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Since Darwin's time, degree of ecological similarity between exotic and native species has been assumed to affect the establishment success or failure of exotic species. However, a direct test of the effect of exotic–native similarity on establishment of exotics is scarce because of the difficulty in recognizing failures of species to establish in the field. Here, using a database on the establishment success and failure of exotic fish species introduced into 673 freshwater lakes, we evaluate the effect of similarity on the establishment of exotic fishes by combining phylogenetic and functional information. We illustrate that, relative to other biotic and abiotic factors, exotic–native phylogenetic and functional similarities were the most important correlates of exotic fish establishment. While phylogenetic similarity between exotic and resident fish species promoted successful establishment, functional similarity led to failure of exotics to become established. Those exotic species phylogenetically close to, but functionally distant from, native fishes were most likely to establish successfully. Our findings provide a perspective to reconcile Darwin's naturalization conundrum and suggest that, while phylogenetic relatedness allows exotic fish species to pre-adapt better to novel environments, they need to possess distinct functional traits to reduce competition with resident native fish species.

Aim: The enemy release hypothesis (ERH) posits that exotic species suffer less enemy damage than natives, which promotes their successful invasion. However, the generality of less damage for exotics remains widely debated. A recent view proposes that enemy release (ER) could change systematically with latitude, potentially helping to explain these inconsistencies. Here, we test whether exotic plant species suffer consistently lower herbivore damage relative to natives and whether ER varies with latitude. Location: Global. Time period: 1960–2018. Major taxa studied: Plants. Methods: Using leaf herbivory data for 1,098 plant species, we compared the herbivory rate between exotic and native plants across all taxa, between the introduced and native range of exotic species and between exotic and native species co-occurring in the same community. We tested the interaction effect between origin (exotic versus native) and latitude to assess variation in ER with latitude. We also examined whether the effect of origin and its interaction with latitude changed with plant growth form (woody versus non-woody). Finally, based on two ER effect-size datasets, two meta-regressions were performed to demonstrate the relationship between ER and latitude. Results: Leaf herbivory rates were commonly lower for exotics than for natives. However, this differential herbivory rate was significant only for woody plants. No significant interactions were found between origin and latitude, indicating that ER did not change with latitude. The meta-regressions also demonstrated that ER was not significantly correlated with latitude. Main conclusions: The widespread lower herbivory rate for exotic compared with native woody plant species supports the ERH for exotic woody plants. Consistent ER with latitude indicates that ER should play a similar role regardless of latitude. One future challenge is to assess the extent to which ER in woody exotic plants translates to performance advantages and thereby influences their invasion success.

Background Asian arowana, Scleropages formosus, is one of the most expensive aquarium fish species worldwide. Its sex, however, cannot be distinguished clearly at any development stage, which impedes captive breeding and species protection for this endangered aquarium fish. Results To discover molecular clues to the sex of Asian arowana, we sequenced 26.5 Gb of PacBio HiFi reads and 179.2 Gb of Hi-C reads for 1 male fish and also sequenced 106.5 Gb of Illumina reads, 36.0 Gb of PacBio Sequel reads, and 80.7 Gb of Hi-C reads for 1 female individual. The final male and female genome assemblies were approximately 756.8 Mb and 781.5 Mb in length and contained 25,262 and 25,328 protein-coding genes, respectively. We also resequenced the genomes of 15 male and 15 female individuals with approximately 722.1 Gb of Illumina reads. A genome-wide association study identified several potentially divergent regions between male and female individuals. In these regions, cd48 and cfap52 could be candidate genes for sex determination of Asian arowana. We also found some structural variations in few chromosomes between male and female individuals. Conclusion We provided an improved reference genome assembly of female arowana and generated the first sequenced genome of 1 male individual. These valuable genetic resources and resequencing data may improve global aquarium fish research.

Intraspecific variation in stoichiometric traits was thought to be an adaptive response to reduce the elemental imbalance between organism and diet in the habitat. Studying the spatial variation of stoichiometric traits of non-native species and the factors contributing to the variation could help to better understand the invasion mechanism of non-native fish. In this study, stoichiometric traits (i.e. carbon [C], phosphorus [P], calcium [Ca] and their ratios) variation in the body and organs of non-native sailfin catfishes

In the last few decades, non-native freshwater fishes have been introduced all over the world for economic purposes, including aquaculture and aquarium trade, as well as improvement for wild stocks resulting in adverse environmental and socio-economic effects. The Guangdong province of China is at a high risk of fish invasions owing to its warm and humid climate, abundance of water courses, flourishing aquaculture and ornamental fish trade, and extensive sea ports. A total of 160 non-native freshwater species were introduced in the Guangdong province and 71.9% of them were imported for aquarium purposes. Fourteen species have established self-sustaining populations and 21 species were found in the main river basin of the Guangdong province. Propagule pressure, rapid evolution and abundant resources in the environment were the factors likely to contribute to successful invasion by non-native fishes. The invasion of non-native fishes in the Guangdong province has already resulted in economic losses, decline of native species, as well as negative impacts on the functional diversity of native fish assemblages. To mitigate these effects and prevent future non-native fish invasions, scientists, policy makers and stakeholders should collaborate on the management of non-native fish introductions by developing risk assessments, statutory regulations, public education and scientific research.

Alien fishes are regarded as one of the major causes of the decline of aquatic fauna and biodiversity. Up to now, more than 500 fish species have been introduced into China from other countries. However, nationwide documentation of the established alien fishes is still lacking and their ecological risk is unclear. We compiled a comprehensive inventory of the colonized alien fish species based on various sources, and then provided a summary of their potential ecological risk. The results indicated that 68 alien fish species (13.44%) have successfully established in the natural waters. These species belong to 12 orders and 29 families. Among them, 56 species (82.35%) were introduced for aquaculture purposes, 11 species (16.18%) were introduced for aquarium and one species (1.47%) was introduced for bio-control. Over 85% of the established fishes were introduced after the 1970s. Geographically, these species are native to 12 regions around the world. Eighteen species and two hybrid species are native to North America which is the most dominant donor. Among these species, 61 can live in freshwater, 41 species can live in brackish and 19 species can live in marine water. Although large number of species, high taxonomic diversity, intensive human activity, diverse geographical origins and high adaptability of non-native species may lead to the increase of invasion risk, previous research about invasive risk just focus on the general impact of aquaculture activities, invasiveness screening using semi-quantitative models and distribution prediction using species distribution models. Further studies will need to be conducted on comprehensive risk assessment, ecological interaction between non-native fish and new environment, on fish species, ecosystem, the impact of human activity and global change on non-native fish colonization.

Non-native fish invasions are among the greatest threats to the sustainability of freshwater ecosystems worldwide. Tilapia and catfish are regularly cultured in South China which is similar to their climate in native areas and may also support their invasive potential. We systematically collected fish from eight main rivers of South China, from 2016 to 2018, to investigate and analyse species&rsquo, composition and the distribution of non-native fishes. The data reveal that non-native fishes are widespread and abundant in the sampled rivers: of the 98,887 fish collected, 11,832 individuals representing 20 species were not native, which were distributed in the 96% sampled sites. Of the non-native fish species, 17 are used in aquaculture and 19 are native to the tropics, 13 are omnivores while the other seven are predators. Based on dissimilarity of the non-native fish species distributions across the eight rivers, the different rivers could be divided into four assemblages. Geographical isolation and temperature were identified as affecting the distribution patterns of non-native fishes, thereby influencing fish species composition, species number, dominant species, and distribution variations in the South China rivers. Species composition of the non-native fishes in these rivers are related to their introduction vector, compatibility with their native habitat, and feeding strategies. Their distribution was mainly influenced by geographical location and temperature. To mitigate the impacts of non-native fish, a series of stricter management practices, systematic monitoring, and more research are needed.

Tilapia is one of the groups of fish species most widely cultured globally. China has been the largest producer of tilapia in the world since 1990s. Guangdong Province produces almost 40% of all tilapia in China because of its suitable geography and weather conditions, and tilapia culture has brought considerable economic benefits. Unfortunately, many of the biological traits that make tilapia popular for culture also contribute to its success as an invader. Tilapia has invaded natural waters and has become the dominant fish in many rivers of Guangdong Province, causing economic loss in capture fisheries, and affecting native fish species, biodiversity and aquatic ecosystems. Poor fishery management, water quality degradation and biodiversity loss have all facilitated the tilapia invasion. Tilapia have filled the niches left vacant by now locally extinct native species resulting from environmental changes in freshwater ecosystems of the province. The introduction of tilapia has both advantages and disadvantages, which should be managed to use effectively the various tilapia species in aquaculture while controlling their spread in natural waters.

Invasive species are a major and growing threat to China’s native freshwater biodiversity. They have caused species extinctions, biodiversity loss, and environmental changes. Mrigal carp (Cirrhinus mrigala), one of the most widespread and invasive of freshwater fish species, now occurs in major rivers throughout southern China. We report the current (to 2017) distribution of mrigal carp throughout southern China, and experiments with temperature, water quality and food availability, that assess possible impacts of this species on populations of native mud carp (C. molitorella)”. In the wild, the mud carp to mrigal carp weight ratio was 1:1.65. Mrigal carp were a dominant species in some rivers of southern China, such as Liuxi River, Zengjiang River and the Zhaoqing section of Xijiang River. Manipulative experiments reveal mrigal carp to be more tolerant of colder temperature, more eutrophic conditions, and lower dissolved oxygen levels than mud carp. In food-limited experiments, mrigal carp displayed no direct aggression towards mud carp, but they did snatch food from them, and excluded them from eating. Mud carp growth was curtailed in the presence of mrigal carp in food-limited treatments, with a growth rate 2.71%, only 17.02% of that in treatments where carp were fed to satiation. In satiation treatments, mrigal carp also grew up to 2.21 times faster than mud carp. Our results indicate that mrigal carp will outcompete mud carp for resources and habitat, and that both its distribution and population will increase in the future.

Human-induced fish introduction in aquaculture always be considered the most important driver of biological invasions in freshwater ecosystems, yet most introduced species fail to establish though having great economic benefits. Explaining the varying success of introduced fish species is a central question both in invasion biology and aquaculture management. Southern China is a good region to test the invasion hypotheses where lots of non-native fish species were cultured and invaded. In this study, we used four human activities related to aquaculture to test their effects on the establishment of non-native fish species in the rivers of southern China. Our results showed that: open-water aquaculture significantly increased the establishment probabilities of non-native species relative to standardised aquaculture in ponds; the establishment and spread of non-native fish species in rivers had no significant correlation to their production and distribution in standardised aquaculture; non-native fish species with low economic value were more prone to escape and establishment in natural rivers, and had higher establishment probabilities in rivers due to the lower fishing pressure. These results indicate that standardised aquaculture and cultivated species with high economic value do not always result in biological invasions. To mitigate the invasion of exotic species caused by aquaculture, stricter management practices and more optimized economic assessments should be implemented for the introduction and cultivation of non-native fish species.

Competitive interactions not only exist between invasive and native fish species but also between different invasive species, especially between those that have broad niche overlap. Nile tilapia (Oreochromis niloticus) and Redbelly tilapia (Tilapia zillii) are the most common invasive tilapia species in the rivers of South China. There may be specific factors that influence their competitive interactions and disturbance patterns, and temperature has been considered the most important factor. To study how temperature affects the distribution patterns and competitive interactions of these two invasive tilapia species, field surveys and laboratory experiments were conducted. Field surveys showed that latitude affected the ratio but not the biomass of all tilapia species. Nile tilapia was more abundant in the southern (warmer) sites, and Redbelly tilapia was more abundant in the northern (colder) sites. The distribution patterns of the two tilapia species were also related to latitude and minimum winter temperature. The results of the laboratory-based temperature experiments further confirmed that Redbelly tilapia can tolerate lower temperatures than Nile tilapia. However, the Nile tilapia were larger in field surveys, and laboratory experiments also showed that Nile tilapia are stronger competitors in warmer water because of their larger body size. Therefore, we suggest that the distribution patterns of these two invasive tilapia species were related to temperature conditions.

Although a large number of fish species have been introduced into Guangdong Province in Southern China, a few species, such as tilapia (Tilapia spp.), North African catfish Clarias gariepinus Burchell, mrigal carp, Cirrhinus mrigala (Bloch) and the sucker mouth catfish (Hypostomus sp.), have established natural populations and can be considered “successful invaders” in large rivers. The specific mechanisms underlying these contrasting results among different introduced fish species remain understudied. The relationship between multiple abiotic–biotic factors and the success of four invasive species was investigated using survey data for the Guangdong Province river ecosystem. In contrast to previous studies that have considered species-specific traits, the focus was on economic, ecological and anthropogenic factors to predict invasion success. Four main predictive indicators were found: (1) successful invaders were of low or no commercial value; (2) successful invaders tolerated a wide range of environmental conditions, including poor water quality; (3) biodiversity loss accelerated the growth of non-native populations; (4) human disturbance facilitated population growth and spread of invasive fish species. To lessen the impacts of invasive fish species, the selection of breeding species and breeding areas, maintenance of water quality and reduction in water pollution, protection of the diversity of fish species and reduction of human interference should be addressed.

Alien fishes are regarded as one of the major causes of the decline of aquatic fauna and biodiversity. Up to now, more than 500 fish species have been introduced into China from other countries. However, nationwide documentation of the established alien fishes is still lacking and their ecological risk is unclear. We compiled a comprehensive inventory of the colonized alien fish species based on various sources, and then provided a summary of their potential ecological risk. The results indicated that 68 alien fish species (13.44%) have successfully established in the natural waters. These species belong to 12 orders and 29 families. Among them, 56 species (82.35%) were introduced for aquaculture purposes, 11 species (16.18%) were introduced for aquarium and one species (1.47%) was introduced for bio-control. Over 85% of the established fishes were introduced after the 1970s. Geographically, these species are native to 12 regions around the world. Eighteen species and two hybrid species are native to North America which is the most dominant donor. Among these species, 61 can live in freshwater, 41 species can live in brackish and 19 species can live in marine water. Although large number of species, high taxonomic diversity, intensive human activity, diverse geographical origins and high adaptability of non-native species may lead to the increase of invasion risk, previous research about invasive risk just focus on the general impact of aquaculture activities, invasiveness screening using semi-quantitative models and distribution prediction using species distribution models. Further studies will need to be conducted on comprehensive risk assessment, ecological interaction between non-native fish and new environment, on fish species, ecosystem, the impact of human activity and global change on non-native fish colonization.

Tilapias are now the most common alien fish in the rivers of South China and the dominant species in many sites. However, wild tilapia species have not been well-characterized or studied systematically. In this study, mitochondrial DNA control regions (mtDNA CR) and morphological characteristics were used to identify invasive tilapia species. Using mtDNA CR sequence, we identified Oreochromis niloticus , Tilapia zillii , Oreochromis aureus , Sarotherodon galilaeus , and hybrids of Oreochromis mossambicus and O. niloticus in the rivers of South China, and characterized their morphological features. Of the 5 species, O. niloticus and T. zillii were the most abundant in the rivers of South China. Furthermore, the distribution of O. niloticus may be related to their large numbers in the aquaculture industry, and the explosion of T. zillii invasion may be related to their strong capacity for environmental adaptation. These findings are beneficial for identifying wild tilapia populations and for the specific control of invasive tilapia species.

Adult sex ratio (ASR) has critical effects on behavior and life history and has implications for population demography, including the invasiveness of introduced species. ASR exhibits immense variation in nature, yet the scale dependence of this variation is rarely analyzed. In this study, using the generalized multilevel models, we investigated the variation in ASR across multiple nested spatial scales and analyzed the underlying causes for an invasive species, the golden apple snail Pomacea canaliculata. We partitioned the variance in ASR to describe the variations at different scales and then included the explanatory variables at the individual and group levels to analyze the potential causes driving the variation in ASR. We firstly determined there is a significant female‐biased ASR for this species when accounting for the spatial and temporal autocorrelations of sampling. We found that, counter to nearly equal distributed variation at plot, habitat and region levels, ASR showed little variation at the town level. Temperature and precipitation at the region level were significantly positively associated with ASR, whereas the individual weight, the density characteristic, and sampling time were not significant factors influencing ASR. Our study suggests that offspring sex ratio of this species may shape the general pattern of ASR in the population level while the environmental variables at the region level translate the unbiased offspring sex ratio to the female‐biased ASR. Future research should consider the implications of climate warming on the female‐biased ASR of this invasive species and thus on invasion pattern.

Evolutionary experience and the phylogenetic relationships of plants have both been proposed to influence herbivore–plant interactions and plant invasion success. However, the direction and magnitude of these effects, and how such patterns are altered with increasing temperature, are rarely studied. Through laboratory functional response experiments, we tested whether the per capita feeding efficiency of an invasive generalist herbivore, the golden apple snail, Pomacea canaliculata, is dependent on the biogeographic origin and phylogenetic relatedness of host plants, and how increasing temperature alters these dependencies. The feeding efficiency of the herbivore was highest on plant species with which it had no shared evolutionary history, that is, novel plants. Further, among evolutionarily familiar plants, snail feeding efficiency was higher on those species more closely related to the novel plants. However, these biogeographic dependencies became less pronounced with increasing temperature, whereas the phylogenetic dependence was unaffected. Collectively, our findings indicate that the susceptibility of plants to this invasive herbivore is mediated by both biogeographic origin and phylogenetic relatedness. We hypothesize that warming erodes the influence of evolutionary exposure, thereby altering herbivore–plant interactions and perhaps the invasion success of plants.

Flatfishes (Pleuronectiformes) exhibit different types of large-scale gene rearrangements. In the present study, the mitochondrial (mt) genome (18,369bp) of a tonguefish, Cynoglossus trigrammus, was determined using de novo mitochondrion genome sequencing. Compared with other flatfishes, the mt genome of C. trigrammus revealed distinct mitogenome architectures that primarily included two striking findings: 1) insertion of an additional long non-coding region (1647bp) making it the second largest genome length among Pleuronectiformes and 2) the translocation of the control region. The reconstructed phylogenetic tree based on 13 mt protein-coding gene sequences recovered the monophyletic suborder Pleuronectoidei and the family Cynoglossidae. These data provide useful information for a better understanding of the mitogenomic diversities and evolution in fish as well as novel genetic markers for studying population genetics and species identification.

Snails are a kind of important aquatic products and dehydration is the main technique in production of snail meal. Apple snail (Pomacea canaliculata) dehydration meets both the demand for a fishmeal substitute in aquaculture and invasive species control in agriculture. In this study, we investigated the percentage of the nutritive material, examined the drying characteristics at 60, 80, 100 and 120°C, respectively, established a drying kinetics model and explored the effect of body morphology on drying efficiency. The results showed that the wet weight percentage of the soft parts was 46.61±6.18%. The drying efficiency was significantly improved with an increase of drying temperature from 60 to 120°C. The drying time increased rapidly when the final moisture content approached its equilibrium value. The Hii et al. model was selected as the best model to describe the drying curves (R 2 >0.99). It provided a relatively accurate prediction between the requirements of moisture content and drying time. There were statistically significant differences (p

Nile tilapia (Oreochromis niloticus) is one of the most widespread invasive fish species, and this species has successfully established populations in the major rivers of Guangdong Province, China. Field surveys and manipulative experiments were conducted to assess the impacts of Nile tilapia on fisheries. We determined that the increase of Nile tilapia in these rivers not only affects the CPUE (catch-per-unit-per-effort) of the fish community and native fish species but also reduces the income of fishermen. In the manipulative experiments, we observed that the growth of native mud carp decreased in the presence of Nile tilapia. Our results suggest that the invasion of Nile tilapia negatively affected the fishery economy and native fish species, and suitable control measurements should be taken.

In this study, we sequenced and assembled the mitochondrial (mt) genome of Osteoglossum ferreirai to re-assess the phylogenetic relationship of the family Osteoglossidae. We determined that the mitogenome of O. ferreirai contains the entire set of 37 mt genes, and the nucleotide composition and gene arrangement were similar to those of other bonytongues. Our phylogenetic analyses exhibited monophyly of the family Osteoglossidae with high bootstrap support, which is in agreement with the currently accepted phylogenetic viewpoint that is based on both morphological and molecular approaches. These findings provide additional informative data for the further study of phylogenetic relationships and help to elucidate a key component of the species radiation process within the family Osteoglossidae.

Ten microsatellites were used to assess the genetic diversity and genetic differences of six wild Oreochromis spp. populations in the primary rivers of Guangdong Province of China, where natural populations have been established. Significant genetic differentiation was observed in Oreochromis spp. populations using “FST” and exact tests. The six populations can be divided into two groups based on the genetic similarity indices. The phylogenetic tree indicated that the HUI (Huizhou) and the SG (Shaoguan) populations formed one cluster, whereas the H (Huazhou), M (Meihua), MU (Muzhou), and ZQ (Zhaoqing) populations formed another cluster. The average mean levels of the observed heterozygosity in the six populations were 0.3972, 0.4264, 0.6977, 0.6335, 0.6680, and 0.6829, respectively. The high genetic diversity observed in most wild tilapia populations suggests that most wild populations are large in size, which is a finding that is supported by field investigations.

Heat-shock protein 70 (HSP70) is one of the most important heat-shock proteins that helps organisms to modulate stress response via over-expression. The HSP70 gene from Pomacea canaliculata was cloned using the RACE approach; the gene is 2,767 bp in length and contains an open reading frame of 1,932 bp, which is encoded by a polypeptide of 643 amino acids. BLAST analysis showed that the predicted amino acid sequence of the P. canaliculata HSP70 gene shared a relatively high similarity with that of other known eukaryotic species that display conserved HSP characteristics. The phylogeny demonstrated a separate clustering of the apple snail HSP70 with other constitutive members from other mollusk species. Quantitative real-time RT-PCR was used to detect the differential expression of HSP70 in both sexes of P. canaliculata at different temperature conditions. These results showed that HSP70 transcript levels decreased slightly under cold shock and increased significantly under heat-shock conditions in both sexes compared to normal temperatures (26 °C). Under cold-shock treatment, the sex effect was not significant. With heat treatment, HSP70 expression could be induced at 36 °C in both females and males, and it peaked at 42 and 39 °C in females and males, respectively. In addition, a clear time-dependent HSP70 expression pattern of the apple snail exposed to the same high temperature (36 °C) was observed at different time points. The maximal induction of HSP70 expression appeared at 12 and 48 h in males and females after heat shock, respectively. The maximal induction in females was significantly higher compared to males under heat stimulus. Taken together, these results strongly suggested that males were more susceptible to heat than females and provided useful molecular information for the ecological adaptability of P. canaliculata against extreme environmental stress.

The genetic structure of the family Osteoglossidae from different geographical regions was examined using the nuclear 18S ribosomal RNA (18S rDNA) sequence. The results showed that the partial length of 18S rDNA was 1277 bp, and they were relatively conserved in the species of the family Osteoglossidae. A total of 62 (4.83%) polymorphic sites were observed, and 28 haplotypes were defined, which were characterized by different haplotype diversity (0.00105–0.900) and nucleotide diversity (0.00321–3.000). Analysis of molecular variance (AMOVA) showed genetic divergence of these species (79.76%). Phylogenetic analysis revealed that 18S rDNA was a suitable genetic marker and was able to distinguish phylogenetic relationships among different Osteoglossidae species, and it also supported current taxonomy. In addition, low genetic diversity of several species provides genetic assessment information and should be taken into consideration to implement a conservation management planning for some species, such as Scleropages formosus green arowana.

Background Mitochondrial (mt) genome sequences are widely used for species identification and to study the phylogenetic relationships among Gastropoda. However, to date, limited data are available as taxon sampling is narrow. In this study we sequenced the complete mt genomes of the freshwater gastropods Radix swinhoei (Lymnaeidae) and Planorbarius corneus (Planorbidae). Based on these sequences, we investigated the gene rearrangement in these two species and the relationships with respect to the ancestral gene order and assessed their phylogenetic relationships. Methods The complete mt genomes of R. swinhoei and P. corneus were sequenced using Illumina-based paired-end sequencing and annotated by comparing the sequence information with that of related gastropod species. Putative models of mitochondrial gene rearrangements were predicted for both R. swinhoei and P. corneus , using Reishia clavigera mtDNA structure as the ancestral gene order. The phylogenetic relationships were inferred using thirteen protein sequences based on Maximum likelihood and Bayesian inference analyses. Results The complete circular mt genome sequences of R. swinhoei and P. corneus were 14,241 bp and 13,687 bp in length, respectively. Comparison of the gene order demonstrated complex rearrangement events in Gastropoda, both for tRNA genes and protein-coding genes. The phylogenetic analyses showed that the family Lymnaeidae was more closely related to the family Planorbidae, consistent with previous classification. Nevertheless, due to the position recovered for R. swinhoei , the family Lymnaeidae was not monophyletic. Conclusion This study provides the complete mt genomes of two freshwater snails, which will aid the development of useful molecular markers for epidemiological, ecological and phylogenetic studies. Additionally, the predicted models for mt gene rearrangement might provide novel insights into mt genome evolution in gastropods.

Fast expansion of aquaculture in China largely relies on the introduction and use of non-native species. However, the introduction and use of non-native species may have negative impacts on local ecosystems and societies. Clarias gariepinus has been widely farmed in China after introduced in 1980 from Africa. However, during aquaculture, this fish species has escaped from farm facilities to the wild. So far, we have little knowledge on the invasion status of this non-native fish in China. In this Chapter, we review the introduction, spread and impacts of C. gariepinus in China, as well as present potential management strategies for this alien fish. Multiple lines of evidence indicate that C. gariepinus has been widely distributed and established population in China and the negative impacts of this alien fish in local ecosystems have been detected. Therefore, we suggest that suitable risk assessment and early waning programs should be well developed to prevent the spread and species-specific fishing tools could be designed to control this alien fish in the wild. We also call for deep investigations on mechanisms of invasions and the technologies of management for C. gariepinus, as well as government and aquaculture industry for proper risk assessment and sound management for sustainable development of aquaculture.

Summary of Radix swinhoei and Planorbarius corneus using Illumina sequencing. Table S2. General characteristics of the mitochondrial genomes of various members of pulmonate gastropods. Table S3. Nucleotide composition and AT- and GC-skews of the mitochondrial protein-coding and ribosomal RNA genes in the complete Radix swinhoei mt genome. Table S4. Nucleotide composition and AT- and GC-skews of the mitochondrial protein-coding and ribosomal RNA genes in the complete Planorbarius corneus mt genome. Table S5. Codon usage of Radix swinhoei mitochondrial protein-coding genes. Table S6. Codon usage of Planorbarius corneus mitochondrial protein-coding genes. Figure S1. Comparison of AT and GC skews among the 30 pulmonate species in Table S2. Circles and triangles separately represent AT and GC skews of the complete mitochondrial genomes. Figure S2. Gene specific strand composition of mitochondrial genome in Radix swinhoei and Planorbarius corneus. Figure S3. Graphical summary of nucleotide composition across complete mitochondrial genomes. Figure S4. Percentage of synonymous codon usage for each amino acid in Radix swinhoei and Planorbarius corneus mitochondrial protein-coding genes. Figure S5. Linear comparison of the gene distribution pattern of mitochondrial genomes between Radix swinhoei and Planorbarius corneus. (DOC 1430Â kb)

Nile tilapia Oreochromis niloticus (L.) is one of the most widely cultured and most widespread invasive fish species globally. It was the most common alien fish species in South China where it has successfully established populations in the major rivers, and became the dominant species in many sites. The distribution of Nile tilapia in the wild in China is limited by the temperature and the biodiversity of native fish, so it was abundant in the rivers with lower biodiversity in South China. A series of ecological problems may have caused by the increase of Nile tilapia, such as the decrease of the CPUE (catch-per-unit-per-effort) and the income of fishermen, influence on growth of native fish species, increase of the fishing pressure on native species, and decrease of the water transparency and water quality. In order to control the population of the Nile tilapia in the wild, an organophosphate drug called “Mie fei ling” was developed and used. Meanwhile, science popularization has been used to strengthen the understanding of the public and to avoid Nile tilapia to be released and escaped from aquaculture. In order to reduce the ecological impact, more investigations should be conducted and suitable control methods should also be determined for this invasive species.

Asian arowana (Scleropages formosus), an ancient teleost belonging to the Order Osteoglossomorpha, has been a valuable ornamental fish with some varieties. However, its biological studies and breeding germplasm have been remarkably limited by the lack of a reference genome. To solve these problems, here we report high-quality genome sequences of three common varieties of Asian arowana (the golden, red and green arowana). We firstly generated a chromosome-level genome assembly of the golden arowana, on basis of the genetic linkage map constructed with the restriction site-associated DNA sequencing (RAD-seq). In addition, we obtained draft genome assemblies of the red and green varieties. Finally, we annotated 22,016, 21,256 and 21,524 protein-coding genes in the genome assemblies of golden, red and green varieties respectively. Our data were deposited in publicly accessible repositories to promote biological research and molecular breeding of Asian arowana.

Quantifying the per capita effects of invasive alien species is crucial for assessing their ecological impact. A major challenge to risk assessment of invasive species was to understand the factors that cause per capita effects to vary in different ecological contexts, particularly in a warming world. By conducting functional response experiments, we estimated the per capita effects (attack rate and maximum feeding rate) of an invasive herbivorous snail, Pomacea canaliculata, toward ten host plant species. We tested whether variation in these effects is related to plant nutritional and physical properties (total N and dry matter content (DMC)) and examined how increasing temperature can shift these relationships. We observed stronger per capita effects (i.e., higher attack rate and maximum feeding rate) by the snail on plants with higher total N, but no direct relationship was found with DMC. A significant interaction effect of total N and DMC on the attack rate indicated that DMC probably adjusted the feeding indirectly. Warmer temperatures reduced correlations between snail functional responses and host plant nutritional properties (total N) by increasing maximum feeding rate for plants of low nutrition, but there was no such effect on attack rates. However, given the nonreplacement design used in our study, the nonsignificant effect of temperature on the attack rate should be caveated. Our result suggests that characterizing the per capita effects of herbivores using functional responses can reveal the mechanisms by which climate change may alter herbivore–plant interactions and, thus, the ecological impacts of introduced herbivores.

The Asian arowana (Scleropages formosus), one of the world’s most expensive cultivated ornamental fishes, is an endangered species. It represents an ancient lineage of teleosts: the Osteoglossomorpha. Here, we provide a high-quality chromosome-level reference genome of a female golden-variety arowana using a combination of deep shotgun sequencing and high-resolution linkage mapping. In addition, we have also generated two draft genome assemblies for the red and green varieties. Phylogenomic analysis supports a sister group relationship between Osteoglossomorpha (bonytongues) and Elopomorpha (eels and relatives), with the two clades together forming a sister group of Clupeocephala which includes all the remaining teleosts. The arowana genome retains the full complement of eight Hox clusters unlike the African butterfly fish (Pantodon buchholzi), another bonytongue fish, which possess only five Hox clusters. Differential gene expression among three varieties provides insights into the genetic basis of colour variation. A potential heterogametic sex chromosome is identified in the female arowana karyotype, suggesting that the sex is determined by a ZW/ZZ sex chromosomal system. The high-quality reference genome of the golden arowana and the draft assemblies of the red and green varieties are valuable resources for understanding the biology, adaptation and behaviour of Asian arowanas.

The present study examined the genetic variation of the family Osteoglossidae from different geographical locations based on the mitochondrial NADH dehydrogenase subunit 2 (ND2) and ATPase subunit 6 (ATPase6) genes; we then re-constructed the phylogenetic relationships using the two sequences in combination. The results showed that the partial sequences of mitochondrial ND2 and ATPase6 of the family Osteoglossidae were 813 bp and 669 bp, respectively. A total of 42 species-specific nucleotide positions of the family Osteoglossidae were found to be useful for molecular identification. The sequence variation showed greater differences (8.3%~28.1% for the combined sequences, 8.3%~26.7% for the ND2 gene, and 9.3%~28.7% for the ATPase6 gene) among the different species of Osteoglossidae, and there was a significant association between the genetic difference and geographical location. Phylogenetic analyses using neighbor-joining, Bayesian inference, and maximum parsimony (MP) methods based on the combined sequences of the two genes were able to distinguish the different species and were in agreement with the existing taxonomy based on morphological characters and in association with the geographical distribution among seven species of the family Osteoglossidae.

The present study examined the genetic variation in the mitochondrial 12S rRNA, 16S rRNA and cytochrome c oxidase subunit 3 (cox3) genes among three varieties of Scleropages formosus, and their phylogenetic relationships were constructed. Among all the examined isolates of S. formosus, sequence variation ranged from 0 to 1.66% for 12S, from 0 to 2.4% for 16S and from 0 to 3.2% for pcox3. AMOVA analysis of the three mtDNA genes showed that the majority of the total molecular variation occurred among varieties within the groups (55.6%) with 48.4% of variation within the varieties. Additionally, a significant genetic differentiation (P < 0.05) was revealed within S. formosus. Phylogenetic analysis based on the combined sequences showed that all S. formosus clustered together and effectively grouped the green arowanas together. These results demonstrate that the three mtDNA sequences are polymorphic but are not suitable markers for comparing the genetic relationships among the different varieties of S. formosus.

This study examined the effect of sodium taurocholate as a feed additive on the pigmentation efficacy of astaxanthin in blood parrot (Cichlasoma synspilum ♀ × Cichlasoma citrinellum ♂). A total of 396 fish were divided into six treatment groups with three replicates per treatment. The following experimental treatments were used: a basal diet (A) without astaxanthin; one diet (B) with 4‰ of astaxanthin; one diet (C) with only sodium taurocholate (600 mg/kg); and three diets with 4‰ astaxanthin plus sodium taurocholate (D, 400 mg/kg; E, 1200 mg/kg; F, 2000 mg/kg). Six fish per group were sampled at 15, 30 and 45 days. At the end of the experiment, the carotenoid content of the skin and the caudal fin in blood parrot fed with a supplementation of sodium taurocholate plus 4‰ astaxanthin was significantly higher than the corresponding values for the fish fed with 4‰ astaxanthin only (P

Insulin-like growth factor I (IGF-1) plays an important role in fish growth and development. As the promoter of IGF-I regulates the expression of IGF-I, polymorphisms in the promoter region could be functionally important to differences in IGF-I expression and function. In this study, the 5′ flanking region (1,770 bp) of the largemouth bass IGF-I gene was cloned, sequenced and characterized. Several putative liver-enriched transcriptional factor binding sites, including HNF-1α, HNF-3β and C/EBP, were found to have multiple copies in the promoter sequence of the largemouth bass IGF-I gene. It did not contain consensus TATA, CCAAT-like or GAGA sequences. Sequencing of 5′ flanking sequences from individual fish revealed the presence of a deletion (GTTT) and two single-nucleotide substitutions, causing two different haplotypes: ATTTTTGTTTTT(A) and ATAATT—TT(B). The haplotypes were tested for their association with growth traits in a population of 91 largemouth bass individuals using polymerase chain reaction. The association analysis was carried out using a general linear model. Results showed the haplotypes had significant effects on body weight and body width (P < 0.05). The individuals with the AA genotype had significantly higher body weight and body width than those with the AB and BB genotypes (P < 0.05). Moreover, the effect of the genotypes on IGF-I mRNA expression in the liver was evaluated through the use of a semiquantitative RT-PCR method. The results showed that the IGF-I mRNA expression levels were affected by the promoter polymorphisms (P < 0.01), and that levels of IGF-I mRNA of the AA genotype in liver were greater than those of both the AB and the BB genotypes (P < 0.05 and P < 0.01). Our results implied that the IGF-I gene could be a potential quantitative trait nucleotide that affects growth traits in largemouth bass.

This study was conducted to evaluate the effect of alfalfa saponins on pigmentation induced by astaxanthin in 540 blood parrot fish (Vieja synspila ♀ × Amphilophus citrinellus ♂). The fish were divided into six treatment groups: basal diet; a diet supplemented with 3‰ astaxanthin; three diets with 3‰ astaxanthin plus 3‰, 6‰ or 12‰ alfalfa saponins respectively; and a diet supplemented with 4‰ alfalfa saponins alone. The fish were maintained in three aquaria per treatment. At 20, 40, 60, and 80 days, 6 blood parrot fish per aquarium were sampled. At the end of the experiment, the carotenoid content of scales, skin, and caudal fin in groups supplied with 3‰ astaxanthin plus alfalfa saponins were significantly higher than the control. The redness values, a*, of the body and caudal fins in these groups increased significantly. Conversely, the cholesterol and triglyceride content decreased significantly. Non-esterified fatty acid content and lysozyme activity were significantly higher in the three groups fed supplemented astaxanthin diets with the addition of alfalfa saponins, than the group fed a diet supplemented with 3‰ astaxanthin alone (P