Nerodia Fasciata Research Articles

Standard and digestive metabolism in the banded water snake, Nerodia fasciata fasciata

Estimating energy costs by respirometry is fundamental to many studies of the ecology, behavior and evolution of reptiles. However, traditional respirometry procedures seldom incorporate objective techniques for removal of outliers from estimates of metabolic parameters. We demonstrate how computer-automated respirometry equipment, which records many respiratory measurements over short intervals, can be coupled with mathematical procedures to produce robust estimates of pre- and post-prandial metabolism in banded water snakes ( Nerodia fasciata fasciata). Standard metabolic rate of N. f. fasciata was estimated to be 1.21 ml O 2/h (mass=30.21±0.74 g) at 25 °C. After ingestion of a fish equaling 20% of their body mass, snakes exhibited a fivefold increase in metabolic rate with peak O 2 consumption rate ( V o 2) reaching 6.5 ml O 2/h. Total cost of digestion was 5.44 kJ, equivalent to approximately 21% of the energy in the meal. Repeated measurements of metabolism in the same individuals revealed that our methods yielded similar results, even when individuals exhibited different patterns of V o 2 variation between respiratory trials. Our results underscore the importance of obtaining many V o 2 measurements, coupled with objective removal of outlier values from estimates of metabolic rate, especially when metabolic values are to be interpreted in a comparative context.

Laser ablation-ICP-MS analysis of dissected tissue: a conservation-minded approach to assessing contaminant exposure.

Minimally invasive sampling techniques are an essential ecotoxicological tool for continuous assessment of contaminant exposure and in instances where it is not desirable or practical to sacrifice the animal. In this paper, we report on the application of laser ablation-ICP-MS (LA-ICP-MS) for sampling of minute (approximately 1 mg, 2-3 mm) tail clips of the banded water snake, Nerodia fasciata, as a means to assess contaminant exposure. The snakes were split into three treatments (n = 8) and were fed three increasing levels (control, medium, and high) of fish contaminated with As, Se, and Sr for 24 months. LA-ICP-MS concentrations of tail clips for all three elements were significantly correlated with the remaining whole tail concentration determined by homogenization, acid digestion, and ICP-MS analysis. Additionally, LA-ICP-MS concentrations for As and Se in the tail clip were similar to the acid digestion solution analysis values for the whole tail, which suggests that these elements are homogeneously distributed. Strontium concentrations were underestimated by LA-ICP-MS when compared to whole tail concentrations. Statistical analysis showed that LA-ICP-MS tail clip concentrations differed significantly according to dietary treatment. Posterior probability error rates from nonparametric discriminant function analysis indicated that LA-ICP-MS analysis of tail clips was useful for predicting exposure to Se with only a 4% probability of misclassification among treatments. Errors associated with misclassification of As were greater (17%) but this was, in part, related to the low concentrations of As in the tail (<1 ppm for the highest treatment). Taken together, the findings from this study suggest that LA-ICP-MS of microdissected tissue shows promise as a nondestructive technique for conservation-minded ecotoxicological studies.

Effects of chronic dietary exposure to trace elements on banded water snakes (Nerodia fasciata)

Little currently is known about the accumulation or effects of contaminants on reptiles. To date, most studies examining reptile exposure to trace elements report tissue burdens of field-captured animals, but seldom provide insight into the dose, duration, or mode of exposure involved. For two years, we fed juvenile banded water snakes (Nerodia fasciata) prey items collected from a coal ash-contaminated site that contained elevated levels of As, Cd, Cu, Se, Sr, and V. With the exception of Cu, snakes accumulated significant concentrations of elements, usually in a dose-dependent manner. Accumulation varied significantly among liver, kidney, and gonads, and in most cases between sexes. Selenium accumulation was most notable, greatly exceeding established toxicity thresholds for other vertebrates. Despite the high concentrations of pollutants accumulated, snakes exposed to the contaminated diet survived through the study and exhibited normal food consumption, growth, condition factor, overwinter survival and mass loss, metabolic rate, and gonadosomatic index. The results of this study confirm that diet can be a significant route of exposure to trace elements in snakes and indicate that further studies on snakes are warranted to better understand their responses to contaminants.

Differential vulnerability of snake species to MPTP:: A behavioral and biochemical comparison in ratsnakes ( Elaphe) and watersnakes ( Nerodia)

The synthetic neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) induces a Parkinsonian-like syndrome in humans and nonhuman primates, and also causes movement disorders in rodents, fish, amphibians and lizards. To date, the effects of MPTP have not been characterized in snakes. In this study, the behavioral and biochemical effects of MPTP were assessed in the black ratsnake Elaphe o. obsoleta and the banded watersnake Nerodia f. fasciata—species that display contrasting behavioral sensitivities to dopaminergic antagonists and to amphibian toxins. We report that MPTP induces depletion of norepinephrine and serotonin in fore, mid and hindbrain regions and depletion of dopamine in fore and midbrain regions in E.o. obsoleta. MPTP also induced a marked reduction in righting ability in E.o. obsoleta. In N.f. fasciata, norepinephrine and dopamine were depleted by MPTP in all three brain regions and serotonin was only significantly reduced in the forebrain. In contrast to E.o. obsoleta, N.f. fasciata demonstrated no behavioral disorders. This study demonstrates a behavioral and biochemical sensitivity to MPTP in E.o. obsoleta that differs from that in N.f. fasciata. The differential sensitivities to monoaminergic modulation may be related to the contrasting diets of these species.

Nondestructive indices of trace element exposure in squamate reptiles

Compared with birds, mammals, fish, and even amphibians, very little is known about the effects of contaminants on reptiles. Recent evidence that many reptile populations may be declining has stimulated demand for toxicological studies of reptiles as well as development of nondestructive sampling techniques useful for assessing and monitoring contaminant exposure. The current study experimentally evaluated the utility of shed skins, tail clips, and blood samples as nondestructive indices of trace element exposure in banded water snakes, Nerodia fasciata. For 13.5 months, snakes were either fed fish from a coal ash-contaminated site or uncontaminated food from a reference site. Snakes fed contaminated prey accumulated As, Cd, Se, Sr, and V in various organs (i.e. liver, kidney, and/or gonads). Moreover, non-parametric discriminant function analysis revealed that snakes could be placed in two groups that reliably reflected their experimental diet based upon Se, Sr, and As concentrations in tail clips, blood, and/or shed skins. We suggest that nondestructive sampling techniques, particularly analyses of blood and tail clips, may be easily applied in evaluations of contaminant exposure in the field and laboratory and may prevent excessive destructive sampling of potentially threatened reptile species.

Evaporative Water Loss in Two Natricine Snakes, Nerodia fasciata and Seminatrix pygaea

Evaporative Water Loss in Two Natricine Snakes, Nerodia fasciata and Seminatrix pygaea

Elevated trace element concentrations and standard metabolic rate in banded water snakes (Nerodia fasciata) exposed to coal combustion wastes

AbstractTrace element concentrations in banded water snakes, Nerodia fasciata, and representative prey items from a site polluted by coal combustion wastes were compared with concentrations in conspecifics from a nearby reference site. Water snakes accumulated high concentrations of trace elements, especially arsenic (As) and selenium (Se), in the polluted habitat. In addition to being exposed to contaminants in water and sediments, snakes in the polluted site are exposed to contaminants by ingesting prey items that have elevated whole‐body concentrations of trace elements, including As, cadmium (Cd), and Se. Snakes from the polluted site exhibited mean standard metabolic rates (SMR) 32% higher than snakes from the reference site. As a result, snakes from the polluted site appear to have elevated allocation of energy to maintenance and theoretically should have less energy available for growth, reproduction, and storage. Our findings are consistent with physiological responses recently documented in other organisms from the polluted site. We hypothesize that long‐term exposure to coal ash–derived trace elements and the resultant accumulation of some elements are responsible for observed increases in SMR.

The fate of Hepatozoon species naturally infecting florida black racers and watersnakes in potential mosquito and soft tick vectors, and histological evidence of pathogenicity in unnatural host species

Haemogregarine parasites, derived from the Florida snakes Coluber constrictor and Nerodia fasciata and ingested by Aedes aegypti, completed sporogony within the hemocoeles of nearly all fed mosquitoes in 14–18 days, and produced oocysts typlcal of Hepatozoon. However, mortalities and morbidity were high in the Culex which had fed on the Coluber. Oocysts were not found in any Ornithodoros turicata (Argasidae) which fed upon either snake host, but many sections of fed ticks had gametocyte-like cells within the gut lumen. Most lizards, Anolis carolinensis and Anolis sagrei, infected per os with oocysts derived from both snake species developed infections. Infections in the lizards were largely confined to hepatic schizonts with few parasites found in erythrocytes. Unlike naturally infected snake hosts, Hepatozoon schizonts in livers of lizards were often either surrounded by an unidentified dark pigment or heavily infiltrated with mononuclear inflammatory cells.

Muscular mechanisms of snake locomotion: an electromyographic study of lateral undulation of the Florida banded water snake (Nerodia fasciata) and the yellow rat snake (Elaphe obsoleta).

Electromyography and cinematography were used to determine the activity of epaxial muscles of colubrid snakes during terrestrial and aquatic lateral undulatory locomotion. In both types of lateral undulation, at a given longitudinal position, segments of three muscles (Mm. semispinalis-spinalis, longissimus dorsi, and iliocostalis) usually show synchronous activity. Muscle activity propagates posteriorly and generally is unilateral. With each muscle, large numbers of adjacent segments (30 to 100) show simultaneous activity. Terrestrial and aquatic undulation differ in two major respects. (1) During terrestrial undulation, muscle activity in a particular region begins when that portion of the body has reached maximal convex flexion and ends when it is maximally concave; this phase relation is uniform along the entire snake. During swimming, however, muscle activity passes posteriorly faster than the wave of vertebral flexion, causing the relation of muscle activity to flexion to change along the length of the snake. (2) In the terrestrial mode, the block of active muscle segments remains approximately constant in size as it passes down the snake, whereas during swimming the number of adjacent active muscle segments increases posteriorly. Despite the fact that Elaphe obsoleta has nearly twice as many body vertebrate as Nerodia fasciata (240 vs. 125), the only difference observed in the swimming of these two species is that a larger number of adjacent muscle segments is simultaneously active in comparable regions of Elaphe obsoleta than in Nerodia fasciata.

Ecological Aspects of Snake Hemogregarine Infections from Two Habitats in Southeastern Louisiana

Snakes representing the genera Agkistrodon, Nerodia, Elaphe, Coluber, Lampropeltis, Farancia, Crotalus, Thamnophis, and Heterodon were captured over a 22-yr period from 2 swamps in southeastern Louisiana, tail-clipped, and thin blood smears made prior to release. A low prevalence (13%, n = 7) was observed only for the mud snake (F. abacura reinwardtii). Prevalence and levels of parasitemia for 322 cottonmouths (A. piscivorus leucostoma), 219 from Sarpy Swamp in St. Charles Parish and 103 from Hebert Center in Plaquemines Parish, were recorded. A short and long gamont form were commonly seen in cottonmouths and other species from both localities; prevalence patterns and results of experimental transmission suggest that these forms represent different species. Congenital infection was observed in 1 brood of banded water snakes (N. fasciata confluens). Preliminary mark-recapture experiments suggest that snakes may retain constant parasitemia levels for 11 mo or longer.

Two New Trypanosomes from North American Snakes

Trypanosoma thamnophis from Thamnophis sirtalis in eastern Canada is the only previously known trypanosome from a North American snake. Trypanosoma yaegeri n. sp. and Trypanosoma hydrae n. sp. are described here from a cottonmouth Agkistrodon piscivorus leucostoma and a broad-banded watersnake Nerodia fasciata confluens, respectively, from southern Louisiana. Trypanosoma hydrae easily infects other colubrid snakes, but not cottonmouths, turtles, or the lizard Anolis carolinensis. There are only a few scattered records of try- panosome infections in Nearctic reptiles, with two named species from lizards, one from turtles, and one from snakes. We describe here two new trypanosomes found in swamp dwelling snakes from Louisiana's Mississippi River delta region, and summarize the earlier observations on try- panosomes of North American reptiles (Table I), with some revised host identifications.

Selenium and glutathione peroxidase activity in blood of the nutria ( Myocastor coypus): Comparison with guinea-pig, rat, rabbit and some non-mammalian vertebrates

1. 1. Plasma selenium and selenium-dependent glutathione peroxidase (GSH-Px) activity in plasma and erythrocytes were measured in the nutria ( Myocastor coypus) and the alligator ( Alligator mississippiensis). Plasma and erythrocyte GSH-Px activity only were measured in the rat, rabbit, chicken, quail, turtle ( Chrysemys picta), snake ( Nerodia fasciata), bullfrog ( Rana catesbiana) and catfish ( Ictalurus punctatus). 2. 2. Plasma GSH-Px activity ranged from a low of 0.021 EU/ml in the bullfrog to a high of 1.97 EU/ml in the alligator. 3. 3. Erythrocyte GSH-Px activity was lower in the nutria (2.8 EU/g Hb) than all other species studied. Whereas the rat had the highest activity (539 EU/g Hb). The variation among the mammalian species studied was greater than between the different orders of vertebrates. There was no relationship between plasma and erythrocyte GSH-Px activity and no phylogenetic pattern in the differences in activity between species. 4. 4. There was a relationship between plasma selenium concentration and enzyme activity: animals with the lowest enzyme activity had lowest selenium levels.

Intrinsic organization of snake lateral cortex.

Lateral cortex is the most laterally placed of the four cortical areas in snakes. Earlier studies suggest that it is composed of several subdivisions but provide no information on their organization. This paper first investigates the structure of lateral cortex in boa constrictors (Constrictor constrictor), garter snakes (Thamnophis sirtalis), and banded water snakes (Natrix sipedon) using Nissl and Golgi preparations; and secondly examines the relation of main olfactory bulb projections to the subdivisions of lateral cortex using Fink-Heimer and electron microscopic preparations. Lateral cortex is divided on cytoarchitectonic grounds into two major parts called rostral and caudal lateral cortex. Each part is further divided into dorsal and ventral subdivisions so that lateral cortex has a total of four subdivisions: dorsal rostral lateral cortex (drL), ventral rostral lateral cortex (vrL), dorsal caudal lateral cortex (dcL) and ventral caudal lateral cortex (vcL). Systematic analyses of Golgi preparations indicate that the rostral and caudal parts each contain distinct populations of neurons. Rostral lateral cortex contains bowl cells whose dendrites arborize widely in the outer cortical layer (layer 1). The axons of some bowl cells can be traced medially into dorsal cortex, dorsomedial cortex and medial cortex. Caudal lateral cortex contains pyramidal cells whose somata occur in layers 2 and 3 and whose dendrites extend radially up to the pial surface. In addition, three populations of neurons occur in both rostral and caudal lateral cortex. Stellate cells occur in all three layers and have dendrites which arborize in all directions. Double pyramidal cells occur primarily in layer 2 and have dendrites which form two conical fields whose long axes are oriented radially. Horizontal cells occur in layer 3 and have dendrites oriented concentric with the ependyma. Fink-Heimer preparations of snakes which underwent lesions of the main olfactory bulb show that the primary olfactory projections to cortex are bilateral and restricted precisely to rostral lateral cortex. Electron microscopic degeneration experiments indicate that the olfactory bulb fibers end as terminals which have clear, spherical vesicles and asymmetric active zones. The majority are presynaptic to dendritic spines in outer layer 1. These studies establish that lateral cortex in snakes is heterogeneous and contains two major parts, each containing two subdivisions. The rostral and caudal parts have characteristic neuronal populations. Primary olfactory input is restricted to rostral lateral cortex and seems to terminate heavily on the distal dendrites of bowl cells. Axons of some of these cells leave lateral cortex, so that the rostral lateral cortex forms a direct route by which olfactory information reaches other cortical areas. The functional role of caudal lateral cortex is not clear.

The Relation of Sodium and Water Balance to Survival in Sea Water of Estuarine and Freshwater Races of the Snakes Nerodia fasciata, N. sipedon and N. valida

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Chemoreceptive responses of two sympatric water snakes to extracts of commonly ingested prey species

Newborn of two locally sympatric species of water snakes,Nerodia fasciata andN. erythrogaster, were exposed to skin extracts of frequently ingested prey. In southern Louisiana, fish account for 78% of the diet of adultNerodia fasciata and about 15% forNerodia erythrogaster. Anurans comprise most of the remainder of the diets of these water snakes. Responses of naive individuals were compared to the chemoreceptive response profiles of groups of snakes reared on limited diets of fish and/or frogs. All snakes were tested seven times over a nine-month period and ontogenetic changes were apparent. NewbornNerodia fasciata have a strong chemoreceptive response for fish extract that remains unchanged by early dietary restrictions for the first six months of life. After that time their responses are more variable and can be altered by recent feeding experience. In southern Louisiana, this species is the least specialized water snake, an observation supported by these laboratory results. While newbornN. erythrogaster did not respond preferentially to any of the prey extracts, a significant response rate for fish extract is established by two months of age that persists for several months regardless of dietary restrictions. A subsequent shift of the response to frog extract at eight months of age regardless of diet may reflect a maturational process. Field studies are in agreement with these results and support the notion of ontogenetic changes related to predator size and age. This is the first demonstration of an ontogenetic change in chemoreceptive response that is not related to dietary experience.

Feeding in water snakes: An electromyographic study

AbstractSynchronized cinematography and electromyography were used to study feeding behavior in water snakes, Nerodia rhombifera and Nerodia fasciata. While these species swallow their prey by alternate movements of the right and left toothed bones of the skull, the muscles show bilateral asymmetric activity during each movement.Opening of one side of the mouth is initiated by protraction of the palatomaxillary arch and slight depression of the mandible. These movements serve to disengage the teeth from the surface of the prey and correlate with activity of the protractors of the palatomaxillary arch and quadrate. Continued opening results primarily from rotation of the braincase around its longitudinal axis. During the latter half of the opening phase, the rates of protraction of both palatomaxillary arch and mandible increase; this correlates with increased activity of the depressor mandibulae, several of the mandibular adductors and three of the four cervical muscles analyzed. The cervical muscles appear to restrain the prey during the fast segment of mouth opening when the toothed bones reach their maximum displacements from the surface of the prey.Closing of the mouth is initiated by rapid depression of the palatopterygoid joint which correlates with a cessation of activity of the levator pterygoidei. Immediately thereafter, the posterior end of the maxilla is depressed and slightly retracted and the mandible tends to be protracted and slightly adducted. These movements correlate with synchronized activity of the palato‐maxillary protractors, the pterygoideus and the depressor mandibulae. The rest of the closing phase consists primarily of adduction and retraction of the palatomaxillary and mandibular elements relative to the braincase; the toothed bones remain fixed to the surface of the prey while the braincase is moved forward. EMGs indicate that the complex bone movements of the latter stage of mouth opening and the initial stage of mouth closing are dependent upon the simultaneous firing of a number of morphologically antagonistic muscles.

The use of time by sympatric water snakes

Daily and seasonal activity of four sympatric species of Natricine water snakes was studied in southern Louisiana. Daily patterns were monitored nearly continuously from May to October 1975, under natural conditions. Nerodia (Natrix) cyclopion and N. fasciata were mostly diurnally active but N. fasciata became nocturnal in September. Nerodia rhombifera was consistently nocturnal as was Regina grahamii for the months of July, August, and September. Concurrent field studies indicated Regina grahamii was at peak abundance in the study area in March, long before the other species reached their maximum. Nerodia fasciata was the only species to shift its activity from a diurnal to nocturnal pattern and the only species to have a slightly bimodal seasonal abundance. Partitioning of the time resource appears to be an important factor in the coexistence of Nerodia cyclopion and N. rhombifera. They are both piscivorous predators, both are abundant during the warm summer months, and both share similar micro-habitat preferences. Their asynchronous periods of peak activity would serve to reduce competitive interactions.

Tectal efferents in the branded water snake, Natrix sipedon.

Visual information reaches the dorsal thalamus by two distrinct routes in most reptiles. Retinal efferents terminate directly in the dorsal lateral geniculate nucleus (DLGN). Retinal information is also channeled indirectly through the tectum to nucleus rotundus. Retinal projections to DLGN and tectum are also well established in snakes, but the status of the tecto-rotundal link of the indirect visual pathway is uncertain. Thus, tectal efferents were studied with Fink-Heimer methods in banded water snakes (Natrix sipedon). The tectum gives rise to crossed and uncorssed projections to the brainstem reticular formation. Commissural connections are effected with the contralateral tectum via the tectal and posterior commissures. Tectum projects densely to the ipsilateral basal optic nucleus. Bilateral ascending projections reach the pretectal area, nucleus lentiformis mescencephali, lateral habenular nuclei, and posterodorsal nuclei. Ascending projections reach the ventral lateral geniculate and suprapeduncular nuclei. There is a diffuse projection to the central part of the caudal thalamus and a dense, bilateral projection to the DLGN. These results indicate that the relation of the tectum to the dorsal thalamus is different in snakes than in other reptiles. Nucleus rotundus is either absent or poorly differentiated and there is a strong convergence of the direct and indirect visual pathways at DLGN.

Notes on Banded Water Snakes from Georgia

Notes on Banded Water Snakes from Georgia