Distinguished Zoologist Lectures
2015: Steve Jones (University College London, UK) Why so much genetic diversity - a scientist's view of snails in art and the art of snails.
2013: Judy Stamps (University of California at Davis, US)
2009: John Endler (University of Exeter, UK) Elaboration, innovation, speciation and visual signal design in Australian Bowerbirds.
2007: Geoff Parker (University of Liverpool, UK) Sperm competition, fertilisation conflicts and evolution.
2005: Ronald Plasterk (Netherlands Institute for Developmental Biology, The Netherlands) MicroRNAs in animal development.
2003: Sir Gabriel Horn (University of Cambridge, UK) Imprinting: zoology's gift to neuroscience.
2001: Sir John Krebs (University of Oxford, UK) From zoology to government policy.
Why so much genetic diversity - a scientist's view of snails in art and the art of snails
Without diversity there could be no evolution and, as DNA technology now tells us, the amount of variation at the molecular level is vast. But why is it there?
It seems to be the automatic assumption among molecular biologists that most of it is random noise and they might, possibly, be right.
I will talk about another system of inherited variation that was once equally hailed as a classic example of genetic drift, the shell patterns in Cepaea snails, upon which I have wasted much of my scientific career. In fact, those supposed instances of random noise are maintained by a fine balance between ecological patchiness and habitat choice by animals of differing genotype and the attempts to dismiss them as unimportant were wrong.
Just possibly someone may give a talk to a meeting of your Congress five decades from now that makes the same point about sequence variation: and as this is an after-dinner speech I will try to enliven the dull facts of science with some perhaps unexpected insights into the role of snails in art, Dutch art included.
Mammalian brain evolution
Viviparity has played a major role in mammalian evolution particularly in the context of maternalism, which has required radical changes in the functional evolution of the brain.
Viviparity requires the action and interaction of two genomes in one individual and has resulted in a tissue type unique to mammals, namely the trophectoderm which forms the placenta. The foetal placenta exerts considerable influence on the maternal brain, determining neuroendocrine function and behaviour.
Hormones secreted by the placenta act on the maternal brain to suppress maternal sexual behaviour and fertility, increase maternal food intake in anticipation of subsequent foetal demands and promote the synthesis of oxytocin in anticipation of its requirements for parturition, maternal behaviour and milk letdown. In short, the foetal genome determines its own destiny via its placenta.
The question arises as to how the adult maternal brain has evolved to optimise such interactive responding with the developing foetal genome. Maternal imprinting of key regulator genes provides a unique epigenetic transcriptional regulatory mechanism that results in alleles being monoallelically expressed according to parent-of-origin. Among vertebrates, genomic imprinting is restricted to viviparous mammals and has been thought to play a significant role in the evolution of the brain and placenta.
In this talk I will explore the role of genomic imprinting in brain evolution and its key role in synchronising gene expression in brain and placenta at critical developmental times. I will show how the outcome of such genetic developmental co-adaptation positively shapes the next generation's mothering capabilities.
Sperm competition, fertilisation conflicts and evolution
Males and females probably arose through primordial gamete competition coupled with the need for zygote provisioning; recent models show more clearly conditions under which the ESS (evolutionary stable strategy) is for one sex or two sexes.
A primordial sexual conflict probably arose because proto-females experience an advantage if they produce proto-ova that fuse with other ova, rather thatn with proto-sperm. Conflicts over gametic fusion can be pre-fertilisation or post-fertilisation.
Sperm competition appears to be a pervasive selective force shaping adaptation throughout all animal groups. Sperm competition games are ESS models predicting sperm allocation trends across or within species. They predict increased relative testis size and sperm allocation (as a proportion of total reproductive effort) across species as the risk or intensity of sperm competition increases.
Within a species, when immediate risks of sperm competition are low, increased risk usually implies greater sperm allocation by males, though there are cases when it can pay to ejaculate more sperm into virging females. When sperm competition is intense and typically several males compete, sperm allocation (as a proportion of total reproductive effort)should decrease with competition.
Variations in sperm allocation patterns within a species depend on the role a male occupies (first or second to mate), the fairness of the raffle, and on the information available to a male at the time of mating. Recent models include both (i) sperm competition and (ii) sperm selection by females; these are co-evolutionary games involving both intra- and inter-sexual conflict. The ESS depends on costs to females of increasing sperm selection, and on whether males occupy roles favoured or disfavoured by females randcomly or constantly. This alters patterns of sperm allocation for the two roles, something that empiricists need to clarify.
MicroRNAs in animal development
RNA silencing was discovered as an experimental tool; our laboratory is primarily interested in the biological functions. In one line of research we study RNAi as the machinery that protects the genome of C. elegans against transposition in the germ line. We now found that a single episode of RNAi can silence a gene in an inheritable fashion, over more than 40 animal generations. Off-target silencing can also inherit indefinitely
A second research question is the role of microRNAs in vertebrate development. We previously performed computational whole-genome comparisons to predict hundreds of novel microRNAs (Berezikov et al., 2005). We now present experimental confirmation of many of those by a modified RAKE-microarray assay, and the discovery of many novel microRNAs by large scale cloning and sequencing from human, mouse, and zebrafish embryos, using different tissues and different stages.
Following up on recent in situ microRNA detection experiments (Wienholds et al., 2005) we studied the expression of novel microRNAs. To address their role in the development we knocked down miRNAs in zebrafish embryos.
Imprinting: zoology's gift to neuroscience
Sir Gabriel Horn
If memory consists of a mark, or trace made in the brain by a particular experience, where is the mark and what is its nature?
For vertebrate learning and memory, the difficulty of finding an answer to the 'where' question has been a serious obstacle to answering the 'what' question.
Experimental evidence will be given that the difficulty of localising a memory site has largely been overcome in the case of the memory underlying visual imprinting. Visual imprinting is a form of learning through which the young of certain animals, including the domestic chick, learn the characteristics of an object by being exposed to it. This form of learning has many advantages for analysing the neural basis of the memory underlying imprinting and these adavantages will be outlined.
In domestic chicks, a region has been indentified that plays a crucial role in, and serves as storage site for the memory underlying imprinting. The region, in the cerebral hemispheres, is the intermediate and medial part of the hyperstriatum ventrale (IMHV).
In this lecture an account will be given of the changes in neural function that occur in IMHV during the formation of a memory of the imprinting object.