ArticleLiterature Review

Nutrition and Behavior of Degus (Octodon degus)

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Abstract

Octodon degus are herbivorous rodents that are adapted anatomically and behaviorally to utilize a fibrous diet with moderate-to-low levels of nonstructural carbohydrate. Captive degus should consume foods containing nutrients comparable to those consumed by free-ranging animals. The species is highly social, demonstrating a broad array of communication methods that make them appealing as a companion animal species. Controlled research studies with degus have produced a wealth of information that facilitates the care of this species in captivity.

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... Degus have also become popular as pets in the USA and many European countries and are exhibited in many zoos. Objective information regarding husbandry, nutrition and behaviour were recently published by Edwards (2009). There are many references about occurrence and management of diseases in pet rodents. ...
... Hystricomorph rodents lack the ability to properly digest sugar because of divergent evolution in the insulin structure and different physiological activity of insulin others 2004, 2005). Degus fed on high dietary sugar readily develop hyperinsulinaemia with subsequent cataracts, kidney damage and type 2 DM (Spear and others 1984, Datiles and Fukui 1989, Edwards 2009). Murphy and others (1980) documented that DM was the most common disease in a laboratory colony of degus. ...
... Excessive stimuli, including noise and inappropriate lighting levels, should be removed (Longley 2009). Degus should be offered a low-energy, high-fibre diet, which stimulates the animals to chew properly and prevents development of cataracts and diabetes (Edwards 2009). It should comprise high-quality grass hay, fruits and tree branches with leaves, grass and pelleted food ...
Article
Degus are commonly used as laboratory animals; however, over the past few years, they have become increasingly popular as pets. Objectives: The aim of this article was to present disease prevalence in 300 pet degus divided in two age groups (under and above two years). Medical records of degus (Octodon degus), which were presented to the author's clinic in the period from January 2007 to December 2009, were reviewed. The most common diseases in degus were (1) acquired dental disease (60·0%) with significantly higher prevalence in older animals (P<0.001), (2) skin alopecia due to fur chewing (13·33%) and (3) lens cataracts (13·33%). Other common disorders included traumatic injuries to soft tissues (bite wounds and tail slip), traumatic fractures and dietary diarrhoea. Reproductive disorders were most commonly associated with dystocia and pathological changes in the post-natal period. Only 38 degus in a total of 300 animals were healthy. This is the first study to describe the disease prevalence in two age groups of pet degus. The majority of diseases were caused by improper diet, self-mutilation and improper handling; as such client education is necessary to avoid such a high disease prevalence.
... The dental formula is incisors: 1/1, canines: 0/0, premolars: 1/1, and molars: 3/3. When viewed from the occlusal surface, the cheek teeth have a figure-of-eight appearance as indicated by the genus name (Edwards, 2009). As with other hystricognathous rodents, the incisors and cheek teeth are continuously erupting (Jekl et al., 2008). ...
... A review of the nutrition of the degu has recently been published (Edwards, 2009). The degu has a simple glandular stomach. ...
... Unlike the closely related guinea pig, the degu does produce the hepatic enzyme L-gulonolactone oxidase and does not have a dietary requirement for ascorbic acid. Therefore, diets supplemented with ascorbic acid are not required for maintenance of this species (Edwards, 2009). ...
Chapter
This chapter studies the degu, its attributes, and uses as a laboratory animal species. Degus are mostly associated with the study of circadian rhythms due to their diurnal activities in the wild and they have also been established as valuable animal models in the study of a wide range of scientific areas including developmental biology, diabetes mellitus, cataracts, and Alzheimer's disease. The organ systems and physiological processes that have made the degu a useful animal model in various areas of research have been described in detail such as external features, circulatory system, and the nervous system. Due to less established laboratory colonies, much remains to be discovered regarding optimal housing, disease control, and veterinary care of the species. The chapter describes the management, husbandry, nutrition, diseases, and behavioral patterns of the degu. The degu is chosen as an animal for experimental model due to its characteristics such as complex familial and social structure and highly developed vocal repertoire. Also degus are relatively long-lived when compared to many other laboratory rodents. The research models that have been explained are thymic research, Alzheimer's disease, production of antisera, and atherosclerosis.
... Tactile communications consist of nose-to-nose contact, sniffing and nuzzling body areas, such as the perineum, rump, and neck (Edwards, 2009). From the cognitive ecological point of view, thanks to their manual dexterity to manipulate objects, the O. degus also use their tactile ability to integrate the environmental inputs into their neural circuits. ...
... A sugar-rich diet, which readily translates into hyperinsulinemia, is often associated with the onset of cataracts (Lee, 2004). In fact, it has been described that the treatment of diabetic individuals with Sorbinil, an AR-inhibitor, prevents the formation of cataracts (Edwards, 2009;Ethier et al., 1993). ...
... This fact is interesting for its use as a model in endocrinology research but it also represents a potential tool to study diabetes in the context of co-occurrence with other diseases, such as neurodegeneration, AD, Parkinson's disease or visual alterations (Boccardi et al., 2019;Biosa et al., 2018;Hurley et al., 2018;Chen & Zhong, 2013). In wild conditions, degus are herbivorous and they tend to prefer low-carbohydrates and highprotein plants (Edwards, 2009). Consumption of food with higher content in carbohydrates may contribute to the increased incidence of diabetes observed in captive degus (Edwards, 2009). ...
Article
Integrating the multifactorial processes co-occurring in both physiological and pathological human conditions still remains one of the main challenges in translational investigation. Moreover, the impact of age-associated disorders has increased, which underlines the urgent need to find a feasible model that could help in the development of successful therapies. In this sense, the Octodon degus has been indicated as a 'natural' model in many biomedical areas, especially in ageing. This rodent shows complex social interactions and high sensi-tiveness to early-stressful events, which have been used to investigate neurodevelopmental processes. Interestingly , a high genetic similarity with some key proteins implicated in human diseases, such as apolipoprotein-E, β-amyloid or insulin, has been demonstrated. On the other hand, the fact that this animal is diurnal has provided important contribution in the field of circadian biology. Concerning age-related diseases, this rodent could be a good model of multimorbidity since it naturally develops cognitive decline, neurodegenerative histopathological hallmarks, visual degeneration, type II diabetes, endocrinological and metabolic dysfunctions, neoplasias and kidneys alterations. In this review we have collected and summarized the studies performed on the Octodon degus through the years that support its use as a model for biomedical research, with a special focus on ageing.
... Tactile communications consist of nose-to-nose contact, sniffing and nuzzling body areas, such as the perineum, rump, and neck (Edwards, 2009). From the cognitive ecological point of view, thanks to their manual dexterity to manipulate objects, the O. degus also use their tactile ability to integrate the environmental inputs into their neural circuits. ...
... A sugar-rich diet, which readily translates into hyperinsulinemia, is often associated with the onset of cataracts (Lee, 2004). In fact, it has been described that the treatment of diabetic individuals with Sorbinil, an AR-inhibitor, prevents the formation of cataracts (Edwards, 2009;Ethier et al., 1993). ...
... This fact is interesting for its use as a model in endocrinology research but it also represents a potential tool to study diabetes in the context of co-occurrence with other diseases, such as neurodegeneration, AD, Parkinson's disease or visual alterations (Boccardi et al., 2019;Biosa et al., 2018;Hurley et al., 2018;Chen & Zhong, 2013). In wild conditions, degus are herbivorous and they tend to prefer low-carbohydrates and highprotein plants (Edwards, 2009). Consumption of food with higher content in carbohydrates may contribute to the increased incidence of diabetes observed in captive degus (Edwards, 2009). ...
Article
Integrating the multifactorial processes co-occurring in both physiological and pathological human conditions still remains one of the main challenges in translational investigation. Moreover, the impact of age-associated disorders has increased, which underlines the urgent need to find a feasible model that could help in the development of successful therapies. In this sense, the Octodon degus has been indicated as a ‘natural’ model in many biomedical areas, especially in ageing. This rodent shows complex social interactions and high sensi-tiveness to early-stressful events, which have been used to investigate neurodevelopmental processes. Interest-ingly, a high genetic similarity with some key proteins implicated in human diseases, such as apolipoprotein-E, β-amyloid or insulin, has been demonstrated. On the other hand, the fact that this animal is diurnal has provided important contribution in the field of circadian biology. Concerning age-related diseases, this rodent could be a good model of multimorbidity since it naturally develops cognitive decline, neurodegenerative histopathological hallmarks, visual degeneration, type II diabetes, endocrinological and metabolic dysfunctions, neoplasias and kidneys alterations. In this review we have collected and summarized the studies performed on the Octodon degus through the years that support its use as a model for biomedical research, with a special focus on ageing.
... However, blood glucose concentration does not differ between the degu and other mammals (Opazo et al., 2004), probably due to a combination of a higher insulin concentration (Zimmerman et al., 1974) and a higher number of insulin receptors (Dufty et al., 2002). The usual diet of the degu consists of plant material with a naturally low content of sugars and starch (Edwards, 2009). In laboratory animals, a slight increase of carbohydrate intake can lead to hyperglycaemia (Murphy et al., 1978) and chronic feeding of degu with fruit sugars caused diabetes accompanied by kidney damage and cataracts (Edwards, 2009). ...
... The usual diet of the degu consists of plant material with a naturally low content of sugars and starch (Edwards, 2009). In laboratory animals, a slight increase of carbohydrate intake can lead to hyperglycaemia (Murphy et al., 1978) and chronic feeding of degu with fruit sugars caused diabetes accompanied by kidney damage and cataracts (Edwards, 2009). Elevated incidence of amyloidosis and hyperplasia of the islets of Langerhans has been reported but these are independent of glucose levels. ...
Book
Neurodegenerative diseases are the most frequent cause of dementia, representing a burden for public health systems (especially in middle and middle-high income countries). Although most research on this issue is concentrated in first-world centers, growing efforts in South America are affording important breakthroughs. This emerging agenda poses new challenges for the region but also new opportunities for the field. This book aims to integrate the community of experts across the globe and the region, and to establish new challenges and developments for future investigation. We present research focused on neurodegenerative research in South America. We introduce studies assessing the interplay among genetic, neural, and behavioral dimensions of these diseases, as well as articles on vulnerability factors, comparisons of findings from various countries, and works promoting multicenter and collaborative networking. More generally, our book covers a broad scope of human-research approaches (behavioral assessment, neuroimaging, electromagnetic techniques, brain connectivity, peripheral measures), animal methodologies (genetics, epigenetics, proteomics, metabolomics, other molecular biology tools), species (all human and non-human animals, sporadic, and genetic versions), and article types (original research, review, and opinion papers). Through this wide-ranging proposal, we hope to introduce a fresh approach to the challenges and opportunities of research on neurodegeneration in South America.
... However, blood glucose concentration does not differ between the degu and other mammals (Opazo et al., 2004), probably due to a combination of a higher insulin concentration (Zimmerman et al., 1974) and a higher number of insulin receptors (Dufty et al., 2002). The usual diet of the degu consists of plant material with a naturally low content of sugars and starch (Edwards, 2009). In laboratory animals, a slight increase of carbohydrate intake can lead to hyperglycaemia (Murphy et al., 1978) and chronic feeding of degu with fruit sugars caused diabetes accompanied by kidney damage and cataracts (Edwards, 2009). ...
... The usual diet of the degu consists of plant material with a naturally low content of sugars and starch (Edwards, 2009). In laboratory animals, a slight increase of carbohydrate intake can lead to hyperglycaemia (Murphy et al., 1978) and chronic feeding of degu with fruit sugars caused diabetes accompanied by kidney damage and cataracts (Edwards, 2009). Elevated incidence of amyloidosis and hyperplasia of the islets of Langerhans has been reported but these are independent of glucose levels. ...
Article
Alzheimer's disease (AD) is a multifactorial progressive neurodegenerative disease. Despite decades of research, no disease modifying therapy is available and a change of research objectives and/or development of novel research tools may be required. Much AD research has been based on experimental models using animals with a short lifespan that have been extensively genetically manipulated and do not represent the full spectrum of late-onset AD, which make up the majority of cases. The aetiology of AD is heterogeneous and involves multiple factors associated with the late-onset of the disease like disturbances in brain insulin, oxidative stress, neuroinflammation, metabolic syndrome, retinal degeneration and sleep disturbances which are all progressive abnormalities that could account for many molecular, biochemical and histopathological lesions found in brain from patients dying from AD. This review is based on the long-lived rodent Octodon degus (degu) which is a small diurnal rodent native to South America that can spontaneously develop cognitive decline with concomitant phospho-tau, β-amyloid pathology and neuroinflammation in brain. In addition, the degu can also develop several other conditions like type 2 diabetes, macular and retinal degeneration and atherosclerosis, conditions that are often associated with aging and are often comorbid with AD. Long-lived animals like the degu may provide a more realistic model to study late onset AD.
... Animals in the suborder Hystricomorpha (guinea pigs and degus) have physiologic differences associated with DM, and degus may be one of the most common exotic small Endocrine Diagnostics for Exotic Animals mammals to develop DM. 135 In degus, insulin has less than 10% of the biological activity found in other species. 136,137 To counter this, degus have increased numbers of insulin receptors and higher insulin concentrations. 136 DM in degus is related to a highstarch diet and obesity making it similar to type II (adult-onset nontinsulin-dependent) in humans. ...
... 136,137 To counter this, degus have increased numbers of insulin receptors and higher insulin concentrations. 136 DM in degus is related to a highstarch diet and obesity making it similar to type II (adult-onset nontinsulin-dependent) in humans. 138 In f chinchillas, DM, most likely type II, has been reported. ...
Endocrine disease in exotic species is less common than in small animals. Nevertheless, the diagnostic principles used in small animals can be adapted to evaluate endocrine disease in many of the exotic species although species-specific aspects need to be considered. This article covers important diseases such as thyroid dysfunction in reptiles and birds, hyperthyroidism in guinea pigs, and hyperadrenocorticism in ferrets. Glucose metabolism in neoplasms affecting normal physiology, such as insulinoma in ferrets and gastric neuroendocrine carcinoma in bearded dragons, is discussed. Calcium abnormalities, including metabolic bone disease in reptiles and hypocalcemia in birds, are also covered.
... Degus (Octodon degus) have become popular pets and are exhibited in many zoological collections. 1 2 Free ranging degus eat large quantities of relatively low-energy and highly abrasive feeds to meet their energy requirements, resulting in marked wear of their continually growing teeth. 3 Ad libitum provision of pellets, decreases fibre intake and abrasive properties of the diet, resulting in improper wear of teeth, development of spurs and increased occlusal pressure with apical elongation of cheek teeth as a result. 2 4 Therefore, dental disease is highly prevalent (60%) in captive degus 1 and includes malocclusion due to coronal elongation of cheek teeth (spurs or hooks), elongated apices, elodontomas and fractured or elongated incisors. ...
Article
Full-text available
Degus (Octodon degus) are prone to develop dental disease with deleterious health effects. The two studies reported here aimed to determine the prevalence of dental disorders in degus and to identify and evaluate diagnostic tools for determination of prognosis of these disorders. In study A, health data from 225 degus at AAP, Rescue Center for Exotic Animals in the Netherlands, were collated and the prevalence of dental disorders and differences in sex and age at clinical onset of symptoms associated with dental disorders were described. The prevalence was 34.7 per cent and higher (P<0.01) in males than in females. The occurrence of cheek teeth malocclusion was highly positively (P<0.0001) correlated to mortality. In study B, 36 skulls were examined by macroscopic evaluation, radiography and histology. Additionally, the calcium:phosphorus (Ca:P) of mandibular bone in degus with and without dental disorders were determined. There was no significant (P=0.10) difference in Ca:P between the two groups. Quantifying mandibular apical cheek teeth elongation via macroscopic evaluation was highly correlated (P<0.01) to the results obtained via radiography. Examination for apical elongation by palpation and diagnostic imaging should be included in routine health monitoring of degus. Apical elongation appeared to develop before coronal elongation and when cheek teeth malocclusion occurred, prognosis for recovery of dental disease was poor.
... One challenge for social-affective neuroscience programs is to identify simple and yet valid animal models for studying the expression of basic social emotions and their role during different developmental windows, from infancy to adulthood (Colonnello et al., 2011). The Od is a very social animal with a broad array of communication methods (Edwards, 2009). Social animals are susceptible to high infection levels by contact-transmitted parasites due to increased nonspecific interaction. ...
Article
Full-text available
The most popular animal models of Alzheimer's disease (AD) are transgenic mice expressing human genes with known mutations which do not represent the most abundant sporadic form of the disease. An increasing number of genetic, vascular and psychosocial data strongly support that the Octodon degus, a moderate-sized and diurnal precocial rodent, provides a naturalistic model for the study of the early neurodegenerative process associated with sporadic AD. In this minireview we describe and analyze the risk factors that contribute to Alzheimer-like characteristics in the degus, following recent publications, and establish some guidelines for future studies in this model of natural aging associated with the disease. Given the heterogeneity of current data derived from the diverse transgenic animal models of AD, now may be the time for the degus to become a strong attractor for academic research labs and companies involved with AD. This may help to understand the mechanisms responsible for the early neurodegenerative process associated with this devastating disease.
... One of their more salient characteristics is their longevity. Degus can live up to 8 years in captivity (Lee, 2004), which makes them good candidates for studies on the effects of aging and the associated plethora of degenerative and metabolic disorders like diabetes, amyloidosis and atherosclerosis (Edwards, 2009;Homan et al., 2010). Moreover, they are highly social animals with a mostly diurnal circadian profile (Lee, 2004), which makes them more appropriate models for the study of the circadian rhythms, its disorders and possible treatments than the exclusively nocturnal mice and rats. ...
Article
The common degu (Octodon degus) is an emerging model in biomedical science research due to its longevity and propensity to develop human-like conditions. However, there is a lack of standardized techniques for this non-traditional laboratory animal. In an effort to characterize the model, we developed a chromatic pupillometry setup and analysis protocol to characterize the pupillary light reflex (PLR) in our animals. The PLR is a biomarker to detect early signs for central nervous system deterioration. Chromatic pupillometry is a non-invasive and anesthesia-free method that can evaluate different aspects of the PLR, including the response of intrinsically photosensitive retinal ganglion cells (ipRGCs), the disfunction of which has been linked to various disorders. We studied the PLR of 12 degus between 6 and 48 months of age to characterize responses to LEDs of 390, 450, 500, 525 and 605 nm, and used 5 with overall better responses to establish a benchmark for healthy PLR (PLR+) and deteriorated PLR (PLR-). Degu pupils contracted up to 65% of their horizontal resting size before reaching saturation. The highest sensitivity was found at 500 nm, with similar sensitivities at lower tested intensities for 390 nm, coinciding with the medium wavelength and short wavelength cones of the degu. We also tested the post-illumination pupillary response (PIPR), which is driven exclusively by ipRGCs. PIPR was largest in response to 450 nm light, with the pupil preserving 48% of its maximum constriction 9 s after the stimulus, in contrast with 24% preserved in response to 525 nm, response driven mainly by cones. PLR-animals showed maximum constriction between 40% and 50% smaller than PLR+, and their PIPR almost disappeared, pointing to a disfunction of the iPRGCs rather than the retinal photoreceptors. Our method thus allows us to non-invasively estimate the condition of experimental animals before attempting other procedures.
... Nikiforuk and Fraser [10] stated that the occurrence of enamel hypoplasia did not show the relation to the plasma phosphate concentration. Enamel defects of degus seen in present study were similar with previously described effect of low calcium diet, despite the fact that calcium dietary levels were in upper recommended dose for the degus [52] and diet was high in phosphorus with improper Ca:P ratio. ...
... Another major limitation to the study of the pathogenesis of metabolic disorders in humans is the lack of relevant animal models with which to carefully investigate the biological mechanisms underlying the effects of sugar consumption on energy balance and its relationship to metabolic disease [24]. In previous years, the native rodent species of central Chile, the degu (Octodon degus), has been proposed as a well suited model to study diet-induced disorders [25,26]. Degus has a predisposition to develop non-obese diabetes that is often accompanied by cataracts when regularly fed a sugar-containing diet [9,27,28]. ...
Article
Full-text available
There has been a progressive increase in the incidence of fructose-induced metabolic disorders, such as metabolic syndrome (MetS). Moreover, novel evidence reported negative effects of high-fructose diets in brain function. This study was designed to evaluate for the first time the effects of long-term fructose consumption (LT-FC) on the normal ageing process in a long-lived animal model rodent, Octodon degus or degu. Moreover, we could replicate human sugar consumption behaviour over time, leading us to understand then the possible mechanisms by which this MetS-like condition could affect cognitive abilities. Our results support that 28 months (from pup to adulthood) of a 15% solution of fructose induced clinical conditions similar to MetS which includes an insulin-resistance scenario together with elevated basal metabolic rate and non-alcoholic fatty liver disease. Additionally, we extended our analysis to evaluate the impact of this MetS-like condition on the functional and cognitive brain processes. Behavioural test suggests that fructose-induced MetS-like condition impair hippocampal-dependent and independent memory performance. Moreover, we also reported several neuropathological events as impaired hippocampal redox balance, together with synaptic protein loss. These changes might be responsible for the alterations in synaptic plasticity and transmitter release observed in these cognitively impaired animals. Our results indicate that LT-FC induced several facets of MetS that eventually could trigger brain disorders, in particular, synaptic dysfunction and reduced cognition.
... Their full genome has been sequenced by the National Human Genome Institute and reported by the Broad Institute of MIT and Harvard. Degus can live up to 10-12 years in captivity, which makes them ideal for investigating the effects of aging and age-related diseases (Edwards, 2009;Homan et al., 2010;Ardiles et al., 2013). As they age, degus develop signs of inflammation in the brain and in the retina, as well as cognitive deterioration (Van Groen et al., 2011;Inestrosa et al., 2015;Chang et al., 2020). ...
Article
Full-text available
The aging process and age-related diseases such as Alzheimer’s disease (AD), are very heterogeneous and multifactorial, making it challenging to diagnose the disease based solely on genetic, behavioral tests, or clinical history. It is yet to be explained what ophthalmological tests relate specifically to aging and AD. To this end, we have selected the common degu (Octodon degus) as a model for aging which develops AD-like signs to conduct ophthalmological screening methods that could be clinical markers of aging and AD. We investigated ocular health using ophthalmoscopy, fundus photography, intraocular pressure (IOP), and pupillary light reflex (PLR). The results showed significant presence of cataracts in adult degus and IOP was also found to increase significantly with advancing age. Age had a significant effect on the maximum pupil constriction but other pupil parameters changed in an age-independent manner (PIPR retention index, resting pupil size, constriction velocity, redilation plateau). We concluded that degus have underlying factors at play that regulate PLR and may be connected to sympathetic, parasympathetic, and melanopsin retinal ganglion cell (ipRGC) deterioration. This study provides the basis for the use of ocular tests as screening methods for the aging process and monitoring of neurodegeneration in non-invasive ways.
... Degus has also gained prominence as a valued model for many different diseases, such as those related to lipid metabolism and atherosclerosis (Homan et al., 2010), diabetes mellitus (Edwards, 2009), cataracts and retinal degeneration (Datiles, 1989;Brown and Donnelly, 2001;Du et al., 2015), cancer (Lester et al., 2005;Ardiles et al., 2013;Svara et al., 2020), and neurodegenerative disorders such as AD (Inestrosa et al., 2005;van Groen et al., 2011;Hurley et al., 2018). Aging degus spontaneously develop some neuropathological hallmarks of AD, such as Aβ accumulation, tau hyperphosphorylation, and cognitive impairments when reaching the age of 3-4 years (Inestrosa et al., 2005;Ardiles et al., 2012;Braidy et al., 2012;Deacon et al., 2015;Hurley et al., 2018). ...
Article
Full-text available
Aging is a progressive functional decline characterized by a gradual deterioration in physiological function and behavior. The most important age-related change in cognitive function is decline in cognitive performance (i.e., the processing or transformation of information to make decisions that includes speed of processing, working memory, and learning). The purpose of this study is to outline the changes in age-related cognitive performance (i.e., short-term recognition memory and long-term learning and memory) in long-lived Octodon degus . The strong similarity between degus and humans in social, metabolic, biochemical, and cognitive aspects makes it a unique animal model for exploring the mechanisms underlying the behavioral and cognitive deficits related to natural aging. In this study, we examined young adult female degus (12- and 24-months-old) and aged female degus (38-, 56-, and 75-months-old) that were exposed to a battery of cognitive-behavioral tests. Multivariate analyses of data from the Social Interaction test or Novel Object/Local Recognition (to measure short-term recognition memory), and the Barnes maze test (to measure long-term learning and memory) revealed a consistent pattern. Young animals formed a separate group of aged degus for both short- and long-term memories. The association between the first component of the principal component analysis (PCA) from short-term memory with the first component of the PCA from long-term memory showed a significant negative correlation. This suggests age-dependent differences in both memories, with the aged degus having higher values of long-term memory ability but poor short-term recognition memory, whereas in the young degus an opposite pattern was found. Approximately 5% of the young and 80% of the aged degus showed an impaired short-term recognition memory; whereas for long-term memory about 32% of the young degus and 57% of the aged degus showed decreased performance on the Barnes maze test. Throughout this study, we outlined age-dependent cognitive performance decline during natural aging in degus. Moreover, we also demonstrated that the use of a multivariate approach let us explore and visualize complex behavioral variables, and identified specific behavioral patterns that allowed us to make powerful conclusions that will facilitate further the study on the biology of aging. In addition, this study could help predict the onset of the aging process based on behavioral performance.
... In the laboratory environment, a slight change in carbohydrate intake leads to development of persistent hyperglycemia and glycosuria (Murphy et al. 1978). Animals fed a diet of simple fruit sugars can readily develop diabetes mellitus along with kidney damage and cataracts (Edwards 2009). The high susceptibility of this animal to develop diabetes shortly after streptozotocin injections, or secondary to minimal changes in its diet, makes it an attractive animal model for the study of the pathophysiology of diabetes mellitus. ...
Article
Full-text available
One major goal of integrative and comparative biology is to understand and explain the interaction between the performance and behavior of animals in their natural environment. The Caviomorph, Octodon degu, is a native rodent species from Chile, and represents a unique model to study physiological and behavioral traits, including cognitive and sensory abilities. Degus live in colonies and have a well-structured social organization, with a mostly diurnal-crepuscular circadian activity pattern. More notable is the fact that in captivity, they reproduce and live between 5 and 7 yr and show hallmarks of neurodegenerative diseases (including Alzheimer's disease), diabetes, and cancer.
Article
The impact of pelleted diets with different mineral compositions on the crown size of the mandibular cheek teeth, as well as the mandibular bone and cheek teeth density, in degus (Octodon degus) was investigated. A total of 28 animals were randomly divided into four groups and fed different calcium or phosphorous dietary content, in the presence or absence of UV light, for 14 months. Dental radiographs and CT images of the head were taken, and the crown size of premolar and molar teeth was recorded. Apical and coronal crown elongation of all cheek teeth and significantly smaller relative cheek teeth and mandibular densities were recorded in degus fed a high-phosphorus diet with an improper calcium:phosphorus ratio. A diet with a calcium:phosphorus ratio of 1:1 was also responsible for the rapid development of dental disease with subsequent severe health impairment.
Article
The main aim of this study was to investigate the impact of pelleted diet of different mineral composition on the sonographic and CT appearance of kidneys in degus (Octodon degus). A total of 35 animals were randomly divided into five groups, fed diets containing different calcium and phosphorus contents (13.5 g/kg calcium and 6.3 g/kg phosphorus, or 9.1 g/kg calcium and 9.5 g/kg phosphorus) and given different amounts of exposure to UV light. Endoscopic examination of the oral cavity as well as renal ultrasonography and CT was performed four times at four-month intervals throughout the study. After 14 months of feeding an experimental diet, all degus were euthanased and subsequently all kidneys were collected for histopathological examination. Animals fed a diet with high dietary phosphate and improper calcium to phosphorus ratio showed severe nephrocalcinosis. Ultrasonographic and CT kidney abnormalities presented as hyperechogenicity and hyperdensity (interpreted as nephrocalcinosis), respectively. The most striking changes were seen at the corticomedullary zone. Ultrasonography and CT correlated in all cases with histopathological findings. Dental disease developed quickly in groups fed diets with an improper calcium and phosphorus content, with obvious apical and coronal elongation of all the teeth. A possible influence of UV light access could not be proved in this study.
Article
A 3-month-old female degu (Octodon degus) was presented because blood was noticed in its cage. On physical examination, firm masses were palpable within the caudal abdomen and traces of blood appeared to be coming from the patient’s vaginal opening. Radiographic images showed areas of ill-defined mineralization within the uterus, consistent with fetus formation. Three fetuses could be identified. Ultrasound examination of the degu failed to confirm viable fetal heartbeats. Pregnancy failure with fetal death was suspected. Overnight 1 fetus was passed, but medical therapy with oxytocin failed to induce delivery of the 2 remaining fetuses by the following morning. The degu was therefore anesthetized, an ovariohysterectomy was performed, and the patient made an uncomplicated recovery. Histopathological examination of the fetuses failed to identify any abnormalities. In the uterus, histology confirmed a minimal to mild diffuse, chronic active endometritis. The definitive cause of fetal death was not identified.
Article
Plains viscachas (Lagostomus maximus) are large South American, fossorial rodents susceptible to diabetic cataracts. Various aspects of their digestive physiology were studied in three different experiments with nine male and seven female adult animals and six different diets (total n of feeding trials = 35). Viscachas achieved mean retention times of 23–31 hr, which is of a magnitude also recorded in horses; these did not differ for solute or small particle (<2 mm) markers. Secondary marker excretion peaks indicated coprophagy, and were rarer on high-protein as compared to grass hay-only diets. Mean resting metabolic rate was, at 229 kJ/kg0.75/day, lower than expected for a mammal of this size. Digestible energy requirement for maintenance was 445 kJ/kg0.75/day. At 1.6–2.7 L/day, viscachas produced more methane than expected for a hindgut fermenter of their size. On diets that included concentrate feeds, viscachas excreted glucose in their urine, corroborating reports on the susceptibility of this species for diabetes when kept on energy-dense food. Viscachas had a similar apparent digestibility of protein, lipids, and macrominerals as other rodents, rabbits, or domestic horses. This suggests that whether or not a species practices coprophagy does not have a major influence on these measures. Viscachas resemble other hindgut fermenters in their high apparent calcium digestibility. With respect to a digestibility-reducing effect of dietary fiber, viscachas differed from rabbits and guinea pigs but were similar to horses, suggesting that small body size needs not necessarily be linked to lower digestive efficiency on high-fiber diets. Zoo Biol. XX:1–15, 2015. © 2015 Wiley Periodicals, Inc.
Article
The purpose of this chapter is to provide supplemental normative values and references for a number of the species. Some values may not be widely applicable to contemporary housing and husbandry conditions. The normative values presented here have been influenced by the laboratory test, animal source, animal genotype, age, gender, blood sampling method, use of anesthesia, or feed or housing conditions of the animals tested. Some normative values may have been derived from feral or newly confined animals. For this reason, it is always recommended that control tests be run concurrently with tests for animals that are suspected to be ill prior to making final diagnostic conclusions or selecting treatment regimens.
Article
Although a new landscape of social finance institutions (SFIs) is evolving rapidly in Europe, the academic literature on the structures of legitimation that characterize the development of social finance has been limited. This paper addresses this gap: (1) by conceptualizing social finance (SF) as a pre-paradigmatic field where leading SF institutions have spontaneously adopted different investment rationalities and logics to achieve positive social impact through financing and banking activities; (2) by discussing dominant institutionalization patterns, empirically exploring the institutionalization of SF at the organizational, inter-organizational and institutional levels. A sample of seventeen SF institutions in three European countries, i.e. Ireland, Italy and the UK, was examined. The analysis highlighted that two forms of SF, i.e. social impact investment and ethical banking, guide the institutionalization and paradigm-building process. These two forms both assume the production of social impact, i.e. impact on society, the environment and sustainable development, as a distinguishing trait from commercial financial approaches, but differ in terms of business models and products and services provided to customers. Dominant institutionalization patterns reflect the social-embeddedness of these institutions. The convergence of the two dominant models would be desirable in order to further facilitate the development of social finance as a new paradigm in the financing and banking industry, alternative to commercial finance.
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Background: Degus, in comparison to other exotic mammals, are infrequently brought to veterinary practices. Even though they are not encountered often, it is important for veterinary practitioners to understand how to deal with this species, and advise owners of the best possible care. Aim of the article: This article aims to ensure that readers are comfortable with not only the ideal care of this species, but also how to perform an accurate clinical examination, diagnose and treat some of the most common issues in this species.
Chapter
Degus have become popular as pets in many European countries, are becoming more popular in North America, and are exhibited in many zoos. Degus (Octodon degus) are social diurnal porcupine-like rodents and belong to the family Octodontidae. Compared with other commonly kept pet rodents, information on the medical management of degus is limited but increasing over the past decade. This chapter summarized the published information and the authors clinical experience in degu medicine and brings here objective information regarding anatomy, husbandry, nutrition and common diseases management.
Article
Endocrine diseases in rabbits, guinea pigs, chinchillas and degus Endocrine disorders present far less frequently in rabbits, guinea pigs, chinchillas and degus than they do in canine and feline species. Furthermore, in cases where these disorders do present, the manifestation is much more species specific than would be expected from the ubiquitous canine/feline model. The following article provides an overview of the major endocrine disorders known to present in the aforementioned species, and includes symptomatic, diagnostic and therapeutic discussions.
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During lactation, both the nutritional and energetic requirements of suckling change gradually. These changes normally are accompanied by modifications in chemical composition of the milk. We investigated the temporal course of milk composition during lactation in a precocial caviomorph rodent, the "degu" (Octodon degus) under laboratory condition. Female degus were kept in laboratory during gestation and lactation and fed with commercial food pellets. Milk was collected at three stages of lactation: early (days 5-8, n = 12), middle (days 15-21, n = 7) and late (days 26-40, n = 6), and analyzed for protein, carbohydrates, lipids, ash, total solids and energy. On average, carbohydrates decreased from 3.1 ± 0.3 % (early) to 1.1 ± 0.3 % (late) during lactation; lipids, protein, ash, total solids and energy remained about the same. Lipids, the main component of the milk, were 17.3 % and protein remained near 4.4 %. Over lactation, total energy concentration of milk remained near 4.0 kJ mL-1. The maintenance of milk composition during lactation may be related to the initially high energetic and nutritional requirements associated with a precocial reproductive mode.
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It has been hypothesized that mammals using food with low energy content should exhibit basal metabolic rates (BMR) lower than those expected on the basis of their body mass (mb), ie species that exploit food with low energy content and/or high cost of digestion tend to have low, mass-independent metabolic rates. The herbivorous caviomorph burrowing rodent Octodon degus (mb nearly 200g) is an inhabitant of semi-arid and mediterranean communities of Chile. Individuals maintained during 27 wk with a diet high in dietary fiber showed significantly lower BMRs (28%) than those feeding a low fiber. Daily food intake and ingestion rates of individuals under a high-fiber diet were significantly higher than animals maintained with a low-fiber diet. The same pattern was obtained for total feces production and rate of feces production. Total intake and rate of ingestion of proteins were not significantly different between treatments, but a significantly higher amount of protein was excreted by individuals exposed to a high-fiber diet. Apparent digestibility of dry matter, energy, and protein were consistently lower in individuals maintained with high fiber. A significant correlation was found between digestibility and the basal metabolic rate of individuals sugesting that elevated digestibilities on high-quality diets allow increased basal rates of metabolism. Although small mammals like degus may select sparsely distributed plants of high quality in their habitat, their capability to drop their metabolic demands may help them meet their nutritional and energy requirements when nutritional conditions deteriorate. -from Authors
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We examined the effect of food quality on ingestion, digestion, and metabolic rate during pregnancy and lactation in Octodon degus, a precocial rodent, under laboratory conditions. We also examined standard energetics during reproduction in relation to litter size and litter mass. Resting metabolic rate increased significantly during lactation, and that increase resulted from variations in food quality. The highest increase (39%) in resting metabolic rate was found in lactating females maintained on high-quality food when compared with nonreproductive females. Although food intake was always higher during lactation, the maximum intake was observed among lactating females that were given high-quality food. A significant positive correlation also was found between resting metabolic rate and food intake during early lactation, which revealed an increase in energy processing during that demanding period. Significant positive relationships also were found between resting metabolic and ingestion rate relative to litter mass and size. Allocation of energy in O. degus during lactation did not follow the mode typical of precocial rodents. In contrast, conversion efficiency of metabolizable energy into tissue growth appears to be linked to environmental quality of food.
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The social play behavior of six mammalian species (Rodentia, Pinnipedia, Artiodactyla, Carnivora) is described and compared. Locomotor and Rotational Movements, e.g., jumping, running, and headshaking, occurred in all species and predominated in the rodent play. These movements are similar in form to anti-predator and “protective” responses and result in an immediate but temporary cessation of sensory stimulation from conspecifics. Investigation of body odors was the most important stimulus eliciting Locomotor-Rotational Movements in the rodents. In the larger mammals, body odor sniffing was enhanced during play, but specialized signals from other sensory modalities elicited and maintained play interactions. The possible functions of a heightened exchange of olfactory information during juvenile social development are discussed.
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Animals must match their foraging and digestion to seasonal changes in availability and quality of food. When these parameters decline, the animal's performance limits for extracting energy and nutrients may be challenged. In the laboratory, we investigated daily patterns of food processing on a low-quality (high-fiber) diet of alfalfa in an herbivorous, day-active rodent, the degu (Octodon degus), which inhabits semiarid central Chile. We manipulated timing of food availability, from continuous availability down to as little as 5 h/d. Degus maintained weight while digesting only 53% of dry-matter consumption. With food continuously available in a metabolic cage, the animals ate more food and deposited about twice as much feces in the day as at night. Continuous 24-h behavioral observation revealed that degus were actually defecating at the same rate both night and day but then ingesting most of the feces they produced at night. Further experimental treatments challenged animals with limited periods of food availability that matched natural foraging patterns. With either 11 h of daytime food availability or only 5 h (in morning and afternoon periods of 2.5 h each), degus consumed as much food as those with 24-h food availability. Continuous 24-h behavioral observations revealed in the 11-h group that nearly all feces produced at night were reingested and nearly none were reingested in the day, whereas the 5-h group resorted to further coprophagy during the 6-h midday interval with no food. Despite these differences in timing of food intake and coprophagy in response to the three experimental treatments, the degus were defecating at the same rate both night and day, which indicated a constant rate of output from the colon. This suggests a range of adjustments of digestive physiology to the timing of gut function by balancing coprophagy with ingestion of food. Overall, 38% of 24-h feces production was reingested, and 87% of this coprophagy occurred at night. The ingestion of feces during parts of the day when food is unavailable provides for continued intake into the digestive tract and appears to represent an increase in overall efficiency of gut use.
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Octodon degus is a desert rodent of northern Chile, adapted to survive with a limited supply of water. This rodent has a high degree of fecal dehydration, related to colon water absorption. With the hypothesis that aquaporins (AQPs) might be present in the colon epithelium of O. degus and involved in fluid absorption, we studied colon water absorption in vivo and the distribution of AQPs and Na(+) transporters by immunocytochemistry. AQP-1 was found in apical and basolateral membranes of surface-absorptive and crypt epithelial cells. AQP-8 was found in the cytoplasm of enterocytes of surface colon. AQP-3 immunolabeling, on the other hand, was absent from the epithelium but present in a subepithelial fibroblast layer, pericryptal cells, and muscularis mucosae. The hydration state did not modify the amount of immunostaining for any of the AQPs. Colon water absorption was markedly decreased by the mercurial agent p-chloromercuribenzenesulfonic acid and was not affected by water deprivation. The NHE3 isoform of Na(+)/H(+) exchanger and alpha-1 subunit of the Na(+)-K(+)-ATPase were found in apical and basolateral membranes of surface-absorptive cells, respectively. These results suggest that colon water absorption is mostly transcellular and mediated by water channels like AQP-1. Apical Na(+)/H(+) exchanger and basolateral Na(+)-K(+)-ATPase in surface cells could be part of the Na(+) absorption pathway. It is hypothesized that this transport is necessary to provide an osmotic gradient for water absorption. The roles of AQP-8 and AQP-3 in water absorption remain to be established.
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The environmental modification of an organism's physiology in the field is often hypothesized to be responsible for allowing an organism to adjust to changing biotic and abiotic environmental conditions through increases in biological performance. Here, we examine the phenotypic flexibility of water flux rate, urine osmolality and the expression of kidney aquaporins (AQP; or water channels) in free-ranging Octodon degus, a South American desert-dwelling rodent, through an integrative study at cellular, systemic and organismal levels. Water flux rates varied seasonally and were significantly lower in austral summer than in winter, while urine osmolality was higher in summer than during winter. The observed water influx rate during summer was 10.3+/-2.3 ml day(-1) and during winter was 40.4+/-9.1 ml day(-1). Mean urine osmolality was 3137+/-472 mosmol kg(-1) during summer and 1123+/-472 mosmol kg(-1) during winter. AQP-2 medullary immunolabeling was more abundant in the kidneys of degus captured during summer than those captured during winter. This immunoreactivity was higher in apical cell membranes of medullary collecting ducts of degus in summer. AQP-1 immunostaining did not differ between seasons. Consistently, AQP-2 protein levels were increased in medulla from the summer individuals, as judged by the size of the 29 kDa band in the immunoblot. Here, we reveal how the integration of flexible mechanisms acting at cellular, systemic and organismal levels allows a small desert-dwelling mammal to cope with seasonal water scarcity in its semi-arid habitat.
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Hystricomorph rodents are a group of species that belong to the suborder Hystricognathi. They mainly inhabit South American (caviomorph) and African (phiomorph) habitats. This group of rodents has a divergent insulin structure. For example, insulin in this group of rodents exhibits only 1-10% of biological activity in comparison to other mammals. Therefore, hystricomorph rodents may hypothetically be unable to regulate blood glucose concentration as non-hystricomorph mammals. In this work we evaluated blood glucose concentration in nine species of caviomorph rodents, with emphasis on species belonging to the families Abrocomidae, Ctenomyidae and Octodontidae. Specifically we: (1) measured glucose concentrations after a fasting period; and (2) conducted a glucose tolerance test. In the latter assay we used Octodon degus as a representative species of the genus Octodon. Results showed that blood glucose concentration values after fasting, and in the glucose tolerance test, were within the expected range for mammals. We postulate that this group of rodents has compensatory traits that may permit the maintenance of standard values of plasma glucose.
Article
Dietary chemistry and an animal digestive physiology should be considered in any explanation of behavioral patterns of food use, as both influence dietary preference. In the degu Octodon degus (Molina, 1782), a generalist herbivorous rodent inhabiting central Chile, we determine the profitablity of natural food-plant items by measuring digestive characteristics, such as retention time and assimilation rate while also considering the effects of food chemistry. Under our experimental conditions, degus seem to select food based on at least two complementary factors, plant nutritional value (water content and the nitrogen:fiber ratio) and digestive function. We found that dry-matter intake was negatively and significantly correlated with mean retention time, that is O. degus ate more food when mean retention time was shorter and vice versa. A higher food intake concomitant with a shorter mean retention time, allow degus to process more food per unit time resulting in a higher assimilation rate than alternative food sources. We conclude that both food quality and the digestive physiology of animals should be considered in explaining the underlying processes of foraging ecology.
Article
It has been assumed that the feeding habits of vertebrates predispose the variety of intestinal differentiations and the composition of the microbial biota living in their intestinal tracts. Consequently, the presence of methanogenic bacteria in the various differentiations of the large intestine and the foregut of herbivorous vertebrates had been attributed primarily to the existence of anaerobic habitats and the availability of carbon dioxide and hydrogen originating from the fermentative microbial digestion of plant-based diets. However, Australian ratites, many murids, and several New World primates lack methanogens, despite their intestinal differentiations and their vegetarian feeding habits. Crocodiles, giant snakes, aardvarks, and ant-eaters on the other hand release significant amounts of methane. A determination of methane emissions by 253 vertebrate species confirmed that competence for intestinal methanogenic bacteria is shared by related species and higher taxa, irrespective of different feeding habits. In "methanogenic" branches of the evolutionary tree, a variety of differentiations of the large intestine evolved and, in some cases, differentiations of the foregut. In contrast, the lack of competence for methanogens in chiropterans/insectivores and carnivores apparently has precluded the evolution of specialized fermenting differentiations of the digestive tract. Our observations reveal that the presence of intestinal methanogenic bacteria is under phylogenetic rather than dietary control: competence for intestinal methanogenic bacteria is a plesiomorphic (primitive-shared) character among reptiles, birds, and mammals. This competence for methanogenic bacteria has been crucial for the evolution of the amniotes.
Article
Complex polysaccharides such as cellulose, hemicellulose, and lignin (fiber) are important structural constituents of plants that often are difficult for small herbivorous mammals to digest. These polysaccharides may affect the efficiency with which food is digested and with which nutrients and energy are transformed and allocated. To determine how small herbivorous mammals cope with such high-fiber food, I used as a model the herbivorous, caviomorph octodontid rodent Octodon degus, the degu, an inhabitant of the semiarid and Mediterranean environments of northern and central Chile. When given a choice, degus minimized fiber intake, showing pronounced preferences for food containing low fiber. Because low-fiber items are not available in the field during the dry season, I postulated that observations of degus feeding on grass containing a high percentage (nearly 60%) of fiber during summer are more likely the consequence of necessity than of choice. I suggested that during nutritional bottlenecks, degus operate according to the principles of foraging theory and principles governing digestion. Degus seemed to compensate for the low digestibility of high-fiber food by increasing the volume of digesta in the alimentary canal as a consequence of changes in rates of food intake and, hence, increases in turnover time of digesta. The digestive responses allowed them to increase the amount of energy obtained from fiber and to satisfy their maintenance energy costs during temporal exposures to different levels of food fiber.
Article
Data on activity and social behavior of the Chilean degu, Octodon degus, were gathered by direct observation of animals, some of which had been marked for individual recognition. Data from autopsies and external inspection of trapped animals suggested that most reproduction occurs in September at the latitude of Santiago. Degus are diurnal and show morning and evening activity peaks. Social organization is based on group territories, at least during the period after emergence of the young. Mound building (collecting a pile of sticks, stones, and cow dung) was associated with territorial marking. Females of the same social group may rear their young in a common nest burrow. Octodon degus burrows are sometimes used by Abrocoma bennetti, a similar sized rodent, and on two occasions nest burrows were found to be shared by young and mothers of both species.
Article
The food habits of seven species of small mammals were analyzed for a 15-month period during a live-trapping and snap-trapping study in a semiarid thorn scrub community in north-central Chile. The species included four cricetids (Akodon olivaceas, A. longipilis, Phyllotis darwini, and Oryzomys longicaudatus), two caviomorphs (Octodon degus and Abrocoma bennetti), and a didelphid (Marmosa elegans). The community was characterized by a semiarid mediterranean climate with low winter precipitation and frequent fog formation. Dominant physical features included high cover of spiny evergreen and drought-deciduous shrubs, low ground cover of herbaceous plants, and open sandy areas. Year-round food habit trends indicated three functional trophic guilds and one omnivorous species. A. longipilis and M. elegans were insectivorous, O. degus and A. bennetti were herbivorous, P. darwini and O. longicaudatus were granivorous, and A. olivaceus was omnivorous. This pattern of trophic specialization agrees generally with other studies of various species in the Chilean region, and suggests contrasts with patterns in the mediterranean and desert communities of North America and Argentina.
Article
Scaling of basal rate of metabolism (BMR) to body mass was studied in grazing rodents inhabiting different environments of Chile. Observations support previous general predictions for scaling of BMR in small grazing mammals (high scaling parameters and cost of endothermy at small body sizes). A species-specific analysis of the mass-independent basal rate, suggests that BMR varies with the design features of the organisms and with biotic and abiotic environmental factors (e.g., food quality, habitat characteristics), even within trophic groups. In general, these factors seem not to be independent.
Article
Five captive adult female degus (Octodon degus) were offered leaves and twigs to eat from three woody (Adesmia bedwellii,Porlieria chilensisandProustia pungens) and two suffruticose (Baccharis paniculataandChenopodium petiolase) shrubs that provide cover in their natural habitat. The degus discriminated among the plant species, consuming lower amounts ofP. chilensis. Daily body mass losses of degus were significantly higher when they were fed uponP. pungensandP. chilensis. The nutritional value of plants, concomitant with degu nutritional requirements, may explain changes in shrub cover previously found to follow removal of degus from experimental plots.
Article
The type of food, differentiation of the large intestine and stomach, and methane production, as well as life history data, are considered in Insectivora, Rodentia and Lagomorpha. When food containing plant cell wall material is eaten, there is either a differentiation of the stomach or the large intestine. In animals with low body mass and little differentiation of the gastrointestinal tract, methane production is low, but structures essential for microbial digestion of plant cell wall material, such as haustration of the colon or formation of a caecum, can be found in many methane-producers. Animals with a body mass < 500 g and a weaning time < 20 days are non-producers of methane. Establishment of a balanced microbial population in the gastrointestinal tract requires some time. Many non-producers of methane wean their young in < 10 days, but many producers need > 50 days for the weaning process. Caviomorpha, Thryonomyidae and Hystricidae seem to have ‘opened the door’ to the use of low quality food by microbial fermentation, but some of them have to ‘pay’ for this extension of the food range by an extended weaning period, which also means an extended dependency on the mother.
Article
1. The role of physiological complexity in animal foraging ecology was investigated through experiments to determine how animals manage time and energy during patch use under thermoregulatory costs. The Degu Octodon degus (Molina 1782), a diurnal rodent inhabiting the semiarid environments of central Chile, was studied.2. Previous studies reported that Degus are constrained to specific foraging areas mainly by limits to thermal tolerance and food quality. Predation risk may also be important. Because new evidence shows that physiological processes are important in shaping foraging ecology, it was hypothesized that Degu foraging behaviour is influenced by the risk of hyperthermia as well as by the advantages of gathering food efficiently.3. Feeding trials were conducted in an experimental arena with food offered in an experimental patch containing sand and placed under a heater. Using video cameras, the overall time budget was measured, including frequency and duration of patch visits, and events of food gathering. Besides ambient temperature (high or low), handling time was manipulated by using husked and unhusked sunflower seeds, and searching time by using two seed distributions.4. Ambient temperature and husk state as well as ambient temperature and seed distribution interacted in their influence on both handling time and searching efficiency. These results imply that a thermally risky patch affects both parameters associated with patch use and diet selection and that this effect disappears when animals are not risking hyperthermia.5. Degus decreased the frequency of patch visits under thermoregulatory costs. This behaviour resulted exclusively from the effect of ambient temperature. Data on time use suggest that direct exposure to higher environmental temperatures is avoided through changes in the duration of patch visits. Degus harvested food items in shorter foraging bouts when food was under a stressful thermal patch.6. In conclusion, a time-minimizing foraging behaviour, in face of Degus’ thermoregulatory physiology and related risks, was observed.
Article
The energetics and burrowing behaviour of the semifossorial Octodon degus (Rodentia: Octodontidae) were investigated and compared with that of more specialized fossorial rodents. An open-flow respirometry system was used to record energy expenditure of single degus inside respirometers partially filled with soft (moist) or hard (dry) soil. In addition, digging behaviour was recorded in groups of three animals inside a large terrarium under controlled conditions of food, photoperiod and temperature. In the field, the digging activity of degus was monitored, along with seasonal variations in rainfall, content of soil moisture and soil hardness. Mass-specific metabolic rate during digging was found to be higher in animals burrowing in soft soils compared to hard soil. However, animals burrowing in soft soil removed more soil per min than animals in hard soil. Thus, gram per gram, excavating in hard soil was energetically more expensive. The digging cost of semifossorial degus tends to be either similar to or above those of similarly sized, but more fossorial, rodents. In the field, heightened digging activity coincided with the occurrence of rainfall, greater content of soil moisture and relatively soft soil conditions. Degus generally use their front feet and teeth to shear the soil; disposal of accumulated debris being carried out by moving their front and hind feet backwards. We also observed the establishment of digging chains when two or three individuals burrowed at the same site. As far as digging is concerned, the behaviour of degus is similar to that of other fossorial rodents, such as African bathyergids and the more closely related South American ctenomyids.
Article
The food preferences of Octodon degus are examined in laboratory test. Results indicate that degus prefer new rather than mature leaves of Chilean matorral shrubs, and that degus do not discriminate between new leaves (equivalents of shrub seedlings) of different shrub species. The significance of degus preferences in relation to matorral composition is discussed.
1.1. The activity of l-gulonolactone oxidase (EC 1.1.3.8) in livers of 49 species of eutherian mammals varied intraspecifically among individuals; coefficients of variation were 0.2 to 0.4 in many species.2.2. Differences observed in l-gulonolactone oxidase activity among strains of laboratory rats and domestic rabbits are probably genetically controlled.3.3. Pronounced sex differences in l-gulonolactone oxidase activity were found in some species, particularly in the genera Peromyscus, Reithrodontomys and Onychomys.4.4. Mormota monax exhibited seasonal variation in l-gulonolactone oxidase somewhat like that previously observed in Sylvilagus floridanus; no such seasonal variation was found in Sciurus carolinensis.5.5. Hibernation did not affect l-gulonolactone oxidase activity in Spermophilus tridecemlineatus.6.6. In four species of rodents, Microtus ochrogaster, Tylomys panamensis, Octodon degus and Sigmodon hispidus, l-gulonolactone oxidase activity was not affected by the level of dietary ascorbate.
Article
6 litters of Octodon degus were studied from birth to 10 days of age. Newly-born degus (mean weight 14.6 g) had open eyes, upper and lower pigment, fur, and teeth. Within 3-4 hours of birth they were able to walk supporting their full weight, right themselves rapidly, sit upright on their haunches, or rear upright with support, and vocalize. By the 1st or 2nd day, the young animals displayed functional grooming (face washing, hind-paw scratching, rapid head-shake). Solid food was ingested from day 6, although newborns chewed wood chips and 3-day olds gnawed dried faeces. Young degus were tested daily in an open field apparatus and showed increased activity and exploration, with repeated testing while decreasing distress vocalization after the 4th or 5th day. Degus are proposed for the study of developmental topics since their degree of development at birth allows for immediate testing. The degus studied here seem to be more fully developed at birth than those studied in Britain.
1. Digestibilities of feed and turnover time (1/k), Transit time (TT) and mean retention time (MRT: 1/k + TT) of fluid and particle markers were measured in the guinea-pig (Cavia porcellus), degu (Octodon degus) and leaf-eared mouse (Phyllotis darwini) fed a diet containing 50% alfalfa. 2. The digestibility of fibre and the retention time of digesta were highest in the guinea-pig followed by the degu and lowest in the leaf-eared mouse. 3. The difference in the retention time of digesta, resulting from the variation in the digestibility of fibre, between the three animals can be considered to be related to their body mass.
Article
The degu, Octodon degus, is a South American hystricomorph rodent that is of interest because it develops spontaneous diabetes mellitus and has been found to have islet amyloidosis. To help clarify these problems we have cloned cDNAs encoding islet amyloid polypeptide (IAPP), insulin, and glucagon precursors from this species. The predicted amino acid sequence of degu IAPP is very similar to that of nonamyloid-forming guinea pig IAPP. In contrast, degu insulin and the C-terminal region of degu glucagon are highly divergent from those of other mammals, as is also the case in the guinea pig, suggesting the existence of some form of positive evolutionary pressure on these hormones of carbohydrate metabolism in the hystricomorph rodents.
Article
The Octodon degus has been reported to have higher aldose reductase activity in the lens compared to the gerbil and rat. When made diabetic the degus develop cataracts within 4 weeks. We have been able to completely prevent cataract formation in diabetic degus using Pfizer's sorbinil for up to 6 months. This is further evidence of the role of aldose reductase in the formation of cataracts in diabetes.
1. The concentrations of 136 urine samples from four species of small mammals were compared using osmometry, refractometry and a colorimetric test for urea concentration. 2. To obtain a wide range of concentrations (430-3950 mOsm/kg), urine samples were collected under normal and dehydration conditions. 3. Regression analyses of paired values indicate that measurements of total solids concentration (refractometric method) permit evaluations of urine osmolality and estimations of the concentration of urea with a high degree of confidence.
Article
The ability to synthesize ascorbic acid is absent in the insects, invertebrates, and fishes. The biosynthetic capacity started in the kidney of amphibians, resided in the kidney of reptiles, became transferred to the liver of mammals, and finally disappeared from the guinea pig, the flying mammals, monkey, and man. A similar transition in the biosynthetic ability was observed in the branched evolution of the birds.
Article
Unique alpha-cell crystals, a herpes-like virus, islet amyloidosis, and immunohistochemical reactions of islets are compared in the rodent, Octodon degus, in animals with ordinary and high circulating glucose levels. Results suggest that crystals, virus, and amyloid are independent of blood sugar and bear no obvious relation to one another, although each is more common in older than in young animals. The crystals do not react with anti-glucagon. In the presence of high blood glucose, qualitative histochemical studies demonstrated diminished islet insulin and an unusual reaction with anti-somatostatin: (1) paucity of the usual cells that stain darkly for somatostatin and (2) striking staining of intermediate hue in most islet cells and in (3) multitudes of cell nests in exocrine parenchyma. The intermediate staining reaction may represent a visible demonstration of the paracrine phenomenon.
Article
This study describes infant socialization in captive parent-young units of the caviomorph rodent Octodon degus. Types of parent-young contact (huddling or squatting) and social interaction (body nosing and accompanying behaviors) are described and their ontogenetic trends examined between postnatal Days 1 and 46. Fathers spent less time than mothers in contact with the young. Mother-young contact decreased postnatally, whereas the amounts of mother-young and father-young social interaction, measured in terms of body-nosing exchanges, showed a continuous increase postnatally; sibling interactions also showed a continuous increase. Father-young interactions tended to be dominated by the father. Young reared with the father cohabiting huddled less with their mother, and engaged in less body-nosing, than young reared in the father's absence. Observations suggested that paternal control of the young may curb juvenile interactions. Young observed without their parents in an unfamiliar enclosure did not groom or "play" as in their home cage with parents present, but engaged in relatively more vocalizing, neck-nosing and forepaw-clasping.
Article
Individual Chilean degus (Octodon degus) were maintained in a thermal gradient (14 degrees C to 33 degrees C) for two or more weeks under a 14L:10D light-dark cycle. All animals showed robust daily rhythms of body temperature and locomotor activity consistent with the diurnal habits of the species. They also showed a robust daily rhythm of temperature selection 180 degrees out of phase with the rhythms of body temperature and locomotor activity. These results in a diurnal species extend previous findings of a 180 degrees phase difference between the rhythms of body temperature and temperature selection in nocturnal rodents. The asynchrony between these two rhythms implies an opposition between the circadian system (responsible for the generation of the body temperature rhythm) and the homeostatic system (responsible for the behavioral response of temperature selection that opposes the body temperature rhythm.
Differences in feeding rates and digestive efficiency of alternative experimental diets differing in cellulose or fiber and a secondary metabolite (the hydrolyzable tannin, tannic acid [TA]) were assessed with the herbivorous burrowing caviomorph rodent Octodon degus (degu). Degus live in open scrub subjected to summer droughts. The in vitro activity of the digestive enzyme sucrase was not significantly different between treatments with high and low TA. Analysis of the whole organism allowed us to conclude that in vitro analyses of enzymatic digestive activity and plant defenses cannot be used to explain and fully understand the physiological and behavioral effects of plant defenses on mammalian herbivores. We observed no body mass reduction due to effects of dietary treatments. O. degus seemed to compensate for nutritionally poor food by increasing gut content volume. We conclude that fiber and secondary compounds may influence feeding and digestive strategies and vice versa.
Article
Zoogeographical effects on the basal metabolic rate (BMR) of 487 mammal species were analyzed using conventional and phylogenetically independent ANCOVA. Minimal BMR variance occurred at a "constrained body mass" of 358 g, whereas maximum variance occurred at the smallest and largest body masses. Significant differences in BMR were identified for similar-sized mammals from the six terrestrial zoogeographical zones (Afrotropical, Australasian, Indomalayan, Nearctic, Neotropical, and Palearctic). Nearctic and Palearctic mammals had higher basal rates than their Afrotropical, Australasian, Indomalayan, and Neotropical counterparts. Desert mammals had lower basal rates than mesic mammals. The patterns were interpreted with a conceptual model describing geographical BMR variance in terms of the influence of latitudinal and zonal climate variability. Low and high basal rates were explained in unpredictable and predictable environments, respectively, especially in small mammals. The BMR of large mammals may be influenced in addition by mobility and predation constraints. Highly mobile mammals tend to have high BMRs that may somehow facilitate fast running speeds, whereas less mobile mammals are generally dietary specialists and are often armored. The model thus integrates physiological and ecological criteria and makes predictions concerning body size and life-history evolution, island effects, and locomotor energetics.
Article
The influence of early parental deprivation on the development of tyrosine hydroxylase- and 5-hydroxytryptamine-immunoreactive fiber innervation of subregions of the orbital prefrontal cortex (ventrolateral orbital, lateral orbital and agranular insular cortex) was quantitatively investigated in the precocious lagomorph Octodon degus. Forty-five-day-old degus from two groups were compared: 1) degus which were repeatedly separated from their parents during the first three postnatal weeks, and after weaning they were reared in social isolation; and 2) degus which were reared undisturbed in their families. Compared with the normal control animals the ventrolateral orbital prefrontal cortex and agranular insular cortex of the deprived animals displayed significantly increased density of tyrosine hydroxylase-immunoreactive fibers (up to 172% in the ventrolateral orbital prefrontal cortex and up to 143% in the agranular insular cortex). The lateral orbital prefrontal cortex showed increased 5-hydroxytryptamine-positive fiber densities (up to 118%). This altered balance between the serotonergic and dopaminergic cortical innervation in the orbital prefrontal cortex may reflect an anatomical and functional adaptation, which may be triggered by an altered activity of these transmitter systems during the phases of parental separation and social isolation.
Article
Octodon degus is a moderate-sized, precocious, but slowly maturing, hystricomorph rodent from central Chile. We have used this species to study a variety of questions about circadian rhythms in a diurnal mammal that readily adapts to most laboratory settings. In collaboration with others, we have found that a number of fundamental features of circadian function differ in this diurnal rodent compared with nocturnal rodents, specifically rats or hamsters. We have also discovered that many aspects of the circadian system are sexually dimorphic in this species. However, the sexual dimorphisms develop in the presence of pubertal hormones, and the sex differences do not appear until after gonadal puberty is complete. The developmental timing of the sex differences is much later than in the previously studied altricial, rapidly developing rat, mouse, or hamster. This developmental timing of circadian function is reminiscent of that reported for adolescent humans. In addition, we have developed a model that demonstrates how nonphotic stimuli, specifically conspecific odors, can interact with the circadian system to hasten recovery from a phase-shift of the light:dark cycle (jet lag). Interestingly, the production of the odor-based social signal and sensitivity to it are modulated by adult gonadal hormones. Data from degu circadian studies have led us to conclude that treatment of some circadian disorders in humans will likely need to be both age and gender specific. Degus will continue to be valuable research animals for resolving other questions regarding reproduction, diabetes, and cataract development.
Article
Animals process and allocate energy at different seasons at variable rates, depending on their breeding season and changes in environmental conditions and resulting physiological demands. Overall total energy expenditure, in turn, should either increase in some seasons due to special added demands (e.g. reproduction) or it could simply remain at about the same level, in which case the animals must show compensatory rebalancing of other expenditures that can be reduced. To test for the alternative hypotheses of seasonal variability or compensation, we measured total daily energy expenditure (DEE) in free-living degus (Octodon degus) at four seasons and followed this with determinations of basal metabolic rate (BMR) in the laboratory in the same individuals. DEE varied seasonally but was only significantly different (lower) in summer (non-breeding season), with a DEE:BMR ratio of only 1.6, whereas autumn, winter and spring DEE values were statistically indistinguishable from one another and showed DEE:BMR ratios ranging from 1.9 to 2.2. Our values of DEE in the field fall within the broad range of allometric expectation for herbivorous mammals in general, but the ratios of DEE:BMR are lower than expected. This, together with the lack of strong major shifts in total levels of DEE, suggests that degus are showing compensatory shifts among various categories of energy expenditure that allow them to manage their overall energy balance by minimizing total expenditure.
Mammals of the World Baltimore (MD): The Johns Hop-kins University Press
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How To Care for Your Degu. England (UK): Kingdom Books
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A Complete Pet Owner's Manual. New York: Barron's; 2001
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