The thesis of this heuristic discussion is that the frog morphotype arose via a regulatory mutation that truncated vertebrae-forming somitogenesis and not via selection on structural genes. This truncation, along with many collaborative events (e.g., other skeletal elements, viscera, jaws, and mouthparts) required to maintain a viable organism, produced the essence of a prototadpole. With the presumed confines of metamorphosis, only something resembling a frog could metamorphose from such a highly paedomorphic larva. Larvae and adults were further altered by other less deep regulatory changes and subsequent selection to produce characters correlated with systematics and ecology.

Previously published studies concerning the social behavior of red-backed salamanders (Plethodon cinereus) reported that in the forest (1) some male-female pairs co-inhabit territories even during the summer noncourtship season, and that in laboratory experiments (2) these pairs act as if they are socially monogamous, (3) males aggressively punish female partners that become polyandrous, and (4) females aggressively punish male partners that become polygynous. Past studies suggest that males and females freely choose their pair-partners in the forest and that sexual intimidation functions to keep partners monogamous. However, this inference is based on several underlying assumptions, which we test in the present study. We performed a series of experiments using randomly established pairs to test the assumptions that ‘natural’ pairs are more than an effect of familiarity between individuals and that extended housing as ‘pairs’ in the laboratory does not account for pair-like behavior. We found no evidence that members of either sex punished the opposite sex when laboratory–created pairs were housed together for either five or 30 days. Therefore, we conclude that the ‘pair-like’ behavior of natural pairs represents more than familiarity and that extended housing together does not account for that behavior.

During intraspecific interactions involving males, females and subadults, acoustic as well as visual signals were observed in the diurnal frog Phrynobatrachus krefftii. Strikingly, interactions between adult males are highly dominated by inflations of the bright yellow subgular vocal sac without sound production. We studied the signaling behavior in males of P. krefftii at the Amani Nature Reserve, Usambara mountains, Tanzania, from November 2001 to March 2002. Under nonmanipulated conditions, we registered 641 male-male interactions involving 31 individuals during 323 hours of observation. Most (496 or 77 % ) inflations of the vocal sac were purely visual; the remainder (145 or 23%) of the signals were bimodal, and accompanied by sound production. To test whether exclusive visual signaling can be evoked under experimental conditions, we introduced tethered males into the visual field of 28 residents, registering the elicited responses over 10 minutes after the introduction. Unimodal (i.e., exclusive visual) signals (825 out of 1106 responses) dominated over vocal-sac inflations accompanied with sound production. In seven selected focal males, the rate of exclusive visual signaling (0.57 signals/min), however, was more frequent than under nonmanipulated conditions (0.13 signals/min). Phrynobatrachus krefftii is the first species of anuran amphibians reported to perform nonaudible vocal-sac inflations during intraspecific male-male signaling behavior.

Temperature is a crucial factor in the development of oviparous organisms. Under natural conditions, the eggs of many species are subjected to changing thermal environments, but most laboratory studies have incubated eggs at constant temperatures. To evaluate the phenotypic effects of different thermal means and variances and to separate temperature effects from maternal effects, eggs from 10 clutches of smooth softshell turtles (Apalone mutica) were equally distributed among six temperature treatments that reflect thermal conditions observed in natural nests: two eggs each at a mean of 28.5 or 32.5 C, with ranges of ± 0, 2, and 4 C. In addition to embryonic traits (change in egg mass, hatching success, and incubation length), we measured and evaluated body size, swimming performance, and righting time of the hatchlings. The interaction between mean temperature and temperature fluctuation exerted a significant influence on eight of the ten traits we measured, indicating that fluctuating temperatures do not have equivalent phenotypic effects at different mean temperatures. Clutch of origin also was responsible for explaining a large fraction of the variation for nearly all of the traits. Altogether, these results suggests that clutch effects are pervasive and that thermal effects during embryonic development are complex and deserve further investigation.

Behavioral thermoregulation is used by tortoises (Family Testudinidae) to moderate the effects of daily and seasonal fluctuations in ambient temperature on their body temperature. Extensive use is made of refuges to facilitate this behavioural thermoregulation. The Nama-Karoo in South Africa experiences wide temperature fluctuations both daily and seasonally. We investigated the seasonal use of refuges by the leopard tortoise (Geochelone pardalis) and the orientation of the tortoises within the refuges. Turtles used a wide variety of refuges, with Lycium spp., Eberlanzia ferox, Opuntia ficus, and grass clumps being preferred. Seasonal variation in the use of these refuges depended on whether the refuges were used as forms or shelters. Tortoises in spring and winter often remained in the same refuge for the entire season or returned to the same refuge on consecutive nights. We found seasonal and behavioral variation in (a) the orientation of the tortoises within a refuge, and (b) the portion of the shell of each leopard tortoise within a refuge that was exposed to solar radiation. Tortoises in winter and spring maximized the amount of solar radiation received on their shells, while tortoises in summer and autumn minimized the solar radiation received. Consequently, using a combination of refuge type, and body orientation, leopard tortoises appear to passively thermoregulate and thus control for temperature fluctuations experienced in an extreme environment.

We tested the roles of shelter and prey odor cues on the prestrike movement patterns of the dusky pigmy rattlesnake, Sistrurus miliarius barbouri. In the first experiment, prey odors—mouse, frog, lizard, plus control—were presented in various combinations with and without shelters. The pigmy rattlesnake initially preferred sites with both frog odor and shelter. However, this changed over a 23-h period so that shelter alone became the most preferred feature of the microhabitat choices. The initial 2 h pigmy response was similar to that reported for the western rattlesnake (Crotalus viridis), in that they responded differently to the four choice combinations of shelter and prey odor. This initial pigmy response differed in that only frog odor (but not mouse or lizard odor) affected their initial choices. Our work also indicates that when foraging, novel prey odors (frog) initially attracted their attention, but preference for this odor soon declined. In the second experiment, we examined the preference for prey odors by simultaneously presenting all three prey odors plus control (water). The snakes exhibited no prey odor preference during the first 2-h or during the total 23-h of the trials. In both experiments, the pattern of circadian activity was the same. Circadian activity showed two peaks, one shortly before onset of the nocturnal phase and the second just before midnight; thereafter, activity gradually declined so that most snakes were in, and remained in, a shelter by morning when the diurnal phase began. In these experiments, active movement in pigmy rattlesnakes occurred nocturnally and by day they remain in settled locations. While in such settled positions, the pigmy rattlesnakes coiled into stereotypic ambush postures facing the opening in their shelter where prey would most likely pass.

Among vertebrates, sex is determined by environmental or genotypic sex determination, such that sex is determined by incubation environment or by the genetic contribution of parents, respectively. The selective advantage of one mechanism over the other is unclear and our understanding of the evolution of environmental sex determination (ESD) is obscured by the lack of description of the mechanism's genetic architecture. In this study, a reptile with environmental sex determination, the leopard gecko, Eublepharis macularius, was tested for a genotype × environment interaction (G×E) with respect to sex-determining response to incubation temperature. Five sires were each mated to five unique dams. The eggs from each sire/dam combination were randomly assigned to one of three incubation temperatures and resultant hatchling sex ratios were measured. Temperature and temperature × dam (sire) interaction significantly affected treatment group sex. We report a statistically significant effect of genotype by environment interaction (G×E) on the offspring sex in E. macularius. G×E for ESD may provide an opportunity for evolution for different threshold conditions for sex determination in this ESD species.

Newly discovered populations of Rhyacotritonidae were investigated for taxonomic identity, hybridization, and sympatry. Species in the genus Rhyacotriton have been historically difficult to identify using morphological characters. Mitochondrial (mtDNA) 16S ribosomal RNA sequences (491 bp) and allozymes (6 loci) were used to identify the distribution of populations occurring intermediate between the previously described ranges of R. variegatus and R. cascadae in the central Cascade Mountain region of Oregon. Allozyme and mitochondrial sequence data both indicated the presence of two distinct evolutionary lineages, with each lineage corresponding to the allopatric distribution of R. cascadae and R. variegatus. Results suggest the Willamette River acts as a phylogeographic barrier limiting the distribution of both species, although we cannot exclude the possibility that reproductive isolation also exists that reinforces species' distributions. This study extends the previously described geographical ranges of both R. cascadae and R. variegatus and defines an eastern range limit for R. variegatus conservation efforts.

A new species in the genus Vibrissaphora was found during a 2003 survey of the southern part of Yunnan Province, China. The new species appears intermediate between the genera Vibrissaphora and Leptobrachium. Unlike other species of Vibrissaphora, it has a small body size similar to L. chapaense, but has spines on each side of the upper lip characteristic of Vibrissaphora. The spines are much smaller and more numerous than are those of any species of Vibrissaphora, including the sympatric V. ailaonica.

A new species of the Hypsiboas benitezi group is described from the western Amazon Basin. The new species is characterized by its medium size (SVL 24.4–31.2 mm in adult males, 26.0–36.0 mm in adult females), absence of nuptial excrescences, palpebral membrane lacking golden reticulation, and a mental gland in males. The dorsal surfaces of living frogs are bright yellowish green to tan, and frequently bear an X-shaped mark; the parietal peritoneum, pericardium and sclera are covered by guanophores. The new species differs from other members of the Hypsiboas benitezi group (H. benitezi, H. lemai, H. microderma, H. pulidoi, H. rhythmicus, and H. roraima), by the combination of a dorsal X-shaped marking, absence of golden reticulation on palpebral membrane, and central portion of abdominal parietal peritoneum, pericardium, and sclera covered by guanophores. The new species has been confused with Hyloscirtus albopunctulatus (as Hyla albopunctulata) in the past, but the study of the type series of the latter indicates that they represent different species. Hypsiboas hutchinsi is excluded from the H. benitezi group and transferred to the H. semilineatus group, as it shares with H. geographicus and H. semilineatus the absence of a projecting spine in the prepollex (the only known species of Hypsiboas with this character state), presence of pigmented nuptial excresences, reticulated palpebral membrane, and finely tuberculated skin.