91 research outputs found

    Seasonal sexual cycle of Nerodia taxispilota (Serpentes: Colubridae) at the northeastern edge of its range

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    The seasonality of the sexual cycle of Nerodia taxispilota at the northeastern edge of its range was elucidated from specimens collected over a two-year period (1978-1979) from the Appomattox River near Hopewell, Virginia. The investigation centered on morphological changes in the testis of males and vitellogenesis and embryo development in females. Related reproductive parameters also studied were body size differences, seasonal sex ratios, comparative tail lengths, and tail mutilation. Male and female cycles closely resembled those of other temperate zone colubrids. Spermatogenesis began in May and testis size peaked in late August. Testis length showed a time lag when compared with weight and volume. Sperm produced during summer were stored in the vas deferens through winter and used the following spring. The female cycle is apparently annual. Vitellogenesis occurred only in spring, ovulation was in mid-June, and parturition was probably in late August or early September. The number of young increased with increasing female body size with mean clutch size of full-term embryos 28.0. Females were generally larger than males. Sex ratio was about 1:1 in spring and summer, however males predornina ted in fall. Males had comparatively longer tails than females. The amount of tail breakage was about equal for both sexes

    Herpetofaunal Inventories of the National Parks of South Florida and the Caribbean: Volume III. Big Cypress National Preserve

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    Amphibian declines and extinctions have been documented around the world, often in protected natural areas. Concern for this trend has prompted the U.S. Geological Survey and the National Park Service to document all species of amphibians that occur within U.S. National Parks and to search for any signs that amphibians may be declining. This study, an inventory of amphibian species in Big Cypress National Preserve, was conducted from 2002 to 2003. The goals of the project were to create a georeferenced inventory of amphibian species, use new analytical techniques to estimate proportion of sites occupied by each species, look for any signs of amphibian decline (missing species, disease, die-offs, and so forth.), and to establish a protocol that could be used for future monitoring efforts. Several sampling methods were used to accomplish these goals. Visual encounter surveys and anuran vocalization surveys were conducted in all habitats throughout the park to estimate the proportion of sites or proportion of area occupied (PAO) by each amphibian species in each habitat. Opportunistic collections, as well as limited drift fence data, were used to augment the visual encounter methods for highly aquatic or cryptic species. A total of 545 visits to 104 sites were conducted for standard sampling alone, and 2,358 individual amphibians and 374 reptiles were encountered. Data analysis was conducted in program PRESENCE to provide PAO estimates for each of the anuran species. All of the amphibian species historically found in Big Cypress National Preserve were detected during this project. At least one individual of each of the four salamander species was captured during sampling. Each of the anuran species in the preserve was adequately sampled using standard herpetological sampling methods, and PAO estimates were produced for each species of anuran by habitat. This information serves as an indicator of habitat associations of the species and relative abundance of sites occupied, but it will also be useful as a comparative baseline for future monitoring efforts. In addition to sampling for amphibians, all encounters with reptiles were documented. The sampling methods used for detecting amphibians are also appropriate for many reptile species. These reptile locations are included in this report, but the number of reptile observations was not sufficient to estimate PAO for reptile species. We encountered 35 of the 46 species of reptiles believed to be present in Big Cypress National Preserve during this study, and evidence exists of the presence of four other reptile species in the Preserve. This study found no evidence of amphibian decline in Big Cypress National Preserve. Although no evidence of decline was observed, several threats to amphibians were identified. Introduced species, especially the Cuban treefrog (Osteopilus septentrionalis), are predators and competitors with several native frog species. The recreational use of off-road vehicles has the potential to affect some amphibian populations, and a study on those potential impacts is currently underway. Also, interference by humans with the natural hydrologic cycle of south Florida has the potential to alter the amphibian community. Continued monitoring of the amphibian species in Big Cypress National Preserve is recommended. The methods used in this study were adequate to produce reliable estimates of the proportion of sites occupied by most anuran species, and are a cost-effective means of determining the status of their populations

    DNA Double-Strand Breakage as an Endpoint to Examine Metal and Radionuclide Exposure Effects to Water Snakes on a Nuclear Industrial Site

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    This study examined metal levels (especially U and Ni) in the tail tissues of water snakes from contaminated (Tim’s Branch) and reference areas on the Department of Energy’s Savannah River Site (SRS). Home ranges of snakes were quantified to determine the ratio of the habitat that they use in relation to the contaminated areas to better estimate exposure Compared to conventional methods that do not. The exposure assessment indicated that water snakes in the contaminated areas could expect U exposure at 3–4 orders of magnitude greater than the Agency for Toxic Substances and Disease Registry’sMinimum Risk Level (MRL) from ingestion of amphibians and fish. Ni and U, in addition to Se, Mn, and Cu, were related to increased DNA double-strand breakage (DDSB) in water snakes.We report burdens for each metal individually, but the results of the DDSB indicated that these metals did not behave independently, but as a suite. If we did not have a secondary endpoint (DDSB), we might have assumed from the exposure predictions and tissue burden analyses that U was the sole metal of concern to water snakes in Tim’s Branch. These data also imply that these toxicants do not biomagnify at the spatial and temporal scale of this study

    The amphibians and reptiles of the Altamaha River, Georgia

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    Field surveys of 59 sites conducted in 1999–2012 and a review of existing museum specimens documented 29 species of amphibians (13 salamanders, 16 anurans) and 36 species of reptiles (1 crocodilian, 5 lizards, 19 snakes, 11 turtles) from the Altamaha River, Georgia and lowland habitats within its associated floodplain. Field sampling methods including visual encounter surveys, dipnetting, frog call surveys, and binocular/canoe/swim surveys for turtles. All were conducted in several distinct habitat types: The river mainstem, the river floodplain (which includes bottom-land hardwood forest, alluvial swamps, and oxbow lakes), and perennial seepages associated with north-facing bluffs. Biogeographically, the Altamaha River is a notable influence on the distributions of many amphibians and reptiles. Pitvipers are mostly absent in floodplain habitats along the river; the absence of what is generally perceived as a common semi-aquatic viper (Cotttonmouth, Agkistrodon piscivorus) from floodplain wetlands along much of the Altamaha River is intriguing and merits further study. Continued investigations and regular monitoring of reptilian and amphibian populations along the Altamaha River, a remarkable Coastal Plain stream and a wilderness waterway par excellence, are warranted

    Molecular Studies of Thamnophiine Snakes.

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    Variation in alleles at gene loci encoding proteins was used to determine zoogeographic and evolutionary differentiation in thamnophiine snakes. Differentiation among populations within a species, among species within a genus, and among genera was investigated. In the southern banded water snake, Nerodia fasciata, analysis by F-statistics and genetic distances of allele frequencies indicated that extensive differentiation has occurred between those forms adapted to a saltwater environment (N. f. clarkii and N. f. compressicauda) and those adapted to a freshwater environment (N. f. fasciata, N. f. confluens, and N. f. pictiventris). Habitat disturbance is imputed as the causal agent in the breakdown of reproductive barriers between the two differentially adapted groups. The total genetic diversity within Nerodia fasciata is of the same order as found in related taxa. However, the molecular evidence indicates secondary contact with reticulate evolution in some populations of Nerodia fasciata. Genetic distances separating taxa of the saltwater group are no greater than those between infrasubspecific populations. It is proposed that the saltwater-adapted snakes constitute a distinct species, Nerodia clarkii, containing the subspecies N. c. clarkii, N. c. compressicauda, and N. c. taeniata, and that the name Nerodia fasciata be limited to include the subspecies N. f. fasciata, N. f. confluens, and N. f. pictiventris. Both phenetic and cladistic analyses of allelic data from all species of the genus Nerodia and a composite of representatives of the genus Thamnophis indicate that Nerodia is composed of three lineages, the taxispilota lineage, the cyclopion lineage, and the sipedon lineage. Further, it is indicated that the genus Thamnophis is actually a member of the sipedon lineage, thus making the genus Nerodia paraphyletic. Erection of new genera to accommodate the taxispilota and cyclopion lineages is recommended. The retention of the genus Thamnophis is recommended as all members share a unique derived character state and thus form a natural group. Representatives of all thamnophiine genera were analysed for allelic variation and the resulting data were used to create hypotheses of the systematic relationships of these snakes using both phenetic and cladistic methods. A similar phylogeny was indicated using both of these approaches. The genus Storeria was seen to be a highly derived early offshoot of the main thamnophiine line. The molecular data suggest that the genus Regina is polyphyletic and that the four species in this genus are the result of three distinct radiations

    ELEMENT LEVELS IN SNAKES IN SOUTH CAROLINA: DIFFERENCES BETWEEN A CONTROL SITE AND EXPOSED SITE ON THE SAVANNAH RIVER SITE

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    Levels of 18 elements, including lead, mercury, selenium, and uranium, were examined in three species of snakes from an exposed and reference site on the Department of Energy’s Savannah River Site in South Carolina. We tested the hypotheses that there were no differences as a function of species, and there were no difference between the exposed and control site for blood and muscle (tail) samples for banded water snake (Nerodia fasciata), brown water snake (N. taxispilota) and cottonmouth (Akistrodon piscivorous). The banded water snakes collected were significantly smaller than the other two species. For blood, there were significant species differences only for barium, copper, selenium, uranium and zinc, while for muscle tissue there were significant interspecific differences in aluminum, arsenic, barium, cobalt, cesium, copper, iron, lead, mercury, manganese, strontium, vanadium and zinc, suggesting that muscle tissue in the tail is a better indicator of potential interspecific differences. It is also easier logistically to collect tail tissue than blood. Where one species had significantly higher levels than the other species in muscle tissue levels, cottonmouth had higherlevels of five elements (aluminum, cobalt, lead, mercury, vanadium), brown water snake had two (lead, strontium), and banded water snake had only barium. There were few significant differences between the control and reference site for levels of blood, but several for muscle tissue. All three species had significantly higher levels of arsenic and manganese at Tim’s Branch than the reference site, and nickel and uranium were significantly higher for banded watersnake and cottonmouth, the larger species. Individuals with high exposure of one element were exposed to high levels of other elements

    The development of the skull of the Egyptian cobra Naja h. haje (Squamata: Serpentes: Elapidae)

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    Background: The study of craniofacial development is important in understanding the ontogenetic processes behind morphological diversity. A complete morphological description of the embryonic skull development of the Egyptian cobra, Naja h. haje, is lacking and there has been little comparative discussion of skull development either among elapid snakes or between them and other snakes. Methodology/Principal Findings: We present a description of skull development through a full sequence of developmental stages of the Egyptian cobra, and compare it to other snakes. Associated soft tissues of the head are noted where relevant. The first visible ossification centres are in the supratemporal, prearticular and surangular, with slight ossification visible in parts of the maxilla, prefrontal, and dentary. Epiotic centres of ossification are present in the supraoccipital, and the body of the supraoccipital forms from the tectum posterior not the tectum synoticum. The venom glands are visible as distinct bodies as early at stage 5 and enlarge later to extend from the otic capsule to the maxilla level with the anterior margin of the eye. The gland becomes more prominent shortly before hatching, concomitant with the development of the fangs. The tongue shows incipient forking at stage 5, and becomes fully bifid at stage 6. Conclusions/significance: We present the first detailed staging series of cranial development for the Egyptian cobra, Naja h. haje. This is one of the first studies since the classical works of G. de Beer and W. Parker that provides a detailed description of cranial development in an advanced snake species. It allows us to correct errors and misinterpretations in previous accounts which were based on a small sample of specimens of uncertain age. Our results highlight potentially significant variation in supraoccipital formation among squamates and the need for further research in this area

    First Report of a Hepatozoon sp. (Apicomplexa: Adeleina: Hepatozoidae) from Midland Water Snake, Nerodia sipedon pleuralis (Ophidia: Colubridae), from Missouri

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    Intraerythrocytic hematozoans of the genus Hepatozoon (Miller, 1908) occur in the gamont stage in birds, mammals, and all groups of reptiles (Telford 2009). For example, one group of reptiles, the North American watersnakes of the genus Nerodia, are important hosts of a variety of these parasites (Gibbons and Dorcas 2004). The northern watersnake, Nerodia sipedon sipedon (Linnaeus, 1758) has been previously reported to harbor He. sipedon Smith, Desser, and Martin, 1994 from Ontario, Canada (Smith et al. 1994; Smith and Desser 1998). However, another widely ranging subspecies, the midland watersnake, N. s. pleuralis (Cope, 1892), has not previously been reported as a host nor has any snake, to ourknowledge, been reported from Missouri with these hemoparasites. Here, we document, with photomicrographs and select measurements, the first report of a Hepatozoon sp. in N. s. pleuralis, as well as documentation, to our knowledge, from any ophidian host in Missouri. In addition, a summary of intraerythrocytic hematozoans of North American watersnakes and  swampsnakes is provided

    ELEMENT LEVELS IN SNAKES IN SOUTH CAROLINA: DIFFERENCES BETWEEN A CONTROL SITE AND EXPOSED SITE ON THE SAVANNAH RIVER SITE

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    Levels of 18 elements, including lead, mercury, selenium, and uranium, were examined in three species of snakes from an exposed and reference site on the Department of Energy’s Savannah River Site in South Carolina. We tested the hypotheses that there were no differences as a function of species, and there were no difference between the exposed and control site for blood and muscle (tail) samples for banded water snake (Nerodia fasciata), brown water snake (N. taxispilota) and cottonmouth (Akistrodon piscivorous). The banded water snakes collected were significantly smaller than the other two species. For blood, there were significant species differences only for barium, copper, selenium, uranium and zinc, while for muscle tissue there were significant interspecific differences in aluminum, arsenic, barium, cobalt, cesium, copper, iron, lead, mercury, manganese, strontium, vanadium and zinc, suggesting that muscle tissue in the tail is a better indicator of potential interspecific differences. It is also easier logistically to collect tail tissue than blood. Where one species had significantly higher levels than the other species in muscle tissue levels, cottonmouth had higherlevels of five elements (aluminum, cobalt, lead, mercury, vanadium), brown water snake had two (lead, strontium), and banded water snake had only barium. There were few significant differences between the control and reference site for levels of blood, but several for muscle tissue. All three species had significantly higher levels of arsenic and manganese at Tim’s Branch than the reference site, and nickel and uranium were significantly higher for banded watersnake and cottonmouth, the larger species. Individuals with high exposure of one element were exposed to high levels of other elements
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