Prenatal alcohol exposure is known to have many profound detrimental effects on human fetal development (fetal alcohol spectrum disorders), which may manifest into lifelong disabilities. Although hearing deficiency is a recognized effect, how alcohol affects the auditory/vestibular systems has not been well studied. This is the first study that used the zebrafish, Danio rerio, as a model organism to investigate morphological effects of alcohol on the developing octavolateral system (auditory, vestibular and lateral line). Zebrafish embryos of two hours post fertilization (hpf) were treated in 2% alcohol for 48 hours and screened at 72 hpf for morphological defects of the inner ear and lateral line neuromasts. Inner ear size and otoliths of zebrafish from both alcohol-treated and control groups were examined using light microscopy. Zebrafish were stained with fluorescent vital dyes to visualize lateral line hair cells using confocal microscopy. The size of neuromasts and length of kinocilia were measured using scanning electron microscopy. Results reveal that alcohol treatment during the early development impairs the formation of otoliths, neuromasts and their hair cells, as well as ear size and kinocilium length. We observed several otolith phenotypes including zero, one, two abnormal, two normal and multiple otoliths for alcohol-treated zebrafish. Fetal alcohol exposure appears to severely impact the size of both anterior and posterior lateral line neuromasts. Our results indicate that early fetal alcohol exposure most likely results in functional defects of the octavolateral system due to inner ear and lateral line dysmorphology.

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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O grupo Batoidea engloba as raias e seu monofiletismo é bem corroborado. Contudo, as inter-relações filogenéticas dentro do grupo ainda são discutíveis. Algumas filogenias consideram Pristiformes como grupo basal de Batoidea, enquanto outras consideram Torpediniformes como mais basal. O grupo dos Rhinobatiformes é visto como monofilético por alguns autores e como parafilético por outros. O grupo dos Myliobatiformes também apresenta problemas em suas inter-relações: alguns autores consideram Hexatrygon como grupo mais basal, outros consideram Urotrygon, além de outras hipóteses para a filogenia deste grupo. A distribuição dos canais do sistema sensorial de linha lateral apresenta grande variação entre os grupos de Batoidea e, apesar deste sistema não ser muito bem estudado em elasmobrânquios, constitui uma importante fonte de caracteres filogenéticos. Dessa forma, buscou-se, neste projeto, descrever a distribuição e a morfologia dos canais do sistema de linha lateral do grupo Batoidea, levantando possíveis caracteres de relevância sistemática que auxiliem na resolução dos problemas filogenéticos neste grupo. Com base na análise dos padrões encontrados em 55 espécies pertencentes a 39 gêneros e 18 famílias de Batoidea e em informações revisadas da bibliografia, foram propostos 13 caracteres, os quais foram discutidos de acordo com questões filogenéticas dentro de Batoidea. Assim, puderam ser abordados problemas como o grupo basal de Batoidea e o posicionamento dos gêneros Platyrhina e Zanobatus, além de discussões acerca do monofiletismo de Myliobatiformes e seus grupos internos / Batoidea includes all the rays and its monophyly is well-corroborated. However, the phylogenetic interrelationships within the group are still debatable. Some phylogenies consider Pristiformes as the basal group of Batoidea while others considered Torpediniformes the most basal group. Rhinobatiformes are seen as a monophyletic group by some authors and as paraphyletic by others. Phylogenetic positioning problems also are found within the genders of Torpediniformes, Rhinobatiformes, Rajiformes and Myliobatiformes. The distribution of the canals of the lateral line sensory system presents wide variation between batoid groups, and although this system is not well studied in elasmobranchs, its constitutes an important source of phylogenetic characters. The master\'s project bound to this proposal aimed to describe the distribution and morphology of the canals of the lateral line sensory system in Batoidea, gathering possible characters with phylogenetic relevance which may help elucidate the phylogenetic problems in this group. Based on the analysis of the patterns found in 55 species of 39 genders an 18 families of Batoidea and on information reviewed from literature 13 characters were proposed, which one was discussed according the phylogenetic questions within Batoidea. Therefore, problems such as the basal group in Batoidea and the position of Platyrhyna and Zanobatus could be discussed as much as the monophyly of Myliobatiformes and its internal groups

O sistema látero-sensorial dos peixes é responsável, dentre outras funções, pela percepção de vibrações e de movimentos na água. A unidade funcional desse sistema é denominada neuromasto, o qual pode estar presente na superfície ou em ranhuras da pele, ou também em canais que percorrem ossos dérmicos, alcançando a superfície externa da pele por intermédio de poros. O padrão de ossificação dos canais sensoriais cefálicos é conservado em diversas linhagens de peixes de tal forma que esse complexo morfológico representa uma rica fonte de informações filogenéticas, sendo amplamente utilizado em análises cladísticas de vários grupos de Ostariophysi, como, por exemplo, em Siluriformes. No entanto, o sistema láterosensorial cefálico de Characiformes, uma das mais diversificadas ordens de teleósteos e também um membro de Ostariophysi, nunca havia sido descrito em detalhes, sendo suas implicações filogenéticas pouco investigadas. O presente trabalho teve como objetivo realizar uma análise exploratória da homologia dos diversos elementos que compõem o sistema látero-sensorial em Characiformes, especificamente de: 1) levantar informações sobre os padrões de ramificação e de ossificação dos canais sensoriais cefálicos de todas as suas principais linhagens; 2) mapear as terminações destes ramos, os poros sensoriais, que se abrem na superfície da pele; e 3) identificar as principais implicações filogenéticas relacionadas a este sistema dentre os Characiformes e demais Ostariophysi. Para tal, foram analisados um total de trinta e seis táxons da ordem Characiformes, englobando representantes de todas as suas famílias e principais subfamílias. Além destes, outros treze componentes da ordem Ostariophysi, bem como sete demais Teleostei foram incluidos na análise como representantes do grupo-externo. Um dos principais resultados do presente estudo foi a constatação de que a disposição dos canais do sistema látero-sensorial cefálico, e o número de poros associados a cada um destes canais pouco variou dentre as diferentes famílias de Characiformes, mantendo-se também relativamente contantes nos demais Ostariophysi, e apresentando-se altamente informativas em um contexto filogenético. A complexidade morfológica desse sistema deixa implícito que o mesmo pode representar uma grande fonte de informações anatômicas combinando-os com demais caracteres morfológicos. Os resultados apresentados no presente trabalho indicam que os canais e poros da linha látero-sensorial cefálica constituem mais uma evidência de que novas fontes de caracteres morfológicos, apesar de não tradicionais, têm muito a contribuir com o entendimento das relações de parentesco entre peixes. / The laterosensory system of fishes is responsible, among other functions, for the perception of water movement and vibration. The functional unit of this system is the neuromast, which can be present on the skin surface or in grooves on it, or also in canals that are distributed along dermic bones, reaching the skin surface by pores. The ossification pattern related to the laterosensory canals is conserved among distinct fish lineages so that this morphological complex may represent a rich source of phylogenetic information. This system has been extensively used in cladistics analysis on several Ostariophysans, such as in Siluriformes and Cypriniformes. However, the laterosensory system of Characiformes, one of the most diverse order of teleost and also a member of the superorder Ostariophysi, has not been described in details yet, and its phylogenetic implications are poorly investigated. The present study aimed on performing an investigation on the laterosensory system components of Characiformes, having as its main goals: 1) a description of the cephalic laterosensory canals and branches for all main lineages of the order; 2) a characterization the canals ending points, i.e. the pores that open on the skin surface; and 3) a interpretation of the main philogenetical implications related to the laterosensory system among Characiformes and Ostariophysi. In order to accomplish these goals, a total of thirty-six Characiformes taxa were analysed, encompassing all families and main subfamilies of this order. Added to that, another thirteen representatives of other Ostariophysans, as well as seven taxa of other Teleostei were included to the comparative analysis as out-group material. As one of the main results of this survey is the acknowledgement that the distribution of the canals os the laterosensory system, as well as the number of branches and pores in association to this complex show little variation between the different lineages of Characiformes, keeping relatively stable among other Ostariophysi. This is interpreted as evidence that morphological traits in relation to this system may be very informative on a phylogenetical context when combined to other sources of characters. Therefore, these results indicate that features of the canals and pores of the laterosensory system may be one more source of anatomical characters, that even not traditionally used, are potentially informative on what regards the the relationship of fishes.

The lateral line canal system is a sensory organ found in all teleost fish that has a wide range of morphological variation. Variation in morphology may often be the result of evolutionary necessity where the need for function dictates form. Xiphister mucosus is an amphibious Stichaeid fish that inhabits the rocky intertidal zone of the northeastern Pacific Ocean. The rocky intertidal is considered an extreme environment where crashing waves and ebbing tides may require the specialization of adaptations for surviving the many abiotic stressors encountered there. The lateral line trunk canal of Xiphister is regarded as unique among teleosts with multiple, branching, zigzag shaped canals that are morphologically complex. The X. mucosus canal was found to not serve as a mechanosensory organ, rather the findings presented here suggest a new role as a water transport organ. This may be an exaptation to help X. mucosus avoid desiccation during low tides when the fish remain upon the rocky shore and exposed to dehydration. While emersed, Xiphister relies on cutaneous respiration as its primary means of aerial respiration.

Elasmobranchs (sharks, skates and rays) possess a sophisticated array of sensory systems that are, undoubtedly, of great importance to their survival. Representing the earliest group of extant jawed vertebrates, detailed study of elasmobranch sensory biology can provide much-needed information on the evolution of vertebrate sensory systems. Some sensory modalities have been studied in detail in several species, but few studies have examined and compared multiple sensory systems within a particular genus. By examining the morphology and physiology of the different sensory systems, correlations can be made within both an ecological and a phylogenetic context. The primary advantage of studying the sensory systems of closely related species is that any differences between them are more likely to reflect functional ecological adaptations rather than the effects of phylogenetic separation. Wobbegongs sharks (Orectolobidae) are a distinctive group of benthic sharks that are characterised by a highly patterned, dorso-ventrally compressed body. Wobbegongs are ambush predators that employ a unique ‘sit and wait’ strategy. Their morphologically distinct body shape, sedentary lifestyle and mode of predation suggest that wobbegong sharks may differ from other elasmobranchs in how they employ their different sensory systems. In this study, four wobbegong species that vary in life-history and/or habitat were examined: the Western wobbegong, Orectolobus hutchinsi, the spotted wobbegong, O. maculatus, the ornate wobbegong, O. ornatus and the dwarf spotted wobbegong, O. parvimaculatus. Vision and olfaction were assessed in all four species. Detailed assessment of electroreception and mechanoreception (lateral line) was conducted only for O. maculatus and O. ornatus. Morphology, physiology and molecular genetics were examined in the visual system, and morphological assessment was conducted for the olfactory, electroreceptive and mechanosensory lateral line systems. The retinae of all four wobbegong species are duplex; rod and cone photoreceptors can be distinguished easily on the basis of morphology. The wavelength of maximum absorbance (λmax) of the rod visual pigment is 496 nm in O. hutchinsi, 484 nm in O. maculatus, 498 nm in O. ornatus and 494 nm in O. parvimaculatus. Absorbance spectra of cone visual pigments were only obtained from O. maculatus and O. ornatus. Only one spectral type of cone was measured in each species, with max values at 553 nm and 560 nm, respectively. Partial sequences were obtained for the rh1 opsin gene in all four species, and for the lws opsin gene in every species except O. parvimaculatus. The apparent presence of only one cone pigment raises the possibility that wobbegongs do not have colour vision. The topographic distribution of cells within the ganglion cell layer of Orectolobus hutchinsi show a weakly elongated central visual streak of increased cell density, mediating a higher spatial resolving power of 2.06 cycles deg-1 in the frontal visual field. Retinal topography of O. maculatus and O. parvimaculatus are similar, with both possessing a dorsal horizontal streak facilitating increased spatial resolving power in the lower visual field. Orectolobus parvimaculatus also possesses an area of increased cell density in the naso-ventral region of the retina mediating acute vision in the upper caudal region of the visual field. Spatial resolving power reaches 3.51 cycles deg-1 and 3.91 cycles deg-1 in O. maculatus and O. parvimaculatus, respectively. The topographical variation in retinal sampling indicates that different regions of the visual field are relatively more important and may reflect interspecific differences in behaviour and habitat. The mean number of lamellae in the olfactory rosette is 47.0 for Orectolobus hutchinsi, 48.7 for O. maculatus, 40.7 for O. ornatus and 55.7 for O. parvimaculatus. Olfactory sensory epithelial surface area is comparable in O. hutchinsi, O. maculatus and O. ornatus, while O. parvimaculatus has a significantly larger surface area, relative to body size, compared to the other three species. Olfaction appears to be relatively more important in O. parvimaculatus, especially during low light conditions, when vision is limited. The distribution of ampullary electroreceptive pores and mechanosensory lateral line pores (pored and non-pored canals) is almost entirely concentrated on the dorsal region of the head in both O. maculatus and O. ornatus. This suggests that both sensory systems are well-adapted and specialised to detect prey swimming overhead when the wobbegong is sitting motionless, thereby facilitating its unique, predatory, “lie-in-wait’ ambush strategy. Orectolobus hutchinsi and O. ornatus appear to be well-suited to both diurnal and nocturnal activities, whereas O. maculatus and O. parvimaculatus are probably most active under low light conditions. Sensory system information inferred from this study correlates well with what is known of the diet and habitat of the four wobbegong species examined. Therefore, in the absence of other biological data, sensory neurobiological approaches can be used to predict such bio-ecological factors as predatory strategy, habitat preference, and behaviour. Electrophysiology and behavioural approaches will provide major advances in future studies in order to understand how each of the different senses is integrated at both peripheral and central levels and how such studies are vital to our understanding of evolutionary and ecological processes.

Multimodal sensory input directs simple and complex behaviors in animals. Most research to date has been limited to studies of individual senses rather than multiple senses working together, leading to important advances in our comprehension of the sensory systems in isolation, but not their complementary and alternative roles in difficult behavioral tasks, such as feeding. In the marine environment, a prey item might emit an odor, create a hydrodynamic disturbance, such as from gill movements or swimming, be visible to the predator, produce a sound, and/or produce a weak electrical field. Therefore, the goal of this study was to investigate the integration of olfaction, mechanoreception by the lateral line system, vision, and electroreception in a marine animal. Sharks were chosen as a model organism in which to investigate multisensory integration because of their sensitivity and acuity, the presence of the same suite of sensory modalities in all species, the availability of experimental animals from different species, habitats and ecologies, and the rich literature on sharks' prey capture behavior. Two approaches were used: controlled artificial stimuli, delivered to the animals, were used to determine the spatial and concentration characteristics of odor encounters that guide the initial orientation to an odor plume in the far field in a model elasmobranch, the smooth dogfish, Mustelus canis; and sensory deprivation was used to restrict the availability of natural cues emanating from live prey items in order to elucidate the complementary and alternating roles of the senses in detecting, tracking, orienting to, striking at, and ultimately capturing prey. In the latter experiments, three species of sharks from different ecological niches were investigated: benthic, suction-feeding nurse sharks (Ginglymostoma cirratum) that hunt nocturnally for fish; ram-biting bonnetheads (Sphyrna tiburo) that scoop crustaceans off the bottom of seagrass beds; and ram-feeding blacktip sharks (Carcharhinus limbatus) that rapidly chase down midwater teleost prey. In orienting to odor patches, bilateral time differences between the nares are more important than concentration differences, such that animals turn toward the side stimulated first, even with delayed pulses of higher concentration. This response would steer the shark into each oncoming odor patch, helping the animal maintain contact with an odor plume. Sensory deprivation experiments revealed similarities and differences among species in terms of which senses they choose to focus on for particular behaviors, likely as a result of differences in the environments that they hunt in, type of prey consumed, and foraging strategies used, as well as anatomical differences in the central nervous system and the sensory organs. In most cases, multiple senses can be used for the same behavioral task. Thus, sharks are capable of successfully capturing prey, even when the optimal sensory cues are unavailable, by switching to alternative sensory modalities, which indicates that feeding behavior is plastic. Nurse sharks rely primarily on olfaction for detection. Olfaction in combination with vision, the lateral line, or touch is required for tracking. Nurse sharks orient to prey using the lateral line, vision, or electroreception, but will not ingest food if olfaction is blocked. Capture is mediated by the electrosensory system or tactile cues. Bonnetheads normally detect prey using olfaction, rely on olfactory-based tracking until they are close to the prey, then vision to line up a strike, and finally electroreception to time the jaw movements for capture. They can detect, orient, and strike visually in the absence of olfactory cues. Blacktip sharks also detect prey using olfaction or vision. Olfaction is used in combination with vision or the lateral line system for tracking. Long-distance orientation and striking is visually mediated, but strike precision relies on lateral line cues and an increase in misses occurs when this system is blocked. In the absence of vision, short-range orientation and striking can occur using lateral line cues. Capture is mediated by electroreception or tactile cues. Collectively, these results were used to develop species-specific sensory hierarchies for shark feeding behavior in a captive environment, the first such hierarchies to cover a complete behavioral sequence in a vertebrate.