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Publication
Ontogenetic development of the inner ear saccule in a vocal teleost fish : Implications for auditory reception and communication
Abstract(s)
Os peixes consistem no maior grupo de vertebrados e exibem uma diversidade excecional na estrutura e função dos seus sistemas sensoriais e comunicativos. A família Batrachoididae tornou-se importante no estudo do funcionamento dos sistemas auditivo-vocal no contexto da comunicação acústica. Um estudo recente relatou um paralelismo entre a diferenciação vocal e o aumento da sensibilidade auditiva em Halobatrachus didactylus, sugerindo uma potencial interação entre os circuitos auditivo-vocal durante o desenvolvimento. Os objectivos deste estudo foram: 1) verificar alterações ontogenéticas no principal órgão auditivo periférico (sáculo) que possam explicar o aumento da sensibilidade auditiva em H. didactylus; 2) comparar características morfológicas do sáculo entre Batracoidideos.
Espécimes em etapas ontogénicas distintas foram fixados e o seu sáculo removido, marcado com faloidina e analisado. A área do sáculo aumentou 10x, ocorrendo mudanças na sua forma. Os padrões principais de orientação das células ciliadas (CC) estabeleceram-se cedo no desenvolvimento pós-embrionário, com algumas variações subsequentes nas regiões rostral e caudal. A adição de CC aumentou rapidamente em relação ao crescimento epitelial, resultando numa redução de 1.6x na sua densidade. A densidade de células de suporte (CS) diminui significativemente. O aumento da área do epitélio deveu-se principalmente ao aumento da área da superfície apical de CS em conjunto com a adição de CC.
Comparações interespecíficas revelaram um padrão duplo comum com algumas diferenças nas regiões rostral e caudal que poderão explicar diferenças na sensibilidade auditiva.
Enquanto tais alterações ontogenéticas poderão facilitar a sensibilidade do sáculo, potenciando a comunicação acústica, outras características estruturais e moleculares deverão ser investigadas.
ABSTRACT: Fishes, the largest group of vertebrates, display an exceptional diversity in structure and function of sensory and communication systems. The Batrachoididae has become an important family to study mechanisms of auditory-vocal functions for social communication. A recent study reported that vocal differentiation parallels developmental improvements in auditory sensitivity in Halobatrachus didactylus, suggesting a potential coupling between vocal-auditory circuitry. The goals of this study were: 1) to verify developmental changes in the main auditory endorgan (saccule) that may account for ontogenetic auditory improvements in H. didactylus; and 2) to compare saccular morphological features among Batrachoididae species. Different size groups, from posthatched fry to adults, were PFA-fixed and their saccule removed for phalloidin-staining and structural analysis. Saccular epithelium area increased circa 10x with development, along with significant changes in shape (i.e. caudal region ratio). Most of hair cell (HC) orientation patterns seem to be established early in postembryonic development, with a few variations mostly in the rostral and caudal regions. HC addition increased rapidly in relation to epithelium growth, resulting in 1.6x decrease in HC density. Supporting cell (SC) density decreased throughout development. SC apical surface increased significantly and together with HC addition explained the sensory epithelium growth. Interspecific comparisons within Batrachodidae revealed a common “dual pattern”, but also differences in the rostral and caudal regions that may explain different auditory sensitivities. While such developmental changes may facilitate in part saccular sensitivity and enhance social acoustic communication, other structural and molecular features of the saccule should be investigated.
ABSTRACT: Fishes, the largest group of vertebrates, display an exceptional diversity in structure and function of sensory and communication systems. The Batrachoididae has become an important family to study mechanisms of auditory-vocal functions for social communication. A recent study reported that vocal differentiation parallels developmental improvements in auditory sensitivity in Halobatrachus didactylus, suggesting a potential coupling between vocal-auditory circuitry. The goals of this study were: 1) to verify developmental changes in the main auditory endorgan (saccule) that may account for ontogenetic auditory improvements in H. didactylus; and 2) to compare saccular morphological features among Batrachoididae species. Different size groups, from posthatched fry to adults, were PFA-fixed and their saccule removed for phalloidin-staining and structural analysis. Saccular epithelium area increased circa 10x with development, along with significant changes in shape (i.e. caudal region ratio). Most of hair cell (HC) orientation patterns seem to be established early in postembryonic development, with a few variations mostly in the rostral and caudal regions. HC addition increased rapidly in relation to epithelium growth, resulting in 1.6x decrease in HC density. Supporting cell (SC) density decreased throughout development. SC apical surface increased significantly and together with HC addition explained the sensory epithelium growth. Interspecific comparisons within Batrachodidae revealed a common “dual pattern”, but also differences in the rostral and caudal regions that may explain different auditory sensitivities. While such developmental changes may facilitate in part saccular sensitivity and enhance social acoustic communication, other structural and molecular features of the saccule should be investigated.
Description
Dissertação de Mestrado apresentada ao ISPA - Instituto Universitário
Keywords
Epitélio do sáculo Células ciliadas Audição Ontogenia Halobatrachus didactylus Saccular epithelium Hair cell Hearing Ontogeny