Open Access. Powered by Scholars. Published by Universities.®
- Institution
- File Type
Articles 1 - 16 of 16
Full-Text Articles in Life Sciences
Tubulin Evolution In Insects: Gene Duplication And Subfunctionalization Provide Specialized Isoforms In A Functionally Constrained Gene Family, Mark G. Nielsen, Sudhindra R. Gadagkar, Lisa Gutzwiller
Tubulin Evolution In Insects: Gene Duplication And Subfunctionalization Provide Specialized Isoforms In A Functionally Constrained Gene Family, Mark G. Nielsen, Sudhindra R. Gadagkar, Lisa Gutzwiller
Mark G. Nielsen
Background: The completion of 19 insect genome sequencing projects spanning six insect orders provides the opportunity to investigate the evolution of important gene families, here tubulins. Tubulins are a family of eukaryotic structural genes that form microtubules, fundamental components of the cytoskeleton that mediate cell division, shape, motility, and intracellular trafficking. Previous in vivo studies in Drosophila find a stringent relationship between tubulin structure and function; small, biochemically similar changes in the major alpha 1 or testis-specific beta 2 tubulin protein render each unable to generate a motile spermtail axoneme. This has evolutionary implications, not a single non-synonymous substitution is …
The Larvae Of Eurycea Junaluska (Amphibia: Caudata: Plethodontidae), With Comments On Distribution, Travis Ryan
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
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.
Does Sex Influence Post-Reproductive Metamorphosis In Ambystoma Talpoideum?, Travis Ryan, Gabrielle Swenson
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.
Growth And The Expression Of Alternative Life Cycles In The Salamander Ambystoma Talpoideum (Caudata: Ambystomatidae), Travis Ryan, Raymond Semlitsch
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 …
Evaporative Water Loss In Two Natricine Snakes, Nerodia Fasciata And Seminatrix Pygaea, Christopher Winne, Travis Ryan, Yale Leiden, Michael Dorcas
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
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 fewer …
Effects Of Hydroperiod On Metamorphosis In Rana Sphenocephala, Travis J. Ryan, Christopher T. Winne
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 …
Geographic Distribution. Farancia Abacura., Kate Ingram, Travis Perry, Travis Ryan
Geographic Distribution. Farancia Abacura., Kate Ingram, Travis Perry, Travis Ryan
Travis J. Ryan
Geographic distribution of the mud snake.
Ultrastructure Of The Reproductive System Of The Black Swamp Snake (Seminatrix Pygaea). I. Evidence For Oviducal Sperm Storage, David Sever, Travis Ryan
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 glands …
Hatching Asynchrony, Survival, And The Fitness Of Alternative Adult Morphs In Ambystoma Talpoideum, Travis J. Ryan
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 representing …
Seminatrix Pygaea. Diet., Mark Mills, Travis Ryan, Sean Poppy, Anthony Mills, Michael Dorcas
Seminatrix Pygaea. Diet., Mark Mills, Travis Ryan, Sean Poppy, Anthony Mills, Michael Dorcas
Travis J. Ryan
Diet of black swamp snake.
Sex And Size Interaction And Standard Metabolic Rate Of Paedomorphic Ambystoma Talpoideum: Size Does Matter, Travis Ryan, William Hopkins
Sex And Size Interaction And Standard Metabolic Rate Of Paedomorphic Ambystoma Talpoideum: Size Does Matter, Travis Ryan, William Hopkins
Travis J. Ryan
We measured the standard metabolic rate of paedomorphic Mole Salamanders (Ambystoma talpoideum) from South Carolina. Despite an absence of body size differences between females and males, analysis of covariance demonstrated metabolic rates (mL O2/h) were significantly influenced by an interaction between sex and body size. The interaction appeared as a result of changes in the size-metabolism relationship in males (a steeper slope in the size-metabolism regression in small males as compared to large males), whereas the relationship remained constant in females, regardless of size. We hypothesize that the observed differences are attributable to differences in reproductive physiology between the sexes. …
Intraspecific Heterochrony And Life History Evolution: Decoupling Somatic And Sexual Development In A Facultatively Paedomorphic Salamander, Travis J. Ryan, Raymond D. Semlitsch
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
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 1.27 mm/mo, …
Exploring Behavioral And Hormonal Flexibility Across Light Environments In Guppies From Low-Predation Populations, Gita R. Kolluru
Exploring Behavioral And Hormonal Flexibility Across Light Environments In Guppies From Low-Predation Populations, Gita R. Kolluru
Gita R. Kolluru
No abstract provided.