147 research outputs found


    Get PDF
    Number of Pages: 5Integrative BiologyGeological Science

    Tantilla hobartsmithi

    Get PDF
    Number of Pages: 2Integrative BiologyGeological Science

    Winter Movements of Louisiana Pine Snakes (Pituophis ruthveni) in Texas and Louisiana

    Get PDF
    Despite concerns that the Louisiana Pine Snake (Pituophis ruthveni) has been extirpated from large portions of its historic range, only a limited number of studies on their movement patterns have been published. Winter movement patterns are of particular interest since it has been hypothesized that impacts of management practices would be reduced during the winter. Using radiotelemetry, we determined winter movement patterns of Louisiana Pine Snakes (11 males, 8 females) in 5 study areas (2 in Louisiana and 3 in Texas). Movements during winter (November–February) were greatly curtailed compared to the remainder of the year; however, snakes occasionally undertook substantial movements. Relocations were typically within the snake’s previous active-season home range, and movements were more frequent in the early portion of winter. All hibernation sites were within Baird’s Pocket Gopher (Geomys breviceps) burrow systems at depths ranging from 13–25 cm. Louisiana Pine Snakes did not use communal hibernacula, nor did individual snakes return to previously used sites in successive years

    Hybridization among whiptail lizards.

    Get PDF
    43 p. : ill. (some col.) ; 26 cm. "October 11, 2010."The natural origin of diploid parthenogenesis in whiptail lizards has been through interspecific hybridization. Genomes of the parthenogens indicate that they originated in one generation, as the lizards clone the F₁ hybrid state. In addition, hybridization between diploid parthenogens and males of bisexual species has resulted in triploid parthenogenetic clones in nature. Consequently, the genus Aspidoscelis contains numerous gonochoristic (= bisexual) species and numerous unisexual species whose closest relatives are bisexual, and from whom they originated through instantaneous sympatric speciation and an abrupt and dramatic switch in reproductive biology. In order to study this phenomenon more closely, with hopes (unfulfilled) to witness the origin of parthenogenetic cloning in one generation, we maintained whiptail lizards in captivity. For more than 29 years, we caged males of bisexual species with females of bisexual and of unisexual species in attempts to obtain laboratory hybrids. Hybrids were raised to adulthood to see whether they would reproduce, but none did. The hybrid status of suspected laboratory hybrids was confirmed by karyotypic, allozyme, and morphological analyses, and histological studies were made on reproductive tissues of the hybrids, which were apparently sterile. The present paper focuses on the laboratory hybrids of two bisexual species, A. inornata arizonae ([female]) x A. tigris marmorata ([male]). These three individuals from one clutch of eggs were the only hybrids between two bisexual species that we obtained. The hybrids had a karyotype, allozymes (21 loci tested), and external morphology that were similar to those of A. neomexicana, which is a diploid parthenogen that had a hybrid origin in nature that was the reciprocal cross: A. t. marmorata ([female]) x A. inornata ([male]). Histological study showed that the largest and oldest laboratory hybrid raised, which appeared to be a female with inherited X chromosome of A. t. marmorata, was an intersex with an enormous adrenal. The other hybrid that reached adult size, a male, was also apparently sterile. Later, we review and summarize the information on the other laboratory hybrids we obtained over the years. These include two different combinations of hybrids between a male of a bisexual species and females of unisexual species (one diploid, one triploid), producing triploid and tetraploid hybrids, respectively, as a haploid genome from the male was added to the cloned egg. Considering only those specimens whose hybrid status was confirmed with genetic analyses, a total of only five hybrids from three crosses were obtained over 29 years. The effort involved having a total of 74 males of four species caged with 156 females of nine species, where individuals were caged together for at least six months (or less, if mating behavior was observed). Despite our extensive efforts to provide for their comfort and best health and captive environment, the lizards at times experienced health problems such as metabolic bone disease and a Salmonella infection. These definitely had a negative effect on reproduction, the full extent of which is unknown. Nevertheless, we estimate that successful hybridization among whiptail lizards (i.e., which results in healthy offspring capable of reproduction) is much more rare than we previously thought, although, paradoxically, it is far more common among Aspidoscelis than among nearly all other genera of lizards in the world, with the possible exception of lacertids

    A High Intake of Saturated Fatty Acids Strengthens the Association between the Fat Mass and Obesity-Associated Gene and BMI123

    Get PDF
    Evidence that physical activity (PA) modulates the association between the fat mass and obesity-associated gene (FTO) and BMI is emerging; however, information about dietary factors modulating this association is scarce. We investigated whether fat and carbohydrate intake modified the association of FTO gene variation with BMI in two populations, including participants in the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) study (n = 1069) and in the Boston Puerto Rican Health (BPRHS) study (n = 1094). We assessed energy, nutrient intake, and PA using validated questionnaires. Genetic variability at the FTO locus was characterized by polymorphisms rs9939609 (in the GOLDN) and rs1121980 (in the GOLDN and BPRHS). We found significant interactions between PA and FTO on BMI in the GOLDN but not in the BPRHS. We found a significant interaction between SFA intake and FTO on BMI, which was stronger than that of total fat and was present in both populations (P-interaction = 0.007 in the GOLDN and P-interaction = 0.014 in BPRHS for categorical; and P-interaction = 0.028 in the GOLDN and P-interaction = 0.041 in BPRHS for continuous SFA). Thus, homozygous participants for the FTO-risk allele had a higher mean BMI than the other genotypes only when they had a high-SFA intake (above the population mean: 29.7 ± 0.7 vs. 28.1 ± 0.5 kg/m2; P = 0.037 in the GOLDN and 33.6. ± 0.8 vs. 31.2 ± 0.4 kg/m2; P = 0.006 in BPRHS). No associations with BMI were found at lower SFA intakes. We found no significant interactions with carbohydrate intake. In conclusion, SFA intake modulates the association between FTO and BMI in American populations

    Solving Navigational Uncertainty Using Grid Cells on Robots

    Get PDF
    To successfully navigate their habitats, many mammals use a combination of two mechanisms, path integration and calibration using landmarks, which together enable them to estimate their location and orientation, or pose. In large natural environments, both these mechanisms are characterized by uncertainty: the path integration process is subject to the accumulation of error, while landmark calibration is limited by perceptual ambiguity. It remains unclear how animals form coherent spatial representations in the presence of such uncertainty. Navigation research using robots has determined that uncertainty can be effectively addressed by maintaining multiple probabilistic estimates of a robot's pose. Here we show how conjunctive grid cells in dorsocaudal medial entorhinal cortex (dMEC) may maintain multiple estimates of pose using a brain-based robot navigation system known as RatSLAM. Based both on rodent spatially-responsive cells and functional engineering principles, the cells at the core of the RatSLAM computational model have similar characteristics to rodent grid cells, which we demonstrate by replicating the seminal Moser experiments. We apply the RatSLAM model to a new experimental paradigm designed to examine the responses of a robot or animal in the presence of perceptual ambiguity. Our computational approach enables us to observe short-term population coding of multiple location hypotheses, a phenomenon which would not be easily observable in rodent recordings. We present behavioral and neural evidence demonstrating that the conjunctive grid cells maintain and propagate multiple estimates of pose, enabling the correct pose estimate to be resolved over time even without uniquely identifying cues. While recent research has focused on the grid-like firing characteristics, accuracy and representational capacity of grid cells, our results identify a possible critical and unique role for conjunctive grid cells in filtering sensory uncertainty. We anticipate our study to be a starting point for animal experiments that test navigation in perceptually ambiguous environments