Scott Sakaluk
Illinois State University, Biological Sciences, Faculty Member
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Sexual conflict results in a diversity of sex-specific adaptations, including chemical additions to ejaculates. Male decorated crickets (Gryllodes sigillatus) produce a gelatinous nuptial gift (the spermatophylax) that varies in size and... more
Sexual conflict results in a diversity of sex-specific adaptations, including chemical additions to ejaculates. Male decorated crickets (Gryllodes sigillatus) produce a gelatinous nuptial gift (the spermatophylax) that varies in size and free amino acid composition, which influences a female's willingness to fully consume this gift. Complete consumption of this gift maximises sperm transfer through increased retention of the sperm-containing ampulla, but hinders post-copulatory mate choice. Here, we examine the effects of protein (P) and carbohydrate (C) intake on the weight and amino acid composition of the spermatophylax that describes its gustatory appeal to the female, as well as the ability of this gift to regulate sexual conflict via ampulla attachment time. Nutrient intake had similar effects on the expression of these traits with each maximised at a high intake of nutrients with a P:C ratio of 1:1.3. Under dietary choice, males actively regulated their nutrient intake bu...
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Nuptial gifts produced by males and transferred to females during copulation are common in insects. Yet, their precise composition and subsequent physiological effects on the female recipient remain unresolved. Male decorated crickets... more
Nuptial gifts produced by males and transferred to females during copulation are common in insects. Yet, their precise composition and subsequent physiological effects on the female recipient remain unresolved. Male decorated crickets Gryllodes sigillatus transfer a spermatophore to the female during copulation that is composed of an edible gift, the spermatophylax, and the ampulla that contains the ejaculate. After transfer of the spermatophore, the female detaches the spermatophylax and starts to eat it while sperm from the ampulla are evacuated into the female reproductive tract. When the female has finished consuming the spermatophylax, she detaches the ampulla and terminates sperm transfer. Hence, one simple function of the spermatophylax is to ensure complete sperm transfer by distracting the female from prematurely removing the ampulla. However, the majority of orally active components of the spermatophylax itself and their subsequent effects on female behavior have not been ...
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Despite keen interest in extra-pair mating in birds, its adaptive significance remains unresolved. Here, we use a multi-year dataset to test whether traits of a female's social mate influence her propensity to produce extra-pair... more
Despite keen interest in extra-pair mating in birds, its adaptive significance remains unresolved. Here, we use a multi-year dataset to test whether traits of a female's social mate influence her propensity to produce extra-pair offspring in a population of house wrens, and whether producing extra-pair young has consequences for a female's fitness through effects on offspring survival. Females were most likely to produce extra-pair offspring when paired with old males and when paired with males on poor-quality territories, although this latter effect was marginally nonsignificant. Among offspring, the cutaneous immunity of within-pair young decreased as the age of their sires increased, but cutaneous immunity of extra-pair young was not affected by the age of their extra-pair sires or by the age of the males rearing them. Extra-pair offspring were more likely than within-pair offspring to return as breeding adults to the local population, with extra-pair sons being more like...
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Mass or body-size measures of 'condition' are of central importance to the study of ecology and evolution, and it is often assumed that differences in condition measures are positively and linearly related to fitness. Using... more
Mass or body-size measures of 'condition' are of central importance to the study of ecology and evolution, and it is often assumed that differences in condition measures are positively and linearly related to fitness. Using examples drawn from ecological studies, we show that indices of condition frequently are unlikely to be related to fitness in a linear fashion. Researchers need to be more explicit in acknowledging the limitations of mass-based condition measures and accept that, under some circumstances, they may not relate to fitness as traditionally assumed. Any relationship between a particular condition measure and fitness should first be empirically validated before condition is used as a proxy for fitness. In the absence of such evidence, researchers should explicitly acknowledge that assuming such a relationship may be unrealistic.
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A major component of sex-allocation theory, the Trivers-Willard model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is... more
A major component of sex-allocation theory, the Trivers-Willard model (TWM), posits that sons and daughters are differentially affected by variation in the rearing environment. In many species, the amount of parental care received is expected to have differing effects on the fitness of males and females. When this occurs, the TWM predicts that selection should favour adjustment of the offspring sex ratio in relation to the expected fitness return from offspring. However, evidence for sex-by-environment effects is mixed, and little is known about the adaptive significance of producing either sex. Here, we test whether offspring sex ratios vary according to predictions of the TWM in the house wren (Troglodytes aedon, Vieillot). We also test the assumption of a sex-by-environment effect on offspring using two experiments, one in which we manipulated age differences among nestlings within broods, and another in which we held nestling age constant but manipulated brood size. As predicted...
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The spermatophore transferred by the male decorated cricket Gryllodes supplicans to the female during copulation includes a large gelatinous portion (spermatophylax), which the female removes and feeds on immediately after mating. Females... more
The spermatophore transferred by the male decorated cricket Gryllodes supplicans to the female during copulation includes a large gelatinous portion (spermatophylax), which the female removes and feeds on immediately after mating. Females usually removed and ate the smaller sperm-containing portion (ampulla) within 1 to 7 minutes after fully consuming or losing the spermatophylax. Complete sperm transfer requires that the ampulla remain attached for a minimum of 50 minutes; this corresponds to the average time at which females actually removed ampullae, 52.0 +/- 2.2 minutes after mating. These results indicate that nuptial feeding of the female cricket functions to deter females from removing the sperm ampulla before sperm transfer is complete.
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Nuptial food gifts given by males to females at mating are widespread in insects, but their evolutionary origin remains obscure. Such gifts may arise as a form of sensory trap that exploits the normal gustatory responses of females,... more
Nuptial food gifts given by males to females at mating are widespread in insects, but their evolutionary origin remains obscure. Such gifts may arise as a form of sensory trap that exploits the normal gustatory responses of females, favouring the selective retention of sperm of gift-giving males. I tested this hypothesis by offering foreign food gifts, synthesized by males of one cricket species, to females of three non-gift-giving species. Females provisioned with novel food gifts were 'fooled' into accepting more sperm than they otherwise would in the absence of a gift. These results support the hypothesis that nuptial food gifts and post-copulatory female mating preferences coevolve through a unique form of sensory exploitation.
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... The surface areas of terraria were increased by the addition of egg cartons ... Regardless, the extended reten-tion of the ampulla after consumption of the spermatophylax along with ... I also thank DT Gwynne, GK Morris, JS Quinn, and... more
... The surface areas of terraria were increased by the addition of egg cartons ... Regardless, the extended reten-tion of the ampulla after consumption of the spermatophylax along with ... I also thank DT Gwynne, GK Morris, JS Quinn, and WA Snedden for their helpful comments on the ...
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... We studied the frequency of mating, the fate of the spermatophore, and progenyproduction of individual females as a function of single or double matings in the housecricket, Acheta domesticus, and the field cricket, Gryllus integer. ...
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... SCOTT K. SAKALUK and DANTON H. O'DAY Department of Zoology, Erindale College, University of Toronto, Mississauga, Ontario L5L 1C6 Abstract Can. Ent. 116: 1585-1589 (1984) The use of Hoechst (33258) stain in quantifying... more
... SCOTT K. SAKALUK and DANTON H. O'DAY Department of Zoology, Erindale College, University of Toronto, Mississauga, Ontario L5L 1C6 Abstract Can. Ent. 116: 1585-1589 (1984) The use of Hoechst (33258) stain in quantifying spermatozoa contained in the sper-matheca ...
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... Page 3. 204 SCOTT К. SAKALUK ... males. In this regard, Sakaluk & Cade (1980, 1983) suggested that female crickets, by mating repeatedly, might gain nutritional benefits through the consumption of additional... more
... Page 3. 204 SCOTT К. SAKALUK ... males. In this regard, Sakaluk & Cade (1980, 1983) suggested that female crickets, by mating repeatedly, might gain nutritional benefits through the consumption of additional sper-matophores. ...
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Cryptic female choice in crickets occurs through the premature removal of a male's spermatophore after copulation, which terminates sperm transfer. Although it is known that this behavior can directly influence the paternity of... more
Cryptic female choice in crickets occurs through the premature removal of a male's spermatophore after copulation, which terminates sperm transfer. Although it is known that this behavior can directly influence the paternity of offspring, its effects on female fitness have not been directly assessed. We tested the hypothesis that spermatophore removal by female house crickets (Acheta domesticus) confers fitness benefits
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... Scott K. Sakabk Ecology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA ... larger than those of long-winged males, but this difference was due entirely to the spermatophylax portion of... more
... Scott K. Sakabk Ecology Group, Department of Biological Sciences, Illinois State University, Normal, IL 61790-4120, USA ... larger than those of long-winged males, but this difference was due entirely to the spermatophylax portion of the sper-matophore; spermatophylaxes of ...
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Antennae are important sensory organs in insects because they enable the perception of chemical and tactile cues believed to be important in sex recognition and mating in various species. To examine the role of the antennae in the mating... more
Antennae are important sensory organs in insects because they enable the perception of chemical and tactile cues believed to be important in sex recognition and mating in various species. To examine the role of the antennae in the mating behaviour of decorated crickets, Gryllodes ...
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Although post-copulatory mate guarding occurs in a variety of crickets, its adaptive significance remains largely unknown. Mate guarding may function to prevent females from prematurely removing the externally attached sperm ampulla,... more
Although post-copulatory mate guarding occurs in a variety of crickets, its adaptive significance remains largely unknown. Mate guarding may function to prevent females from prematurely removing the externally attached sperm ampulla, thereby ensuring maximum insemination. This hypothesis was tested in decorated crickets, Gryllodes supplicans, by comparing ampulla retention times of females guarded by their mates with those of unguarded females.
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Insectivorous Mediterranean house geckos, Hemidactylus tursicus, are found in the field close to the burrows of calling male decorated crickets, Gryllodes supplicans. In playback experiments where adult geckos were presented with calls of... more
Insectivorous Mediterranean house geckos, Hemidactylus tursicus, are found in the field close to the burrows of calling male decorated crickets, Gryllodes supplicans. In playback experiments where adult geckos were presented with calls of these crickets or calls of frogs as ...
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... Animal Behaviour 44:867-879. Thornhill, R., and P. Sauer. 1992. Genetic sire effects on the fighting ... Age determination of adult field crickets: methodology and field applications. Canadian Journal of Zoology 65:1564-1566.... more
... Animal Behaviour 44:867-879. Thornhill, R., and P. Sauer. 1992. Genetic sire effects on the fighting ... Age determination of adult field crickets: methodology and field applications. Canadian Journal of Zoology 65:1564-1566. ANNE-KATRIN EGGERT* SCOTT K. SAKALUK ...
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... Investment in the spermatophylax, however, is probably determined by a more complex array of trade-offs involving the degree to which ... Thus, the spermatophylax can be viewed as a maleparental investment, assuming that it... more
... Investment in the spermatophylax, however, is probably determined by a more complex array of trade-offs involving the degree to which ... Thus, the spermatophylax can be viewed as a maleparental investment, assuming that it contributes to offspring fathered by the investing ...
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... Anne-Katrin Eggert 1,2 ,; Scott K. Sakaluk 1. ... of season on burial depth is probably mediated by soil properties that may have changed over the 2-month course of the study; later in the season, carcasses are buried less deeply,... more
... Anne-Katrin Eggert 1,2 ,; Scott K. Sakaluk 1. ... of season on burial depth is probably mediated by soil properties that may have changed over the 2-month course of the study; later in the season, carcasses are buried less deeply, possibly because the soil is drier and harder for the ...