Abstract

Stress can lead to various health problems. Exposure to stress is linked to several diseases including cancer, hypertension, diabetes, mental disorders, and heart attacks. Stress stimulates several pathways that produce free radicals, which increases oxidative stress. This results in functional and structural damage to organs, such as the brain, which is highly sensitive to oxidative stress Vitamin E is a naturally occurring potent antioxidant used for various purposes. The main purpose of the current study was to evaluate how vitamin E protects the brain and to what extent it affects antioxidant levels in rats subjected to two hours per day of immobilization stress, the form of stress with the strongest effect. The rats were immobilized by folding their limbs in and wrapping them in netting to prevent movement, while allowing their tails to be extended. The rats were then hung upside down. The effect of vitamin E was tested by intraperitoneally injecting rats with 40 mg/kg of vitamin E daily. Oxidative stress parameters were determined at the completion of the experiment. A dramatic decrease in malondialdehyde (MDA) levels and an increase in catalase (CAT), including glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD), has been shown by vitamin E in the brain. The effects of vitamin E were significantly higher in the acute and chronic stress groups than in the control group. Vitamin E can decrease oxidative stress in stressed rats, indicating that it exerts therapeutic and protective effects owing to its antioxidant properties.

Introduction

Stress is a normal factor in everyday vernacular and a fundamental aspect of the human condition. Millions of missed working days are attributed to stress, which is acknowledged globally as the main contributor to chronic illnesses (e.g., Am. Psychol. Assoc. 2019, UK Health Saf. Executive 2019). It has been reported that stress affects every aspect of life. Furthermore, stress is known to have both direct and indirect negative effects on health via changes in neuroendocrine and autonomic functions (O’Connor et al., 2021).

Activation of the HPA axis, which causes an increase in corticosterone levels in the brain, is a key mechanism linked to stress-induced behavioral problems. Rapid depolarization caused by elevated corticosterone levels causes glutamate to be released into limbic and cortical areas. An increase in metabolic rate and mitochondrial dysfunction may result from glutamate overproduction. An increase in the metabolic rate results in a conflict between the generation of ROS and antioxidant system activity, which causes the generation of more free radicals. Nucleic acids, proteins, and lipids are just a few cellular components that oxidatively damage these free radical species oxidatively damage (Samarghandian et al., 2017).

Free radicals are associated with oxidative stress. Free radicals are highly reactive with unpaired electrons and atoms. An increase in the levels of antioxidants and free radicals can lead to oxidative stress.

Conclusion

Levels of the antioxidants GSH, SOD, and CAT in the brain were significantly higher in the vitamin E group than in the acute and chronic stress groups (controls). Vitamin E also significantly reduced MDA levels and oxidative stress in stressed rats. These findings suggest that vitamin E can prevent and relieve stress.

Abstract

Introduction

Species Implicated in Human Infestations

Biology and Life Cycle

Epidemiology of C. lectularius and C. hemipterus

Clinical Relevance

Control

Laboratory Collection, Identification, and Reporting

Specimen collection and handling

Morphologic features of adults and nymphs

Identification of the species of cimicids reported from humans

Reporting

References

Abstract

The world has experienced a major global resurgence of bed bug infestations over the past 2 decades. While bed bugs do not serve as vectors of disease, their bites and household infestations result in significant psychological distress, clinical manifestations, and economic costs. Most human bed bug infestations are caused by the “common bed bug,” Cimex lectularius, or the “tropical bed bug,” C. hemipterus. Zoonotic cimicids also occasionally feed on humans. Bites are the most commonly reported manifestation of infestations, although findings may be subtle and overlooked for some time. The bugs can be submitted to the laboratory for identification, and therefore, clinical microbiologists should be familiar with their key identifying features and how they can be differentiated from similar-appearing arthropods. This review covers the biology and epidemiology of bed bugs; aspects of laboratory collection, identification, and reporting; and the clinical implications of bed bug infestations.

Introduction

“Good night, sleep tight; don’t let the bed bugs bite.” This version of the well-known rhyme was first published in 1896 in the book What They Say in New England by Clifton Johnson, but variations of this verse can be found in the literature in the decades before [1]. While a seemingly innocent bedtime rhyme, it reflects the reality of life in colonial New England, in which residents went to bed hoping not to be bitten by these blood-sucking pests while they were sleeping. We now know that bed bugs have long been associated with human habitats, being found in references throughout history and from archaeological sites dating back 3,500 years [2]. Bed bugs were thought to have spread throughout Asia and Europe in the early centuries of the Common Era, and later traveled to the Americas aboard ships of early European sailors [3]. By the 1900s, bed bugs were estimated to be in 1/3 of the dwellings in European cities and disproportionately affected those living in poor, crowded neighborhoods. While bed bugs do not serve as vectors of disease, their bites and household infestations result in psychological distress, a range of unpleasant clinical manifestations, property loss, and other substantial economic costs [4, 5, 6]. It was only with the widespread household use of dichloro-diphenyl-trichloroethane (DDT) and other potent long-lasting pesticides throughout the 1940s to 1960s that the prevalence of bed bug infestations significantly decreased worldwide [3].
Unfortunately, the world is now experiencing a major resurgence in bed bug infestations, with an explosion of reports beginning around the turn of the century [4, 7]. Although the exact cause of this resurgence is unknown, it is thought to be due to multiple factors, including widespread resistance to commonly used pesticides, increased domestic and international travel, and the decline in public health pest control programs that occurred in the latter half of the 1900s [8].

Highlights

Abstract

Keywords

1. The rationale and the early days

2. The glorious seventies – The birth of our family

3. From then onward

4. GnRHs – The basic and the applied

5. A few concluding thoughts

Acknowledgements

References

Abstract

Driven by the broad diversity of species and physiologies and by reproduction-related bottlenecks in aquaculture, the field of fish reproductive biology has rapidly grown over the last five decades. This review provides my perspective on the field during this period, integrating fundamental and applied developments and milestones. Our basic understanding of the brain-pituitary–gonadal axis led to overcoming the failure of farmed fish to ovulate and spawn in captivity, allowing us to close the fish life cycle and establish a predictable, year-round production of eggs. Dissecting the molecular and hormonal mechanisms associated with sex determination and differentiation drove technologies for producing better performing mono-sex and reproductively-sterile fish. The growing contingent of passionate fish biologists, together with the availability of innovative platforms such as transgenesis and gene editing, as well as new models such as the zebrafish and medaka, have generated many discoveries, also leading to new insights of reproductive biology in higher vertebrates including humans. Consequently, fish have now been widely accepted as vertebrate reproductive models. Perhaps the best testament of the progress in our discipline is demonstrated at the International Symposia on Reproductive Physiology of Fish (ISRPF), at which our scientific family has convened every four years since the grandfather of the field, the late Ronald Billard, organized the inaugural 1977 meeting in Paimpont, France. As the one person who has been fortunate enough to attend all of these meetings since their inception, I have witnessed first-hand the astounding evolution of our field as we capitalized on the molecular and biotechnological revolutions in the life sciences, which enabled us to provide a higher resolution of fish reproductive and endocrine processes, answer more questions, and dive into deeper comprehension. Undoubtedly, the next (five) decades will be similarly exciting as we continue to integrate physiology with genomics, basic and translational research, and the small fish models with the aquacultured species.

1. The rationale and the early days
Growing up I was fascinated by the sea, and I always wanted to be a marine biologist engaged in research that would explore ocean life to the benefit of society. Following this childhood passion, I studied biology as an undergraduate and in 1974 I enrolled in an Oceanography MSc program, both at the Hebrew University of Jerusalem. At that time, we already knew that the world was headed for a major fishery crisis, as overfishing was rampant and marine/coastal pollution was adversely impacting the spawning grounds of many marine species. When it was time to choose my Master’s thesis research topic, I decided to pursue marine aquaculture, which back then was in its infancy. The first bottleneck to be resolved in finfish aquaculture was the inability of many commercially important marine fish to reproduce reliably when raised in captivity. The budding mariculture industry had to rely on harvesting wild juvenile fish or broodstock, transporting them to the farming operation and growing them to harvest size (for juveniles) or stripping them to obtain eggs and sperm for the production of fertilized eggs, larvae and juveniles (for broodstock). These were, of course, very unreliable and unpredictable practices, as wild juveniles/broodstock were only available seasonally for a limited time, and in some years they could not be found at all. This led me (and several others in the field) to study fish reproductive biology and endocrinology, with the eventual goal of enabling predictable reproduction in captive fish and closing their life cycles. We hypothesized that fish do not reproduce in captivity because they do not experience the conditions of a spawning ground, and that the absence of these environmental conditions, which are difficult/impossible to simulate in captivity, causes a hormonal failure that is responsible for the lack of captive reproduction.

Highlights

Abstract

Keywords

1. Introduction

2. Methods

3. Results

4. Discussion

Credit statement

Declaration of Competing Interest

Acknowledgement

Appendix. Supplementary materials

References

Abstract

In the UK the now widespread non-native grey squirrel produces problems for the forestry industry through damage from bark stripping and threatens the survival of native species most notably the red squirrel which, mainly as a result of resource competition and transmission of infection, has suffered dramatic declines. Reducing grey squirrel numbers is essential to decrease this species’ ecological and environmental impact.

Using an individual-based model operating in a fine scaled landscape of well-mixed woodlands with reliable seed production we develop novel effort-based mechanisms explicitly representing the probabilistic interaction of individual squirrels with either traps or bait hoppers to capture the density-dependant efficiency of culling and fertility control respectively. We also integrate a habitat-based resistance to inter-patch movement to describe more realistically the source-sink dynamics in regional scale populations.

We use this new framework to compare the relative effort of population management at a landscape scale using both culling and fertility control, alone and combined as part of an integrated, sequential, approach. We also exploit our spatially-explicit framework to demonstrate how we might identify neighbourhoods within our study area where management may be easier (quicker and cheaper) or more difficult (sub-populations resistant to management), to enable the prediction of an optimal spatial and temporal deployment of management effort.

Our results agree with previous studies on the relative efficiency of culling in eradicating squirrels, as well as on the substantial “costs” of this approach. Despite an assumption of lower deployment costs, our findings suggest that, at least for the initial squirrel densities assumed, fertility control alone is unlikely to achieve rapid enough reduction to prove a viable cost-effective alternative to completely replace culling. However, when applied to the low density populations following short-term culling, eradication could be achieved within the same timescales as continuous culling alone but with substantially lower costs.

1- Introduction

2- In vitro studies

3- In vivo studies

4- Conclusion(s)

References

Abstract

Stem cell, one of the most exciting research areas of 21st century, is considered to have broaden the horizons of the field of biology, in general and medicine, in particular. Stem cells, owing to their unique characteristics like self-renewal, multiplication and differentiation are considered to provide an ‘all-in-one-solution’ for diverse clinical problems. Among various stem cell types, mesenchymal stem cells (MSCs) are being made the subject of the most of the studies on their therapeutic applications. It is attributable to their readily available sources, ability to immunemodulate and differentiate into mesodermal and extra-mesodermal tissues. MSCs in contrast to pluripotent stem cells carry minimal risk of teratoma formation and are free from any ethical concern. MSCs have been evaluated under innumerable studies but the definitive applications of these cells are slow, plausibly due to the incomplete understanding of their cellular physiology. Goat MSCs (gMSCs) have been isolated, culture expanded, characterized from various tissue sources and studied for their potential in vivo applications mostly in relation to human translational models. The current review throws some light on gMSC sources, characterization and potential therapeutic applications.

Introduction

The stem cells constitute an important element in the discipline of regenerative medicine that aims to address numerous incurable diseases through tissue regeneration (Gugjoo and Amarpal, 2018; Gugjoo et al. 2019). The specialized properties of selfrenewal, multiplication and differentiation of stem cells make them potential candidates for an all-in-one therapeutic solution to diverse clinical ailments. Among various stem cell types, mesenchymal stem cells (MSCs) make subject of most of the therapeutic applications (Gugjoo et al. 2019). MSCs are available in almost all the tissue types and have easy isolation and culture processes. The cells are plastic in nature, and have immunomodulatory and/ anti-inflammatory properties with minimal risk of teratogenicity and associated ethical issues unlike that of embryonic stem cells (Song et al. 2013; Gugjoo et al. 2019).

1- Introduction

2- Material and methods

3- Results

4- Discussion

References

Abstract

The use of CRISPR-Cas9 has revolutionized functional genetic work in many organisms, including more and more insect species. However, successful gene editing or genetic transformation has not yet been reported for chelicerates, the second largest group of terrestrial animals. Within this group, some mite and tick species are economically very important for agriculture and human health, and the availability of a gene-editing tool would be a significant advancement for the field. Here, we report on the use of CRISPR-Cas9 in the spider mite Tetranychus urticae. The ovary of virgin adult females was injected with a mix of Cas9 and sgRNAs targeting the phytoene desaturase gene. Natural mutants of this laterally transferred gene have previously shown an easy-to-score albino phenotype. Albino sons of injected virgin females were mated with wild-type females, and two independent transformed lines where created and further characterized. Albinism inherited as a recessive monogenic trait. Sequencing of the complete target-gene of both lines revealed two different lesions at expected locations near the PAM site in the target-gene. Both lines did not genetically complement each other in dedicated crosses, nor when crossed to a reference albino strain with a known genetic defect in the same gene. In conclusion, two independent mutagenesis events were induced in the spider mite T. urticae using CRISPR-Cas9, hereby providing proof-of-concept that CRISPR-Cas9 can be used to create gene knockouts in mites.

Introduction

Mites and ticks are members of the chelicerates, the largest group of terrestrial animals after insects. The two-spotted spider mite, T. urticae, and other spider mites are important crop pests worldwide. This herbivore species is at the extreme end of the generalist-to specialist spectrum and can feed on a staggering 1,100 plant species. Not surprisingly, it is currently reported as the ‘most resistant’ pest worldwide, as it developed resistance to more than 90 acaricides (Mota-Sanchez and Wise, 2019; Van Leeuwen and Dermauw, 2016; Van Leeuwen et al., 2015). In 2011, a 90 Mb high-quality Sanger-sequenced genome became available for this species (Grbic et al., 2011). This allowed to disentangle some of the molecular mechanisms underlying resistance, whether to man-made pesticides or plant secondary compounds. The extreme adaptation potential of T. urticae was associated with specific gene expansions in known detoxification enzyme families, such as cytochrome P450 monooxygenases, glutathione-S-transferases, carboxyl-choline esterases, an unexpected repertoire of ABC and MFS transporters, and a proliferation of cysteine peptidases (Dermauw et al., 2013a; Dermauw et al., 2013b; Grbic et al., 2011; Santamaría et al., 2012).

1- Introduction

2- Materials and methods

3- Results

4- Discussion

5- Conclusion

References

Abstract

Qinchuan cattle is one of the five yellow cattle breeds in China with good performance of meat. The proliferation and differentiation level of muscle and fat are closely related to the growth and development of the organism and are the key factors affecting the quality of meat. In order to study the effect of lncRNA on the fat tissues of Qinchuan cattle, six calf and adult bovine adipose tissues were selected for high-throughput sequencing. We obtained 3,716 lncRNA candidates from calves and adult cattle fat samples, among them 789 lncRNA were annotated and 2,927 lncRNA were novel lncRNA. A number of lncRNAs were highly abundant, and 119 lncRNA were differentially expressed between two developmental stages. We further validated several differentially expressed lncRNAs using qPCR, and the results were consistent with the sequencing data. Therefore, we conclude that lncRNA may play an important role in adipose tissue in different age groups of cattle.

Introduction

Fat is synthesized from glycerin and fatty acids and is an important part of the organism. As the core of the nutritional value of meat, it has a positive effect on the appearance, texture, flavor, hardness and shelf life of the meat1 . However, the excessive deposition of fat not only affects meat quality, but also risks to human health. Therefore, clarifying the regulation mechanism of lipogenesis is of great significance for improving meat quality. Lipogenesis is a complex and elaborate procedural regulation process involving a series of transcription factors2 . At present, more and more researchers have reported on the biological processes of fat synthesis. 3, 4 Numerous studies have shown that the peroxisome proliferator-activated receptor (PPARγ) and CCAAT/enhancer-binding protein α (C/EBPα) play a key role in this process. However, lipogenesis involves multiple gene expression, signal transduction, and network regulation. The process is complex and new regulatory factors are constantly being identified. Recent studies have shown that long noncoding RNAs (lncRNAs) also have important regulatory effects on adipogenesis, but there are few studies in cattle.

1- Introduction

2- Methods

3- Results

4- Discussion

5- Conclusion

References

Abstract

Transmissible vaccines may provide a promising solution for improving the control of infectious disease, particularly zoonotic pathogens with wildlife reservoirs. Although it is well known that heterogeneity in pathogen transmission impacts the spread of infectious disease, the effects of heterogeneity on vaccine transmission are largely unknown. Here we develop and analyze a mathematical model that quantifies the potential benefits of a transmissible vaccine in a population where transmission is heterogeneous between two subgroups. Our results demonstrate that the effect of heterogeneity on the benefit of vaccine transmission largely depends on the vaccine design and the pattern of vaccine administration across subgroups. Specifically, our results show that in most cases a transmissible vaccine designed to mirror the transmission of the pathogen is optimal. If the vaccination effort can be preferentially biased towards a given subgroup, a vaccine with a pattern of transmission opposite to that of the pathogen can become optimal in some cases. To better understand the consequences of heterogeneity on the effectiveness of a transmissible vaccine in the real world, we parameterized our model using data from Sin Nombre virus in deer mice (Peromyscus maniculatus). The results of this analysis reveal that when a vaccination campaign is limited in vaccine availability, a traditional vaccine must be administered primarily to males for the spread of Sin Nombre virus to be prevented. In contrast, a transmissible vaccine remains effective even when it cannot be preferentially administered to males.

Introduction

Zoonoses, particularly those circulating in wildlife populations, are a primary source of pathogens that infect humans [1]. The burden of such pathogens on human populations can be profound, as demonstrated in the 2014–2015 West African Ebola virus epidemic. The virus was transmitted from wild animal populations such as fruit bats and apes [2], and resulted in over 11,000 human deaths and cost over 3.6 billion dollars [3]. Such outbreaks highlight the need to develop costeffective strategies that mitigate zoonotic spillover into human populations. One strategy for reducing the spillover potential of zoonoses is to decrease the prevalence of infectious disease within wildlife reservoir populations. Both culling [4] and mass vaccination [4,5] have been used to control pathogens in wildlife reservoir populations. Though both strategies have been successful in some cases [4], the costs of implementation and the difficulties of delivering vaccine to wild animals limit their scope of applicability [6]. Transmissible vaccines are a novel tool that might overcome some of these challenges, allowing for pathogen reduction or even the prevention of pathogen spread in wildlife reservoirs.

Toxascaris leonina and Trichuris sp. are soil-transmitted helminths (STHs) infecting domestic and wild mammals. The antagonistic effect of the saprophytic filamentous fungi Mucor circinelloides and Verticillium sp. was examined on eggs of T. leonina passed in the feces of captive lynxes (Lynx lynx) kept in a zoological park. The activity of M. circinelloides and Trichoderma atrobrunneum was tested on eggs of Trichuris sp. shed by captive dromedaries (Camelus dromedarius). The parasiticide activity was assessed by measuring the ovistatic (delayed development) and ovicidal (non-viability) effects on eggs placed in Petri plates, and by spraying spores directly onto fecal samples. Based on the observation of that hyphae of M. circinelloides, Verticillium sp. and T. atrobrunneum adhered to the eggshells, penetrated and destroyed the inner embryo, an ovicidal type 3 effect was concluded. Development of eggs of T. leonina and Trichuris sp. in the feces was delayed in the presence of all fungi, and one third remained at the stage of zygote. A significant reduction of T. leonina viable eggs was recorded in the feces sprayed spores of M. circinelloides (58%) or Verticillium sp. (67%). Fifty percent of the eggs of Trichuris sp. became into non-viable by 30 days after the exposure to either M. circinelloides or T. atrobrunneum. It is concluded that distribution of the filamentous fungi M. circinelloides, Verticillium sp. and T. atrobrunneum constitutes a novel approach to conduct the biological control of the STHs (T. leonina and Trichuris sp.) affecting wild animals captive in a zoological park.

Introduction

Soil-transmitted helminths (STHs) are parasites involving roundworms (ascarids), hookworms and whipworms which can affect animals and humans. Infection occurs through the accidental ingestion of infective eggs in contaminated soil or food (Vandemark et al., 2010; Elsheika, 2011), which develop in the feces from unembryonated eggs shed by adult female worms localized in the intestine (Mateus et al., 2014; Hoopes et al., 2015). Embryonation happens in the feces or ground after several weeks, resulting in that a second stage larva (L2) originates inside the eggs of ascarids, which becomes into infective (Hendrix, 2014), whereas in the case of whipworms the eggs are infective when a L1 larva develops inside (Felsmann et al., 2017). The role of rodents as paratenic hosts has been indicated in the transmission of Toxocara and Toxascaris (Okulewicz et al., 2012), and thus it has been pointed that the cycles of these nematodes could be considered as non-strictly monoxenous (Reperant et al., 2007). Some ascarid species have zoonotic potential, as Toxocara canis, T. cati, Baylisascaris procyonis, Ascaris suum or Toxascaris leonina, frequently detected in domestic (cats, dogs, pigs) and wild mammals (foxes, wolves, lynxes, raccoons) (Okulewicz and Buńkowska, 2009; Dado et al., 2012; Carver et al., 2012; Beiromvand et al., 2013; Neves et al., 2014; Figueiredo et al., 2016). The zoonotic role of Trichuris spp. has been also reported (Gałęcki et al., 2015; Felsmann et al., 2017; Gawor and Borecka, 2017). As indicated for other STHs, control of ascarids regularly comprises the administration of anthelmintics together with adequate hygiene (Alemu et al., 2011). Despite successful deworming is frequently administered among captive wild carnivores in zoo gardens (lions, lynxes, foxes, wolves), they infected again by helminths because their maintenance in the same parcels enhances that ground is permanently contaminated by eggs passed in the feces (Fagiolini et al., 2010; Maesano et al., 2014). In the same way, frequent infection by Trichuris sp. in dromedaries has been also described (Gurler et al., 2010; Eo et al., 2014). The eggs of ascarids and whipworms are very resistant to chemical and climatic factors, thus can remain infective in the soil for several years (Gavin et al., 2005; Overgaauw and van Knapen, 2013; Gałęcki et al., 2015; Gawor and Borecka, 2017). Nevertheless, there is insufficient information regarding measures to reduce the presence of infective stages in the ground. Prior investigations reported that certain saprophytic soil fungi perform an antagonistic activity on eggs of T. canis and A. suum, based on their ability to adhere to the eggshell, penetrate and destroy the embryo inside (Carvalho et al., 2010; Cortiñas et al., 2015).

Providing care for groups of animals is a major part of practicing zoologic medicine. Herd health is key to the mindset of a zoo clinician no matter the species encountered, be it avian or artiodactylid. In addition to the classic examples of group treatment involving chemotherapeutics (discussed in detail later), zoo clinicians also practice herd health by preventing disease from entering the collection. Before traveling to a new institution, most animals undergo a preshipment examination, which serves as a screening tool for common infectious diseases specific to that taxa, and provides a snapshot of that individual’s health. Diagnostics commonly included in a preshipment examination are a complete blood count, serum or plasma biochemistry, imaging, and fecal examination. On arrival to a new institution, most animals undergo a quarantine period, often 30 to 90 days, in addition to another thorough examination. All of these precautionary measures are vital to ensure that infectious disease does not enter an institution, and also provide the opportunity for targeted therapy if needed, before the animal is placed within its new social group. It is highly recommended that all animals that die within a zoologic setting receive a thorough gross necropsy with histopathology to try and determine the cause of death. Then, if an infectious cause is diagnosed, therapy for the remaining group of animals is based on the pathology findings. Another way that zoo clinicians can try to limit the need for group treatment is to have a working knowledge of which taxa can be safely housed together. In addition to such factors as size and potential for trauma, knowledge of how certain infectious diseases interact with various species can prevent future outbreaks. For example, Entamoeba invadens is transmitted from clinically healthy herbivorous tortoises to snakes when they are housed together, causing the snakes to develop severe ulcerative colitis and hepatitis.1 If a disease outbreak does occur, practicing vigilant biosecurity to try and limit transmission is key to decreasing the number of animals affected and needing treatment. Depending on the etiologic agent footbaths, isolation, and appropriate personal protective equipment may be used.2 When treatment is needed in a zoologic setting it presents unique challenges. One obstacle commonly encountered is that few pharmacokinetic studies have been performed in the species commonly found in zoos, so doses are often extrapolated from their closest domestic relative. Although extrapolation from domestics is done easily for some taxa, such as exotic canids, felids, or equids, there are species with no domestic counterpart, such as marsupials or invertebrates. Several different types of interspecies scaling have been described in the literature, with allometric scaling considered the most accurate.3 However, there are limiting factors to consider when using allometric scaling, such as the route of elimination and the extent of metabolism of the selected therapeutic agent.3 An additional challenge is that often accurate body weights cannot be obtained, so estimated weights are used, which can increase the risk of underdosing or overdosing an animal.4 Group treatment is not common for some taxa, such as large carnivores, and individual treatment is advised when possible. Once a dosage has been selected and a weight obtained or estimated, the next question is how to administer the drug to the animal. Treatment options are heavily dependent on the species, and are covered in detail in the following sections. Group treatment is not standard for all taxa, so only the most common species are discussed.

Abstract

This review summarizes the current status of the known extant genuine polyploid anuran and urodelan species, as well as spontaneously originated and/or experimentally produced amphibian polyploids. The mechanisms by which polyploids can originate, the meiotic pairing configurations, the diploidization processes operating in polyploid genomes, the phenomenon of hybridogenesis, and the relationship between polyploidization and sex chromosome evolution are discussed. The polyploid systems in some important amphibian taxa are described in more detail.

Frequent Occurrence of Bisexual Polyploid Amphibians

Polyploidization has been documented across a wide range of animal taxa. These include turbellarians, annelids, mollusks, crustaceans, and insects [Gregory and Mable, 2005], teleost fishes [Schultz, 1980; Le Comber and Smith, 2004], reptiles [Gregory and Mable, 2005], and amphibians [Bogart, 1980; Kawamura, 1984; King, 1990; Schmid et al., 2010; Evans et al., 2012]. In parthenogenetically reproducing animal species, polyploidy is observed relatively frequently [for reviews, see White, 1973; Fujita and Moritz, 2009]. In sexually reproducing animals, however, polyploid species are rare. Possible barriers to polyploidization include the presence of sex chromosomes [Muller, 1925], the prevalence of cross-fertilization [White, 1973], and the histological complexity of advanced animals [Stebbins, 1950]. These barriers may explain why polyploidy is much rarer in animals than in plants [Orr, 1990; Otto and Whitton, 2000].

Snails and schistosomes have a coevolutionary relationship spanning more than 200 million years [1]. Schistosomes are parasitic, with a life cycle alternating between a gastropod mollusc and vertebrate hosts (Figure 1). They have strong host specificity, particularly for the gastropod first intermediate host, in which they undergo their larval development [2,3], and which also dictates the geographical distribution of schistosomiasis (see Glossary) [4–6]. Yet, not every encounter between a schistosome and a snail species deemed compatible results in the infection of the latter [7]. Understanding the basis of this compatibility polymorphism is the core interest of many studies investigating snail–schistosome interactions. Such knowledge is expected to be applicable in curtailing diseases caused by schistosomes through transmission blockade at the level of the snail host [2]. Several species of Schistosoma infect humans, but three are responsible for most of the infections: Schistosoma mansoni (infects Biomphalaria snails), Schistosoma haematobium (infects Bulinus snails), and Schistosoma japonicum (infects Oncomelania snails) [8]. Most studies of snail–schistosome interactions utilize the Biomphalaria glabrata–S. mansoni model [9]. From studies of this model, the snail’s immune response (Figure 2, Key Figure) has emerged as an important determinant of the success of S. mansoni infection, acting in concert with host and parasite genetics and epigenetics, proteomic and transcriptomic regulation, and environmental factors [10]. Stress-inducing environmental factors, particularly temperature, have been shown to influence B. glabrata susceptibility to S. mansoni [11–13] by interfering with the capacity of the snail’s immune response to prevent parasite infection [11,12].

Schistosomiasis is the second most widespread human parasitic disease after malaria. It is reported to be endemic in more than 78 countries in the tropical and subtropical areas, in Africa, Asia and Americas. Around 200 million people are estimated to be infected all over the world, with 200 000 death per year (Chitsulo et al., 2000). Infection is caused by a trematode parasite of the genus Schistosoma, which comprises 22 different species. Three of them, Schistosoma mansoni, S. heamatobium and S. japonicum are mainly responsible for human infections. S. mansoni is the causative agent of intestinal schistosomiasis and it is vectored by a freshwater snail from the genus Biomphalaria (Basch, 1976). The compatibility between the pathogen and its host is determined by two main factors, the susceptibility of the host and the infectivity of the parasite. In Biomphalaria, this host/pathogen compatibility is determined by genetic factors but can also be modulated by nongenetic factors, such as temperature (Knight et al., 2015), pollution (Ibrahim, 2006) or UV exposure (Ruelas et al., 2009), and could also be influenced by its microbiota composition. The microbiota of an organism is constituted of all microbial organisms, such as bacteria, fungi and viruses that live within the host in a mutualistic interaction. The microbiota is known to impact host evolution and adaptation by affecting several fitness parameters (Bosch and McFall-Ngai, 2011; Zilber-Rosenberg and Rosenberg, 2008). Notably, it has been shown to play a key role in the interaction between a host and its pathogens. In the mosquito Anopheles gambiae, the microbial flora can limit the infection with Plasmodium falciparum by inhibiting the development of the parasite within the host (Dong et al., 2009). More specifically, although viruses have often been characterized by their pathogenic and harmful effects, they are also an integral part of the microbiota and they can modulate host-parasite interaction in invertebrates (Martinez et al., 2015; Pradeu, 2016). For example, PolyDNA viruses are able to manipulate the immune system of parasitoid wasps (Burke and Strand, 2012), while SSRNA DcPv can modify the behavior of a ladybird parasitized by a parasitoid wasp to protect the parasitoid larvae (Dheilly et al., 2015b). More generally, it is widely accepted that viruses can control the immune system of their host for