Fish Invasions in the World's River Systems: When Natural Processes Are Blurred by Human Activities

Because species invasions are a principal driver of the human-induced biodiversity crisis, the identification of the major determinants of global invasions is a prerequisite for adopting sound conservation policies. Three major hypotheses, which are not necessarily mutually exclusive, have been proposed to explain the establishment of non-native species: the “human activity” hypothesis, which argues that human activities facilitate the establishment of non-native species by disturbing natural landscapes and by increasing propagule pressure; the “biotic resistance” hypothesis, predicting that species-rich communities will readily impede the establishment of non-native species; and the “biotic acceptance” hypothesis, predicting that environmentally suitable habitats for native species are also suitable for non-native species. We tested these hypotheses and report here a global map of fish invasions (i.e., the number of non-native fish species established per river basin) using an original worldwide dataset of freshwater fish occurrences, environmental variables, and human activity indicators for 1,055 river basins covering more than 80% of Earth's surface. First, we identified six major invasion hotspots where non-native species represent more than a quarter of the total number of species. According to the World Conservation Union, these areas are also characterised by the highest proportion of threatened fish species. Second, we show that the human activity indicators account for most of the global variation in non-native species richness, which is highly consistent with the “human activity” hypothesis. In contrast, our results do not provide support for either the “biotic acceptance” or the “biotic resistance” hypothesis. We show that the biogeography of fish invasions matches the geography of human impact at the global scale, which means that natural processes are blurred by human activities in driving fish invasions in the world's river systems. In view of our findings, we fear massive invasions in developing countries with a growing economy as already experienced in developed countries. Anticipating such potential biodiversity threats should therefore be a priority.     

Effects of coral transplantation and giant clam restocking on the structure of fish communities on degraded patch reefs

Active restoration is being practiced to supplement conservation activities for the purpose of reversing the trend of reef degradation. In the last decade, the feasibility of different restoration approaches such as coral transplantation and restocking of other marine biota has been the focus of research and relatively few have examined experimentally its effects on the resultant communities. In this study, coral transplantation and giant clam restocking were applied on 25 degraded patch reefs (~ 25 m²) inside a marine sanctuary in Pangasinan, northwestern Philippines to examine their effects on the community structure of reef fishes. Five interventions or treatments were employed: 1) “coral” consisted of transplantation of a combination of Acropora spp. and Pocillopora spp. on concrete blocks; 2) “clam” consisted of restocking of Tridacna gigas; 3) “clam+coral” consisted of restocking of T. gigas with Acropora spp. transplanted on their shells; 4) “shell” consisted of deployment of T. gigas shells; and 5) “control” consisted of no intervention. Fish communities on the patch reefs were monitored monthly for 3 months before the intervention and were monitored further for 11 months after the intervention, including 1 recruitment season. After the intervention, the coral cover and the “other biota” category increased in the coral and clam+coral treatments, due to the transplanted corals and deployed giant clams. Consequently, the complexity of the substrate was enhanced. A month after the intervention, a rapid increase in the abundance and species richness of reef fishes on the coral, clam+coral and clam treatments was observed compared to the shell and control treatments. A change in species composition of reef fish assemblage was also apparent in the coral and clam+coral treatments relative to the clam, shell and control, especially 4 months after the intervention. The present experiment demonstrates the feasibility of improving the condition of degraded patch reefs, which can subsequently enhance the fish community. Results also show the importance of the underlying substratum and the abundance of live corals and clams to reef fishes.     

Construction of an Affordable and Easy-to-Build Zebrafish Facility

In vivo biomedical research is pivotal to translate in vitro findings into clinical advances. Small academic institutions with limited resources find it virtually impossible to build and maintain typical rodent facilities for research. Zebrafish research has been demonstrated to be a valuable alternative for in vivo research in pharmacology, physiology, development and genetic studies. This article demonstrates that a functional zebrafish facility can be built in an easy and affordable manner. We demonstrate that such a facility could be built in about one working day with minimal tools and expertise. The cost of the 27 1.8 L fish tank zebrafish facility constructed in this study was approximately $1,500. We estimate that the maintenance of an initial working 150 fish colony for 3 months is $1,000. This project involved students, who were introduced to aquaculturing of zebrafish for research proposes.     

Alcohol Impairs Predation Risk Response and Communication in Zebrafish

The effects of ethanol exposure on Danio rerio have been studied from the perspectives of developmental biology and behavior. However, little is known about the effects of ethanol on the prey-predator relationship and chemical communication of predation risk. Here, we showed that visual contact with a predator triggers stress axis activation in zebrafish. We also observed a typical stress response in zebrafish receiving water from these conspecifics, indicating that these fish chemically communicate predation risk. Our work is the first to demonstrate how alcohol effects this prey-predator interaction. We showed for the first time that alcohol exposure completely blocks stress axis activation in both fish seeing the predator and in fish that come in indirect contact with a predator by receiving water from these conspecifics. Together with other research results and with the translational relevance of this fish species, our data points to zebrafish as a promising animal model to study human alcoholism.     

Picasso-Hund - ein neuer Name für Lycaon pictus?

Lycaon pictus has been named by a variety of common names, such as “African Wild Dog”, “African Hunting Dog” and their adequates in other languages. The article summarizes the history of naming in that species concluding with a new recommendation by the SSP as well as the EEP for that species to rename it as Painted Dog. As the translation of that name into German is an unhandy term it is suggested to name it “Picasso-Hund” in that language.     

Ampelozyziphus amazonicus Ducke (Rhamnaceae), a medicinal plant used to prevent malaria in the Amazon Region, hampers the development of Plasmodium berghei sporozoites

Most medicinal plants used against malaria in endemic areas aim to treat the acute symptoms of the disease such as high temperature fevers with periodicity and chills. In some endemic areas of the Brazilian Amazon region one medicinal plant seems to be an exception: Ampelozyziphus amazonicus, locally named “Indian beer” or “Saracura-mira”, used to prevent the disease when taken daily as a cold suspension of powdered dried roots. In previous work we found no activity of the plant extracts against malaria blood parasites in experimentally infected animals (mice and chickens) or in cultures of Plasmodium falciparum. However, in infections induced by sporozoites, chickens treated with plant extracts were partially protected against Plasmodium gallinaceum and showed reduced numbers of exoerythrocytic forms in the brain. We now present stronger evidence that the ethanolic extract of “Indian beer” roots hampers in vitro and in vivo development of Plasmodium berghei sporozoites, a rodent malaria parasite. Some mice treated with high doses of the plant extract did not become infected after sporozoite inoculation, whereas others had a delayed prepatent period and lower parasitemia. Our data validates the use of “Indian beer” as a remedy for malaria prophylaxis in the Amazon, where the plant exists and the disease represents an important problem which is difficult to control. Studies aiming to identify the active compounds responsible for the herein described causal prophylactic activity are needed and may lead to a new antimalarial prophylactic.     

Acute stress disrupts performance of zebrafish in the cued and spatial memory tests: the utility of fish models to study stress-memory interplay

The zebrafish (Danio rerio) has emerged as a promising model organism for affective or cognitive neuroscience research, and may be useful to study the interplay between memory and anxiety-related states. To assess the effects of acute psychological stress on spatial and cued memory, adult zebrafish were trained in an aquatic plus-maze for 14 days using food bait as a reward. Two ecologically relevant stressors (alarm pheromone or Indian leaf fish exposure) were applied to acutely stress zebrafish immediately prior to the final (testing) trial. Overall, acute single inescapable stress markedly impaired spatial and cued memory in zebrafish plus-maze test, reducing the number of correct arm entries and time spent in the target arm. This observation parallels rodent and clinical literature on memory-impairing effects of acute stress, strongly supporting the utility of zebrafish in neurobehavioral research.     

Genome wide sequence analysis grants unbiased definition of species boundaries in “Candidatus Phytoplasma”

The phytoplasmas are currently named using the Candidatus category, as the inability to grow them in vitro prevented (i) the performance of tests, such as DNA-DNA hybridization, that are regarded as necessary to establish species boundaries, and (ii) the deposition of type strains in culture collections. The recent accession to complete or nearly complete genome sequence information disclosed the opportunity to apply to the uncultivable phytoplasmas the same taxonomic approaches used for other bacteria. In this work, the genomes of 14 strains, belonging to the 16SrI, 16SrIII, 16SrV and 16SrX groups, including the species “Ca. P. asteris”, “Ca. P. mali”, “Ca. P. pyri”, “Ca. P. pruni”, and “Ca. P. australiense” were analyzed along with Acholeplasma laidlawi, to determine their taxonomic relatedness. Average nucleotide index (ANIm), tetranucleotide signature frequency correlation index (Tetra), and multilocus sequence analysis of 107 shared genes using both phylogenetic inference of concatenated (DNA and amino acid) sequences and consensus networks, were carried out. The results were in large agreement with the previously established 16S rDNA based classification schemes. Moreover, the taxonomic relationships within the 16SrI, 16SrIII and 16SrX groups, that represent clusters of strains whose relatedness could not be determined by 16SrDNA analysis, could be comparatively evaluated with non-subjective criteria. “Ca. P. mali” and “Ca. P. pyri” were found to meet the genome characteristics for the retention into two different, yet strictly related species; representatives of subgroups 16SrI-A and 16SrI-B were also found to meet the standards used in other bacteria to distinguish separate species; the genomes of the strains belonging to 16SrIII were found more closely related, suggesting that their subdivision into Candidatus species should be approached with caution.     

Taxonomical status and phylogenetic relations between the “thomasi” and “atticus” chromosomal races of the underground vole Microtus thomasi (Rodentia, Arvicolinae)

Laboratory crosses among wild caught individuals of the chromosomal races “atticus” and “thomasi”, were performed to analyze the degree of interracial reproductive isolation. The fertility of the studied specimens was evaluated by taking into consideration the reproductive success, the litter size and performing comparative histological examination of the testicular material. All studied populations were submitted to classical cytogenetic and mitochondrial analysis (cytochrome b gene), providing new evidences to the potential phylogenetic relations and taxonomical status of the two chromosomal races. The previously described “atticus” populations are divided in two genetically distinct, geographically and reproductively isolated lineages (2.9% total and 2.4% net divergence), which probably derived from different glacial refugia of Southern Greece. Here, we suggest that the lineage, consisting of the populations from Attiki and Evia Island, should be distinguished as a valid species, named Microtus atticus, including the two chromosomal races “atticus” and “evia”. On the contrary, the ex-“atticus” populations from North Peloponnesus belong to the same mitochondrial lineage with the other Microtus thomasi populations and should be considered as a chromosomal polymorphism inside the chromosomal race “thomasi”.     

Neurodegenerative disease-specific induced pluripotent stem cell research

Neurodegenerative disease-specific induced pluripotent stem cell (iPSC) research contributes to the following 3 areas; “Disease modeling”, “Disease material” and “Disease therapy”.“Disease modeling”, by recapitulating the disease phenotype in vitro, will reveal the pathomechanisms. Neurodegenerative disease-specific iPSC-derived non-neuronal cells harboring disease-causative protein(s), which play critical roles in neurodegeneration including motor neuron degeneration in amyotrophic lateral sclerosis, could be “Disease material”, the target cell(s) for drug screening. These differentiated cells also could be used for “Disease therapy”, an autologous cellular replacement/neuroprotection strategy, for patients with neurodegenerative disease.Further progress in these areas of research can be made for currently incurable neurodegenerative diseases.     

Intergenerational transmission of the behavioral consequences of early experience in prairie voles

We examined intergenerational and epigenetic effects of early handling manipulations on the social behavior of the prairie vole (Microtus ochrogaster), a monogamous rodent. Laboratory-born parents and their newborn pups were assigned to either a MAN0 “zero handling” manipulation (transfer with a cup during weekly cage changes) or a MAN1 “gloved handling” manipulation (transfer with a gloved hand). Previous studies from our laboratory (Bales et al., 2007) showed that MAN0 juvenile males that received this manipulation as pups are less alloparental and that MAN0 adult females that received this manipulation as pups display impaired pair-bonding. In the present study, when MAN0 and MAN1 pups reached adulthood, they were mated in three combinations (MAN1 female × MAN1 male; MAN0 female × MAN1 male; MAN1 female and MAN0 male). Once the pairs produced offspring, we examined their parental behavior towards their own pups. The offspring of these pairings (F2 generation) also were tested as juveniles for alloparental behavior. MAN1 females paired with a MAN0 male displayed higher levels of parenting behaviors. In the F2 generation, juvenile offspring with a MAN0 parent were less alloparental than were offspring from other pairs. These results suggest that early experiences can be transmitted intergenerationally.     

Expressed Repeat Elements Improve RT-qPCR Normalization across a Wide Range of Zebrafish Gene Expression Studies

The selection and validation of stably expressed reference genes is a critical issue for proper RT-qPCR data normalization. In zebrafish expression studies, many commonly used reference genes are not generally applicable given their variability in expression levels under a variety of experimental conditions. Inappropriate use of these reference genes may lead to false interpretation of expression data and unreliable conclusions. In this study, we evaluated a novel normalization method in zebrafish using expressed repetitive elements (ERE) as reference targets, instead of specific protein coding mRNA targets. We assessed and compared the expression stability of a number of EREs to that of commonly used zebrafish reference genes in a diverse set of experimental conditions including a developmental time series, a set of different organs from adult fish and different treatments of zebrafish embryos including morpholino injections and administration of chemicals. Using geNorm and rank aggregation analysis we demonstrated that EREs have a higher overall expression stability compared to the commonly used reference genes. Moreover, we propose a limited set of ERE reference targets (hatn10, dna15ta1 and loopern4), that show stable expression throughout the wide range of experiments in this study, as strong candidates for inclusion as reference targets for qPCR normalization in future zebrafish expression studies. Our applied strategy to find and evaluate candidate expressed repeat elements for RT-qPCR data normalization has high potential to be used also for other species.     

Identification of light and dark hypertrophic chondrocytes in mouse and rat chondrocyte pellet cultures

Hypertrophic “light” and “dark” chondrocytes have been reported as morphologically distinct cell types in growth cartilage during endochondral ossification in many species, but functional differences between the two cell types have not been described. The aim of the current study was to develop a pellet culture system using chondrocytes isolated from epiphyseal cartilage of neonatal mice and rats, for the study of functional differences between these two cell types. Hypertrophic chondrocytes resembling those described in vivo were observed by light and electron microscopy in sections of pellets treated with triiodothyronine, 1% fetal calf or mouse serum, 10% fetal calf serum or 1.7 MPa centrifugal pressure at day 14, and in pellets cultured with insulin or 0.1% fetal calf or mouse serum at day 21. A mixed population of light and dark chondrocytes was found in all conditions leading to induction of chondrocyte hypertrophy. This rodent culture system allows the differentiation of light and dark chondrocytes under various conditions in vitro and will be useful for future studies on tissue engineering and mechanisms of chondrocyte hypertrophy.     

Fine structure of spermatozoa in the blackspot sea bream Pagellus bogaraveo (Brünnich, 1768) with some considerations about the centriolar complex

Scanning and transmission electron microscopy were used to investigate the fine structure of the sperm of the sparid fish Pagellus bogaraveo.The spermatozoon of P. bogaraveo belongs, like that of the other sparid fish, to the teleostean “type I” spermatozoon with the flagellar axis insert perpendicular to the nuclear fossa. It has an ovoidal head, a short, cylindrically shaped midpiece and a long tail region. The nucleus reveals a deep invagination (nuclear fossa), in which the centriolar complex is located, and a satellite nuclear notch shaped like a golf club. The two centrioles are perpendicular to each other and show a conventional “9+0” pattern. The distal centriole is attached to the nuclear envelope by means of basal feet and radial fibers made of electron-dense material. Below the basal plate, plasma membrane pinches in, and the necklace, a specialized connection joining axonemal doublets to the plasma membrane, is visible. The short midpiece houses one mitochondrion. The flagellum is perpendicularly and eccentrically with respect to the nucleus and contains the conventional “9+2” axoneme.     

Zebrafish as a model organism for nutrition and growth: towards comparative studies of nutritional genomics applied to aquacultured fishes

Zebrafish (Danio rerio) is a common research model in fish studies of toxicology, developmental biology, neurobiology and molecular genetics; it has been proposed as a possible model organism for nutrition and growth studies in fish. The advantages of working with zebrafish in these areas are their small size, short generation time (12–14 weeks) and their capacity to produce numerous eggs (100–200 eggs/clutch). Since a wide variety of molecular tools and information are available for genomic analysis, zebrafish has also been proposed as a model for nutritional genomic studies in fish. The detailed study of every species employed as a model organism is important because these species are used to generalize how several biological processes occur in related organisms, and contribute considerably toward improving our understanding of the mechanisms involved in nutrition and growth. The objective of this review is to show the relevant aspects of the nutrition and growth in zebrafish that support its utility as a model organism for nutritional genomics studies. We made a particular emphasis that gene expression and genetic variants in response to zebrafish nutrition will shed light on similar processes in aquacultured fish.     

Differences in spatio-temporal behavior of zebrafish in the open tank paradigm after a short-period confinement into dark and bright environments

The open tank paradigm, also known as novel tank diving test, is a protocol used to evaluate the zebrafish behavior. Several characteristics have been described for this species, including scototaxis, which is the natural preference for dark environments in detriment of bright ones. However, there is no evidence regarding the influence of "natural stimuli" in zebrafish subjected to novelty-based paradigms. In this report, we evaluated the spatio-temporal exploratory activity of the short-fin zebrafish phenotype in the open tank after a short-period confinement into dark/bright environments. A total of 44 animals were individually confined during a 10-min single session into one of three environments: black-painted, white-painted, and transparent cylinders (dark, bright, and transparent groups). Fish were further subjected to the novel tank test and their exploratory profile was recorded during a 15-min trial. The results demonstrated that zebrafish increased their vertical exploratory activity during the first 6-min, where the bright group spent more time and travelled a higher distance in the top area. Interestingly, all behavioral parameters measured for the dark group were similar to the transparent one. These data were confirmed by automated analysis of track and occupancy plots and also demonstrated that zebrafish display a classical homebase formation in the bottom area of the tank. A detailed spatio-temporal study of zebrafish exploratory behavior and the construction of representative ethograms showed that the experimental groups presented significant differences in the first 3-min vs. last 3-min of test. Although the main factors involved in these behavioral responses still remain ambiguous and require further investigation, the current report describes an alternative methodological approach for assessing the zebrafish behavior after a forced exposure to different environments. Additionally, the analysis of ethologically-relevant patterns across time could be a potential phenotyping tool to evaluate the zebrafish exploratory profile in the open tank task.     

Raw attitudes, wetland cultures, life-cycles: socio-cultural dynamics relating to Opisthorchis viverrini in the Mekong Basin

Opisthorchis viverrini is one of the most common and medically important food-borne parasites in the Lower Mekong area of Southeast Asia. As we learn more about its ecology, pathology and epidemiology we see the need to consider more deeply the socio-cultural dynamics with which food-borne species complexes are associated. This paper argues that the Mekong region is characterized by strong livelihoods and life-style associations within wetland ecosystems, which are inseparable from human eating habits (“raw attitudes”). Within the fish-rice economies of the region there are many long-cherished food cultures based on eating raw, semi-cooked and fermented fish dishes, which are known to lead to opisthorchiasis, and potentially cholangiocarcinoma. This paper examines evidence from northeast Thailand showing that dedicated health outreach campaigns do help to reduce prevalence of opisthorchiasis over time. For disease prevention and health education approaches to be most effective, they must be sensitive to culture, livelihood economics, gender, and age. Further integrative, inter-disciplinary and international research must incorporate the complex dynamics of parasite ecology, human behavior, socio-economics, and public health awareness.     

Convergent evolution of carrion and faecal scent mimicry in fly-pollinated angiosperm flowers and a stinkhorn fungus

Flowers of many angiosperms attract fly pollinators through mimicry of animal carrion and faeces. This phenomenon of “sapromyiophily” is also evident in the sporophytes of some mosses and fruiting bodies of “stinkhorn” fungi, both of which use flies as agents of spore dispersal. We studied the scent chemistry of a stinkhorn fungus (Clathrus archeri) and seven fly-pollinated plant species with foetid odours to determine the degree to which these organisms mimic the scent of carrion and faeces (reference scent samples were collected from rotting meat, a rat carcass and horse and dog faeces), as well as the degree of convergent evolution between the fungus and angiosperm flowers. We found that scents of both the fungus and angiosperms tended to contain compounds typical of carrion, such as oligosulphides, and of faeces, such as phenol, indole and p-cresol. This study provides compelling new evidence for mimicry of carrion and faeces, as well as a striking pattern of convergence in the putrid scents of the fungus and the angiosperms, relative to those of confamilial species. The syndrome of sapromyiophily thus encompasses at least two kingdoms (Plantae and Fungi) and provides an effective means of exploiting flies as agents of pollen and spore dispersal.