Hugh Loxdale

Hugh Loxdale
Hugh Loxdale Utting 09.09.2016.jpg Hugh Loxdale Utting 09.09.2016.jpg Hugh Loxdale, September 2016
Born
💼 Occupation

Hugh David Loxdale is an entomologist. He was professor of ecology at the Institute of Ecology, University of Jena from 2009 to 2010, president of the Royal Entomological Society from 2004 to 2006, and honorary visiting professor at the School of Biosciences, Cardiff University. Loxdale works on the population biology, ecology, and genetics of insects, especially aphids and their wasp parasitoids. Besides his scientific studies, he is also a poet, having written ten volumes of poetry since 1988.

Education and early career

Hugh Loxdale was educated at Corner Hall Secondary Modern Boys’ School, Hemel Hempstead, Hertfordshire, England from 1962 to 1967, and Apsley Grammar School, Hemel Hempstead (now Longdean School) from 1967 to 1969. On leaving school, he joined the Entomology Department at Rothamsted Experimental Station (now Rothamsted Research), in Harpenden, Hertfordshire, working in the Insect Survey, then run by L.R. (Roy) Taylor (1924–2007), studying the demography of moths and aphids as part of the national light trap and 12.2-metre-high (40 ft) suction trap surveys, respectively.

Scientific contributions

During his time at Oxford, Loxdale designed and development a continuous, circulatory NADH+-coupled enzyme ADP assay system which allowed for the first time accurate measurement of pico-mole quantities of ADP released from small bundles of glycerol-extracted fibres (c. 60μm diam.; c. 1.2 cm. long) during activation by threshold calcium ion concentration [Ca2+] and stretch activation of fibrillar insect flight muscle (IFM), or [Ca2+] activation of vertebrate skeletal muscle; meanwhile the mechanical performance of the fibres could be simultaneously measured by oscillating them at a range of frequencies and amplitudes. From this, he was able to demonstrate that, contrary to theory, the tension cost (ratio of ATPase activity over tension) did not change markedly as a function of the level of activation, i.e. the ATPase versus tension relationships remained essentially constant. It was thus concluded that the rate constant of detachment of myosin from actin during the acto-myosin cross bridge cycle was not, as hitherto assumed, more especially for fibrillar IFM, the rate-limiting step in determining contraction speed of the muscle. Indeed, he was able to demonstrate using ATP solutions buffered with phosphate ions, that the tension cost and mechanical performance could even be dissociated from one another. In light of these findings, Roger H. Abbott formulated a four-state cross bridge cycle as most adequately accounting for the phenomena observed. In addition, using glycerol extracted rabbit psoas muscle fibres activated in the absence of threshold concentrations of calcium ions using reduced ionic strength, Loxdale was also able to demonstrate that magnesium ions are necessary to stabilize the troponin-tropomyosin regulatory system, i.e. maintain this in the non-activated condition.

Loxdale and colleagues were also the first to demonstrate from their studies conducted in Jena that in the tansy aphid M. fuscoviride parasitized by its specialist wasp parasitoid Lysiphlebus hirticornis Mackauer (Hymenoptera: Braconidae), as the local genetic variation of the aphid increased, so did that of its parasitoid. This suggested a fine-grained co-evolutionary tracking to be in operation. Such a scenario is supportive of the Red Queen hypothesis, whereby a host organism (here an aphid) is attempting to evolve away from its antagonist (here a parasitoid), which is meanwhile co-evolving in order to retain the ability to attack it, i.e. keep pace with it in an ecological-evolutionary sense. Loxdale, in collaboration with G.M. Tatchell at Rothamsted, were also the first to determine the insecticide resistance status (here conferred by carboxylesterases, i.e. R1, R2 and R3 genotypes) of the serious agricultural pest the peach-potato aphid, Myzus persicae (Sulzer) captured in the UK network of 12.2. m high suction traps. This involved using pH-buffered glycerol solutions containing antibiotic and gel electrophoresis to identify the level of carboxylesterase gene expression of the individual genotypes (the result of amplification of the E4 and FE4 resistance genes involved) From this work, the spatial and temporal dynamics of this important (and now highly cross-resistant) pest aphid could be followed, thereby leading to more rational and effective control measures in the field.

Loxdale has written a series of overviews, many with colleagues, especially Dr. G. Lushai, highlighting the improbability of strict genetic uniformity in populations of clonal organisms such as aphids. This lack of uniformity is due to the rapid rate of mutation resulting from various mechanisms (e.g. point mutations due to errors of replication, inversion polymorphisms related to transposon effects, etc.) amplified by the huge reproductive potential of the animals concerned, e.g., not only do aphids show ‘telescoping of generations’ such that an adult asexual female has her children and grandchildren within her, but also display so-called ‘genetic inflation’, i.e. the production of a large number of asexual copies produced by a single female (10-100 offspring) in a short time (~ 10-14 days). Hence, a single aphid can, in theory (i.e. without mortality factors such as climate, predators, parasitoids and pathogens) produce enough offspring to cover the entire planet to a depth of many kilometres in a single growing season! This of course has serious potential consequences for the agricultural, horticultural and forestry industries worldwide.

Loxdale has also written overviews on several key areas of biological thought and research. These include the migration and dispersal of insects in relation to their genotype and habitat; intra-clonal genetic variation; rapid evolution in insect populations due to various genetic-ecological mechanisms; population proteomics (with Dr David Biron, Prof. Frédéric Thomas and colleagues); and most recently, on the improbability of generalism in nature, with special reference to insects, work in collaboration with G. Lushai and Professor Jeffrey Harvey. The consensus of these articles is that the act of filling a new ecological niche is of course the fundamental act of specialization for any new species or sub-specific population. Whilst some species may be polyphagous to varying degrees, which the authors define, nevertheless diet breadth tends to involve preference for certain prey items in predatory as well as herbaceous species. Generalism, if it exists, is highly dependent upon an animal's morphology-anatomy, genetics, physiology-biochemistry, and chemistry, especially chemical ecology. This in turn governs the behaviour of the animal concerned and restrains it in terms of its habitat choice and what it can eat. In this light, the age old ‘arms race’ of insect herbivores with plants has led to the plants evolving an armoury of secondary chemical defenses which cause, more often than not, specialisms in terms of host and indeed habitat on the part of the herbivore/s involved. Ultimately, even apparently highly polyphagous species such as the aphid M. persicae, said to attack plants in 40 families, may be because of its highly specialised biochemistry-enzymology. Most aphids are highly specialised on one host or closely related hosts (often in the same genus/family), probably due to biochemical constraints, and if so, perhaps what one is seeing in M. persicae is a unique specialization rather than generalization.

The picture is also complicated by the recent discovery in many species, including M. persicae and other aphids, following the application of high-resolution molecular markers, of morphologically similar/identical cryptic species. The discovery and realization of such cryptic entities is essential for successful pest control, especially including use of natural control agents such as hymenopterous wasp parasitoids and predators, as well as for the conservation of rare and endangered species.

Poetry

Loxdale has written over 500 poems over the last 50 years or so, mainly on natural history themes, often with a philosophical slant. His first poem, Dragonfly, was published whilst he was still at Apsley Grammar School in the 1960s. To date he has published ten volumes of poetry.

• Fascinating Felines (2002) ISBN 9780954334703 Search this book on .
• The Eternal Quest: A celebration of nature in poetry (2003) ISBN 9780954334710 Search this book on .
• Blue Skies in Tuscany (2003) ISBN 9780954334727 Search this book on .
• Bird Words: Poetic images of wild birds (2003) ISBN 9780954334734 Search this book on .
• The Jena Poems (2010) ISBN 9780955392894 Search this book on .
• Love and the Sea (2010) ISBN 9780955392887 Search this book on .
• Nevisian Days: Poetry from a Caribbean Isle (2011) ISBN 9781908241009 Search this book on .
• Bird of Paradise: Selected Poems, 1968-2011 (2011) ISBN 9781908241016 Search this book on .
• Zoooo…Living Poems for Children (2012) ISBN 9781908241139 Search this book on .
• Red Tulips, Selected Poems, 1999-2016 (2017) ISBN 9781908241511 Search this book on .

Honours and awards

In 2017 Loxdale was awarded an MBE in the Queen's New Year Honours list for services to entomology.

External links

Cardiff University School of Biosciences

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