Development of mandibular, hyoid and hypobranchial muscles in the zebrafish: homologies and evolution of these muscles within bony fishes and tetrapods

BackgroundDuring vertebrate head evolution, muscle changes accompanied radical modification of the skeleton. Recent studies have suggested that muscles and their innervation evolve less rapidly than cartilage. The freshwater teleostean zebrafish (Danio rerio) is the most studied actinopterygian model organism, and is sometimes taken to represent osteichthyans as a whole, which include bony fishes and tetrapods. Most work concerning zebrafish cranial muscles has focused on larval stages. We set out to describe the later development of zebrafish head muscles and compare muscle homologies across the Osteichthyes.ResultsWe describe one new muscle and show that the number of mandibular, hyoid and hypobranchial muscles found in four day-old zebrafish larvae is similar to that found in the adult. However, the overall configuration and/or the number of divisions of these muscles change during development. For example, the undivided adductor mandibulae of early larvae gives rise to the adductor mandibulae sections A0, A1-OST, A2 and Aω, and the protractor hyoideus becomes divided into dorsal and ventral portions in adults. There is not always a correspondence between the ontogeny of these muscles in the zebrafish and their evolution within the Osteichthyes. All of the 13 mandibular, hyoid and hypobranchial muscles present in the adult zebrafish are found in at least some other living teleosts, and all except the protractor hyoideus are found in at least some extant non-teleost actinopterygians. Of these muscles, about a quarter (intermandibularis anterior, adductor mandibulae, sternohyoideus) are found in at least some living tetrapods, and a further quarter (levator arcus palatini, adductor arcus palatini, adductor operculi) in at least some extant sarcopterygian fish.ConclusionAlthough the zebrafish occupies a rather derived phylogenetic position within actinopterygians and even within teleosts, with respect to the mandibular, hyoid and hypobranchial muscles it seems justified to consider it an appropriate representative of these two groups. Among these muscles, the three with clear homologues in tetrapods and the further three identified in sarcopterygian fish are particularly appropriate for comparisons of results between the actinopterygian zebrafish and the sarcopterygians

Evolutionary Divergence Among Oligosarcus

The Doce River, in southeastern Brazil, is a coastal drainage, configured since the Late Cretaceous, when South America separated from Africa. Of the 77 native fish species of the Doce River Basin, 37 are potentially endangered - Oligosarcus solitarius, Menezes 1987, is the only endemic species of the quaternary lakes in the middle portion of this drainage and Oligosarcus argenteus, Günther 1864, is distributed in the Doce River channel and headwaters. This study characterizes the morphological, cytogenetic, and mitochondrial DNA variation in the Oligosarcus spp. populations from the Doce and São Francisco River Basins. The principal component analysis indicates three morphological groups. Cytogenetic data corroborate existence of the O. solitarius and O. argenteus fish species in the Doce River Basin, with high levels of population cytogenetic polymorphism. Taking into consideration the Pleistocene-Holocene formation of the lacustrine system in the middle Doce River, with low molecular differentiation and high levels of chromosomal variation among the O. solitarius populations, we concluded that O. solitarius has the highest rate of chromosomal evolution observed in Neotropical freshwater fishes. The morphological and cytogenetic patterns of the Oligosarcus sp. population collected at the Das Velhas River headwaters suggest that it may represent an undescribed species. © Copyright 2015, Mary Ann Liebert, Inc. 2015

Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians

<div><p>We describe two new cynodonts from the early Late Triassic of southern Brazil. One taxon, <i>Bonacynodon schultzi</i> gen. et sp. nov., comes from the lower Carnian <i>Dinodontosaurus</i> AZ, being correlated with the faunal association at the upper half of the lower member of the Chañares Formation (Ischigualasto-Villa Unión Basin, Argentina). Phylogenetically, <i>Bonacynodon</i> is a closer relative to <i>Probainognathus jenseni</i> than to any other probainognathian, bearing conspicuous canines with a denticulate distal margin. The other new taxon is <i>Santacruzgnathus abdalai</i> gen. et sp. nov. from the Carnian <i>Santacruzodon</i> AZ. Although based exclusively on a partial lower jaw, it represents a probainognathian close to <i>Prozostrodon</i> from the <i>Hyperodapedon</i> AZ and to <i>Brasilodon</i>, <i>Brasilitherium</i> and <i>Botucaraitherium</i> from the <i>Riograndia</i> AZ. The two new cynodonts and the phylogenetic hypothesis presented herein indicate the degree to which our knowledge on probainognathian cynodonts is incomplete and also the relevance of the South American fossil record for understanding their evolutionary significance. The taxonomic diversity and abundance of probainognathians from Brazil and Argentina will form the basis of deep and complex studies to address the evolutionary transformations of cynodonts leading to mammals.</p></div

Avaliação da flebografia orbitária em oito casos de síndrome de Tolosa-Hunt

A Síndrome de Tolosa-Hunt (STH) ou oftalmoplegia dolorosa é associada a granulomatose inespecifica de etiologia desconhecida que acomete a fissura orbitária superior. Compromete estruturas nervosas e vasculares causando quadro clínico variável que sempre se associa a dor e apresenta resposta favorável à corticoterapia. Processos inflamatórios, tumores e aneurismas dessa região podem causar sintomas semelhantes. A tomografia computadorizada, a angiografia cerebral e a flebografia orbitária são métodos de imagem indicados para orientar o diagnóstico. Revisamos os resultados destes exames radiológicos de oito pacientes atendidos no Hospital São Paulo no período 1989 a 1991, com diagnóstico de STH segundo os critérios de Hunt e Hannerz. A análise das alterações da flebografia orbitária, de acordo com a sistematização feita por Hannerz e col. mostrou ser este exame inespecífico, porém capaz de orientar melhor o diagnóstico