lobster cockroach Nauphoeta cinerea . Arch Insect Biochem Physiol. 68:144–155.Maklakov AA, Simpson SJ, Zajitschek F, Hall MD, Dessmann J, Clissold F, Raubenheimer D, Bonduriansky R, Brooks RC. 2008. Sex-specific fit - ness effects of nutrient intake on reproduction and lifespan. Curr Biol. 18:1062–1066.Metcalfe NB, Monaghan P. 2001. Compensation for a bad start: grow now, pay later? Trends Ecol Evol. 16:254–260.Ming QL, Lewis SM. 2010. Pheromone production by male Tribolium cas - taneum (Coleoptera: Tenebrionidae) is influenced by diet quality. J Econ Entomol. 103:1915–1919.Moore AJ. 1990. The inheritance of social dominance, mating behav - iour and attractiveness to mates in male Nauphoeta cinerea . Anim Behav. 39:388–397.Moore AJ. 1994. Genetic evidence for the “good genes” process of sexual selection. Behav Ecol Sociobiol. 35:235–241.Moore AJ. 1997. The evolution of social signals: morphological, func - tional, and genetic integration of the sex pheromone in Nauphoeta cinerea . Evolution. 51:1920–1928.Moore AJ, Gowaty PA, Moore PJ. 2003. Females avoid manipulative males and live longer. J Evol Biol. 16:523–530.Moore AJ, Moore PJ. 1999. Balancing sexual selection through opposing mate choice and male competition. Proc Biol Sci. 266:711–716.Mullins DE. 2015. Physiology of environmental adaptations and resource acquisition in cockroaches. Annu Rev Entomol. 60:473–492.Otronen M. 1995. Energy reserves and mating success in males of the yel - low dung fly, Scathophaga stercoraria . Funct Ecol. 9:683–688. Pérez-Cobas EA, Maiques E, Angelova A, Carrasco P, Moya A, Latorre A. 2015. Diet shapes the gut microbiota of the omnivorous cockroach Blattella ger manica . FEMS Microbiol Ecol. 91:1–14.

14 0 0

Downloaded from https://academic.oup.com/beheco/article/28/6/1393/4139803 by guest on 07 January 2022

Jensen et al. • Sex pheromone expression and nutritional history

Rantala MJ, Kortet R, Kotiaho JS, Vainikka A, Suhonen J. 2003. Condition dependence of pheromones and immune function in the grain beetle Tenebrio molitor . Funct Ecol. 17:534–540. Rapkin J, Jensen K, House CM, Sakaluk SK, Sakaluk JK, Hunt J. 2017. The complex interplay between macronutrient intake, cuticular hydro - carbon expression and mating success in male decorated crickets. J Evol Biol. 30:711–727.Raubenheimer D, Jones SA. 2006. Nutritional imbalance in an extreme generalist omnivore: tolerance and recovery through complementary food selection. Anim Behav. 71:1253–1262.Rowe L, Houle D. 1996. The lek paradox and the capture of genetic vari - ance by condition dependent traits. Proc Biol Sci. 263:1415–1421.Ruther J, Matschke M, Garbe LA, Steiner S. 2009. Quantity matters: male sex pheromone signals mate quality in the parasitic wasp Nasonia vitripen - nis. Proc Biol Sci. 276:3303–3310. Schal C, Burns EL, Gadot M, Chase J, Blomquist GJ. 1991. Biochemistry and regulation of pheromone production in Blattella ger manica (L.) (Dictyoptera, Blattellidae). Insect Biochem. 21:73–79.Schal C, Chiang A-S, Burns EL, Gadot M, Cooper RA. 1993. Role of the brain in juvenile hormone synthesis and oocyte development: effects of dietary protein in the cockroach Blattella ger manica (L.). J Insect Physiol. 39:303–313.Schal C, Gu X, Burns EL, Blomquist GJ. 1994. Patterns of biosynthesis and accumulation of hydrocarbons and contact sex pheromone in the female German cockroach, Blattella ger manica . Arch Insect Biochem Physiol. 25:375–391.Schal C, Smith AF. 1990. Neuroendocrine regulation of pheromone pro - duction in cockroaches. In: Huber I, Masler EP, Rao BR, editors. Cockroaches as models for neurobiology: applications in biomedical research. Boca Raton (FL): CRC Press. p. 179–200.Schauer C, Thompson C, Brune A. 2014. Pyrotag sequencing of the gut micro - biota of the cockroach Shelfordella lateralis reveals a highly dynamic core but only limited effects of diet on community structure. PLoS One. 9:e85861.Sevala VL, Steele JE. 1989. Absence of a stimulatory effect of the corpus cardiacum on gluconeogenesis in cockroach ( Periplaneta americana ) fat body. J Insect Physiol. 35:1031–1036.Simpson SJ, Abisgold JD. 1985. Compensation by locusts for changes in dietary nutrients: behavioural mechanisms. Physiol Entomol. 10:443–452.Simpson SJ, Raubenheimer D. 2012. The nature of nutrition—a unifying framework from animal adaptation to human obesity. Princeton (NJ): Princeton University Press.Smith AF, Schal C. 1990. Corpus allatum control of sex pheromone pro - duction and calling in the female brown-banded cockroach, Supella longi - palpa (F.) (Dictyoptera: Blattellidae). J Insect Physiol. 36:251–257.

South SH, House CM, Moore AJ, Simpson SJ, Hunt J. 2011. Male cock - roaches prefer a high carbohydrate diet that makes them more attrac - tive to females: implications for the study of condition dependence. Evolution. 65:1594–1606.Sréng L. 1990. Seducin, male sex pheromone of the cockroach Nauphoeta cinerea : isolation, identification, and bioassay. J Chem Ecol. 16:2899–2912. Sréng L, Léoncini I, Clément JL. 1999. Regulation of sex pheromone production in the male Nauphoeta cinerea cockroach: role of brain extracts, corpora allata (CA), and juvenile hormone (JH). Arch Insect Biochem Physiol. 40:165–172.Steiger S, Stökl J. 2014. The role of sexual selection in the evolution of chemical signals in insects. Insects. 5:423–438.Sørensen A, Mayntz D, Raubenheimer D, Simpson SJ. 2008. Protein-leverage in mice: the geometry of macronutrient balancing and conse - quences for fat deposition. Obesity. 16:566–571.Tillman JA, Seybold SJ, Jurenka RA, Blomquist GJ. 1999. Insect phero - mones—an overview of biosynthesis and endocrine regulation. Insect Biochem Mol Biol. 29:481–514.Tinker KA, Ottesen EA. 2016. The core gut microbiome of the American cockroach, Periplaneta americana , is stable and resilient to dietary shifts. Appl Environ Microbiol. 82:6603–6610.Tomkins JL, Radwan J, Kotiaho JS, Tregenza T. 2004. Genic capture and resolving the lek paradox. Trends Ecol Evol. 19:323–328.Toubiana W, Khila A. 2016. The benefits of expanding studies of trait exaggeration to hemimetabolous insects and beyond morphology. Curr Opin Genet Dev. 39:14–20.Weaver RJ, Pratt GE. 1981. Effects of starvation and feeding upon corpus allatum activity and oöcyte growth in adult female Periplaneta americana . J Insect Physiol. 27:75–83.Weddle CB, Mitchell C, Bay SK, Sakaluk SK, Hunt J. 2012. Sex-specific genotype-by-environment interactions for cuticular hydrocarbon expres - sion in decorated crickets, Gryllodes sigillatus : implications for the evolution of signal reliability. J Evol Biol. 25:2112–2125.Wilder SM, Raubenheimer D, Simpson SJ. 2015. Moving beyond body condition indices as an estimate of fitness in ecological and evolutionary studies. Funct Ecol. 30:108–115.Woodhead AP, Stay B. 1989. Neural inhibition of corpora allata in protein-deprived Diploptera punctata . J Insect Physiol. 35:415–421. Young HP, Bachmann JA, Schal C. 1999. Food intake in Blattella ger manica (L.) nymphs affects hydrocarbon synthesis and its allocation in adults between epicuticle and reproduction. Arch Insect Biochem Physiol. 41:214–224.Zajitschek F, Hunt J, Jennions MD, Hall MD, Brooks RC. 2009. Effects of juvenile and adult diet on ageing and reproductive effort of male and female black field crickets, Teleogryllus commodus . Funct Ecol. 23:602–611.

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