Physiological impacts of temperature variability and climate warming in hellbenders (Cryptobranchus alleganiensis).

Cold-adapted hellbender salamanders that inhabit cool mountain streams are expected to fare poorly under warmer projected climate scenarios. This study investigated the physiological consequences of long-term, naturalistic temperature variation on juvenile hellbenders under simulated current and warmer (+1.6 C) climates vs. controlled steady temperatures. Mean temperature and temperature variability were both important predictors of growth as indicated by monthly body mass change (%), stress as indicated by neutrophil:lymphocyte (N:L) ratio and bacteria-killing ability of blood. Cold exposure in hellbenders was associated with weight loss, increased N:L ratios and reduced Escherichia coli killing ability of blood, and these effects were less pronounced under a warmer climate scenario. These observations suggest that cold periods may be more stressful for hellbenders than previously understood. Growth rates peaked in late spring and late fall around 14-17°C. Hellbenders experiencing warmer simulated climates retained body condition better in winter, but this was counter-balanced by a prolonged lack of growth in the 3-month summer period leading up to the fall breeding season where warmer simulated conditions resulted in an average loss of -0.6% body mass/month, compared to a gain +1.5% body mass/month under current climate scenario. Hellbenders can physiologically tolerate projected warmer temperatures and temperature fluctuations, but warmer summers may cause animals to enter the fall breeding season with a caloric deficit that may have population-level consequences.

Influence of extracellular environment on the motility and structural properties of spermatozoa collected from hormonally stimulated Panamanian Golden Frog (Atelopus zeteki).

A better understanding of the factors influencing the biology of amphibian spermatozoa after release from the testis is a prerequisite to the development of sperm preservation methods. The objective of the study was to determine the effect of extracellular conditions (exposure to water and different temperatures) over time on the sperm motility and structural properties (including morphology and DNA integrity) collected from hormonally stimulated Atelopus zeteki. Following intraperitoneal injection of gonadotropin-releasing hormone agonist (des-Gly10, D-Ala6, Pro-NHEt9 GnRH; 4 µg/g of body weight), human chorionic gonadotropin (hCG, 10 IU/gbw), or Amphiplex™ (0.4 µg/gbw GnRH-A + 10 µg/gbw metoclopramide hydrochloride), spermic urine samples from 27 males were collected and analyzed for sperm motility, morphology and DNA integrity while maintained at room temperature (23 °C), 4 °C, or diluted in water (hypo-osmotic environment) over a period of 46 min post-collection. Percentages of sperm motility and forward progressive motility remained high (>60%) when spermic urine was kept at room temperature or at 4 °C for 46 min regardless of the hormonal stimulation method. Dilution in water at room temperature greatly reduced the percentage of motile spermatozoa and forward progression (<50%) as well as DNA integrity (32.8% of intact cells) after 23 min while morphology did not differ (30.4% of normal cells), regardless of the hormone stimulation. This is the first systematic study on the effect of extracellular environment over time on A. zeteki sperm quality. This will contribute to the development of sperm handling protocols and reproductive technologies for this and other endangered Atelopus species.

Effects of hormonal stimulation on the concentration and quality of excreted spermatozoa in the critically endangered Panamanian golden frog (Atelopus zeteki).

Knowledge of basic gamete biology is critical to better protect and propagate endangered amphibian species and also to develop reproductive technologies combined with germplasm cryopreservation. The objectives of the study were to test different hormonal stimulations and then characterize the quantity and quality of Panamanian golden frog (Atelopus zeteki) spermatozoa. Following intraperitoneal injection of the gonadotropin-releasing hormone agonist (des-Gly10, D-Ala6, Pro-NHEt9--GnRH 1, 2 or 4 µg/g of body weight), human chorionic gonadotropin (hCG; 5 or 10 IU/gbw), or Amphiplex™ (0.4 µg/gbw GnRH-A + 10 µg/gbw metoclopramide hydrochloride), spermic urine samples from 29 males were collected at different time points (from 0.5 to 24 h post-injection) to analyze the concentration, motility, and morphology of the spermatozoa. Peak of sperm concentration was observed at 3.5 h post injection for all hormonal treatments. Amphiplex™ led to the highest sperm concentrations (4.45 ± 0.07 × 106 cells/mL) followed by 4 µg/gbw GnRH-A (2.65 ± 0.21 × 106 cells/mL). Other stimulation protocols and doses induced sperm production, but at lower levels (ranging from 1.34 to 1.70 × 106 cells/mL). More than 60% of spermatozoa were motile following all treatments but the highest motility (>90%) was obtained from the 10 IU/gbw hCG treatment. Spermic urine samples obtained with all hormone treatments had higher pH (ranging from 7.1 to 7.8) than the urine alone (6.7-6.8). Spermatozoa were filiform and elongated with an apical acrosome, a mitochondrial sheath, a small midpiece and a long tail with an undulating membrane. More than 80% of cells were morphologically normal and 50-70% had intact DNA. These sperm characteristics were not influenced by hormonal treatments. This first comprehensive characterization of sperm samples following optimized hormonal stimulations in A. zeteki lays the foundation for more fundamental studies, reproductive technologies, and future preservation strategies.

A review of the biology and literature of the Gulf Coast Toad (Incilius nebulifer), native to Mexico and the United States.

The Gulf Coast Toad (Incilius nebulifer) is an abundant and widespread species within its range in the United States and Mexico, so it appears on many faunal checklists and is considered in diverse kinds of research. We review the basic biology, distribution, and published history of this species, identifying only those records and publications referable to I. nebulifer, to help researchers identify published works pertaining to I. nebulfer rather than I. valliceps, with which it formerly was considered to be conspecific.

Cryptic impacts of temperature variability on amphibian immune function.

Ectothermic species living in temperate regions can experience rapid and potentially stressful changes in body temperature driven by abrupt weather changes. Yet, among amphibians, the physiological impacts of short-term temperature variation are largely unknown. Using an ex situ population of Cryptobranchus alleganiensis, an aquatic North American salamander, we tested the hypothesis that naturally occurring periods of temperature variation negatively impact amphibian health, either through direct effects on immune function or by increasing physiological stress. We exposed captive salamanders to repeated cycles of temperature fluctuations recorded in the population's natal stream and evaluated behavioral and physiological responses, including plasma complement activity (i.e. bacteria killing) against Pseudomonas aeruginosa, Escherichia coli and Aeromonas hydrophila. The best-fit model (ΔAICc=0, wi=0.9992) revealed 70% greater P. aeruginosa killing after exposure to variable temperatures and no evidence of thermal acclimation. The same model predicted 50% increased E. coli killing, but had weaker support (ΔAICc=1.8, wi=0.2882). In contrast, plasma defenses were ineffective against A. hydrophila, and other health indicators (leukocyte ratios, growth rates and behavioral patterns) were maintained at baseline values. Our data suggest that amphibians can tolerate, and even benefit from, natural patterns of rapid warming/cooling. Specifically, temperature variation can elicit increased activity of the innate immune system. This immune response may be adaptive in an unpredictable environment, and is undetectable by conventional health indicators (and hence considered cryptic). Our findings highlight the need to consider naturalistic patterns of temperature variation when predicting species' susceptibility to climate change.

Access to in vitro fertilization deserves increased regulation in the United States.

In the United States, it is generally accepted that people have the right to reproduce without government interference or regulation. The autonomy of the individual is held in high regard. Before the advent of assisted reproductive technology, heterosexual, monogamous relationships were the legally accepted standard means of human reproduction. In vitro fertilization and other forms of assisted reproductive technology have provided society with a wide array of reproductive possibilities that challenge moral and legal conventions regarding the structure of society and the concept of what constitutes the family unit. At the same time, access to health care is increasingly being recognized as a basic human right. If society is required to accept assisted reproduction as a basic right, it has the right to regulate access for its physical, social, and economic well being.

Tunable few-cycle and multicycle coherent terahertz radiation from relativistic electrons.

We report the generation of tunable, narrow-band, few-cycle and multicycle coherent terahertz (THz) pulses from a temporally modulated relativistic electron beam. We demonstrate that the frequency of the THz radiation and the number of the oscillation cycles of the THz electric field can be tuned by changing the modulation period of the electron beam through a temporally shaped photocathode drive laser. The central frequency of the THz spectrum is tunable from ∼0.26 to 2.6 THz with a bandwidth of ∼0.16 THz.

Exponential growth, superradiance, and tunability of a seeded free electron laser.

Exponential growth and superradiance regimes in a high-gain free electron laser (FEL) are studied in this paper for both a seeded FEL and a Self-Amplified Spontaneous Emission (SASE) FEL. The results are compared to the earlier superrdaince theory and the recent experimental observation. The influence of an initial energy chirp along the electron bunch on the superradiance mode is explored for the first time. With a short seed to increase the initial seed bandwidth, a tunable seeded FEL is possible.

ABCD formalism and attosecond few-cycle pulse via chirp manipulation of a seeded free electron laser.

An ABCD formalism is identified to characterize a seeded Free Electron Laser (FEL) with three chirps: an initial frequency chirp in the seed Laser, an energy chirp in the electron bunch, and an intrinsic frequency chirp due to the FEL process. A scheme of generating attosecond few-cycle pulses is proposed by invoking an FEL seeded by high-order harmonic generation (HHG) from an infrared laser. The HHG seed has generic attosecond structure. It is possible to manipulate these three chirps to maintain the attosecond structure via post-undulator chirped pulse compression.