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Articles 1 - 14 of 14

Full-Text Articles in Life Sciences

The Larvae Of Eurycea Junaluska (Amphibia: Caudata: Plethodontidae), With Comments On Distribution, Travis Ryan Feb 2015

The Larvae Of Eurycea Junaluska (Amphibia: Caudata: Plethodontidae), With Comments On Distribution, Travis Ryan

Travis J. Ryan

Travis J. Ryan's shorter contribution to Copeia 1997.


The Global Decline Of Reptiles, Deja’ Vu Amphibians, J. Whitfield Gibbons, David E. Scott, Travis J. Ryan, Kurt A. Buhlmann, Tracey D. Tiuberville, Brian S. Metts, Judith L. Greene, Tony Mills, Yale Leiden, Sean Poppy, Christopher T. Winne Feb 2015

The Global Decline Of Reptiles, Deja’ Vu Amphibians, J. Whitfield Gibbons, David E. Scott, Travis J. Ryan, Kurt A. Buhlmann, Tracey D. Tiuberville, Brian S. Metts, Judith L. Greene, Tony Mills, Yale Leiden, Sean Poppy, Christopher T. Winne

Travis J. Ryan

Reptile species are declining on a global scale. Six significant threats to reptile populations are habitat loss and degradation, introduced invasive species, environmental pollution, disease, unsustainable use, and global climate change.


Ultrastructure Of The Reproductive System Of The Black Swamp Snake (Seminatrix Pygaea): Part Ii. Annual Oviducal Cycle, David Sever, Travis Ryan, Deborah Patton, Shannon Swafford Feb 2015

Ultrastructure Of The Reproductive System Of The Black Swamp Snake (Seminatrix Pygaea): Part Ii. Annual Oviducal Cycle, David Sever, Travis Ryan, Deborah Patton, Shannon Swafford

Travis J. Ryan

This article is the first ultrastructural study on the annual oviducal cycle in a snake. The ultrastructure of the oviduct was studied in 21 females of the viviparous natricine snake Seminatrix pygaea. Specimens were collected and sacrificed in March, May, June, July, and October from one locale in South Carolina during 1998–1999. The sample included individuals: 1) in an inactive reproductive condition, 2) mated but prior to ovulation, and 3) from early and late periods of gravidity. The oviduct possesses four distinct regions from cranial to caudal: the anterior infundibulum, the posterior infundibulum containing sperm storage tubules (SSTs), the ...


Does Sex Influence Post-Reproductive Metamorphosis In Ambystoma Talpoideum?, Travis Ryan, Gabrielle Swenson Feb 2015

Does Sex Influence Post-Reproductive Metamorphosis In Ambystoma Talpoideum?, Travis Ryan, Gabrielle Swenson

Travis J. Ryan

Shorter communication in the Journal of Herpetology v. 35.


Eurycea Junaluska. Morphology, Travis Ryan Feb 2015

Eurycea Junaluska. Morphology, Travis Ryan

Travis J. Ryan

Morphology of Junaluska salamander.


Growth And The Expression Of Alternative Life Cycles In The Salamander Ambystoma Talpoideum (Caudata: Ambystomatidae), Travis Ryan, Raymond Semlitsch Feb 2015

Growth And The Expression Of Alternative Life Cycles In The Salamander Ambystoma Talpoideum (Caudata: Ambystomatidae), Travis Ryan, Raymond Semlitsch

Travis J. Ryan

Complex life cycles (CLCs) contain larval and adult phases that are morphologically and ecologically distinct. Simple life cycles (SLCs) have evolved from CLCs repeatedly in a wide variety of lineages but the processes that may underlie the transition have rarely been identified or investigated experimentally. We examined the influence of larval growth rate on the facultative expression of alternative life cycles (metamorphosis or maturation as gill-bearing adults [= paedomorphosis]) in the salamander Ambystoma talpoideum. We manipulated growth rates by altering the amount of food individuals received throughout larval development. The expression of alternative life cycles in A. talpoideum is influenced by ...


Evaporative Water Loss In Two Natricine Snakes, Nerodia Fasciata And Seminatrix Pygaea, Christopher Winne, Travis Ryan, Yale Leiden, Michael Dorcas Feb 2015

Evaporative Water Loss In Two Natricine Snakes, Nerodia Fasciata And Seminatrix Pygaea, Christopher Winne, Travis Ryan, Yale Leiden, Michael Dorcas

Travis J. Ryan

Shorter communication in Journal of Herpetology v. 35.


Aspects Of Sex-Specific Differences In The Expression Of An Alternative Life Cycle In The Salamander Ambystoma Talpoideum, Christopher Winne, Travis Ryan Feb 2015

Aspects Of Sex-Specific Differences In The Expression Of An Alternative Life Cycle In The Salamander Ambystoma Talpoideum, Christopher Winne, Travis Ryan

Travis J. Ryan

A recent evolutionary ecological model of facultative paedomorphosis predicts that body size of mature individuals should be larger than immatures of the same cohort. We investigated sex-specific differences in body size and maturation within a single cohort of branchiate (= larval and paedomorphic) mole salamanders, Ambystoma talpoideum. In addition, we also sampled the population after the breeding season, as some individuals began to undergo metamorphosis and leave the pond. The branchiate population was female-biased (62.7%), and mature (paedomorphic) females were significantly smaller than paedomorphic males or immature (larval) females. The majority of male branchiates were mature (86.6%), whereas significantly ...


Effects Of Hydroperiod On Metamorphosis In Rana Sphenocephala, Travis J. Ryan, Christopher T. Winne Feb 2015

Effects Of Hydroperiod On Metamorphosis In Rana Sphenocephala, Travis J. Ryan, Christopher T. Winne

Travis J. Ryan

Hydroperiod, the time a temporary pond holds water, is an important factor influencing recruitment in amphibian populations and structuring amphibian communities. We conducted an experiment to test the effect of hydroperiod on metamorphic traits of the southern leopard frog (Rana sphenocephala), a common amphibian in the southeastern United States. We reared larval R. sphenocephala in artificial ponds at a density of 32 larvae per tank (initial volume = approximately 650 liter). We dried the tanks according to natural patterns, using three different hydroperiods (60, 75 and 90 d). Experimental hydroperiods had a significant effect on the number of metamorphs and the ...


Life History Evolution And Adaptive Radiation Of Hemidactyliine Salamanders, Travis Ryan, R. Bruce Feb 2015

Life History Evolution And Adaptive Radiation Of Hemidactyliine Salamanders, Travis Ryan, R. Bruce

Travis J. Ryan

T.J. Ryan and R.C. Bruce's contribution to: The Biology of Plethodontid Salamanders, R. C. Bruce, R. G. Jaeger, and L. D. Houck, eds. Kluwer Academic/Plenum Publishers, New York.


Ultrastructure Of The Reproductive System Of The Black Swamp Snake (Seminatrix Pygaea). I. Evidence For Oviducal Sperm Storage, David Sever, Travis Ryan Feb 2015

Ultrastructure Of The Reproductive System Of The Black Swamp Snake (Seminatrix Pygaea). I. Evidence For Oviducal Sperm Storage, David Sever, Travis Ryan

Travis J. Ryan

Oviducal sperm storage in the viviparous (lecithotrophic) colubrid snake Seminatrix pygaea was studied by light and electron microscopy. Out of 17 adult snakes examined from May–October, sperm were found in the oviducts of only two specimens. In a preovulatory female sacrificed 14 May, sperm were found in the oviducal lumen and sperm storage tubules (SSTs) of the posterior infundibulum. In a nonvitellogenic female sacrificed 9 June, sperm were found in the lumen and glands of the posterior uterus and anterior vagina, indicating a recent mating. The glands in the posterior infundibulum and vagina were simple or compound tubular, whereas ...


Hatching Asynchrony, Survival, And The Fitness Of Alternative Adult Morphs In Ambystoma Talpoideum, Travis J. Ryan Feb 2015

Hatching Asynchrony, Survival, And The Fitness Of Alternative Adult Morphs In Ambystoma Talpoideum, Travis J. Ryan

Travis J. Ryan

The mole salamander, Ambystoma talpoideum, exhibits both aquatic (gilled) and terrestrial (metamorphosed) adult morphologies. Previous studies have shown the existence of body-size advantages associated with the terrestrial morph in A. talpoideum and other polymorphic salamanders (e.g., A. tigrinum). However, aquatic adult A. talpoideum mature at a younger age and often breed earlier than terrestrial adults. We tested the hypothesis that early maturation and reproduction in aquatic adults increase fitness (irrespective of body size). We reared larval A. talpoideum in mesocosms and varied the timing of hatching, with early-hatching larvae representing the offspring from early-breeding aquatic adults, and late-hatching larvae ...


Intraspecific Heterochrony And Life History Evolution: Decoupling Somatic And Sexual Development In A Facultatively Paedomorphic Salamander, Travis J. Ryan, Raymond D. Semlitsch Feb 2015

Intraspecific Heterochrony And Life History Evolution: Decoupling Somatic And Sexual Development In A Facultatively Paedomorphic Salamander, Travis J. Ryan, Raymond D. Semlitsch

Travis J. Ryan

Morphological features such as size and shape are the most common focus in studies of heterochronic change. Frequently, these easily observed and measured features are treated as a major target of selection, potentially ignoring traits more closely related to fitness. We question the primacy of morphological data in studies of heterochrony, and instead suggest that principal sources of fitness, such as life history characteristics, are not only the chief targets of selection, but changes in them may necessitate changes in other (subordinate) elements of the organism. We use an experimental approach to investigate the timing of metamorphosis and maturation in ...


Larval Life History And Abundance Of A Rare Salamander, Eurycea Junaluska (Plethodontidae), Travis Ryan Feb 2015

Larval Life History And Abundance Of A Rare Salamander, Eurycea Junaluska (Plethodontidae), Travis Ryan

Travis J. Ryan

The larval life history of Eurycea junaluska was studied in three southwestern North Carolina populations. Populations were sampled quarterly over a 13 mo period and size-class analyses were used to evaluate the pattern of larval growth and metamorphosis. Young of the year appeared in the late spring and experienced rapid growth through the first summer. Growth slowed in the second year and metamorphosis usually occured in the summer at about 25.5 mo post-hatching, although some data suggest that either 1yr or 3yr larval periods may be possible. The overall larval growth rate of E. junaluska is estimated at 1 ...