Diss. (sammanfattning) Umeå : Umeå universitet, 2006. / Härtill 3 uppsatser.

Thesis (Ed.D.)--Teachers College, Columbia University, 1970. / Typescript; issued also on microfilm. Sponsor: Paul E. Eiserer. Dissertation Committee: Anne Selley McKillop. Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2006. / Includes bibliography.

Thesis (Ph. D.)--Georgia State University, 2006. / David A. Washburn , committee chair; Claudio C. Cantalupo, Eric J. Vanman, Duane M. Rumbaugh, committee members. Electronic text (102 p. : col. ill.)) : digital, PDF file. Description based on contents viewed July 13, 2007. Includes bibliographical references (p. 79-96).

Behavioural asymmetry (laterality) is widespread among conspicuously bilaterally symmetrical organisms, playing a part in many aspects of life history from reproduction to feeding. Laterality is typically thought to occur due to morphological asymmetry within the brain, in which one hemisphere becomes specialized for a given task. However, the influence of sensory receptor asymmetry on the development of lateralized behaviour has undergone little investigation. The role of inconspicuous receptor asymmetry in behavioural laterality is particularly important, given the ubiquity of small deviations from symmetry. Here I have investigated morphological asymmetry in the lateral line, a series of mechanoreceptors called neuromasts that comprise one of the major sensory modalities of fishes. I examined a subset of the lateral line of 3,987 threespine stickleback from 64 populations from coastal British Columbia, characterizing neuromast count and asymmetry among habitats. Furthermore, I scored 657 stickleback from four experimental transplant populations relocated from stained lakes to unstained ponds, to determine whether or not neuromast count or asymmetry changes in a novel habitat. Neuromast count did not differ between oceanic and freshwater stickleback, or between sympatric lake-stream pairs but did differ among clarity regimes, ranging from a complete lack of neuromasts to a doubling of neuromasts compared to oceanic stickleback. Loss of neuromasts was associated with reduced light transmission, lower pH and a lack of piscivorous fishes. Stickleback with more lateral plates developed more neuromasts and males bore more neuromasts than females. One transplant pond underwent a 70% increase in neuromast count within just a couple of generations, whereas the other three transplant populations underwent more gradual change, suggesting both phenotypically plastic and genetic mechanisms underlying difference in neuromast counts among populations. Asymmetry was widespread among individuals, differing by up to seven neuromasts between the two sides on a single bony plate. However, no populations exhibited a strong directional bias. The degree of absolute asymmetry differed among clarity regimes, with stickleback in stained habitats having less asymmetry in their neuromasts counts. Asymmetry did not differ between oceanic and freshwater populations or sympatric lake-stream pairs. Males exhibited greater asymmetry than females, particularly in large-bodied populations. As with neuromast count, neuromast asymmetry quickly changed in some transplant populations and more gradually in others, increasing by up to 14% in just a couple of generations. To assess the functional consequences of my geographic survey, I experimentally tested 40 stickleback for their response to a simulated predator, localization of vibrations in the dark and rheotaxis. I compared behaviour and laterality to neuromast count and asymmetry measured by fluorescent microscopy. Stickleback with fewer neuromasts were more likely to respond to simulated predator strikes, but other non-lateralized behaviours were independent of neuromast count. The strongest laterality I observed was the ‘hugging’ of the arena wall with the right side 57% of the time, with laterality being present in other behaviours, albeit weakly. While some behaviours correlated with lateral line asymmetry, there was no consistent association between lateralized behaviour and asymmetry in the lateral line. I found that ecological factors such as predation landscape and photo-regime shape both mechanoreceptor count and asymmetry in the lateral line, with potential phenotypic plasticity in both traits. The lateral line’s role in response to a model predator and lateralized behaviour supports the influence of mechanosensory asymmetry in eco-evolutionary dynamics. / Graduate / 2022-05-05

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Lateral biases are evident in a number of behaviors across many organisms. The present work was concerned with the particular lateral phenomenon known as handedness. Previous research has suggested that handedness is not a one-dimensional trait. This study evaluated handedness using two factors: hand preference and hand performance. Hand preference refers to the hand chosen to carry out a given action whereas hand performance refers to each hand’s ability, or skill, at carrying out that action. The relationship between hand preference and hand performance has been studied extensively in adults, but the larger body of work with human infants has only assessed hand preference. The goals of this study were to develop a methodology to measure infant hand performance and to begin to examine the relationship between hand preference and hand performance in development. To this end, thirty-six 11-month-old infants were videotaped completing three tasks. The first task assessed hand preference and consisted of a free-play period during which infants were presented with a series of toys that afforded different types of manipulation. The second and third tasks were novel measures of infant hand performance. The second task assessed the infant’s gross motor skills and involved fitting a ball into the top aperture of a toy. The third task assessed the infant’s fine motor skills by requiring infants to retrieve a Cheerio from a stationary plastic cup. Overall, the majority of infants were found to be right-preferent. This was in agreement with previous studies of hand preference in 11-month-olds as well as the pattern of hand preference seen in adults. There was no group-level asymmetry on either measure of hand performance. Hand preference was regressed on hand performance in an overall model of handedness. The right hand’s performance on each task significantly predicted hand preference scores. This was the first study to demonstrate that hand preference can be predicted by hand performance in infants. Future work will examine infant hand proficiency in greater detail as well as the relationship between hand preference and hand performance in nonhuman primate infants.

No description available.

A long standing axiom in the field of teratology states that the teratogenic period, when most birth defects are produced, occurs during the third to eighth weeks of development post-fertilization. Any insults prior to this time are thought to result in a slowing of embryonic growth from which the conceptus recovers or death of the embryo followed by spontaneous abortion. However, new insights into embryonic development during the first two weeks, including formation of the anterior-posterior, dorsal-ventral, and left-right axes, suggests that signaling pathways regulating these processes are prime targets for genetic and toxic insults. Establishment of the left-right (laterality) axis is particularly sensitive to disruption at very early stages of development and these perturbations result in a wide variety of congenital malformations, especially heart defects. Thus, the time for teratogenic insults resulting in birth defects should be reset to include the first two weeks of development.