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At least 505 records · Page 28Linked to original sources
PubMed1984

Phenotypic basis for a feeding change in an insular population of garter snakes.

Predation on birds, an unusual behavior for the common garter snake (Thamnophis sirtalis), has been observed and documented in an insular garter snake population. Feeding preference tests were performed on naive neonatal snakes and experienced adults from both the island test population and a nearby mainland control population. No significant preference for birds as a prey item was found for either neonates or adults from either population. Therefore, neither a genetic nor an ontogenetic basis for the observed behavior was demonstrable. Birds tainted with a piscine odor, however, elicited a positive feeding response from adult snakes from both geographical sources. We propose that the observed behavior in the field is a result of learning to exploit an abundant, readily available resource already in the predator's repertoire.

Animals↗
PubMed1998

Divergent and common groups of proteins in glands of venomous snakes.

Protein contents of venom-producing glands from the sea-snake Laticauda colubrina (LC) and terrestrial Vipera Russelli (VR) were studied using high-resolution two-dimensional gels: isoelectric focusing followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (IEF/SDS-PAGE) and nonequilibrium pH gradient electrophoresis (NEPHGE) followed by SDS-PAGE. Tentative identities of numerous proteins were established using their amino acid compositions and in certain cases the identities were verified by microsequencing of their N-terminals and internal fragments. As expected, we found several proteins known to be present in the venom of the respective snakes. These include numerous isoforms of phospholipase A2 (PLA2) in both snake glands, various neurotoxins in LC glands and factor IX/factor X-binding protein, hemorrhagic factor and coagulation factor X activating enzyme in Russell's viper glands (VR). Not unexpectedly, we also found a number of cell housekeeping proteins, cytoskeletal proteins, proteins that are necessary for folding, such as heat-shock proteins, protein disulfide-isomerase and peptidyl-prolyl cis/trans isomerases. Unexpectedly, however, the glands of Laticauda colubrina and Russell's viper include a large quantity of antihemorrhagic factor and inhibitor of PLA2, respectively, that have been previously described in snake plasma. The possible reason associated with the presence of these components in venom glands is discussed.

Animals↗
PubMed2002

Histidine uptake in the epidermis of lizards and snakes in relation to the formation of the shedding complex.

Mammalian epidermis utilizes histidine-rich proteins (filaggrins) to aggregate keratin filaments and form the stratum corneum. Little is known about the involvement of histidine-rich proteins during reptilian keratinization. The formation of the shedding complex in the epidermis of snakes and lizards, made of the clear and the oberhautchen layers, determines the cyclical epidermal sloughing. Differently from snakes, keratohyalin-like granules are present in the clear layer of lizards. The uptake of tritiated histidine into the epidermis of two lizards and one snake has been studied by autoradiography in sections at progressive post-injection periods. At 40 min and 1 hr post-injection keratohyalin-like granules were not or poorly labeled. At 3-22 hr post-injection most of the labeling was present over suprabasal cells destined to form the shedding complex, in keratohyalin-like granules of the clear layer, and in the forming a-layer but was low in the forming b-layer, and in superficial keratinized layers. The analysis of the shedding complex in the pad lamellae (a specialized scale used for climbing) of a gecko showed that the setae and the cytoplasm of clear cells among them are main sites of histidine uptake at 4 hr post-injection. In the snake most of the labeling at 4 hr post-injection was localized in the shedding complex along the boundary between the clear and oberhautchen layers. The present study suggests that, in the epidermis of lepidosaurian reptiles, the synthesis of a histidine-rich protein is involved in the formation of the shedding layer and, as in mammals, in a-keratinization.

Animals↗
PubMed1987

Post-testicular change in the reptile sperm surface with particular reference to the snake, Natrix fasciata.

Sperm surface changes occurring in the reptile Wolffian duct have been explored with particular references to the snake, Natrix fasciata. In the snake Wolffian duct there are several proteins not present in serum, the pattern of which changes in concert with the seasonal testicular cycle. Whereas testicular spermatozoa did not bind antibody to duct secretions, all Wolffian duct spermatozoa did so over both head and tail, according to immunofluorescence patterns. Thus, on entering the Wolffian duct, the entire surface of N. fasciata spermatozoa acquires one of more of the duct's secretory components. As indicated by immunofluorescence, immunoelectrophoresis, and immunodiffusion, epitopes on at least some molecules that bind to spermatozoa or that remain free in the duct fluid are shared with those in other Natrix species, but not in more distant reptiles (turtle, anole lizard), nor chicken, rat, or rabbit. In regard to glycoproteins, one prominent con A-reactive band was present in polyacrylamide gel electrophoresis (PAGE) of snake fluid and more were evident in fluid collected from the turtle duct. However, such lectin-reactive elements did not bind to spermatozoa as judged by an absence of any change in snake, turtle and lizard sperm lectin-binding patterns in passing from the testis into and through the Wolffian duct. In all, evidence from these and other species studied begins to suggest that the nature of the post-testicular sperm surface modification displayed in most vertebrates that fertilize internally may differ in sub-therian and therian groups, respectively. There appears to be a relative emphasis on glycosyl-rich surface elements in the latter. The possible significance of these changes for sperm function in the different groups is discussed briefly in terms of sperm survival/storage, as well as capacitation and sperm binding to the zona.

Animals↗
PubMed1993

Subcutaneous compliance and gravitational adaptation in snakes.

Previous studies have implicated morphological adaptations as important counter-measures to gravitational stresses on the circulatory systems of arboreal or climbing snakes. Such features include tight skin and relatively non-compliant tissue compartments that oppose edema formation, but these traits have not been previously studied quantitatively. To provide information on this subject, interstitial fluid pressures were measured in eleven species of snakes using slit-end catheters positioned in subcutaneous tissue located at the base of the tail. Interstitial pressures in all species were typically 0 to +2 mm Hg in normally hydrated tissue, but varied widely when snakes were active or when the tail was curved at the site of measurement. Local compliance of the free fluid space was determined from measurements of pressure while saline was infused via the catheter tip. Such measurements varied from 0.18 microliters/mm Hg in Philodryas baroni, an arboreal species, to 2.3 microliters/mm Hg in Crotalus adamanteus, a ground-dwelling, terrestrial species. In general, compliance of the subcutaneous tissue space was greatest (P < 0.05) in non-climbing and aquatic species of snakes that do not face problems of gravitational edema in dependent tissues. Presumably, the compliance measurements reflect adaptive structural differences related to requirements for counteracting gravitational stresses in the various species.

Adaptation, Biological↗
PubMed2005

Tail loss, body condition and swimming performances in tiger snakes, Notechis ater occidentalis.

In limbless tetrapods such as snakes, propulsive forces are generated by lateral undulations of the body and of the tail. In a large population of tiger snakes from Western Australia, tail loss was extremely common (58% of the individuals) and often very severe (more than two-thirds of the tail was missing in 14% of the cases, and in some instances, the tail was totally lost). Tail loss was not however correlated with body size, mass or body condition of wild individuals, and hence did not influence their abilities to acquire resources. These large venomous snakes exhibit marked aquatic habits. Locomotor tests in controlled conditions revealed that tail loss had a significant negative influence on burst swimming performances. However, no effect was found on routine swimming speed and total distance travelled over 5 min. These results suggest that a long and slender tail, although important for maximal speed, is not necessarily relevant for the locomotor abilities required for successful hunting. Tail-damaged individuals outnumbered intact snakes, suggesting that tail loss did not severely compromise survival. Overall, in this species, a slight deterioration of maximal speed due to severe tail loss probably has a low (undetectable) ecological impact, at least for adults.

Animals↗
PubMed2004

Expression of calbindin-D28K by yolk sac and chorioallantoic membranes of the corn snake, Elaphe guttata.

The yolk splanchnopleure and chorioallantoic membrane of oviparous reptiles transport calcium from the yolk and eggshell to the developing embryo. Among oviparous amniotes, the mechanism of calcium mobilization to embryos has been studied only in domestic fowl, in which the mechanism of calcium transport of the yolk splanchnopleure differs from the chorioallantoic membrane. Transport of calcium is facilitated by calbindin-D(28K) in endodermal cells of the yolk splanchnopleure of chickens but the chorioallantoic membrane does not express calbindin-D(28K). We used immunoblotting to assay for calbindin-D(28K) expression in yolk splanchnopleure and chorioallantoic membrane of the corn snake, Elaphe guttata, to test the hypothesis that the mechanism of calcium transport by extraembryonic membranes of snakes is similar to birds. High calbindin-D(28K) expression was detected in samples of yolk splanchnopleure and chorioallantoic membrane during late embryonic stages. We conclude that calbindin-D(28K) is expressed in these extraembryonic membranes to facilitate transport of calcium and that the mechanism of calcium transport of the chorioallantoic membrane of the corn snake differs from that of the chicken. Further, we conclude that calbindin-D(28K) expression is developmentally regulated and increases during later embryonic stages in the corn snake.

Animals↗
PubMed2001

Molecular systematics and evolution of Regina and the thamnophiine snakes.

Snakes of the tribe Thamnophiini represent an ecologically important component of the herpetofauna in a range of habitats across North America. Thamnophiines are the best-studied colubrids, yet little is known of their systematic relationships. A molecular phylogenetic study of 32 thamnophiine species using three complete mitochondrial genes (cytochrome b, NADH dehydrogenase subunit 2, and 12S ribosomal DNA) recovered a well-supported phylogeny with three major clades: a garter snake group, a water snake group, and a novel semifossorial group. The historically contentious genus Regina, which contains the crayfish-eating snakes, is polyphyletic. The phylogeographic pattern of Thamnophis is consistent with an hypothesis of at least one invasion of northern North America from Mexico.

Animals↗
PubMed2002

Phylogenetic relationships of North American garter snakes (Thamnophis) based on four mitochondrial genes: how much DNA sequence is enough?

The clade of garter snakes (Thamnophis) includes some of the most abundant and well-studied snakes in North America. However, phylogenetic relationships within this group have been little studied. We used DNA sequences of four mitochondrial genes (cytochrome b and NADH dehydrogenase subunits 1, 2, and 4) to estimate relationships among 29 of the 31 recognized species of Thamnophis plus the related species Adelophis foxi. Both maximum parsimony (MP) and maximum-likelihood (ML) analyses of all these genes combined produced well-resolved trees with moderate (70-89%) to strong (90-100%) bootstrap support for most clades. MP and ML trees were very similar, with no strongly supported conflict between the two analyses. These analyses identify a clade of 12 species largely restricted to México (the "Mexican clade"), and a clade containing 15 species that collectively range from Central America to southern Canada (the "widespread clade"). These two groups are identified as sister taxa in both MP and ML analyses. A clade consisting of the ribbon snakes (T. sauritus and T. proximus) and the common garter snake (T. sirtalis) is placed as the sister group to all other Thamnophis (i.e., the Mexican + widespread clades) in our analyses. High bootstrap proportions at several levels in the tree support the inclusion of both Thamnophis validus, which has traditionally been placed in the genus Nerodia, and the poorly known species Adelophis foxi within Thamnophis. We used randomly sampled characters (i.e., standard bootstrapping) and randomly sampled contiguous blocks of characters to examine the effect of number of characters on resolution of and support for relationships within Thamnophis using MP. In general, these analyses indicate that we have reached a point of strongly diminishing returns with respect to the effect of adding mtDNA sequence characters for the current set of taxa; our sample of 3809 mtDNA characters is apparently "enough." The next steps to improve the phylogenetic estimate may be to add nuclear DNA sequences, morphology, or behavior, or to sequence additional mtDNA lineages within species.

Animals↗
PubMed1996

Effects of ovariectomy and estrogen replacement on attractivity and receptivity in the red-sided garter snake (Thamnophis sirtalis parietalis).

Activation of courtship behavior in male red-sided garter snakes, Thamnophis sirtalis parietalis, is independent of the presence of sex steroids. The only consistent treatment that stimulates courtship behavior in males is prolonged exposure to low temperature followed by subsequent warming, mimicking the emergence from hibernation. We investigated whether attractivity and receptivity in female red-sided garter snakes is similarly steriod independent. Female red-sided garter snakes are attractive when they emerge from hibernation and are courted by males; most mate within an hour of emergence. In a series of experiments, groups of females were either ovariectomized (OVEX) in the late spring, fall or while in hibernation. They were tested for attractivity and receptivity upon emergence from hibernation. Females OVEX in the spring were unattractive whereas those OVEX in fall or while in hibernation were attractive. Thus, attractivity appears determined the year before emergence and is dependent on the presence of the ovaries. All OVEX females were unreceptive upon emergence. OVEX females were also given replacement estradiol (E) treatment (either in Silastic capsules or single injections) at various points of their annual cycle. The only treatment that resulted in reinstating receptivity in OVEX females was the injection of E (20 micrograms) one hour prior to emergence. The effectiveness of E in reinstating receptivity was time dependent: the longer the period between emergence and injection, the less effective the same dosage was in stimulating receptive behavior. These experiments suggest that sexual behavior in female red-sided garter snakes is, unlike males, dependent on the presence sex steroid hormones. Although E is naturally at its lowest seasonal level upon emergence, the concentration is sufficient to stimulate receptivity. However, it appears that temperature regulates a time-limited window of sensitivity to E.

Animals↗
PubMed1979

A new animal model with hyperbilirubinemia: the indigo snake.

An unconjugated hyperbilirubinemia has been observed in all species of normal indigo snakes. The plasma clearance of large organic anions such as sulfobromophthalein and unconjugated bilirubin was markedly delayed when compared to other snake species. Endogenous bile flow and biliverdin and bilirubin excretory rates and the excretion of bile pigments after a bilirubin load were measured in various snakes. The indigo snake represents a new animal model in which to study mechanisms important to hepatic anion uptake and biliary transport.

Animals↗
PubMed2006

Snake venom components and their applications in biomedicine.

Snake envenomation is a socio-medical problem of considerable magnitude. About 2.5 million people are bitten by snakes annually, more than 100,000 fatally. However, although bites can be deadly, snake venom is a natural biological resource that contains several components of potential therapeutic value. Venom has been used in the treatment of a variety of pathophysiological conditions in Ayurveda, homeopathy and folk medicine. With the advent of biotechnology, the efficacy of such treatments has been substantiated by purifying components of venom and delineating their therapeutic properties. This review will focus on certain snake venom components and their applications in health and disease.

Animals↗
PubMed2006

Thermal quality influences effectiveness of thermoregulation, habitat use, and behaviour in milk snakes.

We investigated the link between thermal quality and the effectiveness of thermoregulation in milk snakes in a thermally challenging environment. We defined thermoregulatory effectiveness as the extent to which an individual maintains its body temperature (Tb) closer to the preferred range (Tset) than allowed by the thermal quality of its environment. We defined thermal quality as the magnitude of the difference between operative environmental temperatures (Te) and Tset. Because ectotherms regulate body temperatures through choice of habitat and behavioural adjustments, we also examined the link between thermoregulation, habitat use and behaviour. During 2003-2004, we located 25 individuals 890 times, and recorded their Tb. Thermal quality was lower in the spring and fall than in the summer, and was lower in forests than in open habitats. Milk snakes thermoregulated more effectively in the spring than in the summer and fall, and more effectively in the forest than in open habitats. Milk snakes had a strong preference for open habitats in all seasons, which was likely to facilitate behavioural thermoregulation. The preference for open habitats was equally strong in all seasons and, therefore, the higher effectiveness of thermoregulation was not a result of altered habitat use. Instead, milk snakes modified their behaviour and were seen basking more and moved less in the spring than in the summer.

Animals↗
PubMed2005

Parallel arms races between garter snakes and newts involving tetrodotoxin as the phenotypic interface of coevolution.

Parallel "arms races" involving the same or similar phenotypic interfaces allow inference about selective forces driving coevolution, as well as the importance of phylogenetic and phenotypic constraints in coevolution. Here, we report the existence of apparent parallel arms races between species pairs of garter snakes and their toxic newt prey that indicate independent evolutionary origins of a key phenotype in the interface. In at least one area of sympatry, the aquatic garter snake, Thamnophis couchii, has evolved elevated resistance to the neurotoxin tetrodotoxin (TTX), present in the newt Taricha torosa. Previous studies have shown that a distantly related garter snake, Thamnophis sirtalis, has coevolved with another newt species that possesses TTX, Taricha granulosa. Patterns of within population variation and phenotypic tradeoffs between TTX resistance and sprint speed suggest that the mechanism of resistance is similar in both species of snake, yet phylogenetic evidence indicates the independent origins of elevated resistance to TTX.

Animals↗
PubMed1990

The effects of exogenous neuropeptide Y on feeding and sexual behavior in the red-sided garter snake (Thamnophis sirtalis parietalis).

Actively courting adult male red-sided garter snakes were injected with one of two dosages of neuropeptide Y (NPY) or saline into the third cerebral ventricle. Courtship and feeding responses were assessed prior to surgery, 4-5 h and 24 h post-surgery. Feeding behavior was tested by the presentation of a favored food, an earthworm. NPY significantly reduced courtship behavior scores at both low (0.16 nmol) and high (0.77 nmol) doses 4-5 h after surgery. Snakes also took much longer to reach the criterion courtship score at the high dose. Feeding occurred only in snakes treated with NPY. At the low dose 29% ate at 4-5 h and 24 h after surgery; 43% of the snakes treated with the high dose ate 4-5 h post-surgery. When tested the day following injection, animals were courting at levels comparable to presurgery levels and refused food.

Animals↗
PubMed1991

A Blastocystis species from the sea-snake, Lapemis hardwickii (Serpentes: Hydrophiidae).

Observations were made on Blastocystis isolated from the sea-snake, Lapemis hardwickii. Exponential growth of the organism was observed between 2 and 4 days of culture. Vacuolated, amoeboid and granular forms were observed in cultures, similar to B. hominis. The optimal growth temperature for the sea-snake Blastocystis was 24 degrees C compared with 37 degrees C for B. hominis. The karyotypic patterns of B. hominis and the sea-snake Blastocystis were studied in the clamped homogeneous electric field (CHEF) technique and found to be different. Based on the above differences, the sea-snake Blastocystis was designated as Blastocystis lapemi sp. nov.

Animals↗
PubMed1985

Effects of early sex steroid hormone treatment on courtship behavior and sexual attractivity in the red-sided garter snake, Thamnophis sirtalis parietalis.

Previous research has shown that exogenous androgen fails to elicit courtship (chin-rubbing) behavior in adult male or female red-sided garter snakes (Thamnophis sirtalis parietalis). However, gonadectomized and intact newborn male and female red-sided garter snakes given silastic capsules containing testosterone exhibit chin-rubbing behavior; gonadectomized and untreated animals do not show this behavior. Both males and females also exhibit chin-rubbing behavior when treated with testosterone as yearlings. Hibernation stimulates chin-rubbing behavior only in males that have received androgen treatment as a neonate or as a yearling. Previous research has also shown that adult females, but not adult males, are courted if given estrogen treatment. Both newborn males and females will elicit chin-rubbing behavior from adult males if given estrogen treatment, indicating production and release of an attractiveness pheromone characteristic of adult females. Male red-sided garter snake breed for the first time on emergence from their second hibernation, whereas females probably do not breed until their third year of life. These data suggest that in the red-sided garter snake, a species that exhibits a dissociated reproductive tactic, sex steroid hormones act to organize central nervous system mechanisms subserving courtship behavior such that temperature, and not hormonal, fluctuations activate sexual behavior in the adult organism.

Age Factors↗
PubMed1987

Facilitation of courtship behavior in the male red-sided garter snake (Thamnophis sirtalis parietalis) following lesions of the septum or nucleus sphericus.

Courtship behavior in male red-sided garter snakes is limited to the period immediately following spring emergence. Lesions of the septum or nucleus sphericus prior to hibernation facilitate courtship behavior upon emergence the following spring. These lesions also had a significant effect on the reproductive physiology of the male snake. Snakes with lesions in the nucleus sphericus had a significantly higher concentration of circulating androgens compared to the control group. While animals with lesions in the septum exhibited elevated levels of circulating androgens, they were not statistically elevated when compared to the control group. The quantity of sexual granules in the epithelium of the renal sexual segment, a secondary sexual characteristic of male squamate reptiles, was significantly greater in lesioned animals. These results are the first to demonstrate a central inhibitory control of sexual behavior in a snake.

Animals↗