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| EDUCATION This page is for adults interested in science and research. Kids, please go to the Kidz Page where you'll find lots of interesting pictures and stuff about how to keep your leo healthy and happy. You can also take a quiz there about how much you know about leopard geckos. On this page here, people can find research articles about different topics dealing with leopard geckos that might be interesting for breeders, vets, students, scholars, etc. These articles are for personal and educational use only, and not for commercial use. I have hyperlinked the articles to their pdf files, since links might be taken off the Internet. If you cite from those articles, please remember the copyright and give credit to the sources.
DISCLAIMER:
LZRDGRL does not endorse the content of any of those articles, nor recommend you start treating your leopard gecko because of information you obtained from those articles. If you are in doubt about a disease your leopard gecko might have, please take a fecal sample to the veterinary (approximately USD 20; and if necessary, the whole gecko, which is more expensive; approximately USD 75-120). Don't attempt to self-diagnose or self-medicate. Dosage is according to body weight of your leo, and the tiniest mistake may kill it. Please let an expert deal with it. If you cannot afford a vet bill, you should not house an animal. You can give it up for adoption or to a rescue, to make sure it gets properly taken care of. As a leopard gecko keeper, you are responsible for its health and well-being.
Skull of a leopard gecko:
Carnegie Museum of Natural History (CM 67524) ___________________________________________________________________________________________________________
Body Size and Male Combat Kratchovil, L., S., & Frynta, D. (2002). Body size, male combat and the evolution of sexual dimorphism in eublepharid geckos
(Squamata: Eublepharidae). Biological Journal of the Linnean Society, 76, 303–314. Abstract: Lizards of the family Eublepharidae exhibit interspecific diversity in body size, sexual size dimorphism (SSD), head size dimorphism (HSD), occurrence of male combat, and presence of male precloacal pores. Hence, they offer an opportunity for testing hypotheses for the evolution and maintenance of sexual dimorphism. Historical analysis of male agonistic behaviour indicates that territoriality is ancestral in eublepharid geckos. Within Eublepharidae, male combat disappeared twice. In keeping with predictions from sexual selection theory, both events were associated with parallel loss of male-biased HSD and ventral scent glands. Eublepharids therefore provide new evidence that male-biased dimorphic heads are weapons used in aggressive encounters and that the ventral glands probably function in territory marking rather than in intersexual communication. Male-biased SSD is a plesiomorphic characteristic and was affected by at least three inversions. Shifts in SSD and male combat were not historically correlated. Therefore, other factors than male rivalry appear responsible for SSD inversions. Eublepharids demonstrate the full scope of Rensch’s rule (small species tend to be female-larger, larger species male-larger). Most plausibly, SSD pattern hence seems to reflect body size variation. ___________________________________________________________________________________________________________ Chemicals on the Skin and Sex Recognition "Cold Boys" (males hatched at incubation temperatures for females) Dias, B. G., Ataya, R. S., Rushworth, D., Zhao, J., & Crews, D. (2006). Effect of incubation temperature and androgens on dopaminergic activity in the leopard gecko, Eublepharis macularius. Developmental Neurobiology. DOI 10.1002/dneu.
Abstract: Male leopard geckos that hatch from eggs incubated at a female-biased temperature (Tf) behave differently when compared with males hatching at a temperature which produces a male-biased sex ratio (Tm). We investigated the effect of incubation temperature and androgen implantation on aspects of the dopaminergic system of Tf and T males. Our data suggest that more dopamine (DA) is stored in the nucleus accumbens of naive Tf males compared with naive Tm males when they encounter a receptive female conspecific across a barrier. No difference was measured in the preoptic area and the ventral tegmental area (VTA). This difference in intracellular DA levels in a motivationrelated brain nucleus might be correlated with differences in sociosexual behavior observed between the two morphs. There were no differences in tyrosine hydroxylase (TH) expressing cell numbers in the VTA of cholesterol (CH)-implanted naive castrated Tf and Tm males. Only Tf males implanted with testosterone had significantly higher TH immunopositive cell numbers in the VTA compared with CH- and dihydrotestosteroneimplanted Tf males. These data indicate that both the embryonic environment as well as the circulating hormonal milieu can modulate neurochemistry, which might in turn be a basis for individual variation in behavior. _______________________________________________________________________________________________________ Conspecific cues and follicular development LaDage, L. D., & Ferkin, M. H. (2008). Do conspecific cues affect follicular development in the female leopard gecko (Eublepharis macularius)? Behaviour 145, 1027-1039.
Summary: Sexually reproducing organisms must process and respond to internal and external stimuli to successfully synchronize physiological and behavioural processes involved in reproduction. One such cue is an individual’s social environment. Interactions with conspecifics affect a female’s reproductive activity by inducing, suppressing, and/or accelerating reproductive processes. For example, many studies support the theory that the presence of a same-sex conspecific may suppress an animal’s reproductive physiology, whereas an opposite-sex conspecific may stimulate an animal’s reproductive physiology. The present study determined whether exposure to a conspecific male or female affects the onset of follicular development in sexually-experienced female leopard geckos (Eublepharis macularius). The data show that follicular growth was not affected by whether female geckos were housed next to a male conspecific, a female conspecific, or isolated from conspecifics. In addition, the number of days until the initiation of follicular development of female geckos was not affected by whether the females were housed in the presence of a conspecific or in isolation. The results are discussed within the theoretical framework of the effects of social cues on the reproductive physiology of females and the limited empirical data about such effects in squamate lizards. 
Fetus in egg. Picture purchased from www.dragoongecko.com _______________________________________________________________________________________________________ Copulation Holmes, M. M., Putz, O., Crews, D., & Wade, J. (2005). Normally occurring intersexuality and testosterone induced plasticity in the copulatory system of adult leopard geckos. Hormones and Behavior, 47, 439–445.
Abstract: The copulatory neuromuscular system of lizards is highly sexually dimorphic. Adult males possess bilateral penises called hemipenes, which are independently controlled by two muscles, the retractor penis magnus (RPM) and transversus penis (TPN). These structures are not obvious in adult females. However, in adult female leopard geckos (Eublepharis macularius), testosterone induces hemipene growth. We investigated whether these structures develop de novo in adulthood or are histologically present as rudimentary structures in the female leopard gecko. We also investigated the extent of sexual dimorphisms and plasticity in the associated neuromuscular components. To do this, we compared copulatory morphology (sizes of hemipenes, RPM and TPN muscle fibers, and associated motoneurons, as well as motoneuron and RPM fiber number) in adult females treated with testosterone, control females, and control males. All of the geckos possessed hemipenes, RPMs and TPNs, but these structures were indeed vestigial in control females. Testosterone induced striking increases in hemipene and copulatory muscle fiber size in females, but not to levels equivalent to control males. In parallel, males with increased levels of androgenic activity had larger hemipenes, suggesting naturally occurring steroid-induced plasticity. Copulatory motoneurons were not sexually dimorphic in size or number, and these measures did not respond to testosterone. The data demonstrate that the copulatory system of leopard geckos, in which gonadal sex is determined by egg incubation temperature, differs from that of many species (both reptilian and mammalian) with genotypic sex determination. Indeed, the system is remarkable in that adult females have normally occurring intersex characteristics and they exhibit substantial steroid-induced morphological plasticity in adulthood.
Cranial Joints Payne, S. L., Holliday, C. M., & Vickaryous, M. K. (2011). An osteological and histological investigation of cranial joints in geckos. The Anatomical Record 294, 399-405.
Abstract: Cranial kinesis is a widespread feature of gekkotan lizards. Previous studies of kinesis in lizards often described the relevant, mobile joints as synovial, thus characterized by the presence of a synovial cavity lined with articular cartilage. To date however, detailed investigations of cranial joint histology are lacking. We examined eight cranial joints (quadrate–articular, quadrate–pterygoid, quadrate–otooccipital, quadrate– squamosal, epipterygoid–prootic, epipterygoid–pterygoid, basisphenoid–pterygoid, and frontal–parietal) in five gekkotan species (Oeduralesueuerii, Eublepharis macularius, Hemitheconyx caudicinctus, Tarentola annularis, and Chondrodactylous bibronii) using microcomputed tomography and serial histology. Particular focus was given to the relationship between the bony and soft-tissue components of the joint. Our results demonstrate that only three of these joints are synovial: the quadrate–articular, epipterygoid–pterygoid, and basisphenoid–pterygoid joints. The frontal–parietal and quadrate–pterygoid joints are syndesmosis (fibrous), the epipterygoid–prootic and quadrate–otooccipital joints are synchondroses (cartilaginous without a synovial cavity) and the quadrate–squamosal joint was not present. Based on previous descriptions, we determine that the structure of some cranial joints is variable among lizard taxa. We caution that osteology does not necessarily predict cranial joint histology. Although the functional implications of these findings remain to be explored we note that the development of synovial joints appears to be associated with a neural crest origin for the elements involved.
Cryptosporidium ("Crypto")
Deming, C., Greiner, E., & Uhl, E. W. (2008). Prevalence of cryptosporidium infection and characteristics of oocyst shedding in a breeding colony of leopard geckos (Eublepharis macularius). Journal of Zoo and Wildlife Medicine, 39(4), 600-607.
Abstract:
Cryptosporidiosis is an emerging problem in reptile medicine and has been associated with a wasting syndrome in leopard geckos (Eublepharis macularius). This study determined the prevalence of infection in a breeding colony of leopard geckos to be 9.8%. Two groups of 20 geckos, one that was fecal positive for oocysts of Cryptosporidium sp., and one, whose individuals were fecal negative at the inception of the study, were followed for 2 mo. Fecal samples were tested for oocysts every 2 wk, body weights were measured, and a body condition score was assigned for each gecko. Selected geckos from these two groups were euthanized and necropsied. There were statistically significant differences (P < 0.05) between the two groups for mean body weight, mean body condition score, and prevalence of infection. Cryptosporidium sp. infection is endemic in this breeding colony, and there were a large number of geckos with a subclinical or carrier state of infection. These animals continued to be infected with Cryptosporidium sp. but gained weight and remained in good body condition. Only one gecko in the entire group of 40 was confirmed to be negative for oocysts or developmental stages by repeated fecal exams and histopathology. An additional 37 severely emaciated geckos from the breeding colony were euthanized, and all were positive for Cryptosporidium sp. on histopathologic examination of the gastrointestinal tract. The results of this study indicate that although some animals can recover from a clinical infection, if a gecko is severely wasted, it should be euthanized because of the poor prognosis and possible source of infection to other geckos.
Terrell, S. P., Uhl, E.W., & Funk, R. S. (2003). Proliferative enteritis in leopard geckos (Eublepharis macularius) associated with cryptosporidium sp. infection. Journal of Zoo and Wildlife Medicine, 34(1), 69-75. Abstract: Twenty-three leopard geckos (Eublepharis macularius) with various clinical histories of weight loss, anorexia, lethargy, and diarrhea were submitted either intact or as biopsy specimens to the University of Florida Anatomic Pathology Service. Gross necropsy findings in the intact geckos included marked reduction of subcutaneous adipose tissue stores at the tail base and mild thickening and reddening of the small intestine. Histologie examination revealed Cryptosporidium sp. infection associated with hyperplasia and mononuclear inflammation of the small intestine in all geckos. Parasites and lesions were only rarely observed in the stomach and large intestine of geckos. The histologie and ultrastructural lesions in the small intestine of leopard geckos infected with Crypto sporidium sp. have not been well characterized previously. This report implicates Crypto sporidium sp. as the cause of disease in the geckos and describes the range of histologie lesions observed. Xiao, L., Ryan, U. M., Gracyk, T. K., Limor, J., Li, L., Kombert, M., Junge, R., Sulaiman, R. M., Zhou, L., Arrowood, M. J., Koudela, B., Modry, D., & Lal, A. A. (2004). Genetic diversity of cryptosporidium spp. in captive reptiles. Applied and Environmental Microbiology 70(2), 891-899.
Abstract: The genetic diversity of Cryptosporidium in reptiles was analyzed by PCR-restriction fragment length polymorphism and sequence analysis of the small subunit rRNA gene. A total of 123 samples were analyzed, of which 48 snake samples, 24 lizard samples, and 3 tortoise samples were positive for Cryptosporidium. Nine different types of Cryptosporidium were found, including Cryptosporidium serpentis, Cryptosporidium desert monitor genotype, Cryptosporidium muris, Cryptosporidium parvum bovine and mouse genotypes, one C. serpentis-like parasite in a lizard, two new Cryptosporidium spp. in snakes, and one new Cryptosporidium sp. in tortoises. C. serpentis and the desert monitor genotype were the most common parasites and were found in both snakes and lizards, whereas the C. muris and C. parvum parasites detected were probably the result of ingestion of infected rodents. Sequence and biologic characterizations indicated that the desert monitor genotype was Cryptosporidium saurophilum. Two host-adapted C. serpentis genotypes were found in snakes and lizards.
Death in the Egg  
Sometimes, hatchlings don't develop fully, and the fetus dies before hatching. This little one above would have been an Eclipse, from a Stripe Eclipse father and a Reverse Stripe Afghan o'Lantern Eclipse female. The mother was a first time breeder, and the second egg (its clutchmate) was a dud. This baby had a crippled left forearm, and maybe a crippled back. It was a week overdue when I pipped the egg (= cut it open). It would also have had an underbite. From the table of gestation stages below, I would say this fetus was in stage 40 when it died. The head was flattened, and you can see the shallow impression of the external naris already. However, the body coloration was just beginning. Putrefection had already started, hence probably the translucent, loose skin. Below is an embryo that died in the egg around stage 35 (eyelids and feet formed). It was from a Tremper Enigma x Jungle Tangerine Albino pairing. The egg had collapsed and was molding. 
Developmental Effects on Reproduction Crews, D., Sakata, J., & Rehn, T. (1998). Developmental effects on intersexual and intrasexual variation in growth and reproduction in a lizard with temperature-dependent sex Determination. Review. Comparative Biochemistry and Physiology, Part C 119, 229–241.
Abstract: The mechanisms that control growth and reproduction have received considerable attention by molecular and cellular endocrinologists, yet there has been relatively little effort to link these two aspects of physiology. On the other hand, evolutionary biologists have long commented on the relationship between growth and reproduction in many species, yet have generally neglected the mechanisms underlying such complex traits. An approach that integrates the multiple proximate levels promises to provide significant insight into the evolution of neuroendocrine control mechanisms. In this chapter, we take this approach in reviewing environmental influences on growth and reproduction in the leopard gecko, Eublepharis macularius. In this species, incubation temperature during embryonic development not only determines gonadal sex, but also underlies within-sex differences in growth, adult morphology, aggressiveness, reproductive physiology and behaviour, and brain organization. Thus, the leopard gecko is an excellent model to elucidate the developmental interactions among the environment and the endocrine and nervous systems that control growth and reproduction. 
Effect of Incubation Temperature on Phenotypes (deals with scincid lizards, not leopard geckos)
Shine, R., Elphick, M. J., & Harlow, P. S. (1997). The influence of natural incubation environments on the phenotypic traits of hatchling lizards. Ecology, 78(8), 2559-2568.
Abstract: Laboratory studies have shown that incubation environments can affect morphological and behavioral phenotypes of hatchling lizards, but the relevance of this result to natural populations remains unclear. We monitored thermal regimes during the incubation period in 19 natural nests of scincid lizards (Bassiana duperreyi) in montane southeastern Australia, and experimentally translocated eggs among nests to remove the confounding or “nest of origin” (including genetic) factors with incubation conditions. We removed the eggs from the field shortly before hatching, and assessed the hatchlings’ phenotypes (body size, shape, locomotor performance). Most of the effects seen after laboratory incubation were also seen after incuabion in natural nests. Hatchling phenotypes were affected by incubation conditions as well as by “nest of origin” factors and an interaction between the two. Both the mean and the variance of incubation temperatures affected hatchling phenotypes, with male and female hatchlings differing in their norms of reaction. We found no evidence that a female’s choice of nest site depends on the specific norms of reaction of her own offspring. Overall, incubation temperatures induced approximately half as much variance in hatchling phenotypes as did “nest-of-origin” effects. We conclude that incubation-induced phenotypic plasticity in hatchling reptiles may be important in the natural environment, as well as in the laboratory. Effects of Incubation Temperature on Gonadal Sex/ Agonistic Behavior; Effects of Hormones Huang, V., Sakata, J.T., Rhen, T., Coomber, P., Simmonds, S., & Crews, D. (2008). Constraints on temperature-dependent sex determination in the leopard gecko (Eublepharis macularius): response to Kratochvil et al. Naturwissenschaften. DOI 10.1007/s00114-008-0433-5
Abstract: Kratochvil et al. (Naturwissenschaften 95:209–215, 2008) reported recently that in the leopard gecko (Eublepharis macularius) of the family Eublepharidae with temperature-dependent sex determination (TSD), clutches in which eggs were incubated at the same temperature produce only same-sex siblings. Interpreting this result in light of studies of sex steroid hormone involvement in sex determination, they suggested that maternally derived yolk steroid hormones could constrain sex-determining mechanisms in TSD reptiles. We have worked extensively with this species and have routinely incubated clutches at constant temperatures. To test the consistency of high frequency same-sex clutches across different incubation temperatures, we examined our records of clutches at the University of Texas at Austin from 1992 to 2001. We observed that clutches in which eggs were incubated at the same incubation temperature produced mixed-sex clutches as well as same-sex clutches. Furthermore, cases in which eggs within a clutch were separated and incubated at different temperatures produced the expected number of mixed-sex clutches. These results suggest that maternal influences on sex determination are secondary relative to incubation temperature effects. Crews, D. (2003). Sex determination: where environment and genetics meet. Evolution & Development, 5:1, 50-55. Summary: In mammals and birds the genetic constitution established at the time of fertilization determines the type of gonad that develops, whereas in all crocodilians and many turtles it is the temperature experienced during the mid-trimester of embryogenesis that initiates gonadal differentiation. Research with the red-eared slider suggests considerable conservation in the genetic cascades that underlie the sex determination process in vertebrates and, further, that the patterns of expression of these genes appear to reflect phylogenetic relationships, with turtles being more similar to mammals than they are to birds and crocodilians. After the determination and differentiation of an individual’s gonadal sex, epigenetic forces shape those morphological, physiological, and behavioral traits that characterize each individual’s unique sexuality. Research with the leopard gecko thus relates to the fundamental question of what factors determine individual variability, particularly as it relates to sexually dimorphic behaviors. Taken together, this research illustrates how sexuality depends on sex, but sex should not be confused with sexuality. That is, sex is merely a means of categorizing individuals or gonads, whereas sexuality serves as a descriptor of concordant traits each of which is typically sexually dimorphic in its expression. Rhen, T., & Crews, D. (2001). Distribution of androgen and estrogen receptor mRNA in the brain and reproductive tissues of the leopard gecko, Eublepharis macularius. The Journal of Comparative Neurology, 437, 385-397.
Abstract: Incubation temperature during embryonic development determines gonadal sex in the leopard gecko, Eublepharis macularius. In addition, both incubation temperature and gonadal sex influence behavioral responses to androgen and estrogen treatments in adulthood. Although these findings suggest that temperature and sex steroids act upon a common neural substrate to influence behavior, it is unclear where temperature and hormone effects are integrated. To begin to address this question, we identified areas of the leopard gecko brain that express androgen receptor (AR) and estrogen receptor (ER) mRNA. We gonadectomized adult female and male geckos from an incubation temperature that produces a female-biased sex ratio and another temperature that produces a male-biased sex ratio. Females and males from both temperatures were then treated with equivalent levels of various sex steroids. Region-specific patterns of AR mRNA expression and ER mRNA expression were observed upon hybridization of radiolabeled (35S) cRNA probes to thin sections of reproductive tissues (male hemipenes and female oviduct) and brain. Labeling for AR mRNA was very intense in the epithelium, but not within the body, of the male hemipenes. In contrast, expression of ER mRNA was prominent in most of the oviduct but not in the luminal epithelium. Within the brain, labeling for AR mRNA was conspicuous in the anterior olfactory nucleus, the lateral septum, the medial preoptic area, the periventricular preoptic area, the external nucleus of the amygdala, the anterior hypothalamus, the ventromedial hypothalamus, the premammillary nucleus, and the caudal portion of the periventricular nucleus of the hypothalamus. Expression of ER mRNA was sparse in the septum and was prominent in the ventromedial hypothalamus, the caudal portion of the periventricular nucleus of the hypothalamus, and a group of cells near the torus semicircularis. Many of these brain regions have been implicated in the regulation of hormone-dependent, sex-typical reproductive and agonistic behaviors in other vertebrates. Consequently, these nuclei are likely to control such behaviors in the leopard gecko and also are candidate neural substrates for mediating temperature effects on behavior. Rehn, T., Sakata, J. T., & Crews, D. (2005). Effects of gonadal sex and incubation temperature on the ontogeny of gonadal steroid concentrations and secondary sex structures in leopard geckos, Eublepharis macularius. General and Comparative Endocrinology, 142, 289–296. Abstract:
Incubation temperature during embryonic development determines gonadal sex in the leopard gecko (Eublepharis macularius). Incubation temperature and gonadal sex jointly influence the display of sexual and agonistic behavior in adult leopard geckos. These differences in adult behavior are organized prior to sexual maturity, and it is plausible that post-natal hormones influence neural and behavioral differentiation. Here we assessed incubation temperature and sex effects on sex steroid levels in leopard geckos at 2, 10, and 25 weeks of age and monitored the development of male secondary sex structures. Males had significantly higher androgen concentrations at all time points, whereas females had significantly higher 17ß-estradiol (E2) concentrations only at 10 and 25 weeks. Within males, age but not incubation temperature aVected steroid levels and morphological development. Male androgen levels increased modestly by 10 and dramatically by 25 weeks of age, whereas E2 levels remained unchanged over this period. Most males had signs of hemipenes at 10 weeks of age, and all males had hemipenes and open preanal pores by 25 weeks of age. In females, age and incubation temperature affected E2 and dihydrotestosterone (DHT) but not T concentrations. Controlling for age, females from 34 °C have higher DHT and lower E2 levels than females from 30°C. Further, E2 concentrations increased significantly from 2 to 10 weeks, after which E2 levels remained steady. Together, these results indicate that sexually dimorphic levels of steroids play a major role in the development of leopard gecko behavior and morphology. Furthermore, these data suggest that the organizational effects of incubation temperature on adult female phenotype could be, in part, mediated by incubation temperature effects on steroid hormone levels during juvenile development. 
Mack Snow Ghost Jungle hatchling. Picture from www.dragoongecko.com Rhen, T., & Crews, D. (1999). Organization and activation of sexual and agonistic behavior in the leopard gecko, Eublepharis macularius. Reproductive Neuroendocrinology, 71, 252-261.
Abstract: Gonadal sex is determined by the temperature experienced during incubation in the leopard gecko (Eublepharis macularius). Furthermore, both factors, incubation temperature and gonadal sex, influence adult sexual and agonistic behavior in this species. Yet it is unclear whether such differences in behavior are irreversibly organized during development or are mediated by differences in hormone levels in adulthood. To address this question, we gonadectomized adult females and males generated from a female-biased (30°C) and a male-biased (32.5°C) incubation temperature and treated them with equivalent levels of various sex steroids. We found that 17ß-estradiol (E2) activated sexual receptivity in females but not males, suggesting an organized sex difference in behavioral sensitivity to E2. There were also organized and activated sex differences in attractivity to stimulus males. Although females were more attractive than males when treated with E2, both sexes were equally unattractive when treated with dihydrotestosterone (DHT) or testosterone (T). Likewise, sex differences in aggressive and submissive behavior were organized and activated. Attacks on stimulus males were activated by T in males but not in females. In contrast, hormones did not influence flight behavior in males but did affect female submissiveness. Overall, males also evoked more attacks by stimulus males than did females. Nevertheless, females and males treated with androgens evoked more attacks than animals of the same sex that were treated with cholesterol or E2. Incubation temperature had some weak effects on certain behaviors and no effect on others. This suggests that temperature effects in gonadally intact geckos may be due primarily to differences in circulating levels of hormones in adulthood. We conclude that gonadal sex has both organizational and activational effects on various behaviors in the leopard gecko. Rehn, T., Sakata, J. T., Zeller, M., & Crews, D. (2000). Sex steroid levels across the reproductive cycle of female leopard geckos, Eublepharis macularius, from different incubation temperatures. General and Comparative Endocrinology, 118, 322–331.
Abstract: Incubation temperature during embryonic development determines gonadal sex in many reptiles, including the leopard gecko (Eublepharis macularius). In this study, we examined the hormonal and behavioral changes that occur during the reproductive cycle of female leopard geckos from four (i.e., 26, 30, 32.5, and 34°C) incubation temperatures. Controlling for reproductive status, plasma levels of dihydrotestosterone (DHT), testosterone (T), and progesterone (P) varied with incubation temperature but estradiol 17-b (E2) levels did not. Controlling for the effects of incubation temperature, DHT and T levels were low when females were previtellogenic, increased slightly during early vitellogenesis, increased dramatically during late vitellogenesis (i.e., prior to ovulation), and then decreased to previtellogenic levels after ovulation. In contrast, E2 levels increased gradually from the previtellogenic stage to the early vitellogenic stage, peaked during late vitellogenesis, and decreased to previtellogenic levels after ovulation. Levels of P increased from the previtellogenic stage to the early vitellogenic stage, remained elevated during late vitellogenesis, and then decreased after ovulation. Moreover, we determined that females were not sexually receptive when previtellogenic, were somewhat receptive during early vitellogenesis (;20% receptive), were most receptive during late vitellogenesis (;80% receptive), and were again unreceptive after ovulation. Incubation temperature did not influence receptivity. Overall, these data show that hormone levels and behavior change coordinately during the reproductive cycle. Although incubation temperature has persistent effects on endocrine physiology in adult female leopard geckos, these effects are modest compared to hormonal changes across the reproductive cycle.
Embryonic Stages of the Leopard Gecko Wise, P. A. D., Vickaryous, M. K. & Russell, A. P. (2009). An embryonic staging table for in ovo development of Eublepharis macularius, the leopard gecko. The Anatomical Record, 292, 1198-1212. Abstract: Squamates constitute a major vertebrate radiation, representing almost one-third of all known amniotes. Although speciose and morphologically diverse, they remain poorly represented in developmental studies. Here, we present an embryonic staging table of in ovo development for the basal gekkotan Eublepharis macularius (the leopard gecko) and advocate this species as a laboratory-appropriate developmental model. E. macularius, is a hardy and tractable species of relatively large body size (with concomitantly relatively large eggs and embryos), that is widely available and easy to maintain and propagate. Additionally, E. macularius displays a body plan appropriate to the study of the plesiomorphic quadrupedal condition of early pentadactylous terrestrial amniotes. Although not unexpected, it is worth noting that the morphological events characterizing limb development in E. macularius are comparable with those described for the avian Gallus gallus. Therefore, E. macularius holds great promise as a model for developmental studies focusing on pentadactyly and the formation of digits. Furthermore, it is also attractive as a developmental model because it demonstrates temperature-dependent sex determination. The staging table presented herein is based on an all-female series and represents the entire 52 day in ovo period. Overall, embryogenesis of E. macularius is similar to that of other squamates in terms of developmental stage attained at the time of oviposition, patterns of limb and pharyngeal arch development, and features of the appearance of scalation and pigmentation, indicative of a conserved developmental program. Below, you can see a reprint of the 42 enbryonic stages tables from the above article: Wise, P. A. D., Vickaryous, M. K. & Russell, A. P. (2009) |  |  |
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_______________________________________________________________________________________________________ Eye defect (after-birth defect; not hatched like this)
picture right after hatching (no deformity)
Right to display pictures purchased from Haley P., New Hampshire, 07/27/2011. This Mack Snow hatched a few days ago appearing healthy, but since the hatchling's first shed, his left eye seems to be hanging out of its socket. The vet decided against surgically removing the eye at this point in the hatchling's life, and prescribed an oral antibiotic, a probiotic, and an eye ointment to be replaced with artificial tears later.
Fluid Sack 
photo donated by James Lamantia Reverse Stripe hatchling born with a fluid sack around its head, which will probably recede, so the hatchling can lead a normal life.
General Overview Poch, J. (2003). Leopard Gecko. Eublepharis macularius. Unpublished student paper. Retrieved Dec. 28, 2010, from http://usf.usfca.edu/fac_staff/dever/gekkopaper.pdf Introduction: In recent years, reptiles have become increasingly popular to have as pets. This is especially true with the leopard gecko, Eublepharis macularius, which has become the most popular gecko to be kept in captivity. This is because of the relative effortlessness required to care for the geckos and their bright colored pattern. They have also become primary subjects in research concerning hormones and the affected behaviors. They are abspecies of interest because the temperature at which the eggs are incubated determines their sexual dimorphism instead of a genetic component (Viets, Tousignant, Ewert, Nelson and Crews, 1993). This species is also unique in its moveable eyes and absence of the well-studied adhesive toe pads found in most geckos (Virtual Museum of Natural History, 2003). In all, this species can provide important insights into the physiology of geckos which will be covered in the following paper, however additionally studies are needed to comprehend the many aspects of this species.
Growth and Temperature Kellar, A., & De Nardo, D. F. (1995). Behavioral Thermoregulation Increases Growth Rate in a Nocturnal Lizard. Journal of Herpetology, 29(2), 157-162.
Abstract: We tested the hypothesis that thermoregulation increases growth rate in nocturnal lizards. Leopard geckos (Eublepharis macularius) maintained from hatching at 25 C grew at a rate of 0.11 g/day, while geckos allowed to thermoregulate at preferred body temperatures (30 C for 13.5 h per day) grew 1.5 times as fast (0.16 g/day). Long-term thermal treatment had a significant reverse acclimation effect on preferred body temperature (Tp): Tp was 1.2 C lower in thermoregulatory individuals than in those kept at 25 C. Feeding and time of day also had significant but minor effects on Tp. Despite their nocturnal ecology, leopard geckos seem to be typical among lizards in requiring a diurnal heat source for maximal growth. This result provides a physiological explanation for the observation that some nocturnal lizards thermoregulate in burrows during the day, and may have implications for the biogeography of nocturnal ectotherms.
"Hot Girls": Females incubated at 35 degrees C can produce fertile eggs with viable hatchlings Viets, B. E., Tousignant, A., Ewert, M. A., Nelson, C. E., & Crews, D. (1993). Temperature-dependent sex determination in the leopard gecko, Eublepharis macularius. The Journal of Experimental Zoology, 265, 579-683.
Abstract: The leopard gecko, Eublepharis macularius, has ternperature-dependent sex determination (TSD). Previous reports have shown that females are produced predominately at cool incubation temperatures and males are produced predominately at warm incubation temperatures (Pattern Ib). We report here that incubation at even higher temperatures (34 and 35°C) produces mostly females (Pattern 11). The lethal maximum constant incubation temperature for this species appears to be just above 35°C. Although a previous study indicated that females from a warm incubation temperature (32°C) failed to lay eggs, we found that 12 of 14 mature females incubated at 32.5"C, and 5 of 6 mature females incubated at 34°C produced fertile eggs and viable hatchlings.
Moving & Eating: Chemosensory Tongue Flicking and Labial Licking
Cooper, W. E., Jr., DePerno, C.S., & Steele, L. A. (1996). Effects of movement and eating on chemosensory tongue-flicking and on labial-licking in the leopard gecko (Eublepharis macularius). Chemoecology, 7, 179-183.
Summary: Two forms of lingual protrusion, tongueflicking and labial-licking, were differentially affected by combinations of movement and eating conditions in a eublepharid gecko (Eublepharis macularius). Tongueflicking, in which the tongue contacts substrates beyond the lizard's body, occurred at increased rates during locomotion and during locomotion was significantly more frequent after eating than in a baseline condition. Labial-licking, in which a protruded portion of the tongue touches the labial, mental or rostral scales that surround the mouth, increased after eating. Unlike tongue-flick rates, by far the highest labial-lick rates were observed in stationary lizards after eating. The elevated tongue-flicking rates during movement after eating may be a manifestation of a postingestive chemosensory search for prey. In addition to grooming, several possible chemosensory functions of labial-licking are discussed, including gustatory sampling, sampling prey chemicals on the labials for transfer to the vomeronasal system, and redistribution of chemicals on the tongue to enhance transfer. It is suggested that labial-licking might help motionless lizards maintain vigilance for visual prey stimuli associated with the specific chemical prey cues. Another possible explanation for the increased labial-lick rate while motionless after eating is that prey chemicals induce tongue-flicking, but that the distance protruded is lessened and the tongue does not contact environmental substrates. Tongue-flicking while stationary is unlikely to lead to detection of additional prey and might incur detection by the lizard's predators or prey.
Necropsy of Andiamo (Reverse Stripe Eclipse; euthanized after stroke/paralysis in March 2011; one year old)
Noises, Squeaks, Sound, and Hearing (deals with the leopard lizard, Gambelia w. wislizenii, with comparisons to Tokay geckos, and not with leopard geckos, but very interesting!) Wever, E. G., Hepp-Reymond, M.-C., & Vernon, J.A. (1966). Vocalization and Hearing in the Leopard Lizard. Proceedings of the National Academy of Sciences of the United States of America, 55(1), 98-106. Introduction: Most lizards are silent, and only the members of one family, the gekkonids, are noted for their vocal accomplishments. Some of the geckos produce loud and impressive sounds, often described as chirps or squeaks, and these sounds are thought to have a function in mating. A few lizards have been reported to make hissing sounds, especially when disturbed. It is possible that these sounds are not deliberate vocalizations, but represent only a sudden expiration of air as a part of an alarm reaction.
Preoptic area-anterior hypothalamus (POAH) influences sexual behavior but not thermoregulatory rhythms (neurological/brain research) Edwards, N., Kriegsfeld, L., Crews, D. (2004). Neural substrates for sexual and thermoregulatory behavior in themale leopard gecko, Eublepharis macularius. Brain Research, 1029, 77–83.
Abstract: The preoptic area–anterior hypothalamus (POAH) continuum is critical for the integration of environmental, physiological, and behavioral cues associated with reproduction in vertebrates. In the present study, radiofrequency lesions in the POAH abolished sexual behavior in the leopard gecko (Eublepharis macularius). Furthermore, results suggest a differential effect of POAH lesions on those behaviors regarded as appetitive (tail vibration and grip) and those regarded as consummatory (mounting and copulation), with consummatory behaviors being affected to a greater extent. E. macularius is an ectothermic vertebrate that modulates body temperature behaviorally relative to ambient temperature. In vertebrates, the POAH is also an important integrator of thermoregulation. Thus, the present study investigated whether lesions that disrupt reproductive behavior also disrupt body temperature regulation. While virtually all males displayed diurnal rhythms in thermoregulatory behavior prior to surgery, this pattern was abolished in a small proportion of animals bearing POAH lesions. Lesions that abolished thermoregulatory rhythms involved the suprachiasmatic nucleus (SCN), whereas lesions confined to the POAH, while dramatically influencing sexual behavior, did not affect thermoregulatory rhythms or temperature set point. Together, these findings identify the POAH as an important neural locus regulating sexual behavior but not thermoregulation and suggest that the SCN acts as a pacemaker controlling daily behavioral temperature regulation in this species.
Prey and Chemical Discrimination Cooper, Jr., W. E. (1995). Prey chemical discrimination and foraging mode in gekkonoid lizards. Herpetological Monographs, 9, 120-129.
Abstract: Relationships among phylogeny, foraging mode, and prey chemical discrimination by tongue-flicking were investigated by experimentally testing for the presence of lingually mediated prey chemical discrimination in representatives of two families of gekkonoid lizards having different foraging modes. In the experiments, the tongue-flicking and biting responses of each lizard were recorded in response to cotton swabs bearing three classes of stimuli: prey surface chemicals, cologne as a pungency control, and deionized water as an odorless control. In a eublepharid species, Eublepharis macularius, the tongue-flick rate, the proportion of individuals attacking the swab, and a composite measure combining effects of tongue-flicking and attack (TFAS(R)) were significantly higher and the latency to attack significantly shorter in the prey stimulus condition than in the other conditions, which did not themselves differ. In contrast, no tongue-flicking or attacks were observed in any of the conditions for two gekkonid species, Thecadactylus rapicauda and Gekko gecko. Because eublepharids are active foragers whereas gekkonids are ambush foragers, prey chemical discrimination was associated with active foraging, as predicted. Prior to this report, all families of ambush-foraging lizards known to lack prey chemical discrimination belonged to a single clade, Iguania. Actively foraging carnivorous lizards identify prey by chemical cues and belong to Scleroglossa, which includes the families studied here. It is argued that adoption of active foraging may have induced selection for gain of prey chemical discrimination involving tongueflicking in eublepharids. Phylogeny and the presence or absence of prey chemical discrimination are closely related in lizard families because foraging mode is conservative in the major clades Iguania and Scleroglossa.
Social Experience and Territorial/Reproductive Behavior in Male Leopard Geckos Sakata, J. T., Gupta, A., Chuang, C.-P., & Crews, D. (2002). Social experience affects territorial and reproductive behaviours in male leopard geckos, Eublepharis macularius. Animal Behaviour, 26, 487-493.
Abstract: Social interactions have lasting effects on behaviour and physiology in a variety of organisms. In the leopard gecko, Eublepharis macularius, social experience alters neural metabolism and elevates circulating concentrations of androgens. In this study, we assessed the effects of social experience (housing with females versus housing in isolation) on the expression of social behaviours in male geckos (1) when gonadally intact, (2) following castration and (3) following testosterone administration. Given the neural and endocrine changes following social experience, we hypothesized that social experience would increase the capacity to display territorial and courtship behaviour in male leopard geckos. We found that intact males previously housed with females (experienced males) displayed more territorial marking and more activity when exposed to a neutral test arena relative to males housed in isolation (naïve males). Experienced males continued to show more marking and activity in the testing arena relative to naïve males following castration. However, the courtship behaviour of castrated naïve and experienced males did not differ significantly. Following testosterone administration, experienced males again showed more activity in the empty test arena and tended to show more courtship behaviour. In summary, we found support for the hypothesis that social experience leads to changes in territorial and courtship behaviours and, moreover, found that male leopard geckos share some degree of commonality with other vertebrates in behavioural plasticity following social experience.
Tail, dropped Above is the tail of Piglet, a Normal juvenile, dropped on 04/21/2011 after she escaped from her cage through the hole where the power cable goes through. She ran through the living-room and met Lottie, the cat (who is declawed and did not harm her, but startled her so much that Piglet severed and threw off her whole tail, first a big chunk, and then the last segment right behind the vent. She literally gave all she had to distract Lottie and hide under a chaos of cables behind the gecko cage. She hissed loudly.). Piglet survived and is recuperating and regrowing her tail. She is going to be adopted. Below, you see a series of tail-drop process pictures taken by Dennis Blankenship. You will notice that the tail started separating in two different panes. The preserved part folds inside, while the edges of the thrown-off part stick out. The tail is actually an extension of the gecko's spine. By the way, when a tail regrows, there is no bone in it anymore; just muscle. That means it also does not have different segments to throw off anymore. You would think the gecko can still throw off the whole regrown tail, though. Ask a specialist.
License to display purchased from Dennis Blankenship A good research article to read about this is the following: Higham, T. E., & Russell, A. P. (2010). Flip, flop and fly: modulated motor control and highly variable movement patterns of autotomized gecko tails. Biol. Lett., 6, 70-73. doi: 10.1098/rsbl.2009.0577 Abstract: Many animals lose and regenerate appendages, and tail autotomy in lizards is an extremely well-studied example of this. Whereas the energetic, ecological and functional ramifications of tail loss for many lizards have been extensively documented, little is known about the behaviour and neuromuscular control of the autotomized tail. We used electromyography and high-speed video to quantify the motor control and movement patterns of autotomized tails of leopard geckos (Eublepharis macularius). In addition to rhythmic swinging, we show that they exhibit extremely complex movement patterns for up to 30 min following autotomy, including acrobatic flips up to 3 cm in height. Unlike the output of most central pattern generators (CPGs), muscular control of the tail is variable and can be arrhythmic. We suggest that the gecko tail is well suited for studies involving CPGs, given that this spinal preparation is naturally occurring, requires no surgery and exhibits complex modulation.
Testosterone and Sexual Behavior in Females Rhen, T., Ross, J., & Crews, D. (1999). Effects of testosterone on sexual bhavior and mrphology in ault female leopard geckos, Eublepharis macularius. Hormones and Behavior 36, 119–128.
Abstract: The leopard gecko, Eublepharis macularius, is a species in which testosterone (T) is the primary circulating sex hormone in adults of both sexes. There are, however, sex differences in T physiology. Whereas males have prolonged periods with high T levels, T levels cycle in accord with follicular development in females. Specifically, T concentration increases during vitellogenesis, drops after ovulation, and then remains at previtellogeniclevels until eggs are laid and the next follicular cycle begins. To determine the function of T in females, we manipulated both the level and the duration of T elevation using Silastic implants in intact, adult female leopard geckos. Females had low (;1 ng/ml), medium (;100 ng/ml), or high (;200 ng/ml) T levels for either a short (8 days) or a long (35 days) duration. Behavior tests with males were conducted on days 1–5 in the short duration group or on days 29–33 in the long-duration group. For both short- and long-duration groups, T treatment decreased attractivity in females with medium and high T levels compared to females with low T levels. In contrast, females with a medium T level were more receptive than females with a low T level in the short duration group. Females in the long-duration group were unreceptive regardless of T level. Females treated for a long duration also displayed more aggression toward and evoked more aggression from males than short duration females. Short-duration T treatment had no masculinizing effect on female morphology, whereas medium and high T levels for a long duration induced development of hemipenes. Overall, these results suggest that T can both increase and decrease sexual behaviors in the female leopard gecko.
"Translucent" Hatchling (photo: with permission from Kelli Hammack from HISS) 
Radar Enigma x Radar; lived only a few hours; not premature. Genetic mutation? For comparison: here is an interview on geckotime with Ron Tremper mentioning the "blue-bellied" hatchlings
Underdeveloped limbs (birth defect)
The hatchling below was born with a shortened and malformed right front leg. The breeder recorded temperature fluctuations in the incubator. You can see that several digits are missing or stubby. It also has a hunchback.
License to display purchased from Dennis Blankenship
Vermiculite (dangers of ~) Pugsley, S. L., Spratt, D., & Samour, J.H. (1985). Death in leopard geckos (Eublepharis macularius) following ingestion of vermiculite. Laboratory Animals, 19, 284-287.
Summary: This paper details the clinical and post-mortem findings of leopard geckos following ingestion of vermiculite bedding material. Death was attributed to the high magnesium content of the vermiculite.
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