Modelling power‐line collision risk for the Blue Crane Anthropoides paradiseus in South Africa

The Overberg wheatbelt population of Blue Cranes Anthropoides paradiseus in the Western Cape of South Africa is approximately half the global population of this vulnerable species. Blue Cranes are highly susceptible to collisions with overhead power lines, and a spatial model was developed to identify high‐risk lines in the Overberg for proactive mitigation. To ground‐truth this model, we surveyed 199 km of power lines. Although Blue Cranes were the most commonly killed birds found (54% of all carcasses), the model was unable to predict lines with high collision risk for Blue Cranes. Further Geographic Information System (GIS) modelling was undertaken to test a wider range of landscape and power‐line variables, but only the presence or absence of cultivated land could usefully identify lines posing a collision risk. Modelling was limited by a lack of detailed spatial habitat data and recent information on Crane numbers and distributions. We used recent carcass counts to estimate a Blue Crane collision rate, corrected for sample biases, of 0.31/km power line per year (95% CI 0.13–0.59/km/year), which means that approximately 12% (5–23%) of the total Blue Crane population within the Overberg study area is killed annually in power‐line collisions. This represents a possibly unsustainable source of mortality. There is urgent need for further research into risk factors and for mitigation measures to be more widely implemented.     

Modulatory Mechanisms at a Primitive Neuromuscular Synapse: Membrane Currents, Transmitter Release and Modulation by Transmitters in a Cnidarian Motor Neuron

The phylum Cnidaria arose early in metazoan evolution and, assumingmonophyly, is regarded as being close to the ancestral metazoan.The simplicity of structure in the cnidariannervous system isnot reflected in the physiology of neurons. The motor neuronsthat control swimming in the jellyfish Polyorchis penicillatusepitomise this operational complexity. Synchrony in the contractionof the swimming muscle sheets is achieved by compensatingforthe conduction time of motor APs propagating to distant partsof the motor network. This depends on motor APs continuouslydecreasing in duration as they propagate through the networkwhich in turn leads to a decrease in the delay of muscle actionpotential initiation. Two membrane currents are critical forthis mechanism, a fast, transient K⁺ current (I_K-fast). anda transient Ca⁺⁺ current. A PCR-based screen of genomicDNA producedclones having considerable sequence identity with the Shaker,Shal, Shab and Shaw subfamilies. One full-length clone, jShaklwhen expressed in Xenopus oocytes reveals an A-like Shaker currentwhich activates at very positive voltages. Motor neuron activitycan be modulated by two endogenous transmitters, dopamine andFMRFamide-related peptides which are found endogenously. Dopaminecauses a long lasting hyperpolarization by activating a potassiumcurrent that is regulated by D₂ receptors. In addition dopaminereduces action potential duration. Pol-RFamides, on the otherhand have an excitatory effect by blocking the slowly inactivatingcurrent, I_K-slow     

The Effects of Seed Number and Prior Fruit Dominance on the Pattern of Fruit Production in Cucurbits pepo (Zucchini Squash)

Many plants, especially of species with indeterminate reproduction,show first-fruit dominance, in which the presence of developingfruit reduces future fruit maturation by increasing the abortionof later (younger) fruit and by inhibiting subsequent flowerproduction. We examined the effects of seed number on first-fruitdominance by experimentally manipulating the number of pollengrains that were deposited onto stigmas of zucchini squash andthen monitoring flower production, fruit growth, and fruit maturation.Our findings show (1) that fruits containing more seeds growfaster and achieve greater size; (2) that the presence of 6–15-d-oldfruit significantly decreases the probability of female flowerproduction while significantly increasing the probability offruit abortion; (3) that the number of seeds in the prior developingfruit has a significant effect on the probability of flowerproduction and fruit abortion, and (4) that when seed numbervaries among the fruits on a vine the fruit with the fewestseeds are the most likely to abort. It is concluded that thestrength of dominance by a developing fruit depends on the numberof seeds it contains and that this also influences the resultof fruit to fruit competition. Fruit abortion, fruit growth, Cucurbita pepo, size of pollen load, seed number, zucchini, squash     

Free Vehicles and Deep-Sea Biology

SYNOPSIS. A free vehicle is a timed and weighted device releasedfrom a ship in a free fall to the ocean bottom. Instrumentscarried on the free vehicle have been built to take biologicalsamples, sediment samples, water samples, and photographs, andto measure currents, tides, and temperature. The instrumentthen returns to the surface where it is recovered by the ship.A free vehicle system for biological sampling in the deep seais described in detail. It consists of a mast assembly, flotation,hookline and traps, and a magnesium release attached to weights.Different types of magnesium links used include a rod, a wireon pliers, and a series of diamond-shaped beads that drop througha hole after dissolving. A deck plan for launching the freevehicle and its retrieval at sea are described.     

Block of Conduction in Partially Depolarized Cardiac Purkinje Fibres induced by an α-Adrenergic Agent

IF discrete areas of the ventricular conducting system are exposed to high concentrations of K⁺, conduction through these areas is slowed so much that the impulse may re-enter the normal part of the conducting system after the end of the refractory period, thereby evoking another excitation of the heart (refs. 1 and 2 and our unpublished work). This slow conduction results from a slow response that resembles the slow component of the cardiac action potential³ and the action potential of normal fibres of the atrioventricular node⁴. Adrenaline enhances the response of Purkinje fibres, depressed by exposure to high K⁺ concentration⁵ and we now report that an α-adrenergic agent, methoxamine, depresses the slow response at concentrations that do not affect the normal action potential. This finding is of interest because very few of the actions of adrenergic agents on the heart can be attributed to the stimulation of α-receptors⁶, because selective depression of the slow response is further evidence that it differs qualitatively from the response of normal fibres (our unpublished work) and because it suggests that α-adrenergic agents may be useful in the prevention of certain cardiac arrhythmias.     

Isolation of polymorphic microsatellite markers in the sub‐Saharan tree,Acacia (Senegalia) mellifera (Fabaceae: Mimosoideae)

We isolated 11 polymorphic microsatellite markers from Acacia mellifera, a savannah woodland tree in sub‐Saharan Africa and southern Arabia. The loci were screened for polymorphism using 48 Kenyan individuals. Allelic diversity ranged from three to 19 per locus and the polymorphic information content varied from 0.287 to 0.893. These loci will be useful in studies of genetic structure, gene flow and breeding systems.