Electrocardiogram assessment in non-anaesthetized clinically healthy agouti (Dasyprocta primnolopha, Wagler 1831) / Avaliação do eletrocardiograma em cutias (Dasyprocta primnolopha, Wagler 1831) não-anestesiadas clinicamente saudáveis

The agouti is one of the most intensely hunted species throughout the Amazon and the semiarid regions of north-eastern Brazil. Considering the current tendency of wild animal management in captivity, the objective of this study was to determine heart reference values for agouti raised in captivity, based on electrocardiographic assessments (ECG). Adult agouti were selected without clinical signs of heart disease (n=30). The animals were restrained physically and then the ECG was performed. Standardized measurements were taken to establish the statistical analysis of the data. Analysis of the QRS complex showed values compatible with previous reports in peer animals and the limited data available for other wild and exotic species, except for the T wave that showed similar amplitude to the R wave in all the animals studied. The data obtained provided the first reference values for ECG tracings in agouti, contributing to a better understanding of heart electrophysiology in identifying myocardial pathology in these animals.

A cutia é uma das espécies mais intensamente caçados em toda a Amazônia e as regiões semi-áridas do nordeste do Brasil. Considerando-se a tendência atual no manejo de animais silvestres em cativeiro, o objetivo deste estudo foi determinar os valores de referência para o coração cutia criadas em cativeiro, com base em avaliações do eletrocardiograma (ECG). Foram selecionadas cutias adultas e sem sinais clínicos de doença cardíaca (n=30). Os animais foram contidos fisicamente e, em seguida, o ECG foi realizado. Medições padronizadas foram tomadas para estabelecer a análise estatística dos dados. Análise do complexo QRS apresentou valores compatíveis com os relatórios pregressos em animais animais de companhia, assim como para os poucos dados disponíveis para outras espécies selvagens e exóticas, com exceção da onda T, que mostrou amplitude semelhante à onda R em todos os animais estudados. Os dados obtidos permitiram a aquisição dos primeiros valores de referência para os traçados de ECG em cutias, contribuindo para uma melhor compreensão eletrofisiologia cardíaca, na identificação de miocardiopatia nesses animais.

Hystricognathy vs sciurognathy in the rodent jaw: a new morphometric assessment of hystricognathy applied to the living fossil Laonastes (Diatomyidae).

While exceptional for an intense diversification of lineages, the evolutionary history of the order Rodentia comprises only a limited number of morphological morphotypes for the mandible. This situation could partly explain the intense debates about the taxonomic position of the latest described member of this clade, the Laotian rock rat Laonastes aenigmamus (Diatomyidae). This discovery has re-launched the debate on the definition of the Hystricognathi suborder identified using the angle of the jaw relative to the plane of the incisors. Our study aims to end this ambiguity. For clarity, it became necessary to revisit the entire morphological diversity of the mandible in extant and extinct rodents. However, current and past rodent diversity brings out the limitations of the qualitative descriptive approach and highlights the need for a quantitative approach. Here, we present the first descriptive comparison of the masticatory apparatus within the Ctenohystrica clade, in combining classic comparative anatomy with morphometrical methods. First, we quantified the shape of the mandible in rodents using 3D landmarks. Then, the analysis of osteological features was compared to myological features in order to understand the biomechanical origin of this morphological diversity. Among the morphological variation observed, the mandible of Laonastes aenigmamus displays an intermediate association of features that could be considered neither as sciurognathous nor as hystricognathous.

Cranial MRI of small rodents using a clinical MR scanner.

Increasing numbers of small animal models are in use in the field of neuroscience research. Magnetic resonance imaging (MRI) provides an excellent method for non-invasive imaging of the brain. Using three-dimensional (3D) MR sequences allows lesion volumetry, e.g. for the quantification of tumor size. Specialized small-bore animal MRI scanners are available for high-resolution MRI of small rodents' brain, but major drawbacks of this dedicated equipment are its high costs and thus its limited availability. Therefore, more and more research groups use clinical MR scanners for imaging small animal models. But to achieve a reasonable spatial resolution at an acceptable signal-to-noise ratio with these scanners, some requirements concerning sequence parameters have to be matched. Thus, the aim of this paper was to present in detail a method how to perform MRI of small rodents brain using a standard clinical 1.5 T scanner and clinically available radio frequency coils to keep material costs low and to circumvent the development of custom-made coils.

Cardiac magnetic resonance imaging in small rodents using clinical 1.5 T and 3.0 T scanners.

Cardiac magnetic resonance (CMR) imaging can provide noninvasive, high resolution images of heart anatomy, viability, perfusion, and function. However, the adoption of clinical CMR imaging protocols for small rodents has been limited due to the small heart size and rapid heart rates. Therefore, most CMR studies in small rodents have been performed on non-clinical, high-field MR magnets. Because such high-field systems are not readily available at most institutions, the technical aspects that are needed to perform CMR on clinical 1.5 T and 3.0 T MR scanners are presented in this paper. Equipment requirements are presented, and a comprehensive description of the methods needed to complete a CMR exam including the animal preparation, imaging, and image analysis are discussed. In addition, the advanced applications of myocardial tagging and delayed-contrast-enhanced imaging are reviewed for the assessment of regional contractile function and myocardial viability, respectively.

Common rodent procedures.

Rodents are commonly owned exotic animal pets that may be seen by veterinary practitioners. Although most owners presenting their animals do care about their pets, they may not be aware of the diagnostic possibilities and challenges that can be offered by rodents to the veterinarian. Understanding clinical anatomy, proper hand-ling technique, realistic management of emergency presentations,correct and feasible diagnostic sampling, anesthesia, and humane euthanasia procedures is important to enhancing the doctor-client-patient relationship, especially when financial constraints may be imposed by the owner.

Sperm competition and the evolution of male reproductive anatomy in rodents.

Sperm competition is a pervasive selective force in evolution, shaping reproductive anatomy, physiology and behaviour. Here, we present comparative evidence that varying sperm competition levels account for variation in the male reproductive anatomy of rodents, the largest and most diverse mammalian order. We focus on the sperm-producing testes and the accessory reproductive glands, which produce the seminal fluid fraction of the ejaculate. We demonstrate a positive association between relative testis size and the prevalence of within-litter multiple paternity, consistent with previous analyses in which relative testis size has been found to correlate with sperm competition levels inferred from social organization and mating systems. We further demonstrate an association between sperm competition level and the relative size of at least two accessory reproductive glands: the seminal vesicles and anterior prostate. The size of the major product of these glands-the copulatory plug-is also found to vary with sperm competition level. Our findings thus suggest that selection for larger plugs under sperm competition may explain variation in accessory gland size, and highlight the need to consider both sperm and non-sperm components of the male ejaculate in the context of post-copulatory sexual selection.