Autotropism in Fungal Spores

Autotropism was examined in germinating spore pairs of Rhizopusstolonifer, Mucor plumbeus, Trichoderma viride, and Botrytiscinerea. When germinated on agar surfaces the first three speciesexhibited negative autotropism, B. cinerea being neutral inits autotropic behaviour. More pronounced negative autotropismwas shown by the first three species when germinated on a filmof Cellophane applied to an agar surface. Under these conditionsB. cinerea displayed positive autotropism. Spore pairs of R. stolonifer germinated on agar containing cellulosepowder or charcoal showed less negative autotropism than onagar alone. Touching spore pairs of each species showed a markedtendency towards cis-ness, i.e. germ-tubes beginning on thesame side of a line joining the two spore centres, under theculture conditions described, the one exception being the reductionin cis-ness recorded when R. stolonifer was germinated on agarcontaining charcoal. Time courses of germination were determined for single sporesand touching spore pairs of R. stolonifer and M. plumbeus anda significant promotion was obtained in the spore pairs as comparedwith the single spores. Although both these species exhibitmarked negative autotropism there was a strong tendency forthe positive germ-tube, i.e. one beginning more nearly towardsits neighbour, to emerge before the negative germ-tube in thosespore pairs having one germtube positive and the other negativein orientation. Also, in R. stolonifer, the replacement of germination-promotersby germination-inhibitors in filtrates from spore suspensionsas they age is correlated with a change from positive to negativeautotropism in germinating members of (+ –) spore pairs. Possible mechanisms are discussed to account for the observedeffects.     

Distribution of Oriental and German cockroaches, Blatta orientalis and Blattella germanica (Dictyoptera), in the United Kingdom

Results are presented of a survey carried out by Rentokil Ltd on the distribution of the Oriental cockroach Blatta orientalis L. and the German cockroach Blattella germanica L. in the United Kingdom. The known ranges of both species are increased considerably by the findings of the survey, with several new vice-county records for Scotland (including the Western Isles), England and Wales. The frequency at which Blatta orientalis was observed in outdoor habitats may indicate that this species sometimes spreads to new areas without human assistance.     

Symposium Introductory Remarks: A Brief History of Aquatic Microbial Ecology

ABSTRACT This report serves to introduce the symposium on food chains and food webs that is jointly sponsored by the Society of Protozoologists and the Phycological Society of America. A brief history of the field of aquatic microbial ecology is presented with an emphasis on the development of theoretical models that have directed the course of research — research that has shaped the development of new and more complex models of the present. the paper aims to provide historical background for all symposium participants and an introduction to the specific presentations of the four guest speakers.     

The morphology of Opabinia regalis and the reconstruction of the arthropod stem-group

Opabinia regalis Walcott is an enigmatic fossil from the Middle Cambrian Burgess Shale of uncertain affinities. Recent suggestions place it in a clade with Anomalocaris Whiteaves from the Burgess Shale and Kerygmachela Budd from the Greenlandic Sirius Passet Fauna; these taxa have been interpreted as 'lobopods'. Consideration of available Opabinia specimens demonstrates that reflective extensions from the axial region, previously thought to be either gut diverticula or musculature, can be accommodated in neither the trunk nor the lateral lobes that arise from it. They must therefore be external structures independent of the lateral lobes. On the basis of their sub-triangular appearance, size and taphonomy, they are considered here to represent lobopod limbs. Some evidence for the existence of terminal claws is also presented. The question of whether Kerygmachela, Opabinia and Anomalocaris constitute a monophyletic or paraphyletic grouping is considered. While they share several characters, most of these are plesiomorphies. Further, Opabinia and Anomalocaris share several arthropod-like characters not possessed by Kerygmachela. It is concluded that these three taxa probably form a paraphyletic grouping at the base of the arthropods. Retention of lobopod-like characters within the group provides important documentation of the lobopod-arthropod transition. A proper understanding of Opabinia and its close relatives, which may include the tardigrades, opens the way for a reconstruction of the arthropod stem-group. This in turn allows the construction of a speculative but satisfying scenario for the evolution of major arthropod features, including the origin of the biramous limb, tergites and arthropod segmentation. 'Arthropodization' may thus be seen not to be a single event but a series of adaptive innovations. OPABINIA, ANOMALOCARIS, KERYGMACHELA, Burgess Shale, problematica, Lobopodia, Arthropoda.     

Growth models and the expected distribution of fluctuating asymmetry

Multiplicative error accounts for much of the size-scaling and leptokurtosis in fluctuating asymmetry. It arises when growth involves the addition of tissue to that which is already present. Such errors are lognormally distributed. The distribution of the difference between two lognormal variates is leptokurtic. If those two variates are correlated, then the asymmetry variance will scale with size. Inert tissues typically exhibit additive error and have a gamma distribution. Although their asymmetry variance does not exhibit size-scaling, the distribution of the difference between two gamma variates is nevertheless leptokurtic. Measurement error is also additive, but has a normal distribution. Thus, the measurement of fluctuating asymmetry may involve the mixing of additive and multiplicative error. When errors are multiplicative, we recommend computing log  E ( l ) − log  E ( r ), the difference between the logarithms of the expected values of left and right sides, even when size-scaling is not obvious. If l and r are lognormally distributed, and measurement error is nil, the resulting distribution will be normal, and multiplicative error will not confound size-related changes in asymmetry. When errors are additive, such a transformation to remove size-scaling is unnecessary. Nevertheless, the distribution of l  −  r may still be leptokurtic.  © 2003 The Linnean Society of London, Biological Journal of the Linnean Society , 2003, 80, 57–65.     

Isolation and characterization of microsatellite loci from mother‐of‐millions,Bryophyllum delagoense (Crassulaceae), and its hybrid with Bryophyllum daigremontianum, ‘Houghton's hybrid’

Nine microsatellite loci were developed, and are transferable, across the Madagascan succulents Bryophyllum daigremontianum, Bryophyllum delagoense (mother‐of‐millions) and their horticultural hybrid (Houghton's), from enriched libraries of the later two species. For B. delagoense, a tetraploid, three to 13 alleles per locus were found for native Madagascan (H_O = 0.4–1.0), and one to nine in invasive Australian (H_O = 0.0–1.0) samples. In addition for 91 Australian samples, only five multilocus genotypes were found (95% of individuals were of two genotypes), suggesting extensive clonality in its introduced range. These loci will be used to examine genetic diversity, hybrid origin and mating system in natural and introduced populations.     

Methane bubbles in surface peat cores: in situ measurements

The quantification of greenhouse gas sources and sinks is important to understanding the impact of climate change. Methane (CH₄) is a potent greenhouse gas, which, on a global scale, is released largely as a product of anaerobic microbial decomposition and predominantly from wetlands. A zone of intense CH₄ production just below the water table is thought to contribute significantly to the overall flux from peat bogs. We describe the use of membrane inlet quadrupole mass spectrometry (QMS) to confirm the existence of bubbles, their gaseous concentrations and their localization at a fine spatial resolution within intact peat cores. We use the distribution of the noble gas argon (Ar) and the distinct QMS responses to dissolved and gaseous (bubble) phases to identify trapped bubbles with a resolution of 0.6 mm. Bubbles with CH₄ concentrations of up to 20 kPa were widely distributed in the upper 300 mm of the cores with ～11% of all profiles comprising bubbles. The dissolved concentrations responsible for the bubbles were on average 83±80 μm , indicating lower concentrations relative to other QMS studies. We suggest that if the distinction between dissolved and gaseous phases is not made in studies of CH₄ within peat profiles then the prominence of bubbles is likely to result in overestimates of dissolved CH₄ concentrations. Fluxes of CH₄ from peat as a result of drawdown or other perturbation are likely to be large, rapid and short lived because of bubble burst, and also larger than from peat without bubbles. We suggest that the dynamics of fluxes need to be modelled taking into account both gaseous and dissolved phases. Estimates of potential fluxes that assume CH₄ is dissolved are likely to overestimate fluxes if the gaseous phase has not been taken into account.