European corn borer: pheromone polymorphism or sibling species?

Electrophoretic analyses of the (Z) and (E) pheromone-attracted males of Ostrinia nubilalis (Hübner), the European corn borer, in an area of coexistence indicate that these strains are not freely interbreeding. Although the populations are morphologically indistinguishable, studies of allozyme, pheromone, and hybridization suggest that the (Z) and (E) entities are genetically differentiated, perhaps to the status of semi- or sibling species.     

Vertical nitrate fluxes in the oligotrophic ocean

The vertical flux of nitrate across the thermocline in the upper ocean imposes a rigorous constraint on the rate of export of organic carbon from the surface layer of the sea. This export is the primary means by which the oceans can serve as a sink for atmospheric carbon dioxide. For the oligotrophic open ocean regions, which make up more than 75% of the world's ocean, the rate of export is currently uncertain by an order of magnitude. For most of the year, the vertical flux of nitrate is that due to vertical turbulent transport of deep water rich in nitrate into the relatively impoverished surface layer. Direct measurements of rates of turbulent kinetic energy dissipation, coupled with highly resolved vertical profiles of nitrate and density in the oligotrophic eastern Atlantic showed that the rate of transport, averaged over 2 weeks, was 0.14 (0.002 to 0.89, 95% confidence interval) millimole of nitrate per square meter per day and was statistically no different from the integrated rate of nitrate uptake as measured by incorporation of (15)N-labeled nitrate. The stoichiometrically equivalent loss of carbon from the upper ocean, which is the relevant quantity for the carbon dioxide and climate question, is then fixed at 0.90 (0.01 to 5.70) millimole of carbon per square meter per day. These rates are much lower than recent estimates based on in situ changes in oxygen over annual scales; they are consistent with a biologically unproductive oligotrophic ocean.     

Visual and nonvisual auditory systems in mammals. Anatomical evidence indicates two kinds of auditory pathways and suggests two kinds of hearing in mammals

Examination of the structural organization of the auditory system of the brain stem shows that the system is composed of a number of separate ascending pathways. This suggests that there may be at least two auditory systems, analogous to the rod and cone pathways in vision. We examined this possibility by investigating the variation in relative size of the medial and lateral superior olivary nuclei in a number of different mammalian species. The lateral superior olive is present in the hedgehog (an insectivore), cat (acarnivore), and squirrel monkey a(primate), but the medial superior olive is absent in the hedgehog. In a group of animals of the same taxonomic order (rodents) the lateral superior olive was present in all species examined, but the medial superior olive was almost wholly absent in the mouse and very prominent in the chinchilla and guinea pig. The absence of the medial superior olive in some animals is surprising because recent anatomical and physiological work has implicated the nucleus in auditory localization. Because of this implication, the medial and lateral olivary nuclei were examined in three species of bat and one dolphin, all echolocating animals. The medial superior olive was absent in these animals, and the lateral superior olive was prominent. These observations support the idea that the medial and lateral superior olives are nuclei on two different ascending auditory systems. It was also noted that the medial superior olive was always well developed in animals with well-developed eyes, and this suggested that the nucleus is in some way related to the visual system. We examined this idea by studying the relation between the numbers of cells in the medial superior olive and in the nucleus of the 6th cranial nerve (one of the motor nuclei concerned with eye movement) in a number of mammalian species. An approximately linear function was found between the sizes of the 6th nucleus and of the medial superior olive in three primates with cone-cell retinas (squirrel monkey, man, and macaque) and four rodents with rod-cell retinas (mouse, rat, guinea pig, and chinchilla). The cell numbers for the ground squirrel (a rodent with cone-cell retina) fitted an extension of the primate curve, and the cell numbers for the cat (in whose retina rods predominate) fitted an extension of the rodent curve. Thus, it is clear that the medial superior olive is related to the visual system, and that it is present in animals with cone-cell fovea and retina (diurnalanimals) and animals with rod-cell retina (that is, nocturnal animals) having good vision. In nonvisual nocturnal animals the nucleus is small or absent. The medial superior olive is probably not concerned with auditory localization in the psychophysical sense but is probably concerned with the movement of head and eyes in the direction of a sound in space. Localization in the psychophysical sense and fine auditory discrimination probably depend upon the ascending pathway which includes the lateral superior olive.     

Cosmic rays,clouds, and climate

It has been proposed that Earth's climate could be affected by changes in cloudiness caused by variations in the intensity of galactic cosmic rays in the atmosphere. This proposal stems from an observed correlation between cosmic ray intensity and Earth's average cloud cover over the course of one solar cycle. Some scientists question the reliability of the observations, whereas others, who accept them as reliable, suggest that the correlation may be caused by other physical phenomena with decadal periods or by a response to volcanic activity or El Ni?o. Nevertheless, the observation has raised the intriguing possibility that a cosmic ray-cloud interaction may help explain how a relatively small change in solar output can produce much larger changes in Earth's climate. Physical mechanisms have been proposed to explain how cosmic rays could affect clouds, but they need to be investigated further if the observation is to become more than just another correlation among geophysical variables.     

Transplantation of fetal hematopoietic stem cells in utero: the creation of hematopoietic chimeras

Transplantation of normal, immature, fetal hematopoietic cells into a preimmune fetal recipient with a congenital hemoglobinopathy may allow partial reconstitution of normal hemoglobin production without the complications associated with postnatal bone marrow transplantation (immunosuppression and the occurrence of graft versus host disease). In order to test this hypothesis the naturally occurring polymorphism at the beta-hemoglobin locus of the sheep was used as a marker for engraftment and hematopoietic chimerism. Intraperitoneal injection of allogeneic fetal stem cells into normal fetal lambs resulted in hematopoietic chimerism in three of four surviving recipients. This chimerism has been sustained for 6 months after birth and 9 months after engraftment, without evidence of graft versus host disease, and without the use of immunosuppressive therapy.     

Calcium carbonate production of the mare incognitum, the upper windward reef slope, at enewetak atoll

Corals and algal pavement produce calcium carbonate more slowly on the windward reef slope of Enewetak Atoll than on the reef flat despite the high standing crop of reef-building organisms on the slope. The capacity of reefs to remain at or near sea level is therefore not determined primarily by growth on the seaward slope.     

Spontaneous formation of macroscopic chiral domains in a fluid smectic phase of achiral molecules

A smectic liquid-crystal phase made from achiral molecules with bent cores was found to have fluid layers that exhibit two spontaneous symmetry-breaking instabilities: polar molecular orientational ordering about the layer normal and molecular tilt. These instabilities combine to form a chiral layer structure with a handedness that depends on the sign of the tilt. The bulk states are either antiferroelectric-racemic, with the layer polar direction and handedness alternating in sign from layer to layer, or antiferroelectric-chiral, which is of uniform layer handedness. Both states exhibit an electric field-induced transition from antiferroelectric to ferroelectric.