Eulamprus Quoyii Research Articles

The ecology of a host-parasite relationship: Haemogregarines & the eastern water skink, Eulamprus quoyii

The ecology of a host-parasite relationship: Haemogregarines & the eastern water skink, Eulamprus quoyii

SEXUAL DIMORPHISM IN BODY SHAPE WITHOUT SEXUAL DIMORPHISM IN BODY SIZE IN WATER SKINKS (EULAMPRUS QUOYII)

Sexual dimorphism in body size is often accompanied by shape dimorphism. Shape dimorphism may be selected directly, or may be an indirect result of selection for size dimorphism. To determine whether shape differences are likely to have been directly influenced by selection, the indirect effects of size dimorphism on shape can be removed statistically, the approach of most previous studies, or, alternatively, we can examine the patterns of shape dimorphism in species that are not size dimorphic. Here I describe sexual shape dimorphism in adults and neonates of a lizard that is not dimorphic in body length, the eastern water skink (Eulamprus quoyii). In this species, snout–vent length is not significantly different between adult or neonate males and females, but there are significant shape differences between sexes in both adults and neonates. For a given body length, adult males have wider heads, longer limbs, shorter trunk length (the distance between the forelimb and the hindlimb), and greater mass than females. In addition, head width, forelimb length and mass increase significantly more rapidly with body length in adult males than in females, whereas the rate of change of hindlimb length and trunk length with length is not significantly different in males and females. The shape of the body is more similar in neonates than adults, but female neonates have significantly longer trunks than males. The intersexual shape difference in neonate E. quoyii suggests that, although growth rate differences among body parts are the main source of differences in shape between adults, the difference between male and female interlimb lengths is present initially. Shape differences present at birth that are preserved until adulthood are less common than growth differences as a source of adult shape differences. The intersexual shape differences among adult E. quoyii are similar to those reported for species that are sexually size dimorphic, suggesting that selective forces have influenced body shape in similar ways in both size dimorphic and nondimorphic species, and that allometric relationships alone may not be responsible for shape differences between males and females in size dimorphic species.

Epizootiology of blood parasites in an Australian lizard: a mark-recapture study of a natural population

The dynamics of a naturally endemic blood parasite ( Hepatozoon hinuliae) were studied in a lizard ( Eulamprus quoyii) host population, using 2 years of longitudinal data. We investigated how parasite abundance in the population varied over time, examined whether certain host sub-populations were more prone to infection, and compared parasite loads in relation to host reproductive behaviour. We recorded blood parasite infections of 331 individuals, obtained in 593 captures. Prevalence (the proportion of the host population infected) of blood parasites was high; approximately 66% of the lizard population was infected. Probability of infection increased with host age and size, but did not differ between the sexes. Within individuals, parasite load (the intensity of infection within individuals) did not vary over time, and was independent of host reproductive behaviour. Parasite load was significantly higher in males compared to females.

COMPLEX GROWTH RATE EVOLUTION IN A LATITUDINALLY WIDESPREAD SPECIES

The simultaneous effects of selective agents acting on somatic growth rates, their interactions, and their interactions with local environmental conditions that vary across a species' geographic range are potentially complex and poorly known. This is particularly true of viviparous ectotherms whose offspring may be adapted to the gestation environment provided by their mothers. We studied multiple sources of growth rate variation in a widespread, viviparous reptile, including the effect of the maternal environment on growth following parturition. Females in early pregnancy were collected from replicate populations close to the tropical and temperate margins of this species' range. These females completed gestation in either of two different, common environments designed to simulate the thermal and photoperiod environments at the sampling locations. Our experiments revealed complex growth rate evolution between the northern and southern extremes of Eulamprus quoyii's geographic range and local adaptation of growth rates to maternal environments. Unique to this study was the manifestation of these growth rate differences, entrained in utero, but expressed following parturition and maintained through to maturity despite the presence of compensatory growth. In addition to providing the most complete picture to date of the evolution of somatic growth in a viviparous ectotherm, our study suggests that understanding local adaptation to maternal gestation environments, in terms of both mean growth rates and growth rate reaction norms, could change our understanding of how growth rates have evolved in other viviparous ectotherms. Indeed, such local adaptation may provide a selective advantage in the evolution of viviparity.

COMPLEX GROWTH RATE EVOLUTION IN A LATITUDINALLY WIDESPREAD SPECIES

The simultaneous effects of selective agents acting on somatic growth rates, their interactions, and their interactions with local environmental conditions that vary across a species' geographic range are potentially complex and poorly known. This is particularly true of viviparous ectotherms whose offspring may be adapted to the gestation environment provided by their mothers. We studied multiple sources of growth rate variation in a widespread, viviparous reptile, including the effect of the maternal environment on growth following parturition. Females in early pregnancy were collected from replicate populations close to the tropical and temperate margins of this species' range. These females completed gestation in either of two different, common environments designed to simulate the thermal and photoperiod environments at the sampling locations. Our experiments revealed complex growth rate evolution between the northern and southern extremes of Eulamprus quoyii's geographic range and local adaptation of growth rates to maternal environments. Unique to this study was the manifestation of these growth rate differences, entrained in utero, but expressed following parturition and maintained through to maturity despite the presence of compensatory growth. In addition to providing the most complete picture to date of the evolution of somatic growth in a viviparous ectotherm, our study suggests that understanding local adaptation to maternal gestation environments, in terms of both mean growth rates and growth rate reaction norms, could change our understanding of how growth rates have evolved in other viviparous ectotherms. Indeed, such local adaptation may provide a selective advantage in the evolution of viviparity.

Influence of Toe-Clipping on Running Speed in Eulamprus quoyii, an Australian Scincid Lizard

Toe-clipping has been widely used for individual identification of amphibians and reptiles. It is costless and easy to apply and read. An animal's locomotor speed may affect its ability to acquire food, to avoid predation, and to achieve a high social status. Thus, it is of interest to determine whether toe-clipping affects the running speed of lizards. Wild caught Eastern Water Skinks (Eulamprus quoyii) were run in a race track in three consecutive sessions. In the first session, all animals were run with their toes intact. Half of the animals had their toes clipped between the first and second session, whereas the other half were toe-clipped between the second and the third session. Neither the average or maximum running speeds of lizards were affected by toe-clipping.

Energetic cost of a meal in a frequent feeding lizard

Specific dynamic action (SDA) describes the rise in metabolism following feeding in animals and represents the energetic cost of digesting and assimilating a meal. The overall energetic cost of feeding may depend on whether or not an animal is post-absorptive at the time of feeding. The aim of this study was to compare the energetic cost of SDA due to feeding frequently compared with infrequently in the eastern water skink, Eulamprus quoyii. For similar quantities of food, repeated feeding incurred an energetic cost equal to 8.8% of the metabolizable energy of the meal (25 220 J), while single feeding incurred an energetic cost of 9.4% of the metabolizable energy of the meal (26 072 J). Experimental lizards maintained a rise in V ̇ O 2 that was on average 1.8 times greater than the V ̇ O 2 of the unfed controls over a 50-h interval as a result of feeding frequently. This prolonged rise in metabolism resulting from frequent feeding does not result in a higher energetic cost of SDA compared with that resulting from infrequent single feeding.

A molecular phylogeny of the Australian skink genera Eulamprus, Gnypetoscincus and Nangura

Skinks from the genera Eulamprus, Gnypetoscincus and Nangura are a prominent component of the reptile fauna of the mesic forests of the east coast of Australia and have been the subject of numerous ecological studies. Highly conserved morphology and the retention of ancestral traits have limited our understanding of the relationships within and among these genera beyond an initial identification of species groups within Eulamprus. To address this deficit and to explore the relationships between Eulamprus and the monotypic genera Nangura and Gnypetoscincus, sections of two mitochondrial genes (ND4 and 16S rRNA) were sequenced and subjected to Bayesian phylogenetic analysis. This phylogenetic analysis supports recognition of the three species groups proposed for Eulamprus (murrayi, quoyii and tenuis) and indicates that this genus is paraphyletic, with Gnypetoscincus and Nangura being proximal to basal lineages of the tenuis group. To resolve these and broader problems of paraphyly, we suggest that each of the species groups from 'Eulamprus' should be recognised as a distinct genus. The phylogenetically and ecologically distinct water skinks of the quoyii group would be retained within Eulamprus and the diverse species of the tenuis group allocated to Concinnia. We suggest placing the monophyletic murrayi group, endemic to the rainforests of central eastern Australia, in a new genus (yet to be formally described). The sequencing data also revealed the existence of a genetically divergent but morphologically cryptic lineage within E. murrayi and substantial diversity within E. quoyii. There is evidence for two major habitat shifts from rainforest towards drier habitats, one leading to the quoyii group and the second defining a clade of three species within the tenuis complex. These ecological transitions may represent adaptations to general drying across eastern Australia during the late Miocene–Pliocene. Each of the major areas of east coast tropical or subtropical rainforest contains multiple phylogenetically diverse endemic species, reflecting the long-term persistence and high conservation value of wet forest habitats in each area.

Ontogenetic Habitat Shift in the Eastern Australian Water Skink (Eulamprus quoyii)?

Ontogenetic Habitat Shift in the Eastern Australian Water Skink (Eulamprus quoyii)?

Habitat Use and Basking Site Selection in the Water Skink, Eulamprus quoyii

The water skink (Eulamprus quoyii) tends to be restricted to creekside habitats and moist areas. Factors correlated with the relative abundance of E. quoyii were demonstrated using multivariate techniques. Rocky, open creeks supported higher densities of E. quoyii than those in cool forests or thick vegetation, where basking sites were fewer. Rocks correlated well with presence or absence of skinks. Non-random utilization of basking sites occurred in sites where skinks were rare, in contrast to random utilization of basking sites where skinks were common. Basking sites and their associated environmental cues may influence skink abundance. Use of rocky basking sites was associated with substrate temperatures of ca. 29 C, similar to the preferred body temperature (PBT) of 28 C chosen in a thermal gradient. Lighting conditions had no effect on PBT, although a significant drop in PBT to 24 C occurred when skinks were deprived of water. Organisms are non-randomly distributed in space, and patchiness is often attributed to hab- itat selection. An optimal strategy for habitat selection should involve response to indicators of primary limiting variables (Heatwole, 1977;

A study of the sources of nutrients for embryonic development in a viviparous lizard, Sphenomorphus quoyii

1. 1. The Eastern water skink is a viviparous lizard with a simple placenta and a large yolk sac. 2. 2. Changes in wet, dry and ash weights of developing follicles and of the egg and egg components during gestation were analysed. 3. 3. The total wet weight of the whole egg (embryo, yolk plus embryonic fluids and extraembryonic membranes) increases significantly during development. 4. 4. This increase is due to uptake of water and inorganic ions from the mother. 5. 5. Both the water and inorganic ions are incorporated into the developing embryo. 6. 6. Lipid is the principal organic material metabolized and it is estimated that there is sufficient lipid in the yolk for embryonic growth and metabolism. Relatively little protein is metabolized. 7. 7. The results show that embryos take up water and some inorganic ions from the mother but there is no evidence to suggest a dependence on the mother for organic nutrients.