Surface structure and frictional properties of the skin of the Amazon tree boa <Emphasis Type="Italic">Corallus hortulanus</Emphasis> (Squamata,Boidae)

The legless locomotion of snakes requires specific adaptations of their ventral scales to maintain friction force in different directions. The skin microornamentation of the snake Corallus hortulanus was studied by means of scanning electron microscopy and the friction properties of the skin were tested on substrates of different roughness. Skin samples from various parts of the body (dorsal, lateral, ventral) were compared. Dorsal and lateral scales showed similar, net-like microornamentation and similar friction coefficients. Average friction coefficients for dorsal and lateral scales on the epoxy resin surfaces were 0.331 and 0.323, respectively. In contrast, ventral scales possess ridges running parallel to the longitudinal body axis. They demonstrated a significantly lower friction coefficient compared to both dorsal and lateral scales (0.191 on average). In addition, ventral scales showed frictional anisotropy comparing longitudinal and perpendicular direction of the ridges. This study clearly demonstrates that different skin microstructure is responsible for different frictional properties in different body regions.     

On the congruence of morphology,trophic ecology,and phylogeny in Neotropical treeboas (Squamata: Boidae: Corallus)

Nine members of the Neotropical treeboa genus Corallus occur from Guatemala to south‐eastern Brazil and recent studies have provided an inconclusive picture about the relationship between morphology and trophic ecology in these snakes. To construct a more complete picture, we conducted the first study of morphology and diet to consider all nine species. Using adult specimens from museum collections, we examined several morphometric and meristic variables and their possible relationship to Corallus diets. Broadly, we found three basic morphologies within the genus: a short, narrow head and a slender body (C. cookii, C. grenadensis, C. hortulanus, and C. ruschenbergerii), useful for exploiting a wide variety of prey; a relatively stout body with a long, wide head (C. batesii, C. caninus, and C. cropanii) associated with feeding on larger mammalian prey; and an intermediate morphology, found in C. annulatus and C. blombergii, which may be indicative of endotherm generalists. These morphological and dietary patterns exhibit a strong degree of congruence with a recent molecular phylogeny of Corallus and highlight a heretofore unexamined ecological diversification within Corallus. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109, 466–475.     

Determinants of breeding dispersal in the sand lizard, Lacerta agilis, (Reptilia, Squamata)

We studied determinants of breeding dispersal (the distance that an animal shifts its mean home range co-ordinate between reproductive events) in an individually marked population of sand lizards (Lacerta agilis) in south west Sweden during 1987–1991. Female breeding dispersal was not determined by age, size, body condition, or number of partners, and females and males that dispersed further did not experience a higher mortality. However, females with a low reproductive output dispersed further than females that reproduced more successfully, and males that lost in bodily condition dispersed further than males that better maintained body condition. We also looked for relationships between age-differences and band-sharing similarity (DNA fingerprinting = DFP) in three categories of lizards — all females, all males, and males and females — to establish whether males would be likely to mate with close kin. Age-difference was strongly correlated with band-sharing in only one category, males and females. When males were older than females this relationship was not significant. However, when females were older than males, age-difference was strongly correlated with band-sharing. Furthermore, females that were old enough to be the mothers of the courting males shared significantly more bands with these males than did the younger females, including the females of the same age as the males. Although parental-specific DFP bands necessary for establishing paternity among our adult lizards were inaccessible to us, we suggest that our circumstantial evidence strongly suggests that some males mate with their mothers. Males that were more closely related with their neighbours also moved further when we controlled statistically for age and mating success. We suggest that by mating with many partners males not only increase their mating success, but also increase the probability of mating with females with ‘good genes’: mean heterozygosity of parents (as revealed by micro-satellites) were strongly correlated with offspring survival.     

Colonization, genetic diversity, and evolution in the Swedish sand lizard, Lacerta agilis (Reptilia, Squamata)

The Swedish sand lizard ( Lacerta agilis ) is a relict species from the post-glacial warmth period. From the geological history of this region, and more recent data on population fragmentation due to disturbance by man, it can be surmised that the Swedish sand lizards passed through at least one population bottleneck in relatively recent times. We tested this hypothesis by investigating the amount and structuring of genetic variability in six microsatellite loci in ten lizard populations from different parts of Sweden. We contrasted these data against those from a Hungarian population which we have reason to assume strongly resembles the founder population for Swedish sand lizards. The average number of alleles per locus in Sweden was 3.3, and these alleles were common in almost all populations, whereas the average number of alleles in the Hungarian population was 8.0. Likewise, the level of expected heterozygosity was lower in the Swedish populations (0.45) compared to the Hungarian population (0.70). The lower variability in Swedish populations is probably a consequence of a common population bottleneck during the immigration subsequent to the latest glacial period. The remaining variability is strongly subdivided between populations (F_ST=0.30) with the main genetic differences being between rather than within populations. Despite the marked isolation of the populations and the present small population sizes (N= 10–300 adults), the Swedish relict populations show a surprisingly high level of observed heterozygosity, indicating that small population size is probably a recent phenomenon.     

Phylogenetic relationships and heterogeneous evolutionary processes among phrynosomatine sand lizards (Squamata, Iguanidae) revisited

Phylogenetic analyses of DNA sequences were conducted to evaluate four alternative hypotheses of phrynosomatine sand lizard relationships. Sequences comprising 2871 aligned base pair positions representing the regions spanning ND1-COI and cyt b-tRNA(Thr) of the mitochondrial genome from all recognized sand lizard species were analyzed using unpartitioned parsimony and likelihood methods, likelihood methods with assumed partitions, Bayesian methods with assumed partitions, and Bayesian mixture models. The topology (Uma, (Callisaurus, (Cophosaurus, Holbrookia))) and thus monophyly of the "earless" taxa, Cophosaurus and Holbrookia, is supported by all analyses. Previously proposed topologies in which Uma and Callisaurus are sister taxa and those in which Holbrookia is the sister group to all other sand lizard taxa are rejected using both parsimony and likelihood-based significance tests with the combined, unparitioned data set. Bayesian hypothesis tests also reject those topologies using six assumed partitioning strategies, and the two partitioning strategies presumably associated with the most powerful tests also reject a third previously proposed topology, in which Callisaurus and Cophosaurus are sister taxa. For both maximum likelihood and Bayesian methods with assumed partitions, those partitions defined by codon position and tRNA stem and nonstems explained the data better than other strategies examined. Bayes factor estimates comparing results of assumed partitions versus mixture models suggest that mixture models perform better than assumed partitions when the latter were not based on functional characteristics of the data, such as codon position and tRNA stem and nonstems. However, assumed partitions performed better than mixture models when functional differences were incorporated. We reiterate the importance of accounting for heterogeneous evolutionary processes in the analysis of complex data sets and emphasize the importance of implementing mixed model likelihood methods.     

Re-evaluation of the taxonomic status of sand boas of the genus Eryx (Daudin, 1803) (Serpentes: Boidae) in north-eastern Iran using sequences of the mitochondrial genome

The sand boas of the genus Eryx (Daudin, 1803) comprise four species in northe-astern Iran: E. tataricus (Lichtenstein, 1823), E. miliaris (Pallas, 1773), E. elegans (Gray, 1849), and E. jaculus (Linnaeus, 1758). Based on a morphological study of the Eryx species in the area, a high similarity between E. tataricus and E. miliaris on the one side, and E. jaculus and E. elegans on the other side has been well documented, so that they are hardly distinguishable from each other. We analysed sequences of the mitochondrial cytochrome b gene of 29 individuals of morphotypes of this species complex in north-eastern Iran to clarify the phylogenetic relationships. Based on the branch pattern of the phylogenetic trees, the amounts of genetic distances within and between major clades and considering the morphological data, we concluded that the traditional grouping of species within the genus Eryx in north-eastern Iran should be fundamentally revised. We believe that E. elegans is conspecific with E. jaculus, and E. tataricus is conspecific with E. miliaris. Considering the principle of priority, the north-eastern populations of Eryx in Iran should be classified into only two distinct species: E. jaculus and E. miliaris.     

Adaptive maternal cannibalism in snakes (Epicrates cenchria maurus, Boidae)

In many animal species, mothers that produce stillborn offspring or undeveloped ova immediately ingest them. This cannibalism has been interpreted in two ways: (1) as a form of parental care (to prevent disease spreading to healthy littermates, and eliminate predator-attracting scent cues); or (2) to recycle otherwise wasted energy, thus facilitating maternal recovery. Our experimental study on captive Colombian rainbow boas ( Epicrates cenchria maurus ) provides the first quantitative support for this latter hypothesis. We show that by eating their non-viable offspring and undeveloped eggs, female boas can rapidly recycle a significant component of their otherwise wasted reproductive investment. Female boas that ingested non-viable progeny equivalent to half their litter mass exhibited rapid recovery of dorsal musculature and hence were able to constrict prey items more forcefully than were unfed females when tested 2 weeks after parturition. The consequent enhancement of constricting ability may influence maternal survival and foraging success. Thus, maternal cannibalism may be an effective tactic to avoid wasting reproductive resources, and to shorten the period required for recovery from pregnancy.  © 2005 The Linnean Society of London, Biological Journal of the Linnean Society , 2005, 84 , 767–774.     

Thermal biology of Liolaemus occipitalis (Squamata, Tropiduridae) in the coastal sand dunes of Rio Grande do Sul, Brazil.

The thermal biology of the small sand lizard, Liolaemus occipitalis, was studied in the coastal sand dunes at Quint?o Beach (Palmares do Sul, Rio Grande do Sul, Brazil; 30 degrees 24' S and 50 degrees 17' W), between September, 1998 and August, 1999. Liolaemus occipitalis presented a mean body temperature of 30.89 degrees C (SD = 4.43 degrees C; min = 16.4 degrees C; max = 40.2 degrees C; N = 270), that varied on a daily and seasonal basis according to microhabitat thermal alterations. The substrate temperature was the main heat source for thermoregulation of L. occipitalis as in all seasons of the year it was responsible for the animals' temperature variation (82% of the collected lizards in the spring; 60% in the summer; 84% in the fall and 68% in the winter). The results indicate that L. occipitalis is a saxicolous, thigmothermic and heliothermic species that regulates its body temperature through behavioral mechanisms.     

The evolution of sperm ultrastructure among Boidae (Serpentes)

We investigate the evolution of sperm ultrastructure of three species of Boidae (Epicrates cenchria, Boa constrictor amarali, and Corallus hortulanus). Spermatozoa of these species are filiform consisting of a head region, containing the nucleus and acrosome complex, a midpiece, and a tail region subdivided into principal piece and endpiece. Multilaminar membranes and extracellular microtubules were observed next to the plasma membrane of the spermatozoa. The following differences were observed among the species: ridge on acrosome surface in Boa constrictor amarali (absent in Epicrates cenchria and Corallus hortulanus), stopper-like perforatorium base plate in Boa constrictor amarali and Epicrates cenchria (absent in Corallus hortulanus), rounded mitochondria in transverse section in Epicrates cenchria and Corallus hortulanus (irregular in Boa constrictor amarali). We mapped sperm characters onto two phylogenies based on morphological (Kluge in Misc Publ Mus Zool Univ Michigan 178:1–58, 1991) and molecular (Austin in Copeia 2:341–352, 2000) data, using a number of squamate species as outgroups. We identified 31 unambiguous character transformations in the morphological phylogeny and 30 in the molecular phylogeny, but only 13 and 12 transformations, respectively, are possible synapomorphies. We identified novel sperm synapomorphies, which were common between the morphological and molecular phylogenies: absence of perforatorium base plate and mitochondria arranged as sinuous tubes in oblique section (Serpentes), acrosome vesicle not subdivided and fibers 3 and 8 at the anteriormost region of principal piece (Boidae), and absence of an electron dense structure inside the proximal centriole (Elapidae + Colubridae). Our results suggest greater agreement between sperm ultrastructure and gross anatomical characters. In addition, we found no tendency for more homoplasies in the sperm head than in the flagellum, as recorded in previous studies.     

Functional analysis of the throat display in the sand goanna Varanus griseus (Reptilia: Squamata: Varanidae)

The threat behaviour in Varanus griseus was investigated with high-speed cinematography and X-ray films. Lizards exhibit threat display involving throat movements and associated throat, thorax and mouth movements. The functional anatomy of the bucco-pharyngeal region is described and threat displays are kinematically studied and functionally interpreted.     

Population structure of an endemic vulnerable species, the Jamaican boa (Epicrates subflavus)

The Jamaican boa (Epicrates subflavus; also called Yellow boa) is an endemic species whose natural populations greatly and constantly declined since the late 19th century, mainly because of predation by introduced species, human persecution, and habitat destruction. In-situ conservation of the Jamaican boa is seriously hindered by the lack of information on demographic and ecological parameters as well as by a poor understanding of the population structure and species distribution in the wild. Here, using nine nuclear microsatellite loci and a fragment of the mitochondrial cytochrome b gene from 87 wild-born individuals, we present the first molecular genetic analyses focusing on the diversity and structure of the natural populations of the Jamaican boa. A model-based clustering analysis of multilocus microsatellite genotypes identifies three groups that are also significantly differentiated on the basis of F-statistics. Similarly, haplotypic network reconstruction methods applied on the cytochrome b haplotypes isolated here identify two well-differentiated haplogroups separated by four to six fixed mutations. Bayesian and metaGA analyses of the mitochondrial data set combined with sequences from other Boidae species indicate that rooting of the haplotypic network occurs most likely between the two defined haplogroups. Both analyses (based on nuclear and mitochondrial markers) underline an Eastern vs. (Western + Central) pattern of differentiation in agreement with geological data and patterns of differentiation uncovered in other vertebrate and invertebrate Jamaican species. Our results provide important insights for improving management of ex-situ captive populations and for guiding the development of proper in-situ species survival and habitat management plans for this spectacular, yet poorly known and vulnerable, snake.     

Ovarian histology of the placentotrophic Mabuya mabouya (Squamata, Scincidae)

Ovarian structure and folliculogenesis of females at different reproductive stages are described for the viviparous placentotrophic lizard Mabuya mabouya. The small ovaries have a thin wall formed by the ovarian epithelium and a thin tunica albuginea. One to two germinal beds that contain numerous oogonia and developing primordial follicles are derived from the ovarian epithelium and are next to the ovarian hilum. The ovarian cortex contains follicles at different stages of development, corpora lutea, and atretic follicles. The yolk nucleus and Balbiani complex were not evident in the ooplasm of previtellogenic follicles. The follicular epithelium of these follicles is polymorphic, as in other species of Squamata, but the larger cells are spherical and monolayered rather than pyriform. The zona radiata of the preovulatory follicles is less developed than in lecithotrophic species. These features suggest a decrease in metabolic and absorptive processes during follicular growth. In preovulatory follicles (1.5-1.8 mm diameter), primordial yolk vacuoles and small cortical granules are deposited in the ooplasm instead of fatty yolk platelets, so that only one stage of vitellogenesis is observed. Polyovular atretic follicles occur in some females. Follicular atresia is minimal for preovulatory follicles, but is more frequent in follicles with polymorphic epithelia. In the corpus luteum, the luteal tissue is formed from granulosa cells and luteolysis occurs during the late gastrula -- late neurula embryonic stages. Thus, the maintenance of gestation from the pharyngula to preparturition stages seems to be related to secretion of extraluteal progesterone, possibly of placental origin. These observed ovarian features are related to the high degree of placental complexity of this species and show that the evolution of advanced placentotrophy in species of this lineage has been accompanied by concomitant changes in ovarian function.     

Tongue movements in the common boa (Constrictor constrictor)

Tongue movements were studied in Contsrictor constrictor by direct observation and by analysis of motion pictures. Vertical tongue movements consisted of an invariant sequence of protrusion, oscillation up and down, and retraction. Lateral deviation of the tongue occurred only in the company of vertical movements and was correlated with the direction of movement of the snake's head. Flick cluster duration varied from about 80 ms to about 1 s; variation in oscillation phase duration accounted for 69 per cent of the total variation. Oscillation phase duration varied linearly with the number of flicks in the flick cluster, suggesting that flick cluster duration is determined primarily by the number of oscilations which are carried out at a constant rate.     

Mechanical properties of the skin of Xenopus laevis (Anura,Amphibia)

The skin of the aquatic pipid frog, Xenopus laevis, was examined for specific biomechanical features: (1) thickness, (2) maximal strain at break (ε_f), (3) tensile strength (σ_m), (4) modulus of elasticity (E, stiffness), and (5) the area under the stress-strain curve (W) (breaking energy, toughness). Skin freshly removed from dorsal, ventral, and lateral areas of the body was subjected to uniaxial tension. In both sexes, the dorsal skin is thicker than the ventral. The skin of male frogs was consistently thinner in all body regions than that of females. Most biomechanical parameters showed a considerable range of values in both males (ε_f = 59–63%, σ_m = 15–16.5 MPa, E = 33.5–38.4 MPa, W = 3.8–4.5 MJ/m³) and females (ε_f = 102–126%, σ_m = 11.5 MPa, E = 10.4–12 MPa, W = 5.2–6.7 MJ/m³). The disparate ε_f values in males (low) and females (high) might reflect sexual dimorphism. Static stress-strain curves were typicxally J-shaped; with the exception of “toe,” the curves rose approximately linearly with increasing strain. The skin of X. laevis, although heterogeneous in structure, possesses features similar to those found in tissues with aligned collagen fibers such as tendons or fish skin. However, in anurans, the skin seems to play a more passive mechanical role during locomotion than in fish. © 1995 Wiley-Liss, Inc.     

Comparative study of sperm ultrastructure of five species of teiid lizards (Teiidae, Squamata), and Cercosaura ocellata (Gymnophthalmidae, Squamata)

Sperm ultrastructure of five teiid lizards (Callopistes flavipunctatus, Crocodilurus amazonicus, Dicrodon guttulatum, Dracaena guianensis, and Teius oculatus), and the gymnophthalmid Cercosaura ocellata is described for the first time. Comparisons of sperm ultrastructure among these species and with those of previously examined teiids and gymnophthalmids revealed that the two groups of Teiioidea (Gymnophthalmidae and Teiidae), and the two subfamilies of Teiidae (Teiinae and Tupinambinae) could be distinguished on the basis of sperm ultrastructure data. Significant differences in sperm dimensions between Cnemidophorus and Aspidoscelis support the recent splitting of these two lineages into different genera. Our results revealed high levels of inter-generic variability in sperm ultrastructure within Teiidae, which produces a data set useful in analyzing relationships between genera and families. In phylogenetic analyses, however, sampling multiple species within teiid genera is essential and recording sperm measurements may profitably complement qualitative ultrastructural characters, maximizing the information content of these structures.     

Distribution and Variation in the Treeboa Corallus annulatus (Serpentes: Boidae)

The arboreal boid Corallus annulatus has a disjunct distribution in tropical wet forests from extreme southeastern Guatemala to southwestern Ecuador (west of the Andes). The characters upon which subspecies (C. a. blombergi and C. a. colombianus) were described are shown to be of no diagnostic value. Based on a suite of characters (scale, pattern, osteological), Corallus a. blombergi is elevated to species status and Corallus a. colombianus is placed in the synonymy of C. annulatus. Corallus annulatus and C. blombergi are considered to be species that are genuinely uncommon, although not necessarily rare. Resumen La boa arbórea Corallus annulatus tiene una distribución alopatrica en bosques húmedos tropicales desde el extremo sudeste de Guatemala hasta el sudoeste de Ecuador (oeste de los Andes). Demostramos que los carácteres usados para describir las subespecies C. a. blombergi y C. a. colombianus no tienen valor diagnóstico. Basado en carácteres de escamas, patrones, y osteológicos, Corallus a. blombergi es elevado al nivel de especie y Corallus a. colombianus es puesto en sinonimia con C. annulatus. Corallus annulatus y Corallus blombergi son consideradas como especies no verdaderamente comunes, pero no son necesariamente raras.