Comparison of Sperm Number, Spermatophore Size, and Body Size

Comparison of Sperm Number, Spermatophore Size, and

Body Size in Four Cricket Species

Author: Sturm, Robert

Source: Journal of Orthoptera Research, 23(1) : 39-47

Published By: Orthopterists' Society

URL: https://doi.org/10.1665/034.023.0103

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ROBERT STURM

Journal of orthoptera research 2014, 23(1)

Abstract

This paper examines the relationships between male body size,

spermatophore size, and number of sperm per spermatophore, in four

cricket species: Teleogryllus commodus, Acheta domesticus, Gryllus bimaculatus,

and Gryllus assimilis. Within each species, individuals varied considerably in

all three characters measured, and generally, spermatophore size, number of

sperm, and body size were all correlated; i.e., ampulla diameter and sperm

number per spermatophore signiﬁcantly increased with body mass (p <

0.001) according to a linear regression function. Interspeciﬁc investigations

found considerable differences between species: G. assimilis had the largest

mean male body mass and length, largest ampullas, and highest numbers of

spermatozoa per spermatophore, whilst A. domesticus had a small body mass

and length, the smallest ampullas, and lowest sperm numbers. Regression

analyses of all four cricket species revealed similar results as intraspeciﬁc

regression computations. Hence, both intra- and interspeciﬁcally, larger

males produce larger spermatophores containing more sperm, than do

smaller males. These results differ from bush crickets (Tettigoniidae), where

larger male body size does not necessarily correlate with larger ampullas and

more sperm. Possibly male bush crickets have evolved to invest a higher

proportion of their resources in the size of the nuptial gift, as opposed to

number of spermatozoa.

Key words

body mass, spermatophore, sperm number, ampulla, Orthoptera,

Gryllidae

Introduction

Body size, mass, and number of sperm are key components of

male ﬁtness (Thornhill & Alcock 1983; Wedell 1997). Body size

inﬂuences most biological phenomena, making it a determinant

of ﬁtness and a target of natural selection (Whitman 2008). Body

size can determine male reproductive success, because larger males

are often more competitive and can provide more resources and

beneﬁts to females than can small males (Leisnham & Jamieson

2004; Fedorka & Mousseau 2002; Whitman 2008; Saleh et al.

2013). The number of sperm transferred to the female is also an

important component of male ﬁtness (Schaus & Sakaluk 2001), in

part, because of male-male sperm competition (Thornhill & Alcock

1983; Simmons 2001).

In the Ensifera (crickets and katydids), males package their sperm

into a proteinaceous container called a spermatophore (Lehmann

2012), which is typically composed of three parts: 1) a long thin

tube which is threaded into the female spermatheca, 2) an anchor

or attachment plate, which is placed into the female genital tract and

secures the spermatophore to the female, and 3) a sack-like ampulla

which hangs outside the female and holds the sperm. After attach-

ing the spermatophore to the female, the male uncouples from the

female. During the next hour, much of the sperm in the dangling,

external ampulla is transferred through the spermatophore tube

into the female's spermatheca. In many ensiferan species, males

also produce a jelly-like spermatophylax (Greek for 'sperm guard'),

which surrounds the ampulla. The spermatophylax always lacks

sperm and is nutritious for some species (Dewsbury 1982; Mann

1984; Vahed 1994; Reinhold & von Helversen 1997). When pres-

ent, the spermatophylax is commonly eaten by the female, and thus

functions as a nuptial food gift (Voigt et al. 2006, 2008). It also

serves to delay the female from eating the sperm-ﬁlled ampulla,

thus allowing time for sperm to pass from the ampulla into the

female spermatheca (Sakaluk 1984; Gwynne 1990; Simmons 1990;

Simmons & Bailey 1990; Heller & von Helversen 1991). In contrast,

most cricket species do not produce a spermatophylax. Instead,

males physically guard the females to keep them from eating the

sperm-ﬁlled ampulla (Alcock 1994; Sturm 2003).

In those insects that do not pass spermatophores, sperm number

per ejaculate is often correlated with male body size (Ponlawat &

Harrington 2007). But the situation becomes more complex in taxa

that produce spermatophores, because larger males tend to produce

larger spermatophores (Wedell 1993; Lehmann & Lehmann 2009),

and larger spermatophores tend to contain more sperm (Doyle et

al. 2011). Hence, in the Orthoptera, male body size, spermatophore

size, and sperm number should be studied together (Wedell 1997;

Schaus & Sakaluk 2001; Brown 2008; McCartney et al. 2008). In

some crickets, large spermatophores with high sperm numbers are

removed by females signiﬁcantly later than small spermatophores

with low sperm numbers (Simmons 1986). Further, males with

large spermatophores, containing high numbers of sperm, may

attract larger females that are characterized by higher fecundity

(Fedorka & Mousseau 2002). Hence, larger spermatophores may

have reproductive beneﬁts for males beyond simply having more

sperm (Lehmann 2012).

Of course, the number of spermatozoa transferred to the female

during a single mating is an important component of male ﬁtness

(Simmons 2001). Studies on Orthoptera show considerable interspe-

ciﬁc variation in sperm number per spermatophore, adopting values

between several thousand and several million: Gryllodes supplicans:

1.6-2.0 × 10

(Sakaluk 1984), Teleogryllus commodus: 0.8-2.0 × 10

(Sturm 2003), Kawanaphila nartee: 0.2 × 10

(Simmons & Gwynne

1991), Requena verticalis: 0.8-2.0 × 10

(Gwynne 1986, Simmons

et al. 1993), Poecilimon veluchianus: 6.3-10.5 × 10

(Reinhold 1994;

Reinhold & Helversen 1997; McCartney et al. 2010). This remark-

able interspeciﬁc variability in sperm number is thought to be the

result of differential sexual and natural selection among species.

Intraspeciﬁcally, sperm number in Orthoptera can correlate with the

size, age, health, and nutritional status of the male (Sturm 2011),

Comparison of sperm number, spermatophore size, and body size in four

cricket species

robert sturm

Brunnleitenweg 41, A-5061 Elsbethen, Austria. Email: [email protected]

Journal of Orthoptera Research 2014, 23(1): 39-47

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Journal of orthoptera research 2014, 23(1)

ROBERT STURM

and the length of the time between two spermatophore transfers:

generally, the longer the refractory time, the higher the number

of transferred spermatozoa (Reinhold & Heller 1993; Lehmann

& Lehmann 2000, 2009). However, physiological condition itself

inﬂuences the length of the refractory time (Simmons 1988).

In the study presented here, I examine the intra- and interspe-

ciﬁc relationships among male body size, spermatophore size, and

spermatozoa number per spermatophore in four cricket species (T.

commodus, A. domesticus, G. bimaculatus, and Gryllus assimilis). These

four species mostly survive in different habitats. These crickets ex-

hibit similar male refractory periods, but differ in both male body

size and spermatophore size. My hypothesis is that male body size,

spermatophore size, and sperm number per spermatophore are

positively correlated in crickets, both intra- and interspeciﬁcally.

Material and methods

Breeding and keeping of the crickets.—Four cricket species were used in

this study: Teleogryllus commodus (Walker 1869), Acheta domesticus

(Linnaeus 1758), Gryllus bimaculatus (DeGeer 1773), and Gryllus as-

similis (Linnaeus 1758). Three cricket species (Teleogryllus commodus,

Gryllus bimaculatus, Gryllus assimilis) were obtained

from retailers specialized for feed animals, whereas

Acheta domesticus was collected as adults in the ﬁeld

in Austria. All were reared and kept under identical

conditions (constant 25°C, Light:Dark = 12:12 h,

relative humidity ≈ 60%), using an environmental

chamber at the former Institute of Zoology, Univer-

sity of Salzburg. Rearing of early, intermediate, and

late nymphal stages took place in separate plastic

boxes (50 cm × 30 cm × 30 cm), which were ﬁlled

with dry peat soil (thickness of the layer: 3 cm), food

ad libitum, and egg cartons serving as shelter for the

animals. Immediately after their ﬁnal molt adult

animals of each species were separated by gender

and individually kept in ﬁve-liter glass vessels ﬁlled

with crumpled paper. They were provided with food

ad libitum, consisting of standard laboratory diet

(Altromin

1222), lettuce, and water that was placed

into small dishes plugged with cotton wicks (Sturm

& Pohlhammer 2000, Sturm 2002).

Males used for mating (N = 20 per species) were

measured for body length (from the front of the head

to the end of the abdomen, excluding the anten-

nae and cerci) using mechanical Calipers accurate

to 0.02 mm. Fresh, wet body mass was measured

with a Satorius

balance (precision: 10

-4

g). Males

were weighed about 30 min before the experiment

to avoid any inaccuracies resulting from additional food uptake or

excretion.

For the mating process, 5-d old males were placed together with

5-d old virgin females of the same species in respective mating ves-

sels (round glass dishes: di = 30 cm, height = 5 cm). The dishes were

empty and were cleaned after each copulation. Only 15 min were

allotted for copulation to occur in order to prevent males from any

adjustment of their sperm number released into the ampulla in the

presence of the female. Immediately after copulation and spermato-

phore transfer, the sperm-containing capsules were removed from

the females by using soft forceps and a stereomicroscope. Separated

spermatophores were submerged in insect Ringer's solution (Sturm

& Pohlhammer 2000). The ampulla was then measured under the

stereomicroscope (Wild

; Fig. 1a, b). There is some evidence that

male crickets may modify sperm number in response to both intra-

speciﬁc competition and female size (Gage & Barnard 1996). Thus,

a single male is theoretically able to ﬁll a spermatophore with the

highest number of sperm possible or leave it completely empty. In

the present study, such factors were controlled as much as possible.

For example, during the experiments reported here, all males had

similar refractory periods, a single male was always paired with a

Fig. 1. Cricket spermatophores: a) Fresh sper-

matophore of Teleogryllus commodus, showing the

sperm-containing ampulla (amp) and attachment

plate (ap), b) main components of the ampulla in

T. commodus (longitudinal section): apical papilla

(pap), outer membrane (om), inner membrane

(im), sperm mass (spm), and spermatphore tube

(spt), c) electron micrograph of cross section

of T. commodus ampulla, showing the internal

structure (il: inner layer), d) detailed view on the

sperm mass residing in ampulla of T. commodus

(spf: sperm ﬂagella).

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ROBERT STURM

Journal of orthoptera research 2014, 23(1)

single female, and male and female sizes were equally matched as

much as possible.

Sperm counting.—Sperm numbers per spermatophore were estimated

by ﬁrst ﬁxing isolated capsules in a paraformaldehyde-glutaraldehyde

mixture (Karnovsky 1965) for 3 h. Subsequently, they were washed

in sodium-cacodylate buffer, dehydrated in series with increasing

ethanol content (70% to 96%), and critical-point dried. After the

ﬁxation procedure, each oval spermatophore was cut transversely

in the middle (thickest) part of the ampulla, using a razor blade

and a steriomicroscope. The sperm-containing halves were prepared

for electron-microscopy (charged with carbon and sputtered with

gold) and subsequently scanned with a Cambridge

250 SEM at an

accelerating voltage of 10-30 kV (Fig. 1c, d).

The resulting SEM micrographs of uniform magniﬁcation were

analyzed stereographically, as follows (Fig. 2): The cross-sectional

area of the sperm mass revealed on the photograph was covered with

a grid consisting of a pre-deﬁned number of unit squares. The size

of the area was estimated by counting those squares being ﬁlled by

the mass by more than 50%. Afterwards, the photograph was rotated

below the grid by a pre-deﬁned angle and the counting procedure

was repeated. Final size of the sperm mass area was computed by

simply determining the mean value of the single counting results,

M. The number of singly held sperm cells within a single square

unit, N

, was carefully determined under magniﬁcations (Fig. 1

d). By assuming a homogeneous distribution of sperm within the

ampulla the total number of germ cells, N

tot

, was computed accord-

ing to the following equation:

(1)

In the equation noted above, c represents a correction factor, by which

shrinking artifacts and gaps within the sperm mass arising from the

ﬁxation process and cutting of the ampulla are considered (Fig. 1c).

This factor simply denotes the ratio of the unaffected sectional area

of the sperm mass to the whole sectional area of the sperm mass.

The factor was individually computed for each spermatophore

included into this study. By using this correction factor, I believe

that the accuracy of sperm counting is about 90-95%.

Statistical analysis.—Interspeciﬁc differences in male fresh mass, body

length, ampulla diameter, and number of sperm per spermatophore

were analyzed by ANOVA. To examine possible correlations be-

tween body mass and ampulla size or sperm number, least-squares

regression analyses were carried out independently for each species

as well as for all species together. Constants and intersects of the

regression lines were tested for signiﬁcance using Student’s t-test.

Results

Intraspeciﬁc comparisons.—For all four cricket species, both ampulla

diameter and number of sperm contained in the ampulla increase

linearly with body mass (Figs 3, 4). Ampulla diameter (dependent

variable) was highly correlated (p < 0.001) to male fresh body mass

(independent variable) in all four species. Fig. 3 illustrates all four

regression lines, based on the equation y = b

x (linear homogeneous

function). Pearson's correlation coefﬁcients, indicating the accuracy

of the regression ﬁt, varied between 0.57 in the case of A. domesticus

and 0.94 in the case of T. commodus, with r(G. bimaculatus) = 0.87,

and r(G. assimilis) = 0.90.

Sperm number per spermatophore (dependent variable) was also

highly correlated (p < 0.001) to fresh male body mass (independent

variable), for all four cricket species. Contrary to the ﬁrst regression

computation for ampulla diameter, noted above, the calculated re-

gression lines for spermatophore number did not cross the origins of

the graphs and are thus founded on the equation y = b

+ b

x (linear

non-homogeneous function). Goodness of ﬁt (Pearson's correla-

tion coefﬁcients) ranged from 0.72 in the case of G. bimaculatus to

0.88 in the case of T. commodus (Fig. 4). Intersections between the

regression lines and the x-axes of the graphs indicate a theoretical

minimal body mass of the males, below which no spermatophore

formation takes place.

Fig. 2. Determination of the cross-sectional area of the sperm mass (see Fig. 1c) with the help of a simple stereologic counting method.

The cross section photographed in the SEM is covered with a grid consisting of a pre-deﬁned number of square units. Those square

units that are ﬁlled by the sperm mass by more than 50 % are included into the counting and marked by a point. Finally, all counted

square units are summed up. The procedure is repeated several times by rotating the photograph below the grid by a pre-deﬁned angle

(e.g., compare positions 1 & 2). A mean cross-sectional area is computed.

tot

= N

· M · c

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Journal of orthoptera research 2014, 23(1)

ROBERT STURM

Interspeciﬁc comparisons.—Most of the morphological and reproduc-

tive variables analyzed in this study differed signiﬁcantly among the

four cricket species (Fig. 5). A. domesticus was the smallest species

of the study (mass: 724 + 97 mg, length: 19.7 + 1.9 mm, N = 20),

and G. assimilis the largest (mass: 935 + 166 mg, length: 24.1 + 3.6

mm, N = 20). The remaining two cricket species were intermediate

in size: G. bimaculatus (mass: 866 + 115 mg, length: 22.5 + 2.4, N =

20), and T. commodus (mass: 757 + 103 mg, length: 21.3 + 2.2 mm,

N = 20). Parametric tests found signiﬁcant differences (p < 0.05)

of the measured body parameters between all species with three

exceptions (Fig. 5a, b): A. domesticus did not differ signiﬁcantly in

weight from T. commodus. G. bimaculatus did not differ signiﬁcantly

in weight from G. assimilis, and T. commodus did not differ signiﬁ-

cantly in length from G. bimaculatus.

Regarding the diameter of the ampulla, a trend similar to that

derived from body measurements was obtained. As summarized in

Table 1 and Fig. 5c, d, males of A. domesticus produced the small-

est ampulla (D

ampulla

= 0.71 + 0.07 mm, N = 20), whilst G. assimilis

produced the largest (p < 0.05, D

ampulla

= 0.89 + 0.11). Ampullas of

T. commodus averaged 0.76 + 0.09 mm, and those of the Mediter-

ranean ﬁeld cricket G. bimaculatus averaged 0.83 + 0.12 mm in

diameter. There was no signiﬁcant difference in mean diameter

values between A. domesticus vs T. commodus, T. commodus vs G.

bimaculatus or G. bimaculatus vs G. assimilis (Fig. 5c). However, all

other species comparisons in Fig. 5c were signiﬁcant. The number

of sperm contained in the spermatophores ranged from 1.23 × 10

+ 0.65 × 10

(A. domesticus) to 2.21 × 10

+ 1.05 × 10

(G. assimilis,

Table 1), however a signiﬁcant difference was found only between

A. domesticus and G. assimilis Fig. 5d.

In order to obtain more generalized information of possible

correlations between ampulla size and body mass as well as sperm

number and body mass, a linear regression analysis of all four

cricket species was carried out (Fig. 6). Concerning the correlation

between D

ampulla

and body mass (Fig. 6a), D

ampulla

increases by 0.001

mm per each additional mg body mass (p < 0.001, r = 0.91). The

relationship between sperm number and body mass is described

by a regression line with the intercept being located at -2.699 × 10

and the constant b

adopting a value of 5.55 × 10

. Both regression

coefﬁcients are characterized by high signiﬁcance (p < 0.001, r =

0.77; Fig. 6b).

Discussion

This study supports the hypotheses that in crickets, male body

size, spermatophore size, and number of sperm per spermatophore

are positively correlated, both intra- and interspeciﬁcally.

Scaling among traits.—More interesting than the simple correlations

among these three traits, is the phenomenal increase in ampulla vol-

ume and sperm number corresponding to relatively small increases

in body size. This holds true for both intraspeciﬁc and interspeciﬁc

relationships. Hence, for A. domesticus, male body length (for males

who produced spermatophores) varied from 17.4-22.8 mm (a 31%

increase from shortest to longest male), but ampulla diameter varied

Fig. 3. Linear regression

graphs and correlation co-

efﬁcients (r), of ampulla di-

ameter on male body mass

for four species of cricket (N

= 20); a) Acheta domesticus,

b) Teleogryllus commodus, c)

Gryllus bimaculatus, d) Gryl-

lus assimilis.

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ROBERT STURM

Journal of orthoptera research 2014, 23(1)

from 0.61 to 0.83 mm (a 36% increase), corresponding to a 150%

volume increase. Likewise, for G. bimaculatus, male body mass var-

ied by a magnitude of 51% (698-1057 mg), but ampulla diameter

varied over a magnitude of 37% (0.69-0.96 mm), corresponding to

a volume increase of 169%. In T. commodus, body length varied by

a magnitude of 30%, while sperm numbers varied by a magnitude

of 249% (67,000-234,000 sperm/ampulla). Hence, for this cricket

species, an increase in body length by a third nearly triples the number

of sperm. This is due, in part, to the scaling relationship between

length and volume (Volume µ Length

) (Whitman 2008). Hence,

a doubling of body length produces 8 × the volume for isometric

objects. These same relationships linking spermatophore size and

sperm number to body size also exist across species (Fig. 6a, b).

Why should sperm numbers increase so rapidly with small

changes in body size? One can argue that there is an optimal number

of sperm that should be passed to the average female, under average

conditions, and that males should evolve to pass that exact amount.

And certainly, size-invariant traits exist (Emlen & Nijhout 2000). For

example, jumping distance in Schistocerca gregaria is relatively invari-

ant across nymphal instars (Bennet-Clark 1990). Two hypotheses

compete to explain the strong scaling relationships between male

body size and sperm number. The passive scaling hypothesis posits

that these relationships are the result of simple physical/growth

relationships, and that there has been no evolutionary selection

Fig. 4. Linear regression

graphs exhibiting the

intraspeciﬁc dependence

of sperm number per

spermatophore on body

mass of male crickets (N =

20); a) Acheta domesticus,

b) Teleogryllus commodus,

c) Gryllus bimaculatus,

d) Gryllus assimilis.

Species Mass (mg) Length (mm) D

ampulla

(mm) Sperm # (× 10

)

A. domesticus

724 + 97

(509-896)

19.7 + 1.9

(17.4-22.8)

0.71 + 0.07

(0.61-0.83)

1.23 + 0.65

(0.24-1.97)

T. commodus

757 + 103

(567-935)

21.3 + 2.2

(18.7-24.3)

0.76 + 0.09

(0.65-0.88)

1.56 + 0.78

(0.67-2.34)

G. bimaculatus

866 + 115

(698-1057)

22.5 + 2.4

(19.8-25.6)

0.83 + 0.12

(0.69-0.96)

1.76 + 0.87

(0.79-2.67)

G. assimilis

935 + 166

(743-1146)

24.6 + 3.1

(20.5-28.5)

0.89 + 0.11

(0.75-1.03)

2.21 + 1.05

(0.98-3.27)

Table 1. Fresh mass and body length, spermatophore dimensions, and sperm numbers per spermatophore measured for males of four

cricket species (mean + S.D., ranges in brackets, N = 20 per species). Abbreviations: D

ampulla

= diameter of the ampulla.

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Journal of orthoptera research 2014, 23(1)

ROBERT STURM

for larger spermatophores and more sperm in larger males. The

adaptive scaling hypothesis posits that these relationships are the

result of adaptive evolution for males to maximize sperm numbers,

perhaps because of sperm competition. This hypothesis assumes that

each individual male attempts to maximize his reproductive output

(sperm numbers), that sperm and spermatophores are costly, that

individuals differ in health and nutritional status, and that there

are tradeoffs between reproductive output and somatic condition

(Stearns 1992; Simmons 2001). As such, individuals that experi-

enced optimal nymphal conditions generally eclose as large adults

in good condition, and can afford to allocate a greater proportion

of nutritional resources to reproduction (i.e., large spermatophores

containing many sperm). In contrast, stressed nymphs eclose at a

smaller body size, and cannot afford a large reproductive effort, and

hence produce small spermatophores containing fewer sperm. This

idea is supported by the fact that in this study, some exceptionally

small individuals passed spermatophores that lacked sperm (Fig.

4a, c, d). The ﬁelds of scaling, sexual selection, and resource alloca-

tion are complex (Stearns 1992; Emlen & Nijhout 2000; Simmons

2001), and answering the interesting question of why larger crickets

transfer more sperm, awaits further research.

Intraspeciﬁc relationships.—Each cricket species in this study showed

a positive correlation between ampulla diameter and body mass as

well as between sperm number and body mass. This supports the

conclusion that larger and heavier males of A. domesticus, T. commo-

dus, G. bimaculatus, and G. assimilis produce larger spermatophores

containing higher numbers of sperm. This relationship has been

documented for few other crickets (Wedell 1993; McCartney et al.

2008). Correlations between sperm number per spermatophore and

body size were previously noted for T. commodus (Sturm 2011), for

the black-horned tree cricket (Brown 2008), and for bushcrickets

(Wedell 1997). However, McCartney et al. (2008) noted that us-

ing ampulla mass (size) to predict the amount of ejaculated or

transferred spermatozoa could be problematic due to high natural

ﬂuctuations in sperm number. McCartney's warning is strengthened

by the present study, where sperm numbers ﬂuctuated widely around

the mean values (Table 1).

The ﬁndings presented here relate to the ecology, intraspeciﬁc

competition, sexual selection, ﬁtness, and behavior of the four cricket

species. First is that large body size is known to have both advan-

tages and disadvantages (Weissman et al. 2008; Whitman 2008).

In many insect species, larger individuals are more powerful, have

lower mass-speciﬁc metabolic rates (but see Fielding & Defoliart

2008), and more favorable surface-to-volume ratios, which provide

numerous physiological beneﬁts (Whitman 2008). Larger males are

typically more competitive, and can hold larger or better territories,

and win male-male contests (Thornhill & Alcock 1983; Arnott &

Elwood 2009). Larger male orthoptera usually produce louder calls

(Judge et al. 2008; Morris 2008; Römer et al. 2008), and often at-

tract more females than small males (Brown 1999; Lehmann 2007;

Lehmann & Lehmann 2007; Champagnon & Cueva del Castillo

2008). And, as this paper has shown, larger males often provide

larger spermatophores with more sperm. Studies show that female

Orthoptera that mate with larger males, can have higher fecundity

(Gwynne et al. 1984; Honěk 1993; Brown 1997; Fedorka & Mous-

seau 2002), or produce larger offspring (Bretman et al. 2006; Kosal

& Niedzlek-Feaver 1997, 2007; Saleh et al. 2013). In contrast, larger

individuals may require more food, be more conspicuous and less

agile, and suffer higher predation rates (Whitman & Vincent 2008).

Hence, there are numerous interacting beneﬁts and detriments of

large size to males, involving physiological, ecological, and repro-

ductive aspects, and all impact ultimate ﬁtness (Whitman 2008).

The considerable male body size variability within each species,

Fig. 5. Interspecific

comparisons of four

traits among four crick-

et species: a) body

mass, b) body length,

c) ampulla diameter,

d) sperm number per

spermatophore. Ab-

breviations: TC = Teleo-

gryllus commodus, AD =

Acheta domesticus, GB =

Gryllus bimaculatus, GA

= Gryllus assimilis; * = p

< 0.05, ** = p < 0.001

(F-values derived from

the ANOVA uniformly

indicate normal dis-

tribution or close-to-

normal distribution.).

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ROBERT STURM

Journal of orthoptera research 2014, 23(1)

might also cause intraspeciﬁc mating-size incompatibility between

males and females (Weissman et al. 2008), or foster assortative

mating, whereby males and females with similar body sizes tend

to mate (Yuexin et al. 2013). Differences in size among males may

also inﬂuence individual behaviors. Small males who are unable to

compete against larger, more powerful males, may adopt alternative

strategies for gaining access to mating opportunities, such as satellite

or sneaky male tactics (Cade 1981; Thornhill & Alcock 1983,). In

sum, male body size, spermatophore size, and sperm numbers, and

population variation in these traits, have important consequences

for males.

Interspeciﬁc relationships.—The four cricket species studied tended

to differ in mean male body size and mass, ampulla diameter, and

number of spermatozoa, although with considerable overlap among

species. Under laboratory conditions G. assimilis produced the larg-

est males with largest spermatophores and highest sperm numbers,

whilst A domesticus, had the smallest males and spermatophores,

and the lowest sperm numbers.

As George Bartholomew (1981) noted, it is only a slight overstate-

ment to say that the most important attribute of an animal both

physiologically and ecologically is its size. Body size inﬂuences

nearly every aspect of an organism, and as such, is presumed to be a

strong target of evolution, resulting in local adaptation of body size

(Whitman 2008). Presumably, both natural selection and sexual

selection, including both male-male and male-female sexual selec-

tion have inﬂuenced male body size evolution differently in each

of these four cricket species, which, as previously stated, generally

survive in different habitats.

The consequences of the interspeciﬁc differences in body size,

spermatophore size, and sperm number are not known. However,

generally, larger species maintain larger territories and/or lower

population densities than small species (Bonner 2006). Over evo-

lutionary time, large species tend to go extinct at higher rates than

small species (Kingsolver & Pfennig 2007). In contrast, smaller

species are thought to be more resistant to extinction, and diversify

faster, because they produce more generations per unit time and

have higher population densities (LaBarbera 1989).

References

Alcock J. 1994. Postinsemination associations between males and females

in insects: the mate-guarding hypothesis. Annual Review of Entomology

39: 1-21.

Arnott G., Elwood R.W. 2009. Assessment of ﬁghting ability in animal

contests. Animal Behavior 77: 991-1004.

Bartholomew G.A. 1981. A matter of size: an examination of endothermy in

insects and terrestrial vetibrates, pp. 45-78. In: Heinrich B [Ed.] Insect

Thermoregulation. Wiley, New York.

Bennet-Clark H.C. 1990. Jumping in Orthoptera, pp. 173-203. In: Chapman

R.F., Joern A. [Eds] Biology of Grasshoppers. Wiley, New York.

Bretman A., Rodríguez-Munoz R., Tregenza T. 2006. Male dominance

determines female egg laying rate in crickets. Biological Letters 2: 409-411.

Brown W.D. 1997. Courtship feeding in tree crickets increases insemination

and female reproductive life span. Animal Behaviour 54: 1369-1382.

Brown W.D. 1999. Mate choice in tree crickets and their kin. Annual Review

of Entomology 44: 371-396.

Brown W.D. 2008. Size-based mating in both sexes of black-horned

tree cricket, Oecanthus nigricornis Walker (Orthoptera: Gryllidae:

Oecanthidae). Journal of Insect Behavior 21: 130-142.

Cade W. 1981. Alternative male strategies: genetic differences in crickets.

Science 212: 563-564.

Champagnon J., Cueva dell Castillo R. 2008. Female mate choice, calling

song and genetic variance in the cricket, Gryllodes sigillatus. Ethology

114: 223-230.

Cueva del Castillo R. 2003. Body size and multiple copulations in a neotropical

grasshopper with an extraordinary mate-guarding duration. Journal of

Insect Behavior 16: 503-522.

Dewsbury D.A. 1982. Ejaculate cost and male choice. American Naturalist

119: 601-610.

Doyle J.M., McCormick C.R., DeWoody J.A. 2011. The quantiﬁcation

of spermatozoa by real-time quantitative PCR, spectrometry, and

spermatophore cap size. Molecular Ecology Resources 11: 101-106.

Emlen D.J., Nijhout H.F. 2000. The development and evolution of exaggerated

morphologies in insects. Annual Review of Entomology 45: 661-708.

Fedorka K.M., Mousseau T.A. 2002. Tibial spur feeding in ground crickets:

Larger males contribute larger gifts (Orthoptera: Gryllidae). Florida

Entomologist 85: 317-323.

Fig. 6. Interspeciﬁc linear regression analyses showing the depen-

dence of ampulla diameter on male’s body mass (a; N = 80) and the

dependence of sperm number per spermatophore on male's body

mass (b; N = 80). Open circles indicate respective mean values of

the four species summarized in Table 1.

Downloaded From: https://bioone.org/journals/Journal-of-Orthoptera-Research on 27 Aug 2024

Journal of orthoptera research 2014, 23(1)

ROBERT STURM

Fielding D.J., DeFoliart L.S. 2008. Relationship of metabolic rate to body

size in Orthoptera. Journal of Orthoptera Research 17: 301-306.

Gage A.R., Barnard C.J. 1996. Male crickets increase sperm number in relation

to competition and female size. Behavioral Ecology and Sociobiology

38: 349-353.

Gwynne D.T., Bowen B.J., Codd C.G. 1984. The function of the katydid Requena

verticalis spermatophore and its role in fecundity and insemination

(Orthoptera: Tettigoniidae). Australian Journal of Zoology 32: 15-22.

Gwynne D.T. 1986. Courtship feeding in katydids (Orthoptera: Tettigoniidae):

investment in offspring or in obtaining fertilizations. American Naturalist

128: 342-352.

Gwynne D.T. 1990. Testing parental investment and the control of sexual

selection in katydids: the operational sex ratio. American Naturalist

136: 474-484.

Heller K.G., von Helversen D. 1991. Operational sex ratio and individual

mating frequencies in two bushcricket species (Orthoptera, Tettigoniidae,

Poecilimon). Ethology 89: 211-228.

Honěk A. 1993. Intraspeciﬁc variation in body size and fecundity in insects:

a general relationship. Oikos 66: 483-492.

Judge K.A., Ting J.J., Gwynne D.T. 2008. Condition dependence of male

life span and calling effort in a ﬁeld cricket. Evolution 62: 868-878.

Karnovsky M.J. 1965. A formaldehyde-glutaraldehyde ﬁxative of high

osmolality for use in electron microscopy. Journal of Cell Biology 27:

137A-138A.

Kingsolver J.G., Pfennig D.W. 2007. Patterns and power of phenotypic

selection in nature. BioScience 57: 561-572.

Kosal E.F., Niedzlek-Feaver M. 1997. Female preferences for large, heavy

mates in Schistocerca americana (Orthoptera: Acrididae). Journal of

Insect Behavior 10: 711-725.

Kosal E.F., Niedzlek-Feaver M. 2007. Parental size inﬂuence on offspring

phenotype in Schistocerca americana (Orthoptera: Acrididae). Journal

of Orhtoptera Research 16: 51-55.

LaBarbera M. 1989. Analyting body size as a factor in ecology and evolution.

Annual Review of Ecology and Systematics 20: 97-117.

Lehmann G.U.C. 2007. Density-dependent plasticity of sequential mate

choice in a bushcricket. Australian Journal of Zoology 55: 123-130.

Lehmann G.U.C. 2012. Weighing costs and beneﬁts of mating in bushcrickets

(Insecta: Orthoptera: Tettigoniidae), with an emphasis on nuptial gifts,

protandry and mate density. Frontiers in Zoology 9: 19.

Lehmann G.U.C., Lehmann A.W. 2000. Spermatophore characteristics in

bushcrickets vary with parasitism and remating interval. Behavioral

Ecology and Sociobiology 47: 393-399.

Lehmann G.U.C., Lehmann A.W. 2007. Sex differences in "time out"-

from reproductive activity and sexual selection in male bushcrickets

(Orthoptera: Zaprochilinae: Kawanaphila mirla). Journal of Insect

Behavior 20: 215-227.

Lehmann G.U.C., Lehmann A.W. 2008. Bushcricket song as a clue for

spermatophore size. Behavioral Ecology and Sociobiology 62: 569-578.

Lehmann G.U.C., Lehmann A.W. 2009. Condition-dependent spermatophore

size is correlated with male's age in a bushcricket (Orthoptera:

Phaneropteridae). Biological Journal of the Linnean Society 96: 354-360.

Leisnham P.T., Jamieson I.G. 2004. Relationship between male head size

and mating opportunity in the harem defence, polygynous tree weta

Heimideina maori (Orthoptera: Anostomatidae). New Zealand Journal

of Ecology 28: 49-54.

Mann T. 1984. Spermatophores. Development, structure, biochemical

attributes and role in the transfer of spermatozoa. Springer, Berlin,

Heidelberg, New York, Tokyo.

McCartney J., Heller K.G., Potter M.A., Robertson, A.W., Telscher K., Lehmann

G., Lehmann A., Von-Helversen D., Reinhold K., Achmann R. 2008.

Understanding nuptial gift size in bush-crickets: an analysis of the

genus Poecilimon (Tettigoniidae: Orthoptera). Journal of Orthoptera

Research 17: 231-242.

McCartney J., Lehmann A.W., Lehmann G.U.C. 2010. Lifetime spermatophore

investment in natural populations of two closely related bush-cricket

species (Orthoptera: Tettigoniidae: Poecilimon). Behaviour 147: 285-298.

Morris G.K. 2008. Size and carrier in the bog katydid, Metrioptera sphagnorum

(Orthoptera: Ensifera, Tettigoniidae). Journal of Orthoptera Research

17: 333-342.

Ponlawat A., Harrington L.C. 2007. Age and body size inﬂuence male sperm

capacity of the dengue vector Aedes aegypti (Diptera: Culicidae). Journal

of Medical Entomology 44: 422-426.

Reinhold K. 1994. Inheritance of body and testis size in the bushcricket

Poecilimon veluchianus Ramme (Orthoptera: Tettigoniidae) examined

by means of subspecies hybrids. Biological Journal of the Linnean

Society 52: 305-316.

Reinhold K., Heller K.G. 1993. The ultimate function of nuptial feeding

in the bushcricket Poecilimon veluchianus (Orthoptera: Tettigoniidae:

Phaneropterinae). Behavioral Ecology and Sociobiology 32: 55-60.

Reinhold K., von Helversen D. 1997. Sperm number, spermatophore weight

and remating in the bushcricket Poecilimon veluchianus. Ethology 103:

12-18.

Römer H., Lang A. Hartbauer M. 2008. No correlation of body size and high-

frequency hearing sensitivity in neotropical phaneropterine katydids.

Journal of Orthoptera Research 17: 343-346.

Schaus J.M., Sakaluk S.K. 2001. Ejaculate expenditures of male crickets in

response to varying risk and intensity of sperm competition: not all

species play games. Behavioral Ecology 12: 740-745.

Sakaluk S.K. 1984. Male crickets feed females to ensure complete sperm

transfer. Science 223: 609-610.

Saleh N.W., Larsen E.L., Harrison R.G. 2013. Reproductive success and

body size in the cricket Gryllus ﬁrmus. Journal of Insect Behavior DOI:

10.1007/s10905-013-9425-1.

Simmons L.W. 1986. Inter-male competition and mating success in the ﬁeld

cricket, Gryllus bimaculatus (de Geer). Animal Behaviour 34: 567-579.

Simmons L.W. 1988. Male size, mating potential and lifetime reproductive

success in the ﬁeld cricket, Gryllus bimaculatus (de Geer). Animal

Behaviour 36: 372-379.

Simmons L.W. 1990. Nuptial feeding in tettigoniids: male costs and the rates

of fecundity increase. Behavioral Ecology and Sociobiology 27: 43-47.

Simmons L.W. 2001. Sperm competition and its evolutionary consequences

in the insects. Princeton University Press, Princeton, NY.

Simmons L.W., Bailey W.J. 1990. Resource influenced sex roles of

zaphrochiline tettigoniids (Orthoptera: Tettigoniidae). Evolution 44:

1853-1868.

Simmons L.W., Graig M., Llorens T., Schinzig M., Hosken D. 1993. Bushcricket

spermatophores vary in accord with sperm competition and parental

investment theory. Proceedings of the Royal Society of London B 251:

183-186.

Simmons L.W., Gwynne D.T. 1991. The refractory period of female katydids

(Orthoptera: Tettigoniidae): sexual conﬂict over the remating interval.

Behavioral Ecology 2: 276-282.

Stearns S.C. 1992. The Evolution of Life Histories. Oxford University Press,

Oxford. UK.

Sturm R. 2002. Development of the accessory glands in the genital tract of

female Teleogryllus commodus Walker (Insecta, Orthoptera). Arthropod

Structure and Development 31: 231-241.

Sturm R. 2003. The spermatophore in the black ﬁeld cricket Teleogryllus

commodus (Insecta: Orthoptera: Gryllidae): size, structure and formation.

Entomologische Abhandlungen 61: 227-232.

Sturm R. 2011. Sperm number in the spermatophores of Teleogryllus commodus

(Gryllidae) and its dependence on intermating interval. Invertebrate

Biology 130: 362-367.

Sturm R., Pohlhammer K. 2000. Morphology and development of the female

accessory sex glands in the cricket Teleogryllus commodus (Saltatoria:

Ensifera: Gryllidae). Invertebrate Reproduction & Development 38: 13-21.

Thornhill R., Alcock J. 1983. The evolution of insect mating systems. Harvard

University Press, Cambridge.

Vahed K. 1994. The evolution and function of the spermatophylax in

bushcrickets (Orthoptera: Tettigoniidae). PhD thesis, University of

Nottingham.

Voigt C.C., Lehmann G.U.C., Michener R.H., Joachimski M.M. 2006. Nuptial

feeding is reﬂected in tissue nitrogen isotope ratios of female katydids.

Functional Ecology 20: 656-661.

Voigt C.C., Kretzschmar A.S., Speakman J.R., Lehmann G.U.C. 2008. Female

bushcrickets fuel their metabolism with male nuptial gifts. Biology

Letters 4: 476-478.

Downloaded From: https://bioone.org/journals/Journal-of-Orthoptera-Research on 27 Aug 2024

ROBERT STURM

Journal of orthoptera research 2014, 23(1)

Wedell N. 1993. Spermatophore size in bushcrickets: comparative evidence

for nuptial gifts as a sperm protection device. Evolution 47: 1203-1212.

Wedell N. 1997. Ejaculate size in bushcrickets: The importance of being

large. Journal of Evolutionary Biology 10: 315-325.

Weisman D.B., Judge, K.A., Williams S.C. Whitman D.W., Lee V.F. 2008. Small-

male mating advantage in a species of Jerusalem cricket (Orthoptera:

Stenopelmatinae: Stenopelmatus). Journal of Orthoptera Research 17:

321-332.

Whitman D.E. 2008. The signiﬁcance of body size in the Orthoptera: a

review. Journal of Orthoptera Research 17: 117-134.

Whitman D.W., Vincent S. 2008. Large size as an antipredator defense in

an insect. Journal of Orthoptera Research 17: 353-371.

Yuexin J., Bolnick D.I., Kirkpatrick M. 2013. Associative mating in animals.

The American Naturalist. 181: DOI: 10.1086/670160.

Downloaded From: https://bioone.org/journals/Journal-of-Orthoptera-Research on 27 Aug 2024