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Anthony J. Zera - One of the best experts on this subject based on the ideXlab platform.
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The role of juvenile hormone and juvenile hormone esterase in wing morph determination in ModicoGryllus confirmatus
Journal of Insect Physiology, 1996Co-Authors: Anthony J. Zera, Seiji TanakaAbstract:Abstract The role of juvenile hormone (JH) and juvenile hormone esterase (JHE) in regulating wing morph determination was studied in the cricket ModicoGryllus confirmatus . JHE activities were significantly higher in nascent long-winged (LW) vs short-winged (SW) crickets during the latter half but not during the first half of the last stadium. The magnitude and direction of the activity differences were similar to those previously documented between wing morphs of the cricket, Gryllus rubens . In contrast, activities of general esterase, an enzyme or group of enzymes with no demonstrated role in regulating the JH titer in insects, showed no or only minor differences between morphs. The magnitude and direction of the JHE activity variation is consistent with a regulatory role for this enzyme in some aspect of wing dimorphism. However, the timing of the differences (exclusively during the last half of the last stadium) argue against a role in regulating wing length development per se . Single or multiple applications of juvenile hormone-III to nascent LW individuals during the first few days of the last stadium significantly redirected development from long to short wings. Multiple applications of acetone, by itself, also increased the production of short-winged adults. For most treatments, all individuals with shortened wings also had undeveloped flight muscles. These data suggest that JH may play a role in wing morph determination in M. confirmatus but that it affects a different aspect of the polymorphism from JHE.
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juvenile hormone degradation in adult wing morphs of the cricket Gryllus rubens
Journal of Insect Physiology, 1993Co-Authors: Anthony J. Zera, Carrie A Borcher, Sarah B GainesAbstract:Abstract Juvenile hormone—III metabolism was compared between adult wing morphs of the cricket Gryllus rubens to determine if variation in hormone degradation could be responsible for the dramatic fecundity differences between female morphs. As in other insects, hormone was degraded almost exclusively to juvenile hormone acid in dilute hemolymph in vitro, while significant quantities of juvenile hormone acid, diol and acid-diol as well as more polar metabolites were produced in vivo within 1 h after injection of racemic hormone. Activities of the degradative enzyme juvenile hormone esterase in hemolymph ranged from 4 to 14 nmol/min/ml serum during the first 10 days of adulthood in each morph of each sex. Activities were similar to values reported in other adult orthopterans and were substantially lower than those in last-stadium G. rubens. The 70 min in vivo half-life of racemic hormone injected into day 5–6 short-winged females was significantly higher than that of mid-last-stadium G. rubens and was similar to values reported in adult Diploptera punctata, Locusta migratoria and Manduca sexta. The amount of (10-R)- or racemic hormone degraded in vivo within 1 h after injection was strongly correlated with hemolymph juvenile hormone esterase activity in individual day 5–7 but not day 2–3 adults. This indicates that the hemolymph esterase contributes significantly to in vivo metabolism of exogenous hormone during some periods in adults. Midgut, fat body and ovaries exhibited significant activities of both juvenile hormone esterase and epoxide hydrolase, indicating that the hydrolase may contribute to tissue-specific and to whole cricket hormone metabolism. Importantly, no major differences were observed between adult wing morphs with respect to (1) percentage racemic or (10-R)-juvenile hormone—III degraded in vivo, (2) developmental profiles of hemolymph juvenile hormone esterase activity or (3) activities of juvenile hormone esterase or epoxide hydrolase in various non-hemolymph tissues. These data (1) provide no evidence that hormone metabolism differs significantly between adult morphs and (2) contrast with the importance of differential hormone degradation in morph induction during the juvenile stage.
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differential mating success of male wing morphs of the cricket Gryllus rubens
American Midland Naturalist, 1993Co-Authors: Cami L Holtmeier, Anthony J. ZeraAbstract:-Genetically marked individuals were used to study differential mating success between male wing morphs of the cricket, Gryllus rubens. Previous studies of Gryllus rubens and other wing-dimorphic insects have documented that flightless short-winged or wingless females typically attain reproductive maturity earlier and oviposit more eggs relative to their long-winged counterparts. This study was done to determine if flightless males also exhibit enhanced reproductive characteristics. Segregation analyses documented the genetic basis of allozymes used to infer paternity in subsequent experiments. Control experiments documented the absence of effects on mating success independent of wing morph due to (1) the genetic stock from which males were taken; (2) male size; or (3) female wing morph. Mating trials involving a long-winged male, a short-winged male and a female of either wing morph documented no significant differences in the number of progeny sired by male wing morphs. This pattern was true for both the first group of offspring and for the entire set of offspring produced during a 20-day period. Thus, in contrast to females, we observed no increase in reproductive output in males resulting from the loss of the flight apparatus. However, substantial variance in mating success was observed between males independent of wing morph. This result was likely due to the existence of a dominance hierarchy and the increased mating success of the dominant male.
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differential allocation of resources underlies the dispersal reproduction trade off in the wing dimorphic cricket Gryllus rubens
Oecologia, 1993Co-Authors: Simon Mole, Anthony J. ZeraAbstract:The cricket, Gryllus rubens (Orthoptera, Gryllidae), exists in natural populations as either a fully-winged (LW), flight-capable morph or as a short-winged (SW) morph that cannot fly. The SW morph is substantially more fecund than the LW morph. In this study we report on the physiological basis of this trade-off between flight capability and fecundity. Results from gravimetric feeding trials indicate that LW and SW morphs are equivalent in their consumption and digestion of food. However, during the adult stage, the LW morph is less efficient in converting assimilated nutrients into biomass. This may be a consequence of the respired loss of assimilated nutrients due to the maintenance of functional flight muscles in the LW morph. In both morphs the gross biomass devoted to flight muscles does not change significantly during the first 14 days of adult growth while there is a significant biomass gain in ovarian tissue mass during the same period. SW morphs have vestigial flight muscles and gain substantially more ovarian mass relative to the LW morphs. These data are consistent with a trade-off between flight muscle maintenance in the LW morph and ovarian growth in the SW form. This is the first evidence for a life-history trade-off that has a physiological basis which is limited to the allocation of acquired and assimilated nutrients within the organism.
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the dispersal reproduction trade off in the wing dimorphic cricket Gryllus rubens
1993Co-Authors: Simon Mole, Anthony J. ZeraAbstract:The cricket, Gryllus rubens (Orthoptera, Grylli- dae), exists in natural populations as either a fully- winged (LW), flight-capable morph or as a short-winged (SW) morph that cannot fly. The SW morph is substan- tially more fecund than the LW morph. In this study we report on the physiological basis of this trade-off between flight capability and fecundity. Results from gravimetric feeding trials indicate that LW and SW morphs are equivalent in their consumption and digestion of food. However, during the adult stage, the LW morph is less efficient in converting assimilated nutrients into biomass. This may be a consequence of the respired loss of assimi- lated nutrients due to the maintenance of functional flight muscles in the LW morph. In both morphs the gross biomass devoted to flight muscles does not change significantly during the first 14 days of adult growth while there is a significant biomass gain in ovarian tissue mass during the same period. SW morphs have vestigial flight muscles and gain substantially more ovarian mass relative to the LW morphs. These data are consistent with a trade-off between flight muscle maintenance in the LW morph and ovarian growth in the SW form. This is the first evidence for a life-history trade-off that has a physiological basis which is limited to the allocation of acquired and assimilated nutrients within the organism.
Yikweon Jang - One of the best experts on this subject based on the ideXlab platform.
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male responses to conspecific advertisement signals in the field cricket Gryllus rubens orthoptera gryllidae
PLOS ONE, 2011Co-Authors: Yikweon JangAbstract:In many species males aggregate and produce long-range advertisement signals to attract conspecific females. The majority of the receivers of these signals are probably other males most of the time, and male responses to competitors' signals can structure the spatial and temporal organization of the breeding aggregation and affect male mating tactics. I quantified male responses to a conspecific advertisement stimulus repeatedly over three age classes in Gryllus rubens (Orthoptera: Gryllidae) in order to estimate the type and frequency of male responses to the broadcast stimulus and to determine the factors affecting them. Factors tested included body size, wing dimorphism, age, and intensity of the broadcast stimulus. Overall, males employed acoustic response more often than positive phonotactic response. As males aged, the frequency of positive phonotactic response decreased but that of the acoustic response increased. That is, males may use positive phonotaxis in the early stages of their adult lives, possibly to find suitable calling sites or parasitize calling males, and then later in life switch to acoustic responses in response to conspecific advertisement signals. Males with smaller body size more frequently exhibited acoustic responses. This study suggests that individual variation, more than any factors measured, is critical for age-dependent male responses to conspecific advertisement signals.
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Male Responses to Conspecific Advertisement Signals in the Field Cricket Gryllus rubens (Orthoptera: Gryllidae)
2010Co-Authors: Yikweon JangAbstract:In many species males aggregate and produce long-range advertisement signals to attract conspecific females. The majority of the receivers of these signals are probably other males most of the time, and male responses to competitors ’ signals can structure the spatial and temporal organization of the breeding aggregation and affect male mating tactics. I quantified male responses to a conspecific advertisement stimulus repeatedly over three age classes in Gryllus rubens (Orthoptera: Gryllidae) in order to estimate the type and frequency of male responses to the broadcast stimulus and to determine the factors affecting them. Factors tested included body size, wing dimorphism, age, and intensity of the broadcast stimulus. Overall, males employed acoustic response more often than positive phonotactic response. As males aged, the frequency of positive phonotactic response decreased but that of the acoustic response increased. That is, males may use positive phonotaxis in the early stages of their adult lives, possibly to find suitable calling sites or parasitize calling males, and then later in life switch to acoustic responses in response to conspecific advertisement signals. Males with smaller body size more frequently exhibited acoustic responses. This study suggests that individual variation, more than any factors measured, i
Cami L Holtmier - One of the best experts on this subject based on the ideXlab platform.
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in vivo and in vitro degradation of juvenile hormone iii in presumptive long winged and short winged Gryllus rubens
Journal of Insect Physiology, 1992Co-Authors: Anthony J. Zera, Cami L HoltmierAbstract:Abstract Degradation of exogenous juvenile hormone-III was compared between long-winged and short-winged morphs of the cricket Gryllus rubens during the last stadium. This was done to determine if morph-specific differences in haemolymph juvenile hormone esterase activity, which are thought to be important in morph determination, result in corresponding differences in in vivo hormone degradation. Percentage degradation of racemic or (10-R)-juvenile hormone-III was significantly higher in plasma from the long-winged vs the short-winged morph during the mid-stadium while no differences between the morphs were observed early in the stadium. These results paralleled morph-specific differences in plasma juvenile hormone esterase activity. Similar patterns were obtained in vivo, except for early-stadium, short-winged crickets where hormone degradation was much higher than expected based on haemolymph juvenile hormone esterase activity. When esterase activity in long-winged individuals was inhibited in vivo by a trifluoropropanone derivative, there was a corresponding decrease in in vivo hormone degradation. No morph-specific differences were observed in degree of hormone binding by haemolymph components during either the early or mid-stadium, indicating that variation in hormone binders cannot account for differences between morphs in degree of hormone degradation. Importantly, differences between morphs in hormone degradation were much less than differences in haemolymph juvenile hormone esterase activity. These results collectively document morph-specific covariation in haemolymph juvenile hormone esterase activity and in vivo hormone degradation. However, because differences between morphs in hormone degradation are not large, their functional significance with respect to morph determination remains uncertain.
Ronald R Hoy - One of the best experts on this subject based on the ideXlab platform.
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identified auditory neurons in the cricket Gryllus rubens temporal processing in calling song sensitive units
Hearing Research, 2004Co-Authors: Hamilton E Farris, Andrew C Mason, Ronald R HoyAbstract:Abstract This study characterizes aspects of the anatomy and physiology of auditory receptors and certain interneurons in the cricket Gryllus rubens. We identified an `L'-shaped ascending interneuron tuned to frequencies >15 kHz (57 dB SPL threshold at 20 kHz). Also identified were two intrasegmental `omega'-shaped interneurons that were broadly tuned to 3–65 kHz, with best sensitivity to frequencies of the male calling song (5 kHz, 52 dB SPL). The temporal sensitivity of units excited by calling song frequencies were measured using sinusoidally amplitude modulated stimuli that varied in both modulation rate and depth, parameters that vary with song propagation distance and the number of singing males. Omega cells responded like low-pass filters with a time constant of 42 ms. In contrast, receptors significantly coded modulation rates up to the maximum rate presented (85 Hz). Whereas omegas required ∼65% modulation depth at 45 Hz (calling song AM) to elicit significant synchrony coding, receptors tolerated a ∼50% reduction in modulation depth up to 85 Hz. These results suggest that omega cells in G. rubens might not play a role in detecting song modulation per se at increased distances from a singing male.
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effects of a tachinid parasitoid ormia ochracea on the behaviour and reproduction of its male and female field cricket hosts Gryllus spp
Journal of Insect Physiology, 1995Co-Authors: Shelley A Adamo, Daniel Robert, Ronald R HoyAbstract:Abstract The larvae of the tachinid parasitoid fly, Ormia ochracea , develop within the body of their host, the field crickets Gryllus integer and Gryllus rubens . The fly will also develop within the cricket Gryllus bimaculatus , which is not the natural host. For the first 3 days after entering a cricket, the first instar larvae grew inside the large thoracic muscles, but did little damage to the muscles during this time. They then migrated into the abdomen where they moulted, attached themselves to the body wall and fed primarily on the host's muscle and fat body, sparing the digestive system and CNS. Usually the host's reproductive system was only partially damaged. After the larvae entered the abdominal cavity, the host's mating, egg-laying and fighting ability (males) declined. This decline probably occurred due to the tissue damage wrought by the parasitoid. Less energy-demanding behaviours, such as grooming and feeding, were not affected during the entire period of infestation. During the first instar (when the parasitoid is embedded in the host's muscle), male crickets showed an increased tendency to attack other males. This increased incidence of agonistic behaviour occurred before the parasitoid caused significant tissue damage to the host and must therefore have been due to some other effect of the parasitoid.
David A. Gray - One of the best experts on this subject based on the ideXlab platform.
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© 2008 The Authors Journal compilation © 2008 Blackwell Publishing Ltd
2016Co-Authors: David A. Gray, Huateng Huang, Lacey L KnowlesAbstract:Blackwell Publishing LtdMolecular evidence of a peripatric origin for two sympatric species of field crickets (Gryllus rubens and G. texensis) revealed from coalescent simulations and population genetic test
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speciation divergence and the origin of Gryllus rubens behavior morphology and molecules
Insects, 2011Co-Authors: David A. GrayAbstract:The last 25 years or so has seen a huge resurgence of interest in speciation research. This has coincided with the development and widespread use of new tools in molecular genetics, especially DNA sequencing, to inform ecological and evolutionary questions. Here I review about a decade of work on the sister species of field crickets Gryllus texensis and G. rubens. This work has included analysis of morphology, behavior, and the mitochondrial DNA molecule. The molecular work in particular has dramatically re-shaped my interpretation of the speciational history of these taxa, suggesting that rather than 'sister' species we should consider these taxa as 'mother-daughter' species with G. rubens derived from within a subset of ancestral G. texensis.
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molecular evidence of a peripatric origin for two sympatric species of field crickets Gryllus rubens and g texensis revealed from coalescent simulations and population genetic tests
Molecular Ecology, 2008Co-Authors: David A. Gray, Huateng Huang, Lacey L KnowlesAbstract:Species pairs that differ primarily in characters involved in mating interactions and are largely sympatric raise intriguing questions about the mode of speciation. When species divergence is relatively recent, the footprint of the demographic history during speciation might be preserved and used to reconstruct the biogeography of species divergence. In this study, patterns of genetic variation were examined throughout the geographical range of two cryptic sister taxa of field crickets, Gryllus texensis and G. rubens; mitochondrial cytochrome oxidase I (COI) was sequenced in 365 individuals sampled from 48 localities. Despite significant molecular divergence between the species, they were not reciprocally monophyletic. We devised several analyses to statistically explore what historical processes might have given rise to this genealogical structure. The analyses indicated that the biogeographical pattern of genetic variation does not support a model of recent gene flow between species. Instead, coalescent simulations suggested that the genealogical structure within G. texensis, namely a deep split between two geographically overlapping clades, reflects historical substructure within G. texensis. Additional tests that consider the concentration of G. rubens haplotypes in one of the two G. texensis genetic clusters suggest a model of speciation in which G. rubens was derived from one lineage of a geographically subdivided ancestor. These results indicate that, despite the contemporary sympatry of G. texensis and G. rubens, the data are indicative of an peripatric origin in which G. rubens was derived from one of the two historical partitions in the species currently recognized as G. texensis. This proposed model of species divergence suggests how the interplay of geography and selection may give rise to new species, although this requires testing with multilocus data. Specifically, the model highlights how that geographical partitioning of ancestral variation in the past may augment the selectively driven divergence of characters involved in the reproductive isolation of the species today.
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molecular divergence between Gryllus rubens and Gryllus texensis sister species of field crickets orthoptera gryllidae
Canadian Entomologist, 2006Co-Authors: David A. Gray, Paul C Barnfield, M Seifried, Miriam H RichardsAbstract:We assess the degree of sequence divergence in the maternally inherited mitochon- drial cytochrome c oxidase I (COI) and cytochrome b (CytB) genes between two sister species of field crickets, Gryllus rubens Scudder, 1902 and Gryllus texensis Cade and Otte, 2000. We ana- lyzed 1460 base pairs from 10 individuals of each species; individuals were sampled from areas of both allopatry and sympatry. Overall average pairwise mitochondrial sequence divergence be- tween species was 1.4% ± 0.1% (mean ± SD); however, there was almost an order of magnitude more divergence in COI (2.59% ± 2.25%) than in CytB (0.35% ± 0.24%). Gryllus texensis ap- pears to harbor a much greater level of genetic variation than does G. rubens. Phylogenetic trees constructed from these sequences show reasonable separation of species; however, sequences are not reciprocally monophyletic. Gene tree polyphyly may reflect recent species-level divergence and (or) interspecific gene flow. The pattern of sequence divergence and genetic variation in these taxa is consistent with allopatric or peripatric speciation in Pleistocene glacial refugia in the southeastern (G. rubens ancestral lineage) and southcentral United States (G. texensis ances- tral lineage).
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Cricket Song in Sympatry: Species Specificity of Song without Reproductive Character Displacement in Gryllus rubens
Annals of the Entomological Society of America, 2004Co-Authors: Amanda S. Izzo, David A. GrayAbstract:Previous work with the cryptic sister species pair of Þeld crickets, Gryllus texensis Cade & Otte and Gryllus rubens Scudder, has implicated sexual selection in the speciation process. That study examined reproductive character displacement (RCD) in male song and female preference for song in G. texensis. No evidence of RCD was found. Here, we provide a similar analysis of RCD in G. rubens song and examine the songs of both species from areas of sympatry in an effort to document the species-speciÞcity of song in sympatry and to look for individuals with songs indicative of F1 hybrid status. We 1) Þnd no evidence for RCD in G. rubens song, 2) demonstrate the distinctness of song in sympatry, and 3) document the rarity of songs typical of F1 hybrids.
