Showing papers in "Biological Reviews in 1993"

The distribution and nature of colour vision among the mammals.

Abstract: 1. An oft-cited view, derived principally from the writings of Gordon L. Walls, is that relatively few mammalian species have a capacity for colour vision. This review has evaluated that proposition in the light of recent research on colour vision and its mechanisms in mammals. 2. To yield colour vision a retina must contain two or more spectrally discrete types of photopigment. While this is a necessary condition, it is not a sufficient one. This means, in particular, that inferences about the presence of colour vision drawn from studies of photopigments, the precursors of photopigments, or from nervous system signals must be accepted with due caution. 3. Conjoint signals from rods and cones may be exploited by mammalian nervous systems to yield behavioural discriminations consistent with the formal definition of colour vision. Many mammalian retinas are relatively cone-poor, and thus there are abundant opportunities for such rod/cone interactions. Several instances were cited in which animals having (apparently) only one type of cone photopigment succeed at colour discriminations using such a mechanism. it is suggested that the exploitation of such a mechanism may not be uncommon among mammals. 4. Based on ideas drawn from natural history, Walls (1942) proposed that the receptors and photopigments necessary to support colour vision were lost during the nocturnal phase of mammalian history and then re-acquired during the subsequent mammalian radiations. Contemporary examination of photopigment genes along with the utilization of better techniques for identifying rods and cones suggest a different view, that the earliest mammals had retinas containing some cones and two types of cone photopigment. Thus the baseline mammalian colour vision is argued to be dichromacy. 5. A consideration of the broad range of mammalian niches and activity cycles suggests that many mammals are active during photic periods that would make a colour vision capacity potentially useful. 6. A systematic survey was presented that summarized the evidence for colour vision in mammals. Indications of the presence and nature of colour vision were drawn both from direct studies of colour vision and from studies of those retinal mechanisms that are most closely associated with the possession of colour vision. Information about colour vision can be adduced for species drawn from nine mammalian orders.(ABSTRACT TRUNCATED AT 400 WORDS)

Growth in pinnipeds.

Abstract: This review presents summary figures of, and fits growth curves to, data on body lengths (as standard length, SL, whenever possible) of pinnipeds at ages estimated to O.I y. (1) Generalized von Bertalanffy (vB) growth curves are fitted to most data: Lx = L infinity (I - ea(x-x0)b, Lx is length at age x, x0 is the origin of the curve (here chosen a priori as time of initiation of embryonic growth), L infinity is asymptotic length, a (which is negative) determines rate of approach to the asymptote, and b influences the 'shape' of the approach. (2) No single monotonic growth equation suffices for growth in length, which is linear before birth and remains so during early life. The vB equation is only suitable to describe mean lengths of newborns, and animals one or more years old. (3) Also, for males of polygynous species, two functions are needed to account for accelerated growth at puberty. Generally a Gompertz equation is adequate for adult males of these species. (4) The fitted growth equations permit statistical comparisons of sizes and growth rates, as well as of individual variability (as growth-curve residuals), among populations and species. (5) For the following species (including different populations when available), the reliability of data is assessed and parameters of growth curves are presented (with sexes separated where significantly different): walrus, California and Steller sea lions, Antarctic, subantarctic and northern fur seals, Hawaiian monk seal, crabeater, Weddell and Leopard seals, southern and northern elephant seals, bearded, hooded, ringed, Baikal, Caspian, spotted, harbour, harp, ribbon and grey seals. (6) Some novel findings pertain to individual species as follows. Although the Pacific walrus is generally stated to be the larger subspecies, females from Hudson Bay and males from Foxe Basin, in the eastern Canadian Arctic, may be as long as those from the Bering Sea. Although female Weddell seals have been assumed to grow larger than males, there is no significant difference in growth curves fitted to the most complete data. Uniquely among populations examined, the relative variability (absolute growth curve residuals/predicted lengths) of male southern elephant seals is amplified with age. Among ringed seals from Svalbard, the eastern, western and high Canadian Arctic, and the Bering, Chukchi, Okhotsk, Barents and Baltic Seas, asymptotic sizes are larger among those that breed on land-fast ice rather than floes, and size may be more variable in more extreme Arctic environments. The Baikal seal is confirmed as the smallest species of pinniped.(ABSTRACT TRUNCATED AT 400 WORDS)

The relative importance of short‐ and long‐range movement of flying aphids

Abstract: Summary 1. Aphids are notorious pests of world agriculture. Even so, uncertainty persists as to their capacity for successful aerial dispersal. Evidence exists that, under some conditions, aphids can be wind-borne over long distances, i.e. hundreds of kilometers over desert or sea. It has been argued, in the recent past, that this phenomenon may be part of a strategy to locate fresh host plants in new distant areas. However, the proportion of these insects successfully colonizing new hosts is unknown. 2. Other work using meteorological backtracking has also indicated long-distance movement, but the accuracy of such predictions is dubious unless the altitude of transport is known. Mark-releaseecapture experiments with such small insects have limited potential due to large dilution effects. Static ‘snap-shots’ of demographic population densities, using suction traps, cannot accurately distinguish local aerial density fluxes and population movements from a distance. However, genetic and physiological markers may provide more direct information on population mixing; for example, some allozyme studies have shown a limited level of inter-population gene flow. 3. Under suitable conditions, aphids take off, maintain flight and alight in response to the appropriate visual and olfactory cues. Undoubtedly successful long-distance movement occurs from time to time, but its ecological relevance may have been overstated in the past. It may be selectively disadvantageous for aphids to move from areas containing their host plants. In contrast, it is advantageous for aphids to maximise their chances of survival and reproductive success by landing on suitable plant hosts at the earliest opportunity. 4. The clonal nature of aphids (a single genotype may comprise vast numbers of individuals) means that there may be advantages to phenotypic variation between individuals in the readiness to move. Recent evidence indicates that such a variation exists in the duration of the behavioural migratory phase, the initial period of maiden flight when host-plant cues are ignored and when landing is inhibited. 5. The relative biological importance of short- us. long-distance movements is reassessed with reference to plant virus epidemiology and the spread of new genotypes, e.g. insecticide resistance. It is concluded that the biological relevance of short-distance movements have a much greater impact on population and genotype distribution than long-distance movements, which may be comparatively infrequent.

The incidences. mechanisms and evolution of cytoplasmic sex ratio distorters in animals

Abstract: CONTENTS I . Introduction . . . . . . . . . . . . . . . . 122 I1 . The criteria for establishing the existence of cytoplasmic sex ratio distorters . . 123 . . . . 124 111 . The incidences and mechanisms of cytoplasmic sex ratio distortion ( I ) The induction of parthenogenesis . . . . . . . . . . 124 (2) Cytoplasmically induced feminization . . . (A) Crustaceans . . . . . . . . ( a ) Amphipods . . . . . . . . (i) Gammarus . . . . . . . (ii) Orchestia . . . . . . . (b) Isopods . . . . . . . . (i) Armadillidium . . . . . . (ii) Other isopods . . . . . . ( c ) Other crustaceans . . . . . . (B) Non-crustaceans . . . . . . . (3) Male killing: . . . . . . . . . (A) Early male killing . . . . . . . ( a ) Diptera . . . . . . . . (i) Neotropical Drosophila species . . . (a) The nature of the causative agent (p) The mechanism and biology of SRO action (ii) Non-neotropical Drosophila species . . (iii) The population genetics of SR in Drosophila . . . . . 128 . . . . . 128 . . . . . 128 . . . . . 128 . . . . . 129 . . . . . 131

Introgression and incorporation. Strategies for the use of crop genetic resources.

Abstract: Summary 1 In recent decades there has developed a very general appreciation of the need to build, maintain and use collections of crop plants with the primary object of sustaining genetic advance by plant breeding on into the indefinite future. The fact of genetic erosion is universally acknowledged and substantial advances in some practical aspects of genetic resource conservation work have been made. Many good collections have been assembled, though some crops have been poorly served, even ignored, and maintenance, study and utilization of those that have been collected have often left much to be desired. 2 This review is devoted to the most neglected aspect of all, namely utilization. Traditionally, collections have been regarded as sources of ‘genes’, usually disease resistances, to be exploited by backcrossing (Introgression) into adapted stocks. Thousands of such backcrosses have been made, with very varied success; there have been successes but also many failures, due usually to the weakness of ‘vertical resistances’ as protection against adaptable pathogens. By contrast, the need to broaden the genetic bases of many crops, far beyond the confines possible for Introgression programmes, has often been recognized but rarely explored. Thus a distinction is drawn between Introgression and Incorporation as the two fundamental methods of using crop collections (see Fig. 1). 3 Incorporation implies the systematic exploitation of a large array of genetic variability in such a way as to generate a mass of newly adapted stocks usable as parents in breeding programmes. Genetic principles are simple and obvious, always based on recurrent cycles of recombination and mass selection. Progress is likely to be slow (indeed usually must be slow), a fact which has often been a discouragement to such programmes in the past. 4 Examples of long-term, systematic Incorporation programmes are few, and the more important ones are summarized. They relate topotatoes, sugar cane and maize, which are well advanced; and cocoa, oil palm and (prospectively) rubber, which are well begun. Time scales depend upon the biology of the crop and methods; typically, a few decades are necessary to make serious progress. 5 In discussion, the following points are emphasizedthe essential nature of Incorporation (= Base broadening) in all well-bred crops in the longer term and into the indefinite future; the weakness of phenotypic assessment of genetic potential (usually referred to as ‘evaluation’); the fact that Incorporation is esentially simple, even if slow; the nomenclatural confusion that surrounds the terms Genetic Enhancement, Prebreeding, Genetic Vulnerability; the fact that the common stereotype of a crop collection as a collection of seed packets is often wrong because many crops are clonal and/or have short-lived, unstorable seeds; and the socio-politico-bureaucratic complications that arise because of the current collapse of publicly supported research, the associated short-term ideology, and the fact that serious genetic resource work, including Incorporation programmes, demands long-term commitment to the interests of our successors, not just to ourselves.

A coordinate-free approach to the analysis of growth patterns: models and theoretical considerations

Abstract: Developmental biology holds keys to our understanding of morphological pattern formation whether these patterns are expressed in the fossil record or among extant species. Though much is known about osseous growth at the cellular level (e.g. Hall, 1991), we have minimal understanding of the coordinated processes that combine to produce a complex, three-dimensional form. We have proposed a framework for the coordinate-free representation of form, a statistical method for comparing and modelling growth trajectories for complex morphologies, and a means for the eventual elucidation of the role of growth in the evolution of morphology. Our method uses the coordinate locations of biological landmarks to represent form as a matrix of all possible linear distances between landmarks, the form matrix. When two forms are expressed in this way, comparison of these forms is accomplished by computing the ratios of like linear distances, the form difference matrix. When the forms being compared are from a growth series, the matrix of ratios is called a growth matrix. Patterns of growth for two groups can be compared by computing the growth difference matrix. We applied growth difference matrix analysis to the study of sexual dimorphism of ontogeny in the M. fascicularis craniofacial skeleton. Growth matrices describing growth in male and female M. fascicularis were presented along with the growth difference matrix that describes sexual dimorphism of growth to underscore the detailed information available from this analytical technique. The method is quite general and can be applied to two- or three-dimensional data sets of landmark coordinates (cross-sectional or longitudinal) collected from almost any developing structure. The methods that we propose enable us to go beyond a mathematical summary of the comparison of forms and the comparison of growth patterns. We provide examples of how growth patterns might be used in the study of phylogenetic relationships. Our plans for use of this method in the study of evolutionary change assumes that morphological change in the craniofacial skeleton results from evolutionary change in developmental units (as defined by Atchley & Hall, 1991) that underlie morphological structure. We believe we have the basic tools to ultimately propose informed phylogenies based solely on developmental data. This task requires the identification of 'growth features' and the polarization of these features as primitive or derived. It is also advisable to determine a set of primitive growth features for the groups of interest. This will necessitate the inclusion of outgroups in our growth analysis.(ABSTRACT TRUNCATED AT 400 WORDS)

Cellular biology of bone resorption

Abstract: Summary Past knowledge and the recent developments on the formation, activation and mode of action of osteoclasts, with particular reference to the regulation of each individual step, have been reviewed. The following conclusions of consensus have emerged. 1. The resorption of bone is the result of successive steps that can be regulated individually. 2. Osteoclast progenitors are formed in bone marrow. This is followed by their vascular dissemination and the generation of resting preosteoclasts and osteoclasts in bone. 3. The exact pathways of differentiation of the osteoclast progenators to mature osteoclasts are debatable, but there is clear evidence that stromal cells support osteoclast generation. 4. Osteoclasts are activated following contact with mineralized bone. This appears to be controlled by osteoblasts that expose mineral to osteoclasts and/or release a factor that activates these cells. 5. Activated osteoclasts dissolve the bone mineral and digest the organic matter of bone by the action of agents secreted in the segregated microcompartments underlying their ruffled borders. The mineral is solubilized by protons generated from CO, by carbonic anhydrase and secreted by an ATP-driven vacuolar H+-K+-ATPase located at the ruffled border. The organic matrix of the bone is removed by acid proteinases, particularly cysteine-proteinases that are secreted together with other lysosomal enzymes in the acid environment of the resorption zone. 6. Osteoclastic bone resorption is directly regulated by a polypeptide hormone, calcitonin (CT), and locally, by ionized calcium (Ca2+) generated as a result of osteoclastic bone resorption. 7. There is new evidence that osteoclast activity may also be influenced by the endothelial cells via generation of products including PG, NO and endothelin.

Stress, extinctions and evolutionary change: from living organisms to fossils

Abstract: Summary 1. Natural populations are exposed to environmental stress of varying intensities. This provides a reference point for extrapolations from the living biota to fossils and vice versa. 2. Evolutionary change is likely when there are resources in excess of maintenance and survival needs. It is largely precluded at species borders by the metabolic costs of stress; from this follows climatic tracking by species. 3. A relatively small increase in abiotic stress could underlie extinctions of stress-sensitive endemic species and the spread of stress-resistant generalist and widespread species. Widespread fossil species appear resistant to extinction under the stress level of normal background extinctions. 4. Synergistic interactions among generalized stresses should increase the likelihood of extinctions, especially for stresses with energetic consequences. 5. Some marine organisms survived the K-T mass extinction event because of stress-evasion mechanisms such as stress-resistant life-cycle stages with low metabolic rates. 6. In moderately stressed and narrowly fluctuating environments, sufficient genetic variability and metabolic energy should be available to permit adaptation. In these environments phyletic gradualism is expected. 7. In highly stressed and widely fluctuating environments, a punctuated evolutionary pattern is expected whereby stasis occurs most of the time. 8. Evolutionary patterns therefore can vary depending on the details of the interaction between stress, environmental fluctuations, energy availability and genetic variability. 9. Little evolutionary change is expected when the availability of energy is severely restricted. Examples include cave animals in stable but stressed environments and ‘living fossils’ in widely fluctuating but stressed environments. 10. Since the primary effect of abiotic stress may be at the level of energy carriers, a reductionist approach permits generalisations in considering extinctions and conditions under which diversification is likely.

Biological rhythms as organization and information.

Abstract: Summary While it is generally acknowledged that modern science began with the quantification of time in the measurement of linear physical processes in space by Galileo and Newton, the biological sciences have only recently developed appropriate experimental and mathematical methods for the description of living systems in terms of processes of non-linear, recursive dynamics. We now recognize that living organisms have patterns of exquisitely timed processes that are as intricate as their spatial structure and organization. Self-similarities of life processes in time and space have evolved to generate an ensemble of oscillators within which analogous functions may be discerned on many different time scales. The increasing complexity of periodic relationships on and between the many levels of biological organization are uncovered by current research. Recent efforts to reformulate the foundation of physics from the quantum to the cosmological level by using the concept of information as the common denominator integrating time, structure and energy remind us of an apparently analogous suggestion in the chronobiological literature which also describes the periodic dynamics of living systems as information processing. In this paper we review the periodic processes of living systems on all levels from the molecular, genetic and cellular to the neuroendocrinological, behavioural and social domains. Biological rhythms may be conceptualized as the evolution of ever more complex dynamics of information transduction that optimize the temporal integrity, development, and survival of the organism.

Scale-dependent spatial dynamicsmarine birds in the bering sea

Abstract: Summary 1 One of the major developments in ecology has been the recognition of the importance of spatial and temporal scale in describing patterns of distribution and abundance. This article develops a quantitative framework that includes both spatial and temporal scale, then uses it to review what has been learned about a well studied group of mobile organisms — marine birds in the Bering Sea. 2 Review showed that lateral gradients in density are by far the most frequently measured property of birds away from colonies in the Bering Sea. Gradients are related to a variety of environmental factors, depending on spatial scale. 3 Review within a quantitative framework showed that the assumptions for interpreting the spatial dynamics responsible for observed patterns are rarely stated, that interpretations of pattern at sea have focused on individual movements in relation to food concentration, and that little is known about wind and water-driven movements, or rates of death and recruitment away from colonies. 4 Several lines of evidence support the hypothesis that distribution and feeding are linked to the rate of resupply of nekton to birds near the sea surface. 5 The framework provided here permits the relative importance of competing processes to be stated and evaluated as a function of spatial scale. The framework should be useful in summarizing the spatial dynamics of other groups of mobile organisms.

The evolution of consciousnesswilliam james's unresolved problem

Abstract: Summary Part I of this article shows that, for different reasons, neither traditional interactionist dualism nor more modern theories of the mind/body relationship — including functional-state identity theory — provide a satisfactory explanation of the evolution of consciousness. Interactionist dualism leaves us with a philosophical impasse; the more modern theories have not yet succeeded in providing adequate answers to the difficulties that were raised by William James in 1879. Part II of the article disputes Kripke's claim that identity theories are, anyway, untenable because the relevant identities would have to be necessary rather than contingent.