The Induction and Development of Potato Microtubers In Vitroon Media Free of Growth Regulating Substances

Reliable microtuber production has been obtained by culturingnodal explants of potato on Murashige and Skoog medium withoutthe addition of growth regulating substances. The use of sucroseat 8 %, as compared with 4 or 12%, advanced the initiation oftuberization and gave more and larger microtubers. A periodof 1 month under 16 h days, followed by transfer to 8 h photoperiodsgave most rapid microtuber development. A reduction in the totalnitrogen supply or an increase in the ratio of ammonium to nitratereduced the size and number of microtubers Potato, Solanum tubersum L;, microtubers, in vitro induction and development, sucrose, photoperiod, nitrogen nutrition     

Climate change,chytridiomycosis or condition: an experimental test of amphibian survival

Variation in climatic temperature is frequently cited as playing a powerful role in driving host/pathogen dynamics, and as a consequence future patterns of disease are predicted to change owing to global warming. However, the preponderance of data is correlative and few quantitative tests exist that dissect the relative effects of changing temperature on host and pathogen responses. In this study, we experimentally tested the effect overwintering temperature had on the susceptibility of a vertebrate ectothermic host, the common toad Bufo bufo, to infection and mortality caused by Batrachochytrium dendrobatidis (Bd). We show that a ‘poor’ (warmer) overwintering regime increases the probability of infection, supporting the concept that the dynamics of infection are altered by changing environmental temperature profiles. We also show once established, the proliferation of Bd in the host was better in toadlets that experienced a ‘good’ (colder) winter. We find no relationship between survival and the different overwintering regimes or any consistent deleterious influence of disease on survival. Instead, survival is overwhelmingly predicted by measurements of condition (mass, mass lost over winter) that were not determined by overwintering temperature. We conclude that the survival of a cohort of overwintering toadlets is primarily driven by patterns of growth during the larval period rather than winter temperature or infectious disease.     

Musculoskeletal Model of the Upper Limb Based on the Visible Human Male Dataset

A mathematical model of Ihe human upper limb was developed based on high-resolution medical images of the muscles and bones obtained from the Visible Human Male ( HM) project. Three-dimensional surfaces of the muscles and bones were reconstructed from Computed Tomography (CT) images and Color Cryosection images obtained from the VHM cadaver. Thirteen degrees of freedom were used to describe the orientations of seven bones in the model: clavicle, scapula, humerus, radius, ulna, carpal bones, and hand. All of the major articulations from the shoulder girdle down to the wrist were included in the model. The model was actuated by 42 muscle bundles, which represented the actions of 26 muscle groups in the upper limb. The paths of the muscles were modeled using a new approach called the Obstacle-set Method (33) The calculated paths of the muscles were verified by comparing the muscle moment arms computed in the model with the results of anatomical studies reported in the literature, In-vivo measurements of maximum isometric muscle torques developed at the shoulder, elbow, and wrist were also used to estimate the architectural properties of each musculotendon actuator in the model. The entire musculoskeletal model can be reconstructed using the data given in this paper, along with information presented in a companion paper which defines the kinematic structure of the model (26)     

Microsatellite markers developed from Thamnophis elegans and Thamnophis sirtalis and their utility in three species of garter snakes

Previous studies of polyandry and population genetics in garter snakes have been hampered by the limited number of available microsatellite markers. Here we report another six dinucleotide microsatellite markers, doubling the number of previously available loci. The majority of the loci exhibit utility across a broad geographical range for the common garter snake and also cross‐amplify effectively in samples from two other Thamnophis species.     

Female alpine newts (Triturus alpestris) mate initially with males signalling fertility benefits

Gametic asymmetry implies that females invest more per gamete than males do and thus sperm is considered to be a relatively cheap resource. However, contrary to this classic view, sperm has been shown to be frequently in short supply; hence, selection favouring females that mate for fertility benefits should occur. For this reason, we determined whether males signalling fertility are preferred by female newts of the species Triturus alpestris . We performed paired female–male trials using unmated and previously inseminated females to determine potential criteria for female interest in a courting male, to establish what factors lead to successful mating and to assess the importance of female choice for direct and indirect benefits. We found that female interest in any potential mate and mating success decreased once mating had occurred. Furthermore, we detected an increase in spermatophore deposition rate and rapid spermatophore transfer in encounters that resulted in a successful mating. The results obtained indicate that female alpine newts are attracted to males showing signs of relatively high fertility and that females exhibit a decreased propensity to mate once initial sperm reserves have been acquired. Our results support the theory of initial female choice for fertility benefits.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 483–491.