Reproduction In Lizards Research Articles

Stressful Body Temperatures as a Maternal Effect on Lizard Reproduction

Stressful Body Temperatures as a Maternal Effect on Lizard Reproduction

Factors influencing tropical lizard reproduction vary by microhabitat but not forest type

Abstract To understand mechanisms behind enigmatic declines of tropical reptiles, knowledge of species interactions and how they vary over space and time is important. Some tropical lizard population dynamics can be highly influenced by egg survival. Yet relatively few studies have examined relationships between lizard reproductive success and egg predators across forest and microhabitat types. In this study, we examined variation in probability of egg depredation, predatory ant abundance, prey availability, and the number of lizards and eggs encountered across four different forest types (abandoned agroforestry, abandoned plantation, secondary forest, and old-growth forest) and three microhabitats (buttress, fallen log, and leaf-litter) at La Selva Biological Station, Costa Rica. Based on previous studies, we made three hypotheses about how lizard egg abundance, egg survival, and predatory ant numbers would be related across microhabitat and forest type. Of these hypotheses, only one was supported: we found more lizard eggs in buttress and fallen log microhabitats than leaf-litter. We did not observe any differences in lizard reproduction or numbers of invertebrates by forest type alone. Based on patterns observed in this study, we suggest that future studies investigating tropical leaf-litter lizard declines focus on environmental variation at the microhabitat scale.

Perfluorooctanoic acid exposure impact a trade-off between self-maintenance and reproduction in lizards (Eremias argus) in a gender-dependent manner

The trade-off between self-maintenance and reproduction has been explored wildly in reptiles. However, the effects of exogenous pollutants on the life history traits of reptiles have not been paid attention to. In the current study, lizards (Eremias argus), living in the soil polluted by perfluorooctanoic acid (PFOA) were selected as the main focus. Bodyweight, survival rate, clutch characteristics and biochemical analysis (immune response, lipid accumulation, sex steroid secretion, antioxidant level, and metabolomics) were investigated and the results revealed that lizards’ life-history trade-offs are gender-dependent: females were more inclined to choose a “Conservative” life-history strategy. After 60 days of exposure to PFOA, larger body weight, higher survival rate, stronger immune response, and lighter egg mass in females suggested that their trade-offs are more biased towards self-maintenance. Whereas, the “Risk” strategy would more popular among males: reduced body weight and survival rate, and suffering from oxidative damage indicated that males made little investment in self-maintenance.

Australian lizards are outstanding models for reproductive biology research

Australian lizards are a diverse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable diversity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship; mechanisms involved in mating, egg production, and sperm competition; nesting and gestation; sex determination; and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.

Effects of L-Glufosinate-ammonium and temperature on reproduction controlled by neuroendocrine system in lizard (Eremias argus)

In the context of global warming, an important issue is that many pesticides become more toxic, putting non-target organisms at higher risk of pesticide exposure. Eremias argus (a native Chinese lizard) was selected as animal model in this study. As a kind of poikilothermic vertebrate, E.argus is sensitive to temperature change. The experimental design [(with or without L-Glufosinate-ammonium (L-GLA) pollution × two temperatures (25 and 30 °C)] was used in this study for 90 days to identify the chronic effects of the pesticide–temperature interaction on the lizards’ neuroendocrine-regulated reproduction. Survival rate, body weight, clutch characteristics, testicular histopathology, the content of neurotransmitters and related enzyme activity, the level of sex steroid, the expression of Heat shock protein 70 (HSP70), antioxidant system, the accumulation and degradation of L-GLA were examined. Results showed that L-GLA disrupt reproduction of lizards through hypothalamus-pituitary-gonad (HPG) axis. In addition, temperature can not only change the environmental behavior of pesticides, but also alter the physiological characteristics of lizards. Thus, our results emphasized that temperature is an essential abiotic factor that should not be overlooked in ecotoxicological studies.

Low precipitation aggravates the impact of extreme high temperatures on lizard reproduction.

Extreme high temperatures are occurring more frequently with ongoing anthropogenic climate warming, but the experimental tests of the effects of high temperatures on terrestrial vertebrates in natural conditions are rare. In this study, we investigated the effects of extreme high temperatures on female reproduction and offspring traits of multi-ocellated racerunners (Eremias multiocellata) kept in field enclosures in the desert steppe of Inner Mongolia. Our studies indicate that high temperatures significantly affect the gestation period and reproductive output of females and the offspring sex ratio, but have little impact on offspring body size and mass. More interestingly, we found that the effect of extreme high temperatures on female reproductive output was not consistent between two consecutive years that differed in precipitation. Low precipitation may aggravate the impact of climate warming on lizards and negatively affect the survival of lizards in the desert steppe. Our results provide evidence that temperature interacts with precipitation to determine the life history of lizards, and they suggest that a drier and hotter environment, such as the future climate in arid mid-latitude areas, will likely impose severe pressure on lizard populations, which are an important component of the food web in desert areas around the world.

Effects of intense wildfires on the nesting ecology of oviparous montane lizards

In midsummer 2002–2003, intense wildfires raged through the Brindabella Range of south-eastern Australia, including sites where we have studied the ecology of scincid lizards (especially Bassiana duperreyi) for decades. Data-loggers measured the thermal regimes experienced by eggs during these fires (revealing lethally high temperatures in nests under logs in the forest but minimal effect in nests under rocks in clearings). Eggs from forest-clearing nests hatched successfully. Reproductive output of lizards in one area was reduced in the years post-fire (perhaps because of inadequate food [insect] abundance to fuel female reproduction) but soon recovered. The fires reduced vegetation density and thus increased the availability of sun-exposed rocks that serve as potential nest sites. However, the magnitude and duration of these effects differed among sites. Five years after these intense fires, canopy openness (and thus, sunlight penetration to create thermally suitable nest sites) was indistinguishable from pre-fire conditions. Our data reveal strong spatial heterogeneity both in the immediate effects of fire on lizard reproduction and in longer-term post-fire changes in habitat quality. Surprisingly, these intense wildfires had only transitory and local effects on nest-site availability for the heliothermic lizards that we study, but impacts likely were more severe on sympatric taxa that depend upon moist cool microhabitats.

Size Distribution Suggests a Seasonal Effect on Reproduction ofLepidodactylus lugubrison Okinawajima Island, Japan, the Northernmost Distributional Area

Abstract Lepidodactylus lugubris is one of the most widespread geckos distributed throughout tropical Asia and the Pacific, and some populations have been introduced to seasonal subtropical areas. On tropical islands, L. lugubris reproduces throughout the year, and it is considered potentially to be a continuous breeder. Generally reproduction in lizards is greatly affected by climate, and seasonality brings a cyclic reproductive pattern. Therefore, reproduction of invasive populations of L. lugubris in a seasonal subtropical area is likely to be affected by the climate there. In this paper, I report seasonal change in size distribution of L. lugubris in northern Okinawajima Island, Ryukyu Archipelago, Japan, where the species experiences a cold winter season. In early summer, most individuals were adults, and hatchlings did not exist. In autumn, both adults and hatchlings were found, and the size distribution was bimodal (a gap exists between two groups). The change of size distribution between the two s...

The ecology of lizard reproductive output

ABSTRACTAim We provide a new quantitative analysis of lizard reproductive ecology. Comparative studies of lizard reproduction to date have usually considered life‐history components separately. Instead, we examine the rate of production (productivity hereafter) calculated as the total mass of offspring produced in a year. We test whether productivity is influenced by proxies of adult mortality rates such as insularity and fossorial habits, by measures of temperature such as environmental and body temperatures, mode of reproduction and activity times, and by environmental productivity and diet. We further examine whether low productivity is linked to high extinction risk.Location World‐wide.Methods We assembled a database containing 551 lizard species, their phylogenetic relationships and multiple life history and ecological variables from the literature. We use phylogenetically informed statistical models to estimate the factors related to lizard productivity.Results Some, but not all, predictions of metabolic and life‐history theories are supported. When analysed separately, clutch size, relative clutch mass and brood frequency are poorly correlated with body mass, but their product – productivity – is well correlated with mass. The allometry of productivity scales similarly to metabolic rate, suggesting that a constant fraction of assimilated energy is allocated to production irrespective of body size. Island species were less productive than continental species. Mass‐specific productivity was positively correlated with environmental temperature, but not with body temperature. Viviparous lizards were less productive than egg‐laying species. Diet and primary productivity were not associated with productivity in any model. Other effects, including lower productivity of fossorial, nocturnal and active foraging species were confounded with phylogeny. Productivity was not lower in species at risk of extinction.Main conclusions Our analyses show the value of focusing on the rate of annual biomass production (productivity), and generally supported associations between productivity and environmental temperature, factors that affect mortality and the number of broods a lizard can produce in a year, but not with measures of body temperature, environmental productivity or diet.

Foraging Mode and Reproductive Seasonality in Tropical Lizards

Foraging Mode and Reproductive Seasonality in Tropical Lizards

Costs of reproduction in lizards: escape tactics and susceptibility to predation

Increased basking and reduced agility in gravid female southern water skinks (Eulamprus tympanum) suggest that they will be more vulnerable to predators. However, gravid females shift their anti-predator tactics towards crypsis, by allowing potential predators (such as a human observer) to approach more closely than do males and non-gravid females. Gravid females were taken no more frequently than were non-gravid females or males when exposed to two types of natural predators, birds (kookaburra, Dacelo gigas) or snakes (common blacksnakes, Pseudechis porphyriacus) in field enclosures. Both these results suggest that the vulnerability of potential prey in this system is determined by the predator's probability of detecting a potential prey item, not its probability of capturing the prey item after detection. Hence, laboratory-based measures of performance demonstrating reduced escape speed may sometimes have little relevance to actual fitness under field conditions, if the probability that an animal will be taken by a predator depends primarily on whether or not it is seen, rather than on how quickly it can escape.

Decreased Sprint Speed as A Cost of Reproduction in the Lizard Sceloporus Occidentals: Variation Among Populations

ABSTRACT Decreased mobility of gravid females is thought to be an important cost of reproduction in lizards. We measured sprint speeds of female western fence lizards (Sceloporus occidentalis Baird and Girard) before and after they had oviposited. Females from two California populations were about 20% slower when gravid, females from an Oregon population were about 30% slower, and females from a Washington population were about 45 % slower, compared to their speeds after recovering from reproduction. The decrease in sprint speed persisted for several weeks after oviposition, suggesting that reproduction impairs sprint performance by affecting body condition in addition to the burdening effect of eggs. Oregon and Washington females carried more mass (both somatic and clutch mass) per unit body length than California females. On the shorter bodies of Oregon and Washington lizards, eggs may interfere with the mechanics of running, in addition to their effect on the total mass of the female. In addition, gravid females from Washington had significantly higher reproductive investment (mass of clutch relative to the mass of the female after oviposition) than Oregon and California populations. Greater reproductive investment by Washington females increases, the burden carried per unit of body length; we suggest this further impairs sprint performance. Decrements in sprint speed were not significantly correlated with level of reproductive investment (per unit body mass) among females within any of the study populations. However, the burden carried per unit body length was correlated with the sprint speed decrement among gravid females from Oregon. Comparisons within and among populations suggest that differences in morphology among northern and southern populations interact with reproductive investment to produce interpopulation differences in sprint performance for gravid females.

The influence of foraging mode and phylogeny on seasonality of Tropical Lizard reproduction

The influence of foraging mode and phylogeny on seasonality of Tropical Lizard reproduction

Desert lizard reproduction: seasonal and annual variation in Urosaurus ornatus (Iguanidae)

The reproductive cycle and cycles in fat body and liver masses were examined in Urosaurus ornatus from central Arizona. Adult males underwent spermiogenesis from mid-April until late August. The cycle in testes mass was paralleled by cyclical activity in structure of the seminiferous tubules and epididymides. Mass of fat bodies and livers also fluctuated seasonally, showing a distinct increase with declining reproductivity. Yolk deposition in females occurred from May until late August with ovulation occurring from early June until early September. Breeding females comprised two groups: young females in their first breeding season and older females that were in at least their second breeding season. The younger (smaller) group had a mean clutch size of 6.0 and produced only one clutch, whereas the older (larger) group had a mean clutch size of 7.7 and at least a portion of these females produced more than one clutch. For the most part, older females began breeding earlier in the reproductive season than younger females. Females cycled fat body and liver masses with a distinct increase in organ size associated with declining reproductivity. Reproductive intensity varied during a given season but not annually, even though rainfall varied annually.

Parthenogenetic reproduction in lizards: Histological evidence.

Hermaphroditism and sex reversal have not previously been ruled out adequately as possible explanations for the existence of unisexual species of reptiles. Therefore, we examined serial histological sections of the complete urogenital systems of nine F2 specimens belonging to two ontogenetic series of Cnemidophorus exsanguis raised in captivity in isolation from males, as well as the urogenital system of the F1 mother of one of these series. No evidence of spermatozoa or testicular tissue was found in any specimen. Comparative material reveals that the histology of the urogenital tract, including the mesonephric kidney in adults, is similar to that of females of bisexual species of Cnemidophorus. We conclude that C. exsanguis is a unisexual, parthenogenetic species whose normal reproduction does not involve sex reversal, self-fertilization, gynogenesis, hybridogenesis, or spermatozoa in any way whatsoever.

Reproduction in a Nebraska Sandhills Population of the Northern Prairie Lizard Sceloporus undulatus garmani

Reproduction in a Nebraska Sandhills Population of the Northern Prairie Lizard Sceloporus undulatus garmani

Lizard Reproduction: Habitat Specificity and Constraints on Relative Clutch Mass

The iguanid lizard Platynotus semitaeniatus is adapted morphologically and behaviorally to utilize rock crevices to escape predation. Attendant reproductive adaptations reveal an adaptive compromise in which costs incurred from reduced reproductive investment per episode are outweighed by advantages associated with use of a relatively predator-free refugium thereby increasing adult survivorship and thus lifetime reproductive success.

Refractoriness in Female Lizard Reproduction: A Probable Circannual Clock

Postreproductive Cnemidophorus uniparens maintained under free-running conditions of constant darkness for 7 months became reproductive at the same time as controls exposed to a long photoperiod. This lizard exhibits a pause in reproductive activity (refractory period) commencing in late summer in nature and terminating in mid-December in captivity. Both groups terminated refractoriness and started reproducing simultaneously in December despite maintenance of the experimental group in darkness since September. These results confirm the hypothesis that the refractory period in this lizard is under endogenous control.

Reproductive Cycle of a Tropical Teiid Lizard, Neusticurus ecpleopus Cope, in Peru

Collections of a stream-dwelling South American microteiid lizard were made during a 15-month period (1967-1968) at Tingo Maria, Peru. These were analyzed in terms of four seasonal three-month periods of a year. Spermatogenesis was found in all adult males throughout the year, though testis size was significantly reduced during the dry season. The follicular developmental sequence of females is outlined. The female population was reproductively active, fecund and/or ovigerous, throughout the year. The percentage of the population with oviducal eggs dropped sharply from the pre-dry season period to the dry season, but yolked follicle size was maximal during the dry season. Evidence from additional females collected during the dry season of 1971 suggests that reductions in percentage of ovigerous females during the dry season may fluctuate from year to year, depending upon environmental conditions. It was not possible to determine the proximal environmental factors, cues, regulating the reproductive cycles in N. ecpleopus, but rainfall may be involved in the female cycle. Correlations between precipitation changes and female reproductive activities were used in an attempt to identify the selective pressures influencing the reproductive cycle. Seasonal changes in food availability to adult females and hatchlings and effects of flooding on success of incubating eggs may be some selective pressures involved. Also, reproduction in N. ecpleopus is related to two possible evolutionary strategies in lizard reproduction. ALTHOUGH MUCH IS PRESENTLY KNOWN concerning annual reproductive activities of temperate lizards, information on reproduction in tropical species is limited (Tinkle 1969; Tinkle et a-l. 1970). This is particularly unfortunate in that reproductive patterns may be important to our understanding of evolution in the tropics. The purpose of this paper is to describe the reproductive cycle of Neusticurus ecpleopus Cope, an Amazonian basin teiid (microteiid) lizard, and to relate it to what is known of the reproductive cycles of tropical lizards.

Observations on Reproduction in the Southern Coal Skink (Eumeces anthracinus pluvialis Cope)

Little is known of the reproductive potential of the southern coal skink (Eumeaes anthracinus pluvialis), an egg-laying lizard that ranges erratically from western North Carolina southwest to Louisiana and thence northwest to eastern Kansas. Gloyd (1928) collected a female of this species on 3 May 1926 in Franklin County, Kansas, which laid eight eggs between 21 and 23 June. The eggs averaged 6 x 10 mm in size, and six hatched between 24 and 25 July, an incubation period of slightly oorer one month. Taylor (1935) noted this Kansas clutch, but added no additional observations on reproduction in this lizard. Smith and Smith (1952) recorded a female southern coal skink from Oregon County, Missouri, which laid eight eggs (no dategiven) thatranged from 7.0 to 7. 8 mm in width and 12 to 1 3 mm in length at deposition. The eggs increased in sizeathatchingto 11 to 12mminwidthand 16.2 to 18mminlength. Anderson (1965) noted the Oregon County clutch and recorded a female from Camden County, Missouri, which laid eight eggs on 27 May. The eggs averaged 7.5 x 12.5 mm in size. Fitch (1970), in summarizing reproduction in lizards and snakes, did not include an account on Eumeres anthraainus, presumably due to paucity of information about this species. Thus, only three known clutches of eggs have been recorded for Eumeres anthracinus plutZialis, all numbering eight eggs per clutch. On 14 April 1974, a female southern coal skink (University of Kansas, Museum of Natural History-KU 154997) with a snout-vent length of 65.5 mm and a total length of 154.5 mm was collected by Diana Weigmann at Baldwin Woods, Douglas County, Kansas. This specimen was maintained in capacity and laid eleven prolate eggs (KU 154998) on 19 May 1974. The eggs ranged in size from 6.8 to 7.4 mm (SD =0. 14, x= 7.02) in width and 10.8 to 1 1.2 mm (SD=0. 14, x= 10. 76) in length. According to RandallJohnson (who maintained the lizard in captivity), the female exhibited protective behavior. When the eggs and nest were disturbed, the female would curl on top of the eggs. Johnson did not observe aggressive behavior, but another lizard (Leiolopisma laterale) maintained in the same cage was killed by the female. In summary, this clutch is the fourth reported for Eumeces anthrarinus pluvialis. Known dates of egg deposition for three clutches were during May,