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The structure, sizes, and shapes of amphibians and reptiles almost defy imagination; their morphology has long been investigated. However, attitudes about the nature of the contribution of morphology to herpetology and to science in general have changed as research has become more specialized and as new tools, techniques, and theories have been developed. Now, as integration of specialties is of interest to answer complex questions in biology, the contribution of morphology is being clarified. I explore the practice of herpetological morphology over time, with emphasis on research on caecilians, highlighting many of the changes and advances that have occurred. From its beginnings in ancient Greece to current investigations in such areas as systematics, “evo-devo,” and biomechanics, morphology has been highly relevant to understanding biology, and the discipline continues to make major contributions.
Body size and morphology are important traits that can strongly influence the life history of an organism. One important factor affecting these traits is habitat. Urbanization has resulted in the significant modification of many habitats, and thus, it may be a factor affecting the body size and morphology of species living in the urban environment. In this study, we compared body size and morphology in urban and bush populations of the lizard Lophognathus temporalis in and around Darwin, Australia. We made monthly measurements of invertebrate abundance and soil moisture during one year to compare seasonal variation in resource availability between habitats. We also collected all matter excreted by L. temporalis during their first four days in captivity as an index of food consumption in the field. We found that male L. temporalis were larger than females and that urban L. temporalis were larger than bush L. temporalis. Males had longer front limbs, hind limbs, and tails than did females; and in urban populations, they also had larger heads. Urban L. temporalis had longer front and hind limbs than did bush L. temporalis, although head size and tail length were similar for both groups. Resource availability was seasonally more stable in urban habitats than in bush habitats, and urban L. temporalis consumed more than bush L. temporalis all year round. We conclude that differences in resource abundance between habitats may be an important factor contributing to the morphological differences between urban and bush-dwelling L. temporalis.
Tails serve multiple functions in salamanders: energy storage, courtship, antipredator defense, and respiration. Differences in life history strategies between males and females may generate sexual size dimorphism (SSD) in tail length. However, the contribution of tail length to SSD is relatively unstudied. Because the basal member of the desmognathan salamander Phaeognathus hubrichti shows SSD in tail dimensions (females have long, thin tails compared to the shorter, thicker tails of males), we hypothesized that other desmognathans may follow the same pattern. We took standard morphological measurements, aged, and sexed 342 Desmognathus quadramaculatus (the largest species of Desmognathus) and 244 Desmognathus aeneus (one of the smallest species) to determine whether SSD in tail length followed the same pattern as in P. hubrichti. Neither Desmognathus species showed SSD in tail length and the trends were in opposite directions. Males of both species had significantly wider tail diameters than the females. Females had a significantly longer distance between limbs than did males. We also found that all three species differ in resource allocation to different body parts as they mature. This suggests that life history traits, and behavioral and ecological requirements, have a stronger influence on body size than does phylogeny in this group of salamanders.
The skeletal adaptations of Amblyrhynchus cristatus (Marine Iguanas) are of particular interest based on their amphibious lifestyle, which is unique among living lacertilian squamates. The well-known ecological data are applied to new bone histological findings, which revealed expected and unexpected congruencies. The cortical bone matrix consists of avascular lamellar-zonal bone tissue type. The geometrical disposition of the growth marks (i.e., their spacing) shows an unusual pattern for lizards: the growth cycles maintain a constant thickness until the growth is terminated, which is marked by the development of the external fundamental system (efs). Minor resorption processes within the inner periosteal cortical region and the occurrence of these thick growth cycles in A. cristatus result in high mean bone compactness values. The reported life-history data from ecological studies and the hypothesized annuality of the growth cycles indicate that this first decline in annual bone deposition rate is not congruent with the attainment of sexual maturity. In contrast, this event might be indicated by other histological changes in the growth record of A. cristatus, which they share exclusively with their sister group, Conolophus subcristatus (Land Iguana). The bone matrix of the growth zones and annuli differ in their thickness, their color in polarized light, and vary slightly in the amount and shape of osteocyte lacunae in both A. cristatus and C. subcristatus. These well-recognizable growth zones and annuli of the growth cycles change their thickness abruptly within the reported time frame of the attainment of sexual maturity in A. cristatus.
On a small Japanese island, Sado-ga-shima, we identified a frog that differs from Rana rugosa by having a deep yellow coloration of the abdomen and ventral surfaces of the legs. We tentatively refer to it as “yellow morphotype.” To identify any mechanisms of reproductive isolation from R. rugosa, allopatrically distributed on the same island, we artificially crossed the two types and examined the developmental capacity, sex-ratio, and inner-structure of gonads and fertility in the F1 hybrid offspring. Almost all of the reciprocal hybrids became males with a very low abundance of sperm in the testes and show an extremely low fertility when backcrossed to the females of either type. We conclude that the yellow morphotype is reproductively isolated from R. rugosa through all hybrid maleness with scarce fertility and, therefore, presents a species new to science.
The histological characteristics of the gonads and paramesonephric ducts were investigated to allow a quantitative distinction among male, female, and intersex hatchling Green Sea Turtles (Chelonia mydas) from peninsular Malaysia. Hatchling sexes were identified initially as either males or females based on the incubation temperatures, and intersex hatchlings were collected from in situ nests. Traditionally, this assignment is confirmed by qualitative visual assessment of histological sections of the gonads and paramesonephric ducts. We describe a quantitative method for measuring these parameters to distinguish hatchling sex. The thickness of the paramesonephric duct epithelium area, the height of the nucleus in cells within the gonadal cortical epithelium, and the width of the gonadal ridge were measured in sections from 116 hatchlings. Upon examination of the histological material, hatchlings identified initially by incubation temperature as females were found to have significantly thicker paramesonephric duct epithelium and greater gonadal ridge width and cortical epithelium nuclear height compared with hatchlings identified as males. In addition, some hatchlings demonstrated histological characteristics of both sexes (designated here as intersex hatchlings) in some or all of the traditional histological sexing criteria. The “intersex” group could be divided into two subgroups by the quantitative measurements described here. Using this method, hatchlings could be classified as either males, females, or intersexes with a male-appearing gonad and female-appearing duct or a female-appearing gonad and male-appearing duct. The method outlined here provides a quantitative way to distinguish sex and provides insight in intersex grouping in hatchling C. mydas.
Sexual dimorphism in size or shape is common in many reptile species. Amphisbaenians are morphologically specialized for a fossorial life, which might constrain the evolution of sexual dimorphism. This might explain why some amphisbaenian species, but not others, show some type of sexual dimorphism. To understand the differential occurrence of sexual dimorphism in amphisbaenians, studies on a wide number of species belonging to different families and inhabiting different ecological conditions are needed. We measured several morphological variables in a population of the amphisbaenian Trogonophis wiegmanni, a representative of the little-studied family Trogonophidae from North Africa. Results show that males and females have similar body size; but for individuals of similar size, males are heavier, have longer tails, and have larger heads than do females. These differences might be explained by sexual selection, if males with larger heads had advantages in intrasexual contests, or by sexual diet differences. However, most ecological and behavioral aspects of this and other amphisbaenian species remain poorly known, thereby leaving unresolved which selective pressures are responsible for the sexual dimorphism that was evident in this species.
Tail autotomy has clear advantages regarding predator escape, but it also has several associated costs (i.e., impaired locomotion, loss of social status, and reduced growth and reproductive output). We examined the costs of severe autotomy on growth rates of hatchlings of the lacertid lizard Psammodromus algirus during the first weeks of postnatal development. Hatchlings from two populations in central Spain were autotomized on the fifth day after hatching and kept in common garden conditions for 35 days when they were measured again. Hatchlings from both populations, independently of the autotomy treatment, did not differ in the mass gained during the experiment. However, there were differences in body growth between tailless and tailed hatchlings; tailless hatchlings grew at a slower rate than tailed ones, after controlling for the effects of body condition at the onset of the experiment and the resources assimilated. Moreover, independently of their population of origin, hatchlings that invested more in body growth also invested more in regenerating their tails, and no trade-offs were apparent. Because hatchlings were housed in common garden conditions, this result could be attributable to differences in individual capacity to obtain and assimilate resources.
We conducted experimental feeding trials with larval and juvenile Bullfrogs (Lithobates catesbeianus) and Rough-skinned Newts (Taricha granulosa) to assess the accuracy of the scaled mass index (SMI). A control group was fed and a treatment group was starved within a randomized block design. After each of three trials, amphibian tissues were analyzed for lipid, protein, and water content. Mean pretreatment wet weight and SMI of individuals of each species and body form, representing two populations of equal body condition, were similar between control and treatment groups. Starved animals, representing a population in poor condition, had a 17–32% lower SMI than fed animals. Scaled fat and protein or lean mass were strongly correlated (r = 0.85–0.99) with SMI compared with percentages of fat, protein, or lean mass (r = 0.08–0.60). The SMI accurately reflected amphibian energy stores, but the depletion of energy stores differed by species and body form, with tadpoles retaining fat and the other species and body forms depleting fat stores. In addition, factors that we controlled in the laboratory (e.g., hydration, gut fill, reproductive state) may alter mass-length relationships in the field, so we advise collecting some specimens for body composition analyses to ensure the accuracy of the SMI when used in other applications.
New fossil materials of the Diamond-backed Terrapin (Malaclemys terrapin) are described from Late Pleistocene coastal deposits of South Carolina, Georgia, and Florida. Specimens represent isolated carapacial bones from a number of different individuals. The fossils are identified as Malaclemys based on the features of scute sulci and the presence of annuli scars on most specimens. These new fossil records provide evidence that Malaclemys was distributed throughout the southeastern United States during the Late Pleistocene.
Body condition factors have been used as an indicator of health and well-being of crocodilians. We evaluated body condition of Morelet's Crocodiles (Crocodylus moreletii) in northern Belize in relation to biotic (size, sex, and habitat) and abiotic (location, water level, and air temperature) factors. We also tested the hypothesis that high water levels and warm temperatures combine or interact to result in a decrease in body condition. Size class, temperature, and water level explained 20% of the variability in condition of Morelet's Crocodiles in this study. We found that adult crocodiles had higher condition scores than juveniles/subadults but that sex, habitat, and site had no effect. We confirmed our hypothesis that warm temperatures and high water levels interact to decrease body condition. We related body condition of Morelet's Crocodiles to natural fluctuations in air temperatures and water levels in northern Belize, providing baseline conditions for population and ecosystem monitoring.
The monophyly of Microhylidae is supported by an overwhelming accumulation of synapomorphic larval features. Despite the distinctiveness of the microhylid tadpole, few studies have focused on larval development. Microhylid larval morphology is usually described and based on standard tables that imply that developmental events at equivalent stages of overall tadpole development are independent from species-specific patterns of developmental timing. Herein, we present additional developmental data based on external morphology and field data on larval growth for the gastrophrynine microhylidDermatonotus muelleri. We describe internal morphological variation (e.g., skeletal and soft systems) during larval development. The results indicate that the onset of some metamorphic changes occur earlier than those implied in current anuran developmental tables. This study provides baseline information for microhylid species that will allow comparisons of ontogenetic trajectories, heterochronic patterns influencing larval body plan, and the role of larval morphology on the adult microhylid body plan.
Although molecular phylogenetic studies strongly support the monophyly of the Pygopodoidea, which comprise the gekkotan families Diplodactylidae, Carphodactylidae, and Pygopodidae, relationships among these constituent families are less robust. Morphological evidence for a particular three-taxon statement of pygopodoid relationships is hindered by the highly derived postcranial and trophic anatomy of limbless pygopodids relative to limbed gekkotans. We discuss variation in the temporal region of the gekkotan skull and identify a posteriorly dilated squamosal bone with a medially directed process, a character that is shared uniquely within Gekkota and more broadly within extant Squamata, by carphodactylids and pygopodids. The pygopodoid relationships (Diplodactylidae [Carphodactylidae, Pygopodidae]) implied by squamosal morphology are consistent with those receiving the greatest support from the most complete nuclear gene phylogenies.
Si bien, las filogenias moleculares apoyan fuertemente la monofilia de Pygopodoidea (i.e. los gekkotas de las familias Diplodactylidae, Carphodactylidae and Pygopodidae), las relaciones entre las familias que constituyen este clado están débilmente soportadas. La evidencia morfológica para el patrón de ramificación de las tres familias de pygopodoideos esta enmascarada por las extremas modificaciones anatómicas y tróficas de los pygopódidos ápodos con respecto a los Geckos. En este trabajo discutimos las variaciones de la región temporal del cráneo de los Gekkota, e identificamos un hueso escamoso expandido en forma de maza con un proceso medial, el cual es un carácter que solo está presente en carphodactylidos y pygopódidos dentro de los Gekkota, y los escamados vivientes. La morfología del hueso escamoso implica que las relaciones filogenéticas de los pygopodoideos es (Diplodactylidae (Carphodactylidae, Pygopodidae)). Lo anterior es consistente con otras hipótesis derivadas de análisis filogenéticos usando varios genes nucleares.
The Chiricahua Leopard Frog (Lithobates chiricahuensis) occurs in parts of the southwestern United States and northwestern Mexico. In the United States, it is listed as a federally threatened species. Although extensive research has been conducted on populations in the United States, the status of most Mexican populations is unknown. We used mitochondrial and nuclear DNA to identify a population of L. chiricahuensis from the Mexican state of Durango. To better characterize this poorly known population, we examined morphological variation in 30 individuals that included adult males, adult females, and subadult females. Multivariate analyses of 21 size-adjusted body measurements revealed putative shifts in body dimensions associated with gender and ontogeny. Additionally, we observed notable amounts of color pattern variation in female specimens. Our field observations from 2008 suggest that this population is large and thriving. In light of this, a more comprehensive examination may yield valuable conservation insights and have implications for the management of declining L. chiricahuensis populations in the United States.
La rana leopardo de los Chiricahua (Lithobates chiricahuensis), ocurre en partes del suroeste de los Estados Unidos y del noroeste de México. Esta especie está en la lista federal de especies en peligro de los Estados Unidos, como una especie amenazada. Mientras que en los Estados Unidos se ha hecho mucha investigación sobre su estado de conservación, de la mayoría de las poblaciones mexicanas, éste es desconocido. En la presente investigación, utilizamos ADN mitocondrial y nuclear para identificar una población de L. chiricahuensis del estado de Durango. Para caracterizar mejor esta población pobremente conocida, examinamos la variación morfológica en una muestra de 30 individuos que incluyeron machos adultos, hembras adultas, y hembras subadultas. Se hizo un análisis multivariado de 21 medidas corporales ajustadas a la talla, mismas que revelaron cambios putativos de las dimensiones corporales asociados a la ontogenia y al sexo. Además, se observó una gran variación en el patrón del coloración que presentan las hembras. Nuestras observaciones de campo a partir del 2008 sugieren que esta población es grande y próspera. A la luz de este trabajo, el examen más detallado de esta población pudiera rendir datos valiosos sobre la conservación de esta especie los cuales pudieran tener implicaciones para el manejo de las poblaciones del L. chiricahuensis que están declinando en los Estados Unidos.
In this study we investigate hemipenial variation through ontogeny by preparing specimens of known-aged individuals from captive-bred Plains Gartersnakes, Thamnophis radix, descended from a wild population in northern Illinois, USA. We examined males at two different ages (215–254 days, N = 9) and (829–867 days, N = 12) to compare both juvenile and adult morphologies. Hemipenis length increased isometrically with tail length, and there were no significant differences detected between right and left hemipenis length or width. In addition, this study is the first to explore variation in hemipenial morphology within and among litters. We found significant litter effects on hemipenis length, on the elevation (but not the slope) of the relationship between hemipenis length and tail length, and on number of basal hooks, suggesting a possible genetic basis to these characteristics. These results highlight the importance of examining multiple males through ontogeny, as well as reporting body-size measurements for all specimens, to obtain an accurate representation of the hemipenis morphology of a species for comparative ecological, taxonomic, and evolutionary studies.
We describe a new species of agamid lizard of the genus Hypsilurus from northern Papua New Guinea. The new species is characterized by its small adult size, scalational features, small nuchal and dorsal crests, and distinctive dorsal color pattern of brown and white chevrons. It is a member of the H. godeffroyi species group, but otherwise, its closest relative is not obvious. The species is currently known from two of the outlying North Coast ranges, but following the pattern seen in several other species endemic to this region, it will likely prove to occur along much of the northern lowlands of New Guinea.
Feeding ecology is one of the most important aspects in the life history of snakes; however, studies about their trophic ecology are scarce and sometimes inaccurate. Liophis poecylogyrus is a medium-sized snake distributed widely in South America and relatively abundant in the study area. We describe the diet and sexual dimorphism of L. poecilogyrus from northeast Argentina based on the examination of museum specimens, and we compare our data with studies that include representative samples of this species. Amphibians were the most frequent prey (75%), but only one reptile was found (1%). Families represented were: Bufonidae (53%), Leiuperidae (19%), Leptodactylidae (14%), Hylidae (7%), Cycloramphidae (3%), Microhylidae (2%), and Gymnophthalmidae (2%). We observed that L. poecilogyrus has significant sexual size dimorphism in all morphometric characters analyzed but not in scalation variables. Despite the fact that L. poecilogyrus is considered by some to be an omni-carnivore, our data and other quantitative studies on distant populations from South America lead us to suggest that this species eats primarily anurans. The population studied has its own characteristics but retains similarities with geographically nearby and remote populations. This species is a specialist and its feeding habits seem to be conservative both in different populations of the same species and in phylogenetically related species. Sexual size dimorphism may be a common feature of the taxonomic group.
Remote video cameras recorded eight instances of nest excavation and parental transport of offspring to the water by Australian freshwater crocodiles (Crocodylus johnstoni) inhabiting Lake Argyle in northwestern Australia. Parental assistance during hatching appears to be vital for successful emergence of hatchlings from nests in this area.
Pattern of mating, spawning behavior, and sexual size dimorphism were studied in the Indian Common Toad, Bufo melanostictus. Male and female B. melanostictus are sexually dimorphic in size. Adult males are significantly smaller than adult females, and the ratio of body size of females to males was 1:19. For breeding, the majority of males and females segregated on the basis of their size; larger males paired with larger females leaving smaller males to pair with smaller females. A positive correlation between the body sizes of mating partners provided evidence of size-assortative mating. Successful males were larger in length than their unsuccessful competitors. Operational sex ratio was skewed in the favor of males. A stereotypical spawning behavior was observed: At the initiation of spawning by the female, the male juxtaposed his cloaca with that of the female's followed by a few seconds of rigorous toe movements. Spawning was completed within 2–5 h. Subsequently, the female exhibited pseudo-spawning behavior once or twice. In the absence of more eggs, the male quickly released his clasp, and the pair separated.
In colder climates, survival of neonate Timber Rattlesnakes (Crotalus horridus) following dispersal relies heavily on conspecific scent trailing and the ability to locate suitable communal hibernacula. Less is known regarding populations in the southern portion of their range where they are more likely to den solitarily in ephemeral overwintering sites. On 6 August 2009, we captured a post-parturient female Timber Rattlesnake with a litter of 23 neonates in a hardwood thicket within a Longleaf Pine (Pinus palustris) forest in southwestern Georgia. Fourteen of the neonates were radio-tracked to examine their movements and activity range overlap as they dispersed from the natal site. Snakes were tracked for periods of 1–110 days, daily for the first three weeks and at least three times per week thereafter. Dispersal distances increased over time, and overlap of activity ranges was minimal, potentially reducing intraspecific competition between litter mates. Neonates were located predominantly beneath clumps of vegetation or beside coarse woody debris (62.4%), in hardwood tree branches (31.6%), or just off the ground in vegetation or on top of course woody debris (6.0%). Selection of appropriate cover structure may aid in reducing susceptibility to predation.
The general public prefers to support conservation projects that focus on a few, easily “loveable” species; consequently most of biodiversity is neglected. It is essential to redress such bias and to educate children about the value of a wide diversity of organisms, including those labeled by social bias as less appealing. Because snakes are among the most disliked animals, they are suitable candidates for such endeavor. We evaluated the impact of a single field trip on the attitudes of more than 500 schoolchildren. The participants were involved in snake catching and were allowed to manipulate nonvenomous snakes. The organizers limited their intervention to providing natural history information and carefully avoided saying that snakes should be protected. We used pre- and post-field trip questionnaires to gauge the feelings of the children. Although pre-surveys suggested that many schoolchildren like snakes a priori, their attitudes improved following field experience: almost all children declared then that they liked snakes and expressed a strong willingness to protect them. Such change was associated with an increase of the frequency in the responses of the terms linked with affectivity (e.g., “snakes are cute”…). Snake handling was the favorite activity, and physical contact with animals appears to be a crucial element to improve schoolchildren's attitude for an unpopular organism. Our results support the promotion of field trips that include physical contact with wildlife over the current trend in the educational systems that promote virtual approaches.