Cyprinid Fish Species Research Articles

Fish morphology and passage through velocity barriers. Experience with northern straight-mouth nase (Pseudochondrostoma duriense Coelho, 1985) in an open channel flume

Knowing the relationship between size, morphological traits and swimming performance of fish is essential to understand the swimming capacity to successfully surpass these obstacles and the selective pressure that barriers in rivers and streams could exert on fish. Northern straight-mouth nase, an endemic potamodromous cyprinid fish species from the Northwest of the Iberian Peninsula, was selected to carry out volitionally swimming performance experiments in an open channel against three different flow velocities, using telemetry and video cameras. The use of thin-plate spline, on 10 landmarks, evidenced unknown patterns linked to velocity barriers. At lower flow velocity, size is the main factor explaining the swimming performance; thus, large individuals swim up more efficiently. In contrast, at high flow velocities, shape becomes the essential explanatory variable; thereby, streamlined body shapes with a higher relative position of the tail and a narrower caudal peduncle are more efficient. The obtained results show the existence of a relationship between fish morphology and swimming performance, with potential consequences due to selection pressures associated with velocity barriers and their implications on behavioural and dispersal processes. To sum up, velocity barriers could exert a selection pressure on nase populations, so the fishway design and removal should be (re)considered.

Expression profiles and functional characterization of common carp (Cyprinus carpio) T2Rs

Bitter taste perception is mediated by a family of G protein-coupled receptors (T2Rs) in vertebrates. Common carp (Cyprinus carpio), which has experienced an additional round of whole genome duplication during the course of evolution, has a small number of T2R genes similar to zebrafish, a closely related cyprinid fish species, and their expression pattern at the cellular level or their cognate ligands have not been elucidated yet. Here, we showed through in situ hybridization experiments, that three common carp T2R (ccT2R) genes encoding ccT2R200-1, ccT2R202-1, and ccT2R202-2, were specifically expressed in the subsets of taste receptor cells in the lips and gill rakers. ccT2R200-1 was co-expressed with genes encoding downstream signal transduction molecules, such as PLC-β2 and Gαia. Heterologous expression system revealed that each ccT2R showed narrowly, intermediately, or broadly tuned ligand specificity, as in the case of zebrafish T2Rs. However, ccT2Rs showed different ligand profiles from their orthologous zebrafish T2Rs previously reported. Finally, we identified three ccT2Rs, namely ccT2R200-1, ccT2R200-2, and ccT2R203-1, to be activated by natural bitter compounds, andrographolide and/or picrotoxinin, which elicited no response to zebrafish T2Rs, in a dose-dependent manner. These results suggest that some ccT2Rs may have evolved to function in the oral cavity as taste receptors for natural bitter compounds found in the habitats in a species-specific manner.

Effects of fasting on collective movement and fission-fusion dynamics in both homogeneous and heterogeneous shoals of a group-living cyprinid fish species.

The present study aimed to reveal the effect of fasting (21 days) on collective movement and interaction dynamics in both homogeneous (eight members fed a commercial diet or deprived of food) and heterogeneous (four fed + four starved members) shoals of juvenile qingbo (Spinibarbus sinensis). The authors of this study measured the shoaling behaviour in both a commonly used rectangular open arena with no spatial complexity and a radial arm maze. When measured in the open arena, the starved shoals had a faster swimming speed and acceleration rate and a longer interindividual distance than the fed shoals, possibly because of the elevated foraging motivation. Nonetheless, the values of the heterogeneous groups were similar to those of the fed groups. Furthermore, in contrast to the fish in homogeneous shoals, the starved fish in heterogeneous shoals showed a slower acceleration rate and speed than fed members in heterogeneous shoals. These results, combined with the relationships of variables at the among- and within-shoal levels, suggested that starved fish limited their motion in heterogeneous shoals to maintain group cohesion but that the fed fish contributed more to maintaining shoal structure, possibly because of the higher energy expenditure required for movement changes. When monitored in a radial arm maze, starved shoals showed more fission-fusion episodes without sacrificing group cohesion, as they adaptively adjusted the frequency and duration of each majority choice. The among-shoal variation revealed that the heterogeneous groups showed less variation in the open arena but more variation in the radius maze than did the homogeneous groups. This difference might arise because dominant members have opposite effects on shoal behaviour and consensus decisions. In conclusion, the present study showed opposite effects of feeding states on collective behaviour between homogeneous and heterogeneous shoals, possibly because of the complicated interactions among members with different energy storage levels and foraging motivations. Furthermore, the heterogeneous groups showed a difference between shoal behaviour in the open area and exploration in the radial arm maze. Future studies manipulating the personality composition of starved and fed members of heterogeneous groups might yield interesting results.

Comparison of macroinvertebrate assemblages in a stream before and after fine sedimentation by deer‐induced forest floor degradation

AbstractJapan's Sika deer (Cervus nippon) population has steadily increased since the 1990s. Consequent overgrazing of forest floor vegetation has created denuded slopes and increased the fine‐sediment input to nearby headstreams. Given the continuous structure of rivers, it is likely that upstream forest and headstream ecosystems ultimately impact the ecology of downstream ecosystems. To test this prediction, I investigated the taxonomic composition and habitat characteristics of stream macroinvertebrates before and after fine sedimentation infiltration. Fine sedimentation resulted in coverage of highly productive coarse substrates with fine sand and reduced the macroinvertebrate abundance and taxonomic diversity. These changes were influenced by habitat preference; taxa with coarse substrate preference decreased in abundance, while the abundance of taxa that prefer fine substrates increased. However, large armored caddisflies (Goera spp.) dominated after the fine sedimentation, despite their preference for coarse substrates. This rise likely results from the concurrent reduction in the number of the predatory cyprinid fish species, Tribolodon hakonensis, as large armored caddisflies have often been reported to be invulnerable to predation by fishes such as salmonids and sculpins. However, large cyprinids, which are abundant in Japanese rivers, can effectively forage “hard‐armored” organisms using their well‐developed pharyngeal teeth. Collectively the results provide insight regarding the catchment‐scale impacts of deer‐induced forest floor degradation and will help to inform conservation and management efforts.

SOME INFORMATION ON THE CARP FISH SPECIES FEEDING

The article presents the results of studies of feeding characteristics of such cyprinid fish species as the roach Rutilus rutilus caspius (Jakowlev, 1870) and the bream Abramis brama (Linnaeus, 1758) in various parts of the Daghestan coast of the Caspian Sea. The material was sampled along the entire Daghestan coast of the Caspian Sea, from the Kizlyar Bay to the mouth of the Samur river, in different biological seasons in the period of 2017–2018.

Length–weight relationship and condition factor of ten cyprinid fish species from the Caspian Sea, Urmia Lake and Persian Gulf basins of Iran

In this study, the length-weight relationships (LWRs) and condition factor (K) were estimated for 1334 specimens belonging to ten species including Acanthobrama marmid, A. microlepis, A. urmianus, Romanogobio persus, Leuciscus aspius, Luciobarbus capito, L. mursa, L. caspius, Alburnus atropatenae and Petroleuciscus ulanus from the Caspian Sea, Urmia Lake and Persian Gulf basins of Iran. The total length and weight of the individuals varied from 3.4 to 84.5 cm and 0.4 to 6600 g respectively. The values of the slope parameter (b) and condition factor ranged from 2.99 – 3.38 and 0.79 – 1.25 respectively. LWRs with high correlation coefficients were calculated for all species (R2 > 0.95). Based on the results, the allometric growth pattern of the studied species were positive except for L. aspius, L. capito, L. mursa and P. ulanus. This study provides useful data regarding the LWRs and condition factor of ten fish species in Iranian inland waters that can be used in fisheries management, stock assessment and future studies.

Diverse transcriptional patterns of homoeologous recombinant transcripts in triploid fish (Cyprinidae).

Homoeologous recombination (HR), the exchange of homoeologous chromosomes, contributes to subgenome adaptation to diverse environments by producing various phenotypes. However, the potential relevance of HR and innate immunity is rarely described in triploid cyprinid fish species. In our study, two allotriploid genotypes (R2C and RC2), whose innate immunity was stronger than their inbred parents (Carassius auratus red var. and Cyprinus carpio L.), were obtained from backcrossing between male allotetraploids of C. auratus red var.×C. carpio L. and females of their two inbred parents, respectively. The work detected 140 HRs shared between the two triploids at the genomic level. Further, transcriptions of 54 homoeologous recombinant genes (HRGs) in R2C and 65 HRGs in RC2 were detected using both Illumina and PacBio data. Finally, by comparing expressed recombinant reads to total expressed reads in each of the genes, a range of 0.1%-10% was observed in most of the 99-193 HRGs, of which six recombinant genes were classified as "response to stimulus". These results not only provide a novel way to predict HRs in allopolyploids based on cross prediction at both genomic and transcriptional levels, but also insight into the potential relationship between HRs related to innate immunity and adaptation of the triploids and allotetraploids.

Impacts of low-head hydropower plants on cyprinid-dominated fish assemblages in Lithuanian rivers

The meso-scale habitat simulation model MesoHABSIM was applied in three Lithuanian lowland rivers to study the effect of low-head hydropower plants (HPPs) on the fish habitats. Stream flow time series on a daily scale for the period 1970–2015 were used to describe flow regime downstream of HPPs for periods before and after their installation. Conditional habitat suitability criteria were developed for 4 species of cyprinid fish, schneider (Alburnoides bipunctatus), dace (Leuciscus leuciscus), roach (Rutilus rutilus) and vimba (Vimba vimba) to simulate their available habitat at different water discharges. Modelling results showed that HPPs have a significant impact on habitat availability in the low flow period in dry years below HPPs due to insufficient released flow. The environmental flow, as prescribed by the Lithuanian national law, is estimated between 80 and 95% exceedance probability of the mean minimum discharge of 30 days. This flow leads to a significant reduction in frequency and duration of available suitable habitats for vimba and schneider during low flow period. The roach habitat is the least affected. The results of habitat modelling are in line with the actual data on the occurrence and relative abundance of considered fish species in the studied river stretches. A general comparison of the relative abundance of modelled fish species in 42 natural river stretches and 20 stretches below the HPPs also showed that the relative abundance of roach is significantly higher, and that of schneider is significantly lower in river sections below the HPPs than the abundance in natural river sections. All results indicate that the current environmental flow does not secure survival of certain fish species. The applicability of the average low flow release during summer could be a plausible alternative to the current environmental flow in order to maintain ecosystem health and services.

Trends in morphological relationships among Gangetic Cyprinids

Cyprinidae is the predominant and most diverse taxonomic group of freshwater fishes, exhibiting enormous diversity in shape, size and biology. The morphological diversity of Indian Cyprinids especially the Gangetic Cyprinids is largely unquantified. Geometric morphometrics (GM) approach is an efficient tool to quantify overall body shape variations and has wide application in taxonomic, evolutionary and ecological studies. In this study, digital photographs of 47 Cyprinid fish species from Ganga River were used to measure geometric body shape so as to evaluate interspecific morphometric relationships. Combined results of principal component analysis (PCA), canonical variate analysis (CVA) and Cluster analysis (CA) revealed interspecific differences in Cyprinid fishes. Phenogram showed that all the species of different genus like Barilius, Garra, Labeo, Pethia, Schizothorax and Tor are clustered together in their respective group. This indicates that species of respective genus share common phenotypic traits and there is evolutionary relatedness among them. The present study showcases the efficient use of digital images and strongly supports the application of cost–effective GM method in discriminating distinct groups and representing the morphological relationships between species of Cyprinid fishes. Overall, we suggest that the body shape disparity and proximity among groups can therefore be used as an effective approach in rapid diagnosis of a species and understanding evolutionary relationships between species.

Chromosome-level genome assembly of a cyprinid fish Onychostoma macrolepis by integration of nanopore sequencing, Bionano and Hi-C technology.

Onychostoma macrolepis is an emerging commercial cyprinid fish species. It is a model system for studies of sexual dimorphism and genome evolution. Here, we report the chromosome-level assembly of the O.macrolepis genome obtained from the integration of nanopore long-read sequencing with physical maps produced using Bionano and Hi-C technology. A total of 87.9Gb of nanopore sequence provided approximately 100-fold coverage of the genome. The preliminary genome assembly was 883.2Mb in size with a contig N50 size of 11.2Mb. The 969 corrected contigs obtained from Bionano optical mapping were assembled into 853 scaffolds and produced an assembly of 886.5Mb with a scaffold N50 of 16.5Mb. Finally, using the Hi-C data, 881.3Mb (99.4% of genome) in 526 scaffolds were anchored and oriented in 25 chromosomes ranging in size from 25.27 to 56.49Mb. In total, 24,770 protein-coding genes were predicted in the genome, and ~96.85% of the genes were functionally annotated. The annotated assembly contains 93.3% complete genes from the BUSCO reference set. In addition, we identified 409Mb (46.23% of the genome) of repetitive sequence, and 11,213 non-coding RNAs, in the genome. Evolutionary analysis revealed that O.macrolepis diverged from common carp approximately 24.25million years ago. The chromosomes of O.macrolepis showed an unambiguous correspondence to the chromosomes of zebrafish. The high-quality genome assembled in this work provides a valuable genomic resource for further biological and evolutionary studies of O.macrolepis.

Trematodes of cyprinids fish of the Lower Irtysh

The paper presents studies of representatives of cyprinid fish species inhabiting the Lower Irtysh was conducted for invasion by multicellular organisms of the Trematoda class. A total of 54 individuals of Abramis brama, 24 individuals of Rutilus rutilus lacustris and 15 Leuciscus idus were studied. Parasitism of 13 species of trematodes was found in cyprinid fish. The first group consisted of 6 species whose entire life cycle is associated with the aquatic environment, where fish are the final hosts (R. campanula, P. elongatum, A. isoporum, S. globiporum, S. bramae, A. lucii). The second group includes 7 species whose marites are parasitic in birds and mammals (D. chromatophorum, Metorchis sp., H. triloba, I. pileatus, I. platycephalus, O. felineus, P. ovatus). Common to bream, roach, and ide are D. chromatophorum, O. felineus, and R. campanula. Metacercaria I. platycephalus are registered in one bream and two ides. Sexually Mature individuals of the trematode of cyprinid -Sphaerostomum bramae, parasitize in the intestines of bream and roach. The greatest species similarity of trematode fauna is observed between bream and roach, as well as bream and ide, the least similarity of parasites in ide and roach. The dominant species of parasitic community of fish are the following parasites: bream - Sphaerostom bramae, ide - metacercaria Rhipidocotyle campanula & Metorchis sp., roach - Rhipidocotyle campanula.

Detection of cyprinid herpesvirus 1 (CyHV-1) in barbel (Barbus barbus): First molecular evidence for the presence of CyHV-1 in fish other than carp (Cyprinus carpio).

Two adult barbels (Barbus barbus) with visible skin tumours were subjected to histopathological and molecular examinations. The fish were caught in the River Danube near Budapest. Papillomas were found around their oral cavity, at the operculum and at the pectoral fins, while epidermal hyperplasias were seen on the body surface. Cyprinid herpesvirus 1 (CyHV-1) was detected in the kidney of the specimens by polymerase chain reaction (PCR), and barbel circovirus 1 (BaCV1) was found in all internal organs and in the tissues of the tumours. The whole genome of BaCV1 and three conserved genes from the genome of CyHV-1 were sequenced. Previously, BaCV1 had been reported only once from a mass mortality event among barbel fry. The whole genome sequence of our circovirus shared 99.9% nucleotide identity with that of the formerly reported BaCV1. CyHV-1 is known to infect common carp and coloured carp (Cyprinus carpio), and has been assumed to infect other cyprinid fish species as well. We found the nucleotide sequences of the genes of CyHV-1 to be identical in 98.7% to those of the previous isolates from carp. To the best of our knowledge, this is the first molecular confirmation of the presence of CyHV-1 DNA in cyprinid fish species other than carp.

Parapsilorhynchus alluriensis, a new species of cyprinid fish (Teleostei: Cyprinidae) from the Eastern Ghats, of India.

A new species of cyprinid fish, Parapsilorhynchus alluriensis, is described from the Alluri Hills of Andhra Pradesh State, India. It is distinguished from its congeners by the combination of the following characters: A poorly-developed callous pad present behind lower lip; head deep (depth at occiput 47.3-72.3% head length, HL); body stout and deep (depth at dorsal fin origin 17.3-21.7 % standard length, SL); gape width 27.3-32.8% HL; inter-orbital space 33.9-43.2% HL; lower lip rounded; mouth opening situated very close to the anterior tip of snout; upper lip concealed by a poorly-developed rostral fold which is slightly fringed; minute papillae on rostral fold; 3 simple pectoral-fin rays; 33-34 lateral-line scales. A partial phylogeny based on the DNA Barcode COI gene suggests a sister-group relationship between the new species and P. prateri. Till date, the genus consists of four species from the Western Ghats, three from the Eastern Ghats, including the species described herein totaling it to seven from the peninsular India.

Length‐weight relationships of seven cyprinid fish species from the Kaptai Lake, Bangladesh

Length-weight relationships (LWRs) were estimated for seven small indigenous cyprinid fish species including Securicula gora, Osteobrama cotio, Esomus lineatus, Pethia gelius, Megarasbora elonga, Gonialosa manmina and Glossogobius aureus occurring in the Kaptai Lake, Bangladesh. Fish were collected monthly basis between March and October, 2018 from fishermen catches landed in the fish landing center, Rangamati. Fishermen operated lift net (mesh size < 0.5 cm), punti net (mesh size < 0.5 cm) and cast net (mesh size < 0.5 cm) for capturing these species. The value of exponent b ranged between 2.769 and 3.212 and regression parameter r2 was between 0.926 and 0.992. New maximum total lengths were recorded for E. lineatus and G. manmina in this study.

Sugar transporter genes in grass carp (Ctenopharyngodon idellus): molecular cloning, characterization, and expression in response to different stocking densities.

Glucose and fructose play a central role in the metabolism and cellular homeostasis of organisms. Their absorption is co-mediated by two families of glucose transporters, Na+-coupled glucose co-transporters (SGLTs) and facilitative Na+-independent sugar carriers (GLUTs), in the intestine. However, limited information has been available on these transporters in fish. Therefore, we studied glut2, sglt1, and sglt4 genes in grass carp (Ctenopharyngodon idellus). The full-length cDNAs of glut2 was 2308bp, with an open reading frame (ORF) of 503 amino acids (AAs). The full-length cDNAs of sglt1 was 2890bp, with an ORF of 658 AAs. Additionally, the full-length cDNAs of sglt4 was 2090bp, with an ORF encoding 659 AAs. The three deduced AA sequences showed high homology between grass carp and other cyprinid fish species. Based on homology modeling, three-dimensional models of GLUT2, SGLT1, and SGLT4 proteins were created and transmembrane domains were noted. glut2, sglt1, and sglt4 were abundantly expressed in the anterior and mid intestine. In particular, glut2 was markedly expressed in liver (P < 0.05). Additionally, the results indicated that different stocking densities (0.9 or 5.9kgm-2) did not alter intestinal section-dependent expression patterns of the three transporter genes. However, high stocking density impacted segmental mRNA expression levels. This work demonstrated that mRNA expression of sugar transporter genes in the fish intestine was segment specific, and crowding stress may affect the activity of intestinal sugar transporters. These results provided new insights into the relationship between crowding stress and intestinal sugar transporters in fish.

River restoration is prone to failure unless pre-optimized within a mechanistic ecological framework | Insights from a model-based case study

River restoration with the use of in-stream structures has been widely implemented to maintain/improve physical habitats. However, the response of aquatic biota has often been too weak to justify the high costs of restoration projects. The ecological effectiveness of river restoration has thus been much debated over claims that large-scale environmental drivers often overshadow the potential positive ecological effects of locally placed in-stream structures. In this study, we used a two-dimensional hydrodynamic-habitat model to evaluate the ecological effectiveness of habitat restoration with the use of in-stream structures in various water discharges, ranging from near-dry to environmental flows. The habitat suitability of benthic macroinvertebrates and of three cyprinid fish species was simulated for six restoration schemes and at four discharge scenarios, and was compared with a reference model, without in-stream structures. We found that the ecological response to habitat restoration varied by species and life stages, it strongly depended on the reach-scale flow conditions, it was often negative at near-environmental flows, and when positive, mostly at near-dry flows, it was too low to justify the high costs of river restoration. Flow variation was the major environmental driver that our local habitat restoration schemes attempted -but mostly failed-to fine-tune. We conclude that traditional river restoration, based on trial and error, will likely fail and should be ecologically pre-optimized before field implementation. Widespread use of in-stream structures for ecological restoration is not recommended. However, at near-dry flows, the response of all biotic elements except for macroinvertebrates, was positive. In combination with the small habitat-suitability differences observed among structure types and densities, we suggest that sparse/moderate in-stream structure placement can be used for cost-effective river restoration, but it will only be ecologically effective -thus justifying the high implementation costs-when linked to very specific purposes: (i) to conserve endangered species and (ii) to increase/improve habitat availability/suitability during dry periods, thus proactively preventing/reducing the current and future ecological impacts of climate change.

Infection Dynamics of Opisthorchis viverrini Metacercariae in Cyprinid Fishes from Two Endemic Areas in Thailand and Lao PDR.

The infection dynamics of Opisthorchis viverrini metacercariae was analyzed in cyprinid fish from endemic areas in Mukdahan Province, Thailand, and Khammouane Province, Lao PDR. The fish were collected during the cool-dry (November-February), hot-dry (March-May), and rainy (June-October) seasons in 2017. They were examined by the digestion method, and the infection status was statistically analyzed by study area, season, and fish size. The prevalence (no. of fish positive/no. of fish examined × 100) and metacercarial intensities (no. of metacercariae detected/no. of fish positive) of O. viverrini in both study areas depended on season, being high in the cool-dry season and varying in the hot-dry and rainy seasons. In Mukdahan Province, the average prevalence was 18.3% (range 11.0-46.7%, n = 420) and the intensity was 4.07 ± 5.86 cysts/fish (mean ± SD), whereas in Khammouane Province, the prevalence was 51.9% (range 9.1-70.6%, n = 673) and the intensity was 6.67 ± 12.88 cysts/fish. Among the cyprinid fish species examined, the infection was associated with fish body size and predominantly found in Hampala dispar (86.5%), Cyclocheilichthys armatus (73.2%), and Puntius brevis (42.7%). The distribution of O. viverrini metacercariae in fish was skewed, with most of the fish having a low worm burden with an average of four to six cysts/fish. The findings that seasonality, sampling locality, fish size, and species of fish play roles in the risk of O. viverrini infection imply that these host and environmental factors are important for the transmission dynamics and control of O. viverrini.

Using SDS-PAGE and ISSR as biochemical markers for assessment the genetic similarity and protein analysis of some cyprinid fish species

Genetics similarity and protein analysis of some cyprinid fish were studied using Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Inter-simple sequence repeated (ISSR Markers). Species Pethia nigrofasciatus, Barbonymus schwanenfeldii, Puntius tetrazone and Brachydanio rerio were collected from the fish farms in Damietta to study the genetic variability among them. Eleven ISSR primers were tested to assess the effectiveness of ISSR analysis in discriminating among the four applied fish species. We observed varied size of amplified products depending upon the sequence of ISSR primers and genotypes used. A total of 131 discrete amplified products were obtained (size 79 to 1185 bp approximately) with polymorphism 95%. Out of 131 products, 63 bands were species specific markers indicating high level polymorphism among species. The highest and lowest number of ISSR bands detected for primers ISSR 15 and ISSR16 was 18 and 17 respectively. 7 bands were most relevant as found monomorphic in all four species of family: Cyprinidae. Highest similarity observed between Pethia nigrofasciatus and Barbonymus schwanenfeldii 80% and lowest similarity was between Pethia nigrofasciatus and Brachydanio rerio 31 %. The protein analysis by SDS-PAGE produced 29 bands of molecular weight ranging from 11 to 132 KD with polymorphism 14%. This study concludes that ISSR-based DNA analysis bands and protein profile in muscles from Pethia nigrofasciatus and Barbonymus schwanenfeldii are the most closest species compared molecularly compared with other species used in this study.

Anesthetic Activity of Clove Oil (Eugenol) on the Lake Van Fish (Chalcalburnus tarichi Pallas, 1811)

The use of clove oil (eugenol) as an anesthetic for Lake Van fish(Chalcalburnus tarichi), an endemic cyprinid fish species ofLake Van basin, was examined. Induction times were determined to be ≥35, &amp;lt;4, &amp;lt;3, &amp;lt;2, &amp;lt; 2 and ≥1 min at 20, 40,50, 60, 80 and 100 mg/L clove oil concentrations, respectively. Recovery times upon 10 min of exposure to eugenol were determined respectively to be &amp;gt;3, &amp;gt;4,&amp;gt;3, &amp;gt;4,&amp;gt;6 and &amp;gt;8 min clove oil can be considered as a suitable anesthetic for Chalcalburnus tarichi and an optimum anesthetic concentration of 50 mg/L is recommended.

Thallium accumulation in different organisms from karst and lowland rivers of Croatia under wastewater impact

Environmental contextDespite thallium’s high toxicity, water solubility and bioaccumulation tendency, its ecotoxicological relevance is largely unknown. We investigated thallium concentrations in fish, amphipods and parasitic worms from a karst freshwater ecosystem, and estimated total and cytosolic thallium concentrations in intestine of fish from the karst and lowland rivers impacted by wastewater inflow. The study provides the first data on dietary thallium accumulation in the intestine of freshwater fishes. AbstractThe aim of the present research was to investigate the bioaccumulation of thallium (Tl), a technology-critical element, in fish intestine and muscle, gammarids and the fish intestinal parasites, acanthocephalans, and to evaluate their potential as indicators of metal exposure in aquatic environments. Moreover, total and cytosolic (metabolically available and potentially toxic fraction) Tl concentrations were measured and compared between the intestines of brown trout (Salmo trutta Linnaeus, 1758) from the karst Krka River and Prussian carp (Carassius gibelio Bloch, 1782) from the lowland Ilova River. Since there is a scarcity of information on subcellular metal partitioning in the fish intestine, the results of Tl concentrations in acid digested intestinal tissue, homogenate and cytosol represent preliminary data on Tl diet-borne uptake in salmonid and cyprinid fish. In both rivers, samplings were performed upstream (reference site) and downstream (contaminated site) of the wastewater impact in autumn and spring. Total Tl concentrations were much higher in brown trout than Prussian carp, and higher proportions of cytosolic Tl concentrations were observed in the intestinal tissue of brown trout (45–71%) compared with that of Prussian carp (32–47%). Therefore, both indicators showed species- and site-specific differences. Considering different bioindicator organisms, the most effective Tl accumulation was evident in acanthocephalans compared with the fish tissues and gammarids, which confirmed the potential of fish parasites as bioindicators of metal exposure. Trends of spatial and temporal Tl variability were mostly comparable in all indicator organisms and for total and cytosolic Tl concentrations in the intestine of salmonid and cyprinid fish species, which confirmed their application as useful biological tools in metal exposure assessment.