O ovo flexível: influência da água durante a incubação de Iguana iguana
Carregando...
Data
2018-08-17
Autores
Carreira, Laura Borelli Thomaz [UNESP]
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Os ovos de cascas flexíveis são ausentes de reserva hídrica provida pela mãe, e necessitam absorver água, necessária para o seu metabolismo, através do meio de incubação que, em condições naturais, é diretamente influenciado pelo regime de chuvas. Desta forma, com o objetivo central de entender a fisiologia embrionária de répteis que possuem ovos de casca flexível, foram utilizados ovos de iguana verde (Iguana iguana) incubados sob diferentes potenciais hídricos variando de extremamente seco para extremamente úmido, onde foram avaliados parâmetros que refletem a fisiologia do balanço hídrico destes embriões: osmolalidade, massa seca, conteúdo de água e pressão interna dos ovos. Além disso diagnósticos por imagens de microscopia eletrônica de varredura e ressonância magnética também foram aplicados com o intuito de verificar a morfologia da casca destes ovos e a avaliação não invasiva do desenvolvimento embrionário sob diferentes condições hídricas, respectivamente. Dentre os principais resultados encontram-se um aumento bastante significativo da concentração osmótica de fluido alantóico em ambiente extremamente seco resultando em 385 mOsmol/kg. As taxas de massas mostram que os embriões exibem um aumento de 158% em tratamentos extremamente secos quando comparados com tratamentos úmidos. Em condições secas os ovos apresentaram deformação da casca e o embrião representou a maior parte do ovo inteiro, com frações muito pequenas de vitelo e alantoide. A espessura da casca varia conforme a condição hídrica, podendo apresentar uma redução superior a 50%. Além disso, existe um desgaste da casca do ovo ao final da incubação resultante principalmente da ação hídrica, além da degradação por microrganismos, e não da mobilização de cálcio para o embrião conforme ocorre em ovos de casca dura. Também foi possível verificar a presença de fibras internas na casca dos ovos de iguana que, provavelmente, são responsáveis por conferir a capacidade elástica aos ovos suportando absorção de grandes quantidades de água além do crescimento do embrião. As imagens de ressonância magnética permitiram detalhar o desenvolvimento embrionário sob diferentes condições hídricas, revelando variações na morfologia interna e externa (deformações da casca) do ovo, além de mostrar o impacto de ambientes secos na dinâmica espacial do interior do ovo, resultando em pouco espaço para o desenvolvimento do embrião. Afim de complementar o estudo de imagens, foram realizadas capturas de imagens de ressonância de ovos de H. mabouia e C. latirostris, onde pudemos observar pela primeira vez a presença de saco de ar em um ovo reptiliano de jacaré de papo amarelo com 90% de incubação, revelando assim mais uma grande semelhança para com as aves, devido sua proximidade evolutiva. Considerando todos os principais dados obtidos, podemos concluir que a disponibilidade de água para o ovo afeta não só suas respostas fisiológicas como também a morfologia da casca, provocando aspecto deformado e reduzindo sua espessura devido à desidratação. Contudo, embriões de iguana apresentaram uma grande tolerância a ambientes hostis, e mesmo sob condições desfavoráveis foram capazes de completar seu desenvolvimento e eclodir.
The eggs of flexible hulls are absent from the water reserve provided by the mother, and need to absorb water, necessary for its metabolism, through the incubation medium that, under natural conditions, is directly influenced by the rainfall regime. Thus, with the main objective to understand the embryonic physiology of reptiles that have flexible shell eggs, green iguana eggs were used (Iguana iguana) incubated under different water potentials ranging from extremely dry to extremely wet, which were evaluated parameters reflecting the physiology of water balance of these embryos: osmolality, dry mass, water content and internal pressure of eggs. In addition, diagnostic imaging of scanning electron microscopy and magnetic resonance imaging were also applied to verify the shell morphology of these eggs and the noninvasive evaluation of embryonic development under different water conditions, respectively. Among the main results are a very significant increase of the osmotic concentration of allantoic fluid in extremely dry environment resulting in 385 mOsmol / kg. Mass rates show that embryos exhibit a 158% increase in extremely dry treatments when compared to moist treatments. In dry conditions the eggs showed deformation of the shell and the embryo represented the greater part of the whole egg, with very small fractions of calf and allantois. The thickness of the bark varies according to the water condition, being able to present a reduction of more than 50%. In addition, there is a detrition of the eggshell at the end of incubation resulting mainly from the water action, besides the degradation by microorganisms, and not the mobilization of calcium to the embryo as it occurs in eggs of hard shell. It was also possible to verify the presence of internal fibers in the shell of the iguana eggs, which are probably responsible for imparting the elastic capacity to the eggs, supporting the absorption of large amounts of water besides the growth of the embryo. Magnetic resonance images allowed detail embryonic development under different water conditions, showing changes in internal and external morphology (peeling deformation) of the egg, and show the impact of dry environments in the spatial dynamics of the interior of the egg, resulting in little space for the development of the embryo. In order to complement the study of images were performed resonance imaging catch H. mabouia and C. latirostris eggs, where we can observe the first time the presence of air bag in a chat yellow reptilian egg alligator 90% of incubation, thus revealing a great similarity to the birds, due to its evolutionary proximity. Considering all the main data obtained, we can conclude that the water availability to the egg affects not only its physiological responses but also the shell morphology, causing deformed appearance and reducing its thickness due to dehydration. However, iguana embryos presented great tolerance to hostile environments, and even under unfavorable conditions were able to complete their development and hatch.
The eggs of flexible hulls are absent from the water reserve provided by the mother, and need to absorb water, necessary for its metabolism, through the incubation medium that, under natural conditions, is directly influenced by the rainfall regime. Thus, with the main objective to understand the embryonic physiology of reptiles that have flexible shell eggs, green iguana eggs were used (Iguana iguana) incubated under different water potentials ranging from extremely dry to extremely wet, which were evaluated parameters reflecting the physiology of water balance of these embryos: osmolality, dry mass, water content and internal pressure of eggs. In addition, diagnostic imaging of scanning electron microscopy and magnetic resonance imaging were also applied to verify the shell morphology of these eggs and the noninvasive evaluation of embryonic development under different water conditions, respectively. Among the main results are a very significant increase of the osmotic concentration of allantoic fluid in extremely dry environment resulting in 385 mOsmol / kg. Mass rates show that embryos exhibit a 158% increase in extremely dry treatments when compared to moist treatments. In dry conditions the eggs showed deformation of the shell and the embryo represented the greater part of the whole egg, with very small fractions of calf and allantois. The thickness of the bark varies according to the water condition, being able to present a reduction of more than 50%. In addition, there is a detrition of the eggshell at the end of incubation resulting mainly from the water action, besides the degradation by microorganisms, and not the mobilization of calcium to the embryo as it occurs in eggs of hard shell. It was also possible to verify the presence of internal fibers in the shell of the iguana eggs, which are probably responsible for imparting the elastic capacity to the eggs, supporting the absorption of large amounts of water besides the growth of the embryo. Magnetic resonance images allowed detail embryonic development under different water conditions, showing changes in internal and external morphology (peeling deformation) of the egg, and show the impact of dry environments in the spatial dynamics of the interior of the egg, resulting in little space for the development of the embryo. In order to complement the study of images were performed resonance imaging catch H. mabouia and C. latirostris eggs, where we can observe the first time the presence of air bag in a chat yellow reptilian egg alligator 90% of incubation, thus revealing a great similarity to the birds, due to its evolutionary proximity. Considering all the main data obtained, we can conclude that the water availability to the egg affects not only its physiological responses but also the shell morphology, causing deformed appearance and reducing its thickness due to dehydration. However, iguana embryos presented great tolerance to hostile environments, and even under unfavorable conditions were able to complete their development and hatch.
Descrição
Palavras-chave
Herpetologia, Fisiologia embrionária, Potencial hídrico, Osmolalidade, Diagnóstico por imagem, Herpetology, Embryonic physiology, Water potential, Osmolality, Diagnostic imaging