Thesis (M.S.)--University of North Carolina at Wilmington, 2003. / Vita. Includes bibliographical references (leaves : [56]-64).

Thesis (M. Phil.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

No description available.

published_or_final_version / abstract / Biological Sciences / Master / Master of Philosophy

<p>The dissertation work discussed here focuses on the behavioral and physiological aspects of visual sexual signaling in the blue crab, <italic>Callinectes sapidus</italic>. The blue crab has a pair of apposition compound eyes that are relatively acute (1.5 &deg; resolution) for an arthropod. The eyes have two photopigments sensitive to blue (&lambda;_max = 440 nm) and green (&lambda; _max=500 nm) light, allowing for simple color vision. Visual cues and signals are used during antagonistic and sexual communication and primarily involve claw-waving motions. A primary feature of the blue crab morphology is its sexually dimorphic claw coloration; males have blue and white claws and females have red claws. However, despite the potential for interesting color signaling, visual cues have typically been considered non-important, particularly in sexual communication where chemical cues have dominated blue crab signaling studies. </p><p>In a series of experiments designed to simultaneously test the role of visual cues in mating behavior and blue crab color vision, I tested males' responses to photographs of females with differently colored claws. I found that photographs of females elicited male courting behaviors. I also found that males preferred females with red claws over those with white or isoluminant (i.e. matched brightness) gray claws. The discrimination of red from isoluminant grey showed the use of color vision in male mate choice. </p><p>In natural populations, the claws of sexually mature females vary from light orange to deep red. To determine males' abilities discriminate between similar colors, I tested male color preferences for red against several shades of orange varying in brightness. Overall, males showed an innate preference for red-clawed females over those with variations of orange claws. However, in tests between red and orange shades similar in both brightness and hue, male blue crabs did not show a distinct preference, suggesting that males are either not able or not motivated to discriminate between these shades. Further, my results suggest that male blue crabs may use a mixture of chromatic and achromatic cues to discriminate between long-wavelength colors.</p><p>After confirming the use of color in mate choice, I focused on the role of claw color in intraspecific communication. To quantify claw coloration, I measured spectral reflectance of claws of a blue crab population in North Carolina. In both sexes, the color of the claw varied with reproductive maturity and may act as a cue of reproductive readiness. Additionally, there was individual variation in claw color which could indicate individual quality. I have modeled the appearance of claw coloration to the blue crab eye and found that these color differences are visible to the blue crab eye and potentially signal gender, reproductive readiness, and/or individual quality. </p><p>After investigating male mate choice, I began investigating visual aspects of female mating behavior. In the blue crab, like many crustaceans, courtship occurs during the female molting cycle and copulation takes place after the female has shed her exoskeleton. In crustaceans and other arthropods with compound eyes, the corneal lens of each facet is part of the exoskeleton and thus shed during molting. I used optomotor assays to evaluate the impact of molting on visual acuity (as measured by the minimum resolvable angle <italic> &alpha _min</italic>) in the female blue crab. I found that visual acuity decreases substantially in the days prior to molting and is gradually recovered after molting. Prior to molting,<italic> &alpha_min </italic>was 1.8 &deg;, a value approximating the best possible acuity in this species. In the 24 hours before molting, <italic> &alpha _min</italic>increased to a median of 15.0 &deg; (N=12), an eight-fold drop in visual acuity. Six days after molting, <italic> &alpha _min</italic>returned to the pre-molting value. Micrographs of <italic>C. sapidus </italic> eyes showed that a gap between the corneal lens and the crystalline cone appeared approximately five days prior to shedding and increased in width the process progressed. This separation was likely responsible for the loss of visual acuity observed in behavioral tests. Since mating is limited to the female's pubertal molt, a reduction in acuity during this time may have an effect on the sensory cues used in female mate choice. These results may be broadly applicable to all arthropods that molt and have particular importance for crustaceans that molt multiple times in their lifetime or have mating cycles paired with molting.</p> / Dissertation

The variable plumage characteristics of the sub-adult male cohort of the red-winged blackbird (Agelaius phoeniceus) are described. At one extreme of the plumage variation, there are a group of sub-adult males that are indistinguishable from the adult males. These birds can only be correctly aged by cloacal examination for the bursa of Fabricius in the autumn. At the other extreme, approximately 4% of the population are near perfect female-mimics. A simple scoring system based on the interspersion of dark feathers in the epaulet is presented, which permits classification of the sub-adult males into 1 of 6 plumage classes. These epaulet classes are significantly correlated with other traits of the plumage. / Age when entering the prebasic molt, and the physical condition of the sub-adult male may influence the development of the varied plumage characteristics. / The distribution of the plumage characteristics of a population of sub-adult males collected at a major blackbird roost in the province of Quebec is described for birds captured in the fall and spring. The spring plumage characteristics are more variable than the fall, a phenomenon which is not consistent with plumage wear as has been previously reported, but which may be related to a prealternate molt which the birds undergo. The prealternate molt is prevalent in some but not all of the contour feather tracts, and is restricted to females and the sub-adult male cohorts. / An age- and sex-specific spring migration of red-winged blackbirds is examined. Adult males arrive to the spring roosts first, followed by yearling males and then females. A similar pattern of dispersal to the breeding territories is described. Within the subadult male cohort, the birds with the most adult-male like plumage traits arrive at the vernal roosts first. / The characteristics of the prealternate molt and differential spring migration are discussed in relation to the pressures of sexual selection on the respective age and sex cohorts. / The adaptive significance of variable sub-adult male plumages and delayed plumage maturation in passerines is evaluated. Several competing hypotheses have been advanced to describe the phenomenon of delayed plumage maturation. These hypotheses are reviewed, and a test is proposed which unequivocally differentiates between the various alternatives. (Abstract shortened with permission of author.)

Thesis (M.S.)--University of North Carolina at Wilmington, 2006. / Includes bibliographical references (leaves: 111-117)

Orientadora: Silvana Martinez Baraldi Artoni / Banca: Laura Satiko Okada Nakaghi / Banca: Daniela Oliveira / Banca: Selma de Fátima Grossi / Banca: Maria Rita Pacheco / Resumo: A muda forçada em poedeiras comerciais tem sido utilizada visando melhorar o desempenho zootécnico das aves por mais um ciclo de produção de ovos. Utilizou-se 32 galinhas poedeiras Hisex Brown com 58 semanas de idade submetidas a diferentes programas de muda forçada para análise do peso e comprimento das diferentes porções intestinais (duodeno, jejuno, íleo, ceco e cólon-reto), com o auxílio de uma balança de precisão e uma fita métrica, respectivamente. As aves foram alojadas em um galpão de postura com gaiolas (2 aves/gaiola) na Unesp, campus de Jaboticabal e expostas à 17 horas de luz diariamente com água e ração à vontade. O delineamento experimental foi inteiramente casualizado com 4 programas contendo 4 aves e 2 coletas aos 28 e 140 dias. Os programas utilizados foram: método Califórnia, baixo nível de cálcio, alto nível de zinco e baixo nível de sódio. Os dados foram submetidos à análise de variância e em caso de diferença significativa, as médias foram comparadas pelo teste de Tukey. Observou-se que aves submetidas ao método Califórnia por 10 dias tiveram respostas biométricas semelhantes aos animais que tiveram alto nível de zinco adicionado à dieta com menor peso corporal e de vísceras, além de menores comprimentos do intestino, além disso, aos 140 dias houve um aumento do peso corpóreo e, também do peso e do comprimento do intestino. / Abstract: The forced molting in commercial laying hens had being utilized for get better the performance of birds for one more cycle of production of eggs. In this study were used 32 Hisex Brown laying hen with 58 weeks of age submitted to different programs of forced molting. This experiment aimed the weight and length of the intestine (duodenum, jejunum, ileum, cecum and rectum). For the weight measurement was utilized one precision scale and for the length was used a measuring tape. The animals were caged in galvanized cage in aviary of Unesp, campus Jaboticabal and submitted of a program of growing light up to 17 hours a day after the induction period and the birds received water and ration ad libitum. The birds were distributed in a randomized experimental assay with 4 programs containing 4 birds and 2 production cycles (28 and 140 days). The animals were distributed into four programs: Califórnia method (control program), diet with low level of calcium, diet with high level of zinc and diet with low level of sodium. The data were submitted to the variance analysis and in case of significant difference, the averages were compared by the test of Tukey. It was observed that birds submitted to the California program were biometric responses similar to the animals that had high level of zinc added to the diet with smaller corporal weight and of visceras. It was observed that smaller lengths of the intestine and increase of corporal weight to the 140 days and increase of the weight and of the length of the intestine, too. / Doutor

No description available.

Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Specialized skin scales (generation glands) and undifferentiated skin scales were compared in three species of cordylid lizard, viz. Cordy/us cordy/us, Pseudocordy/us micro/epidotus and P. capensis. These skin derivatives were histologically examined and compared, using data existing in literature (Maderson, 1966; 1967; 1968a) with similar structures in gekkonids. Histological descriptions of cordylid skin structure were the same as those shown for gekkonids. Three types of generation glands were identified in cordylids (Van Wyk & Mouton, 1992), and these proved to be different to those existing in gekkonid species. These three types of generation glands were further compared regarding their ecdysis histology, which proved to be identical, thus, these glands differ only on gross morphological structure. Skin of all three species was also compared with regard to ecdysis, and while the histology of all three was identical, shedding activity was shown to differ in all three species. P. micro/epidotus displayed dormancy in the germinative layer for much longer periods of the year than either of the other two species, while P. capensis displayed very little dormancy. C. cordy/us displayed an intermediate pattern of ecdysis activity and dormancy. Autoradiography was performed on all species in both ecdysis activity and dormancy periods, to compare mitotic activity patterns in these periods. Generation gland activity appeared to correlate well with known testosterone peaks in the testicular cycle in all three species. Asynchrony between generation glands and skin scales was shown in all three species. / AFRIKAANSE OPSOMMING: GENERASIEKLIERE EN VERVELLINGSIKLUSSE IN GORDELAKKEDISSE (SAURIA: CORDYLIDAE) Drie spesies gordelakkedisse, Gordy/us cordy/us, Pseudocordy/us micro/epidofus en P. capensis, se gespesialiseerde velskubbe (generasiekliere) en gewone velskubbe word vergelyk. Hierdie velskubbe word deur histologiese metodes geëksamineer en vergelyk, met gebruik van data wat reeds in die literatuur bestaan (Maderson, 1966; 1967; 1968a), met soortgelyke strukture in Gekkonidae. Histologiese beskrywing van Cordylidae veistruktuur was identies met dié van Gekkonidae. Drie tipes generasiekliere was geïdentifiseer in gordelakkedisse (van Wyk & Mouton, 1992), en hulle verskil gedeeltlik van naverwante strukture in Gekkonidae. Hierdie drie tipes generasiekliere was verder vergelyk met betrekking tot hulle vervellingsiklus histologie, wat identies was. Dus verskil hulle net met betrekking tot hulle vorm. Vel is ook vergelyk met dieselfde metodes. Alhoewel daar geen verskille was met betrekking tot hulle histology nie, was die tye van aktiwiteit van kiem-sellae beduidend verskillend in alle spesies. In P. micro/epidofus het die kiem-sellaag russtadium baie langer geduur as in die ander twee spesies, terwyl P. cepensis amper geen russtadium getoon het nie. G. cordy/us het 'n intermediêre gedragspatroon vertoon tussen aktiewe en rustende fase met betrekking tot sy vervellingsiklus. Outoradiografie is gebruik op elke spesie, in beide aktiewe en rustende vervellingsfases, om verskille in mitotiese aktiwiteit te wys. Generasieklier aktiwiteit blyk te korreleer met pieke van testosteroonvlakke van die testikulêre siklus in al drie spesies. Asinkronie is aangetoon tussen generasiekliere en velskubbe in al drie spesies.