Incubation Temperature and Sex Ratio of the Veiled Chameleon (Chamaeleo calyptratus)

2005 ◽  
Vol 39 (3) ◽  
pp. 515-518 ◽  
Author(s):  
Robin M. Andrews
Keyword(s):  
Sex Ratio ◽  
Incubation Temperature ◽  
Chamaeleo Calyptratus

scholarly journals Consistent sex ratio bias of individual female dragon lizards

2006 ◽  
Vol 2 (4) ◽  
pp. 569-572 ◽  
Author(s):  
Tobias Uller ◽  
Beth Mott ◽  
Gaetano Odierna ◽  
Mats Olsson
Keyword(s):  
Genetic Variation ◽  
Sex Ratio ◽  
Incubation Temperature ◽  
Sex Ratios ◽  
Phenotypic Traits ◽  
Female Size ◽  
Offspring Sex Ratio ◽  
Phenotypic Differences ◽  
Sex Ratio Bias ◽  
Offspring Sex

Sex ratio evolution relies on genetic variation in either the phenotypic traits that influence sex ratios or sex-determining mechanisms. However, consistent variation among females in offspring sex ratio is rarely investigated. Here, we show that female painted dragons ( Ctenophorus pictus ) have highly repeatable sex ratios among clutches within years. A consistent effect of female identity could represent stable phenotypic differences among females or genetic variation in sex-determining mechanisms. Sex ratios were not correlated with female size, body condition or coloration. Furthermore, sex ratios were not influenced by incubation temperature. However, the variation among females resulted in female-biased mean population sex ratios at hatching both within and among years.

Environmental regulation of sex determination in reptiles

1988 ◽  
Vol 322 (1208) ◽  
pp. 19-39 ◽  
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Growth And Development ◽  
Incubation Temperature ◽  
Sex Differentiation ◽  
Developmental Time ◽  
Alligator Mississippiensis ◽  
Phylogenetic Implications ◽  
History Of ◽  
Determining Factor

The various patterns of environmental sex determination in squamates, chelonians and crocodilians are described. High temperatures produce males in lizards and crocodiles but females in chelonians. Original experiments on the effects of incubation at 30 °C (100% females) or 33 °C (100% males) on development in Alligator mississippiensis are described. These include an investigation of the effect of exposing embryos briefly to a different incubation temperature on the sex ratio at hatching, and a study of the effects of 30 °C and 33 °C on growth and development of alligator embryos and gonads. A 7-day pulse of one temperature on the background of another was insufficient to alter the sex ratio dramatically. Incubation at 33 °C increased the rate of growth and development of alligator embryos. In particular, differentiation of the gonad at 33 °C was enhanced compared with 30 °C. A hypothesis is developed to explain the mechanism of temperature-dependent sex determination (TSD) in crocodilians. The processes of primary sex differentiation are considered to involve exposure to a dose of some male-determining factor during a specific quantum of developmental time during early incubation. The gene that encodes for the male- determining factor is considered to have an optimum temperature (33 °C). Any change in the temperature affects the expression o f this gene and affects the dose or quantum embryos are exposed to. In these cases there is production of females by default. The phylogenetic implications of TSD for crocodilians, and reptiles in particular, are related to the life history of the animal from conception to sexual maturity. Those animals that develop under optimal conditions grow fastest and largest and become male. A general association between the size of an animal and its sex is proposed for several types of vertebrate.

scholarly journals Temperature-Dependent Sex Determination and Artificial Incubation of Tuatara, Sphenodon Punctatus

2021 ◽  
Author(s):  
◽  
Nicola J Nelson
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Hatching Success ◽  
Conservation Management ◽  
Incubation Temperature ◽  
Management Tool ◽  
Relative Fitness ◽  
Temperature Dependent ◽  
Sphenodon Punctatus ◽  
Artificial Incubation

<p>Juveniles resulting from artificially induced and incubated eggs are often used to found or augment populations of rare reptiles, but both procedures may compromise the health of hatchlings or their fitness in natural environments. I aimed to test whether these procedures affected size or performance of juvenile tuatara, Sphenodon punctatus, New Zealand reptiles with temperature-dependent sex determination (TSD). Size and performance are phenotypic traits likely to influence fitness and eventual lifetime reproductive success, and are thus important measures of the suitability of artificial induction and incubation techniques for conservation management. I incubated 320 tuatara eggs artificially at 18, 21 and 22ºC; 52% of these were obtained by induction, the remainder were collected from natural nests. An additional 25 natural nests were left intact for investigation of TSD and effects of incubation temperature in nature. Juveniles from all incubation regimes were kept for ten months post-hatching in similar rearing conditions and sexed by laparoscopy. Induced eggs were significantly smaller than naturally laid eggs, and resulted in significantly smaller hatchlings, even when variation among clutches was accounted for. Incubation temperature did not greatly influence size at hatching, but was an important determinant of size by ten months of age; initial egg mass was the most important factor affecting size of hatchlings. Data indicate that TSD occurs in nature. The sex of hatchlings from 21 nests was investigated: 10 nests produced 100% male hatchlings, 4 nests produced 100% female hatchlings, and only 7 nests produced mixed sex ratios which ranged from 11% to 88% males. Sex of juveniles was related to temperature with a larger proportion of males produced in warmer nests. The overall percentage of male hatchlings in natural nests was 64%. Hatching success was 65% from natural nests during the 1998/99 season. Incubation temperatures throughout the year ranged from 2.9 to 34.4ºC. Global warming is likely to skew the hatchling sex ratio towards males if female tuatara are unable to select nest sites according to environmental cues. Evidence from size patterns of tuatara incubated in natural nests supports differential fitness models for the adaptive significance of TSD. The evaluation of artificial incubation as a conservation management tool demonstrated that it is a procedure that benefits conservation as it can be used reliably to produce founders; hatching success was 94% during this study. The sex ratio of artificially incubated juveniles can be easily manipulated; the pivotal temperature lies between 21 and 22ºC. Constant artificial incubation conditions resulted in larger juveniles by ten months of age than those from natural incubation. Naturally incubated juvenile tuatara, however, were faster for their size, their reaction norm to predator stimuli was to run, and they were possibly more aggressive, suggesting naturally incubated juveniles could survive better in nature. No firm conclusions can be reached on the quality of artificially incubated juvenile tuatara because further research will be required to establish the relevance of performance test results in nature and consequences of incubation regimes in the longer term with respect to relative fitness of individuals.</p>

Intraspecific genome size variation in a turtle (Trachemys scripta) exhibiting temperature-dependent sex determination

1991 ◽  
Vol 69 (9) ◽  
pp. 2306-2310 ◽  
Author(s):  
Samuel F. Lockwood ◽  
Brenden S. Holland ◽  
John W. Bickham ◽  
Brian G. Hanks ◽  
James J. Bull
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Genome Size ◽  
Incubation Temperature ◽  
Size Variation ◽  
Developmental Rate ◽  
Trachemys Scripta ◽  
Temperature Dependent ◽  
Genome Size Variation ◽  
Different Temperatures

Variation in genome size within and among populations of the pond slider, Trachemys scripta, a species with temperature-dependent sex determination, was investigated. Because genome size has been shown to affect developmental rate in various organisms, as does incubation temperature, it was hypothesized that genome size could influence sex determination in species with environmental sex determination. Significant variation in DNA content was found between geographic populations and among clutches. No significant differences in mean genome size were observed among samples incubated at different temperatures or between sexes of turtles hatched at a temperature that yields a mixed sex ratio. Thus, it appears that sex determination in T. scripta is accomplished in the absence of sex-specific and incubation-temperature-specific differences in genome size. Preliminary data from two populations, however, suggest that genome size may be significantly correlated with the threshold incubation temperature at which a mixed sex ratio is produced.

scholarly journals Developmental plasticity in an unusual animal: the effects of incubation temperature on behavior in chameleons

Behaviour ◽  
2015 ◽  
Vol 152 (10) ◽  
pp. 1307-1324 ◽  
Author(s):  
Cissy J. Ballen ◽  
Richard Shine ◽  
Mats M. Olsson
Keyword(s):  
Developmental Plasticity ◽  
Incubation Temperature ◽  
Thermal Environment ◽  
Activity Level ◽  
Phenotypic Traits ◽  
Fitness Costs ◽  
Slow Development ◽  
Foraging Tactics ◽  
Chamaeleo Calyptratus ◽  
Incubation Temperatures

The thermal environment within a reptile nest can affect the phenotypic traits of hatchlings, and hence (potentially) their fitness. Research on this topic needs to measure phenotypic traits relevant to the species involved; and hence, studies on unusual species need to measure unusual traits. We investigated the effects of two incubation temperatures on the morphology and behaviour of hatchling veiled chameleons (Chamaeleo calyptratus). Colder-incubated eggs exhibited a longer incubation period, but produced larger faster-growing hatchlings. Incubation treatment also affected a chameleon’s activity level and its unique foraging tactics. Cold-incubated animals were more sedentary, caught prey faster, and extended their tongues farther to reach prey than did their warm-incubated counterparts. Thus, the fitness costs of low temperatures in the nest (slow development, and thus late hatching) may be offset by incubation-derived enhancements in hatchling growth rates and foraging abilities.

Absence of temperature-dependent sex determination in northern populations of two cyprinodontid fishes

1991 ◽  
Vol 69 (2) ◽  
pp. 530-533 ◽  
Author(s):  
D. O. Conover ◽  
S. B. DeMond
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Life Histories ◽  
Laboratory Experiments ◽  
Fundulus Heteroclitus ◽  
Incubation Temperature ◽  
Effect Of Temperature ◽  
Temperature Dependent ◽  
Young Of The Year ◽  
Embryonic And Larval Development

We tested for an effect of temperature during embryonic and larval development on the sex ratio of offspring in two cyprinodontid fishes (Fundulus heteroclitus and Cyprinodon variegatus) having life histories in which temperature-dependent sex determination might be expected to occur. In both species, field collections showed that as young of the year recruited to the population, the sex ratio did not vary over time, nor did it deviate from 1:1. In laboratory experiments, there was no influence of incubation temperature on sex ratio in either species and sex ratios were near unity in all treatments. Although there was no evidence of temperature-dependent sex determination in the populations we studied, this result should be confirmed on other populations before it is generalized to the species level.

Transitional range of temperature, pivotal temperatures and thermosensitive stages for sex determination in reptiles

1991 ◽  
Vol 12 (2) ◽  
pp. 169-179 ◽  
Author(s):  
C. Pieau ◽  
N. Mrosovsky
Keyword(s):  
Sex Ratio ◽  
Sex Determination ◽  
Environmental Effects ◽  
Sexual Differentiation ◽  
Incubation Temperature ◽  
Sensitive Stage ◽  
Thermosensitive Period

AbstractThe function relating phenotypic sex ratio to incubation temperature in reptiles can vary in a number of ways in addition to simple differences in the temperatures giving 50% of each sex. This paper offers terminology and definitions for describing these relationships. These definitions accomodate interactions between genetic and environmental effects on sexual differentiation, and variability within populations. The paper also discusses the concept of a sensitive stage/period within incubation during which temperature can affect the direction of sexual differentiation. Thermosensitive period has previously been assessed in a variety of ways. A suggestion for a more general way of defining thermosensitive stage/period is made.

scholarly journals Warmer incubation temperature influences sea turtle survival and nullifies the benefit of a female-biased sex ratio

2020 ◽  
Vol 163 (2) ◽  
pp. 689-704
Author(s):  
Samir Martins ◽  
Elton Silva ◽  
Elena Abella ◽  
Nuno de Santos Loureiro ◽  
Adolfo Marco
Keyword(s):  
Sex Ratio ◽  
Incubation Temperature ◽  
Sea Turtle ◽  
Biased Sex Ratio

Incubation temperature affects sexual differentiation, incubation time, and posthatching survival in desert tortoises (Gopherus agassizi)

1995 ◽  
Vol 73 (11) ◽  
pp. 2091-2097 ◽  
Author(s):  
Vanessa Lewis-Winokur ◽  
Robert M. Winokur
Keyword(s):  
Sex Ratio ◽  
Incubation Time ◽  
Sexual Differentiation ◽  
Hatching Success ◽  
Incubation Temperature ◽  
Seminiferous Tubules ◽  
Temperature Dependent ◽  
Incubation Temperatures ◽  
Male To Female ◽  
Pivotal Temperature

Eggs of captive desert tortoises. Gopherus agassizi, incubated at six temperatures (25, 27, 28, 29, 29.4, and 31 °C) produced 107 specimens. Eggs incubated at 31 °C resulted in a male to female sex ratio of 5:7; all other incubation temperatures resulted in males only. Histological examination of gonads revealed that the testes of newly hatched to 3-month-old individuals showed incomplete and poorly developed seminiferous tubules. Female gonads showed a thickened cortex. Incubation times were longer at lower temperatures. Both hatching success and hatchling survivorship were lower at lower incubation temperatures. We confirm that temperature-dependent sex determination occurs in desert tortoises and that the pivotal temperature is between 31 and 32 °C.

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