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The African catfish Clarias gariepinus is a freshwater species native to nearly all of Africa and a small part of Asia. Due to being a generalist species, highly fertile and able to survive in a wide range of environmental conditions, the African catfish has become invasive in many non-native systems where it was introduced, bringing negative impacts to wild ecosystems. In Brazil, C. gariepinus was introduced from Africa for aquaculture in 1986 and established itself in the wild within a decade, after escaping from aquaculture ponds and being further translocated to be used in recreational fishing. As further evidence of the expansion of this invasive species in Brazil, we sequenced the mitochondrial control region and cytochrome b markers to confirm the occurrence of C. gariepinus in a major river in a protected area in the southeastern region, and to assess its genetic diversity. Morphometric data was also collected to aid species identification and to compare to other invasive populations in Brazil. The analysis of 24 specimens revealed a single haplotype for each marker. The single cytochrome b haplotype is identical to a haplotype from the Democratic Republic of the Congo, unveiling the possible genetic origin of the C. gariepinus lineage that invaded Brazil. Morphometric data suggests consistency in the morphometric traits of C. gariepinus invasive populations in Brazil. The assessment and monitoring of the distribution of C. gariepinus in non-native areas are crucial for the maintenance of native freshwater biodiversity and ecosystem functioning worldwide. [ABSTRACT FROM AUTHOR]

Fish parasitic diseases impose a major economic concern on aquaculture. Identified parasites of Clarias gariepinus include one monogenean, Macrogyrodactylus clarii (gills), three digeneans Orientocreadium batrachoides, Eumasenia bangweulensis and Sanguinicola sp. (intestine), two cestodes Tetracampose ciliotheca and Monobothrioides chalmersius (intestine) and two nematodes Paracamallanus cyathopharynx and Procamallanus pseudolaeviconchus (intestine and stomach). Most nematodes, digeneans and cestodes occurred in all months of the study period. However, M. clarii and Sanguinicola sp. disappeared for 6 and 8 months of the year, respectively. The digenean group was the most dominant followed by the cestode and nematode groups, respectively. The nematodes attained the highest infection rate over the digeneans and cestodes while the monogenean M. clarii recorded the lowest infection rate. The infection level of examined parasites varied seasonally, but no overall significant pattern was detected. E. bangweulensis showed a highly significant difference for all parameters seasonally. A higher prevalence was obvious in males than females for most parasites, and the opposite for the mean intensity except for P. pseudolaeviconchus which was significantly different between females and males in the mean abundance. There were variations in the relationship between the host condition factor and helminth parasite infection levels. O. batrachoides, E. bangweulensis and P. cyathopharynx recorded the highest infection level in class II. The mean prevalence was highly significantly different between host classes for T. ciliotheca, M. chalmersius and P. pseudolaeviconchus. [ABSTRACT FROM AUTHOR]

We report the first record of Platyclarias machadoi Poll, 1977 since its original description. This species was sampled by electrofishing in rapids on the Kwanza River upstream of Capanda Dam in Angola. Morphometric and meristic data for the Kwanza River material were compared to published data from the Platyclarias type series. Osteology was compared between the Kwanza specimens and two Platyclarias paratypes using computed tomography (CT) scans. Prior to this discovery, the genus was known only from the Kwango River in Angola. [ABSTRACT FROM AUTHOR]

The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a "failure to diverge" phenomenon for G. transvaalensis. [ABSTRACT FROM AUTHOR]

Spinitectus spp. (Rhabdochonidae) are enteric nematodes characterized by annular spines. At the anterior end, these spines assist attachment and aid penetration into the host tissue. During parasitological surveys of the Vaal River system from three localities, below the Vaal River Barrage in the Vaal Dam surrounding UJ island and below the Grootdraai Dam, Spinitectus specimens were collected from the stomach lining of the sharptooth catfish, Clarias gariepinus (Burchell, 1822). Histopathological effects induced by Spinitectus petterae Boomker, 1993 on C. gariepinus has not been studied. Thus, the aim of this study was to describe the histopathology induced by S. petterae. For light microscopic examination, tissue samples with attached S. petterae were sectioned and stained with haematoxylin and eosin. Additionally, attached nematodes were also studied using scanning electron microscopy. Leukocytes were counted with the Disector principle. Standard infection parameters (prevalence, mean intensity and abundance) were calculated and compared to host parameters. Prevalence varied greatly (11.77% to 100%) between localities. Histopathology induced by S. petterae to C. gariepinus stomach (cardiac region) consisted of significant leukocyte infiltration, acute ulcerations and chronic granuloma formation. This was similar to the pathology of other Spinitectus occurring in host anterior intestine and stomach, but granuloma formation had not been previously reported and this suggests chronic infection in wild caught fish. [ABSTRACT FROM AUTHOR]

Summary: The study sought to investigate the chronology of events and timing of embryogenesis, as well as breeding performances of three strains of Heterobranchus longifilis from Nigeria. Fish samples were collected from Benue River in Makurdi, Niger River in Onitsha, and Rima River in Sokoto for this study. Induced spawning of the strains was carried out so that egg development could be tracked from fertilization to hatching using a simple microscope. The microphotographs obtained showed that the embryogenesis of the strains followed a similar pattern to those of other members of the family Clariidae, however with changes occurring in the specific timing of the sequences of events (i.e. interstrain and interspecies differences). When the different strains were compared, the study noted similarities (P > 0.05) in the overall breeding performance (except for fertilization rate), survival at different stages of development, timing of embryogenesis, and larvae characteristics. The outcomes of this study, therefore, provide baseline information on what genetic improvement of the species through strain crossing can be attempted in future studies. [ABSTRACT FROM AUTHOR]

Although the vast majority of fossil catfish material is isolated elements such as fin spines, a number of fossil catfishes (Siluriformes) have been named based on articulated crania from Palaeogene formations of Africa. The fossil taxa from marine sediments have been assigned to the extant marine family Ariidae, or have been assumed to have washed into marine sediments from freshwater habitats. The ability to assess the relationships of these fossils without reference to the nature of the geological sediments may provide insight into the history of these families. Most of the taxonomic work on the 11 catfish families found in Africa has focused on soft-tissues or DNA, which is problematic for the fossil material. Here we provide osteological features to distinguish families of African catfishes; eight of the families that are likely to be found in fossiliferous deposits can be distinguished based on a combination of skull features including the morphology of the cranial fontanelle, mesethmoid, and dermal ornamentation. We reassess the familial placement of the Palaeogene catfishes. We find that †Eomacrones wilsoni, from the Palaeocene of Nigeria, belongs in Bagridae s.s. This confirms that bagrids were in Africa much earlier than the Miocene. Because this catfish comes from Palaeocene marine sediments, the biogeographic history of Bagridae needs to be reassessed to consider marine dispersal in this taxon.

The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a “failure to diverge” phenomenon for G. transvaalensis.

The thyroid hormones (THs) play an important role in the regulation of the rate of metabolism, affect the growth and function of different systems in the organism. The aim of this study was to assess serum concentration of total triiodothyronine (T3), total thyroxine (T4) as well as T3/T4 ratio in serum from healthy fresh water fish from Salmonidae, Acipenseridae, Cyprinidae, and Clariidae families to determine species-specific reference intervals. Mean concentrations of T3 and T4 levels varied significantly among fish. Finally, the test results show clear differences in the serum concentration of the T3 and T4 and give new insight into the thyroid hormones reference values in some commercial fresh water fish species. [ABSTRACT FROM AUTHOR]

Abstract Background Monogenean flatworms are the main ectoparasites of fishes. Representatives of the species-rich families Gyrodactylidae and Dactylogyridae, especially those infecting cichlid fishes and clariid catfishes, are important parasites in African aquaculture, even more so due to the massive anthropogenic translocation of their hosts worldwide. Several questions on their evolution, such as the phylogenetic position of Macrogyrodactylus and the highly speciose Gyrodactylus, remain unresolved with available molecular markers. Also, diagnostics and population-level research would benefit from the development of higher-resolution genetic markers. We aim to offer genetic resources for work on African monogeneans by providing mitogenomic data of four species (two belonging to Gyrodactylidae, two to Dactylogyridae), and analysing their gene sequences and gene order from a phylogenetic perspective. Results Using Illumina technology, the first four mitochondrial genomes of African monogeneans were assembled and annotated for the cichlid parasites Gyrodactylus nyanzae, Cichlidogyrus halli, Cichlidogyrus mbirizei (near-complete mitogenome) and the catfish parasite Macrogyrodactylus karibae (near-complete mitogenome). Complete nuclear ribosomal operons were also retrieved, as molecular vouchers. The start codon TTG is new for Gyrodactylus and for Dactylogyridae, as is the incomplete stop codon TA for Dactylogyridae. Especially the nad2 gene is promising for primer development. Gene order was identical for protein-coding genes and differed between the African representatives of these families only in a tRNA gene transposition. A mitochondrial phylogeny based on an alignment of nearly 12,500 bp including 12 protein-coding and two ribosomal RNA genes confirms that the Neotropical oviparous Aglaiogyrodactylus forficulatus takes a sister group position with respect to the other gyrodactylids, instead of the supposedly ‘primitive’ African Macrogyrodactylus. Inclusion of the African Gyrodactylus nyanzae confirms the paraphyly of Gyrodactylus. The position of the African dactylogyrid Cichlidogyrus is unresolved, although gene order suggests it is closely related to marine ancyrocephalines. Conclusions The amount of mitogenomic data available for gyrodactylids and dactylogyrids is increased by roughly one-third. Our study underscores the potential of mitochondrial genes and gene order in flatworm phylogenetics, and of next-generation sequencing for marker development for these non-model helminths for which few primers are available.

Aim: The formation history of Africa's current river basins remains largely unknown. In order to date changes in landscape and climate, we studied the biogeography of the African freshwater fish with the largest natural distribution. We also validated biogeographical units. Location: Continental Africa. Taxon: Clarias gariepinus sl. Methods: We investigated mitochondrial cytb sequences of 443 individuals from 97 localities, using a haplotype network and a genetic landscape analysis. We inferred a dated phylogeny using maximum likelihood and Bayesian inference approaches and reconstructed ancestral areas with S‐DEC and S‐DIVA models. Microsatellite genotyping complemented the mitochondrial approach in the Congo basin, where the latter revealed complex patterns. Results: Limited differentiation is found in northern and south‐western Africa, and sharp genetic differentiation in the continent's east and centre. Populations with affinities to neighbouring basins occur at the edges of the Congo province. High diversity exists in the south of the Congo basin. The Zambezi province is partitioned into eastern, central and western sectors. In the east, specimens were related to those from the Congo. In the west, they were similar to Southern representatives. Phylogenetic inference placed the origin of C. gariepinus in the East Coast, with intraspecific diversification starting around the Great Lakes. These events occurred ca. 4.8–1.65 and 2.3–0.8 MYA respectively. Main conclusions: Clades of C. gariepinus sl. show a clear geographical signature. The origin of C. gariepinus in the East Coast and diversification around the Great Lakes coincided with the periods of increased aridity. Low genetic differentiation in northern and southern Africa may result from connectivity during recent periods of higher rainfall. In contrast to other widespread African freshwater fish, colonization rather than extinction seemed to mediate distribution patterns. This can be explained by a high ecological tolerance. We highlight the species' suitability to study landscape and climate evolution at various scales. [ABSTRACT FROM AUTHOR]

Two clariids, Heterobranchus bidorsalis (65) and Heterobranchus longifilis (15), and two claroteids, Auchenoglanis occidentalis (31), and Chrysichthys auratus (19) from River Galma were examined for gastrointestinal nematodes from May 2016 to February 2017. Overall, five species of nematodes were recovered from the clariids and claroteids. The nematodes were distributed as follows: in Heterobranchus bidorsalis, Procamallanus laevionchus (12.31%), Paracamallanus cyathopharynx (9.23%) and Rhabdochona sp. (1.54%); in Heterobranchus longifilis; Paracamallanus cyathopharynx (6.67%); in Auchenoglanis occidentalis: Procamallanus laevionchus (25.81%); in Chrysichthys auratus: Procamallanus laevionchus (5.26%), Contracaecum sp. (5.26%) and Spirocamallanus spiralis (15.79%). Nematode prevalence in C. auratus was higher in the wet than in the dry season; however, prevalence of infection in A. occidentalis, H. longifilis and H. bidorsalis was higher in the dry than in the wet season. Prevalence of nematode infection was also higher in male than in female H. longifilis while it was higher in female A. occidentalis, C. auratus and H. bidorsalis than males of the same species. Nematode prevalence was higher in larger (24.0-31.9cm) Heterobranchus bidorsalis and Auchenoglanis occidentalis. Prevalence of infection was higher in smaller (8.0-15.9cm) Chrysichthys auratus. It is recommended that a larger sample size of especially Heterobranchus longifilis and Chrysichthys auratus, of which only 15 and 19 specimens respectively, were examined during the period of this study, be examined, to have a clearer picture of their infection by nematodes in River Galma. [ABSTRACT FROM AUTHOR]

The present study was carried out to analyse the effect of water temperature on two components: (1) growth performance, and (2) gastric emptying time (GET) of African catfish Clarias gariepinus fingerlings. After 70 days, it was observed that experimental temperatures had no significant effects on the growth performance parameters, except for food conversion ratio (FCR) and food conversion efficiency (FCE). GET observation through X-radiography denoted that the shortest GET (10 h) was observed in fish reared at 32 °C and the longest GET (16 h) was observed in fish reared at 26 °C. The rapid digestion rate coincides with the FCR and FCE obtained in this study. Considering the limited scope of our study, more extensive studies on the impact of water temperature on other fish physiological parameters should be pursued. A better understanding of this research topic would be beneficial for the growth of African catfish fingerling aquaculture.

In the present study, a possible nature immunostimulant and growth promoter—humic substances (HS) originating from Siberian leonardite mineraloid—were tested on juvenile Clarias gariepinus performance. Feed additive was applied onto commercial pelleted feed at four HS levels—0, 1, 3, and 6% w/w (HS0, HS1, HS3, HS6, respectively). Diets were tested in five repetitions (in total, n = 1800 individuals, mean body weight 28.1 ± 6.2 g) for 56 days. Growth and production parameters, fish condition and somatic indices, and overall mortality were evaluated after 14, 28, 42, and 56 days of exposure. Whereas, plasma samples were collected only after 0, 28, and 56 days, when fish health status was assessed with biochemical parameters (total proteins, TP; alanine aminotransferase, ALT; aspartate aminotransferase, AST; lactate dehydrogenase, LDH; cholesterol, CHOL; triglycerides, TAG) and fish antioxidant status with glutathione (reduced glutathione, GSH; oxidized glutathione, GSSG; glutathione ratio GSH/GSSG). Although a significantly positive effect of HS feed additive on growth performance was not found in the present study, moderately positive effects were found regarding biochemical parameters (ALT, AST, LDH, CHOL, and TAG) and antioxidants (GSH/GSSG ratio) that were improved especially in the HS3 group.

Các chỉ tiêu đo rất quan trọng trong việc phân tích hình thái trên cá. Tuy nhiên, việc đo đạc thường tốn nhiều thời gian, công sức và khó lặp lại khi kiểm tra sai số.Phương pháp phân tích hình ảnh đã và đang được ứng dụng rộng rãi trong việc đo các chỉ tiêu hình thái trên nhiều loài sinh vật. Nghiên cứu này nhằm mục đích kiểm nghiệm tính hiệu quả của phương pháp phân tích hình ảnh trong việc thực hiện các chỉ tiêu đo của hai nhóm hình thái cá (1) nhóm cá có dạng hình ống, đại diện là các loài cá trê (giống Clarias), (2) nhóm cá có hình dạng thân dẹp bên, đại diện là cá ba kỳ đỏ (Cyclocheilichthys apogon). Nguyên lý của phương pháp này là chuyển đổi dữ liệu hình ảnh ở đơn vị Pixel thành đơn vị đo thông dụng thông qua một tỉ lệ “SCALE” được xác định trên hình ảnh của mẫu cá được chụp cùng với thước đo. Các mẫu vật lần lượt được đo bằng phương pháp thông thường với thước vi cấp và được phân tích hình ảnh để xác định độ dài trên ứng dụng tpsDig. Phân tích tương quan (correlation) được thực hiện giữa các số liệu thu được từ hai phương pháp để so sánh sự tương đồng giữa hai phương pháp đo. Kết quả cho thấy đa số các chỉ tiêu đo (17 trên tổng số 25 chỉ tiêu) đều có hệ số tương quan cao (r>0,85), thể hiện tính chính xác cao của phương pháp phân tích hình ảnh trên cả hai dạng kiểu hình cá. Phương pháp phân tích hình ảnh có triển vọng ứng dụng cao trong các nghiên cứu hình thái cá để rút ngắn thời gian phân tích, giảm thiểu khả năng sai sót về dữ liệu hay kiểm tra lại việc đo đạc trong trường hợp xảy ra sai sót hay mất mẫu vật.

Trong nghiên cứu này, đặc điểm hình thái của một nhóm cá trê “lạ” thu ở huyện đảo Phú Quốc, tỉnh Kiên Giang được so sánh với các loài cá trê thuộc giống Clarias đã được định danh gồm cá trê trắng (Clarias cf. batrachus), cá trê vàng (C. macrocephalus), cá trê Phú Quốc (C. gracilentus) nhằm bổ sung thông tin thành phần loài trong giống Clarias. Tổng cộng 129 mẫu cá trê đã được thu thập và phân tích hình thái dựa vào 22 chỉ số sinh trắc hình thái (tỉ lệ số đo hình thái so với chiều dài chuẩn và chiều dài đầu). Về hình dáng bên ngoài, các nhóm cá trê có thể được phân biệt được với nhau bằng hình dạng thân, màu sắc, hình dạng đầu và đặc biệt là hình dạng gai vi ngực. Nhóm cá trê “lạ” có cạnh ngoài gai vi ngực với các răng to rõ và dễ dàng phân biệt với các nhóm khác. Tất cả các chỉ số sinh trắc đều khác biệt có ý nghĩa thống kê giữa bốn nhóm cá (p< 0,05). Kết quả phân tích thành phần chính (Principal Component Analysis- PCA) cũng thể hiện sự sắp xếp rõ ràng của bốn nhóm cá, trong đó nhóm cá trê vàng và nhóm cá “trê lạ” gần giống nhau hơn so với hai loài trê trắng và trê Phú Quốc. Hai thành phần chính (Principal Component - PC1 và PC2), giải thích lần lượt 46,3% và 22,6% sự khác biệt về số đo của bốn nhóm cá. Ngoài ra, phân tích nhóm còn cho thấy 100% các cá thể cá trê được xếp đúng vào từng nhóm ban đầu. Kết quả nghiên cứu này thống nhất với kết quả của nghiên cứu trước: cá trê “lạ” có thể không phải là con lai giữa cá trê vàng và cá trê Phú Quốc.

Background: Monogenean flatworms are the main ectoparasites of fishes. Representatives of the species-rich families Gyrodactylidae and Dactylogyridae, especially those infecting cichlid fishes and clariid catfishes, are important parasites in African aquaculture, even more so due to the massive anthropogenic translocation of their hosts worldwide. Several questions on their evolution, such as the phylogenetic position of Macrogyrodactylus and the highly speciose Gyrodactylus, remain unresolved with available molecular markers. Also, diagnostics and population-level research would benefit from the development of higher-resolution genetic markers. We aim to offer genetic resources for work on African monogeneans by providing mitogenomic data of four species (two belonging to Gyrodactylidae, two to Dactylogyridae), and analysing their gene sequences and gene order from a phylogenetic perspective. Results: Using Illumina technology, the first four mitochondrial genomes of African monogeneans were assembled and annotated for the cichlid parasites Gyrodactylus nyanzae, Cichlidogyrus halli, Cichlidogyrus mbirizei (near-complete mitogenome) and the catfish parasite Macrogyrodactylus karibae (near-complete mitogenome). Complete nuclear ribosomal operons were also retrieved, as molecular vouchers. The start codon TTG is new for Gyrodactylus and for Dactylogyridae, as is the incomplete stop codon TA for Dactylogyridae. Especially the nad2 gene is promising for primer development. Gene order was identical for protein-coding genes and differed between the African representatives of these families only in a tRNA gene transposition. A mitochondrial phylogeny based on an alignment of nearly 12,500 bp including 12 protein-coding and two ribosomal RNA genes confirms that the Neotropical oviparous Aglaiogyrodactylus forficulatus takes a sister group position with respect to the other gyrodactylids, instead of the supposedly 'primitive' African Macrogyrodactylus. Inclusion of the African Gyrodactylus nyanzae confirms the paraphyly of Gyrodactylus. The position of the African dactylogyrid Cichlidogyrus is unresolved, although gene order suggests it is closely related to marine ancyrocephalines. Conclusions: The amount of mitogenomic data available for gyrodactylids and dactylogyrids is increased by roughly one-third. Our study underscores the potential of mitochondrial genes and gene order in flatworm phylogenetics, and of next-generation sequencing for marker development for these non-model helminths for which few primers are available. [ABSTRACT FROM AUTHOR]

In the present study, investigation were carried out on gills of African cat fish Clarias gariepinus exposed to sub lethal concentrations (80mg/ml,400mg/ml and 800mg/ml) of 2 -Methyltetrahydrofuran for 10 days. Lesions were observed in gills tissue of treated fish for long term exposure to Methyltetrahydrofuran (2MTHF). The occurrence and degree of alteration were positively related with the concentration of 2MTHF. Histological examination of the gills of fish treated with 80 mg/ml of 2MTHF for 10 days showed architectural loss, necrosis and desquamation of epithelial layer. Histological examination of the gills of fish treated with 400 mg/ml of 2MTHF for 10 days showed architectural loss, necrosis and mild vaccuolation. The gill filament exhibited telangiectesis, disorganisation of secondary gill lamellae and complete vaccuolation of gills treated with 800 mg/ml of 2MTHF for 10 days. The study indicated that 2MTHF had marked effects on the cytoarchitecture of the gills of C. gariepinus. The degree of vaccuolation and necrosis were positively related with the concentration of 2MTHF. [ABSTRACT FROM AUTHOR]

The examination of material representing one of Lake Tanganyika's six previously recognized endemic catfish lineages, has revealed the presence of an additional genus of clariid, described here as Pseudotanganikallabes new genus. This genus is represented by a single species, Pseudotanganikallabes prognatha sp. nov., which is distinguished from all other clariids by its lack of an infraorbital series, the presence of multiple osseous connections between the swim bladder capsules and elements of the neurocranium, the absence of an ethmoid notch, the presence of a very large, egg-shaped occipital fontanelle and the extension of the lower lip beyond the margin of the upper jaw. A combination of additional external and molecular characters serves to further distinguish this taxon from all currently recognized clariid species. Phylogenetic analysis of mitochondrial ( cytb) and nuclear (18S-ITS1-5.8S-ITS2-28S) sequence data supports the creation of a new genus for this species, as it appears to represent an independent, monophyletic lineage within the family Clariidae. [ABSTRACT FROM AUTHOR]

The study determined the variation in the morphological and meristic features among four populations of Clarias gariepinus Burchell, 1822 obtained from Owena Dam and River Oluwa in Ondo State and Rivers Omo and Ogbere in Ogun State, both in Nigeria. A total of ninety five (95) and one hundred and twenty (120) fish specimens collected from Ondo and Ogun states respectively were measured using standard procedures and the results were analysed using Analysis of variance and multivariate analyses. The results obtained from the ANOVA and Principal Component Analyses of Clarias gariepinus from the four populations revealed heterogeneity for most of their characters. Therefore, the morphological differences between the wild African catfish found in Ondo and Ogun state populations could be linked to genetic differences or environmental factors or a combination of both factors. Hence, this study concluded that the populations are different which could imply high genetic diversity if molecular marker techniques are employed in further studies. [ABSTRACT FROM AUTHOR]

All of the 166 Clarias gariepinus catfishes in Lake Tana, Ethiopia, were examined for trematode infestation in 2006-2009. Seven trematode species- Eumasenia bangweulensis, Astiotrema reniferum, Orientocreadium batrachoides, Paralecithodendrium chilostomum, Phyllodistomum bavuri, P. tana, and Cladorchiidae gen. sp.-as adult were found. The common catfish parasites were Eumasenia bangweulensis (20% prevalence and 1-62 intensity of invasion), Orientocreadium batrachoides (30% prevalence and 1-31 intensity of invasion), Phyllodistomum bavuri (24.8% prevalence and 1-8 intensity of invasion), Ph. tana (17.6% prevalence and 1-23 intensity of invasion), and Ph. bavuri. Astiotrema reniferum (three specimens were only found) was a rare species; Paralecithodendrium chilostomum was an accidental parasite of catfish. All these trematodes were first recorded in Ethiopia and Eastern Africa. [ABSTRACT FROM AUTHOR]

Clariid catfish are favorite food fish especially in African and Asian continents. Recently there has been preference for particular species or hybrids of these species based on quality assurance and value addition. Consequently, this study aimed to evaluate the possible effect of different catfish species and their hybrids on proximate composition and sensory attributes. Catfish species, Clarias gariepinus ( CC), Heterobranchus bidorsalis ( HH), with their hybrid ( CH), and reciprocal hybrid ( HC) were evaluated for sensory variables - cognitive (sweet, salty, sour, bitter, and recent characteristic taste 'umami') and qualitative (texture, aroma, flavor, and color) tests; and nutritional variables - proximate composition (moisture, protein, ether/fat, and ash). A 5-point hedonic scale from 'neutral/neither like nor dislike' to 'excellent/like extremely' was employed in sensory testing. The results showed similar ( P > 0.05) high moisture contents (>70%) in all species and high but different ( P < 0.05) ash contents (11-14%) that suggested good sources of mineral elements. The parent species CC and HH had higher ash contents than CH or HC. The crude protein contents were high and similar ( P > 0.05) across species (>57%). Fat or ether extract was different ( P < 0.05) and tended to be higher for species with Clarias as the female parent than Heterobranchus. Sensory analysis showed the parent species, CC and HH, more favorably rated for sweet and umami than the hybrids, CH and HC. However, CH was less sour and bitter than all other species and HC better than CH for salty but similar to CC and HH. All fish species were very well liked for texture, but the parent species were superior in flavor than the hybrids. All species were very well liked for aroma, color, and overall acceptability except HC, which was moderately liked. HC rated inferior to the other species overall in sensory attributes. All the fish species did not rate 'excellent/like extremely' for any attribute. It can be concluded that the parent catfish species possess better sensory qualities than hybrids, but all species need exogenous enhancement to their natural sensory components. [ABSTRACT FROM AUTHOR]

Light intensity during the early life stages of fish can have profound effects on their survival, developmental rate, yolk utilization efficiency and body size. Here, these aspects were analysed during two separate experiments (with or without exogenous food) on two distinct progenies of African sharptooth catfish, at five different light intensities (<0.1, 70, 500, 2500 and 8000 Lx; 24L:0D, 27.2°C). The duration of the egg incubation period (from 1.01 to 1.25 days post fertilization, dPF) was inversely proportional to light intensity, as hatching took place at more precocious developmental stages with increasing light intensity, i.e. at significantly ( P < 0.05) shorter body length and slightly more abundant remaining yolk at 8000 Lx in comparison to <0.1 Lx. At the start of exogenous feeding (4 dPF), most of these differences had vanished. During the period of mixed feeding (until the end of yolk absorption, 11 dPF), growth decreased significantly with increasing light intensity. Daily mortality rates after hatching varied very little between light intensities. Mortality during egg incubation increased significantly ( P < 0.05) with increasing light intensity, whereas it varied very little between light intensities thereafter, with the best survival rates since fertilization until the end of yolk absorption obtained at intermediate light intensities (70-2500 Lx). These results could be useful for improving the performance of African sharptooth catfish hatcheries. [ABSTRACT FROM AUTHOR]

L’examen de Clarias pachynema Boulenger, 1903 (Clariidae), Ctenopoma petherici Günther, 1864 (Anabantidae) et Parachanna obscura (Günther, 1861) (Channidae), capturés dans le bassin du Nkam au Cameroun, a révélé la présence de deux espèces nouvelles de Myxosporidies du genre Myxidium Bütschli, 1882, toutes parasites de la vésicule biliaire. Les espèces inédites sont : Myxidium nkamensis n. sp., parasite de Clarias pachynema; M. sangei n. sp., qui forme des spores dans la paroi de la vésicule biliaire de Parachanna obscura. Deux autres espèces, Myxidium petrocephali Fomena et Bouix, 1986 et M. distichodi Kostoïngué, Faye et Toguebaye, 1998, ont été retrouvées chez des hôtes nouveaux. Leur diagnose est complétée. La liste des espèces de Myxidium parasites des poissons d’eau douce d’Afrique est donnée.

L’étude des monogènes parasites branchiaux de trois espèces de poissons du genre Clarias Scopoli, 1777 (Clariidae) : C. pachynema, C. jaensis et C. camerunensis, pêchés dans le bassin du Nyong (Cameroun) a permis de récolter trois nouvelles espèces placées dans le nouveau genre Birgiellus, respectivement Birgiellus mutatus n. sp. chez Clarias pachynema, B. calaris n. sp. chez C. jaensis et B. kellensis n. sp. chez C. camerunensis. Le genre Birgiellus, voisin du genre Quadriacanthus, s’en distingue par la morphologie de la barre transversale ventrale formée d’une pièce unique (deux bras distincts chez Quadriacanthus) et par les uncinuli IV peu différents des autres (plus grands chez les Quadriacanthus). Birgiellus calaris diffère de B. mutatus par les anchors ventraux plus longs et plus épais, la morphologie de la barre transversale ventrale, la taille des pièces sclérifiées des appareils copulateurs mâle et femelle, avec la pièce accessoire mâle munie d’un talon, un manche trapézoïdal plus long et un crochet plus épais. Birgiellus kellensis, proche de B. calaris, s’en écarte par la taille plus faible des anchors dorsaux et ventraux, des barres transversales, du pénis, et de la pièce accessoire male, sans talon, mais avec une lame mince supplémentaire. En référence à l’article 8.5.2 du Code international de nomenclature zoologique (1999), le genre Birgiellus et les espèces B. mutatus et B. calaris remplacent respectivement le genre Claridectes et les espèces C. clarisa et C. alacris, initialement décrits par Birgi (1987), mais dont les spécimens n’ont jamais été déposés dans un musée. L’étude de la spécificité parasitaire de ces trois espèces montre qu’elle est du type oïoxène.

Sixty specimens of African sharptooth catfish Clarias gariepinus (Clariidae) were collected during the period of March 2014-February 2015 from boat landing sites and fishermen of the River Nile at Beni Suef Governorate, Egypt, and examined for the presence of digenean parasites. The morphology of these parasites was studied by using light microscopy to describe morphological and morphometrically measurements for different body parts. Three digenean species belonging to three different genera were collected from various organs within the examined fish species. A certain degree of site specificity was also observed, with Thaparotrema botswanensis being found only in the gall bladder of C. gariepinus, while both Pseudoholorchis clarii and Glossidium pedatum were found only in the intestine and thus seem to occupy a certain niche within their host. This study represent as the first record of T. botswanensis and G. pedatum from C. gariepinus, as well as the first report of the genera from the River Nile in Egypt. In addition, re-description of P. clarii clarifies measurements for some body parts. [ABSTRACT FROM AUTHOR]

The nervous systems of three Tylodelphys metacercariae (T. mashonense, Tylodelphys spp. 1 and 2) co-occurring in the cranial cavity of the catfish, Clarias gariepinus, were examined by the activity of acetylthiocholine iodide (AcThI), with the aim of better understanding the arrangement of sensillae on the body surface and the nerve trunks and commissures, for taxonomic purposes. Enzyme cytochemistry demonstrated a comparable orthogonal arrangement in the three metacercariae: the central nervous system (CNS) consisting of a pair of cerebral ganglia, from which anterior and posterior neuronal pathways arise and inter-link by cross-connectives and commissures. However, the number of transverse nerves was significantly different in the three diplostomid metacercariae: Tylodelphys sp. 1 (30), Tylodelphys sp. 2 (21) and T. mashonense (15). The observed difference in the nervous system of the three metacercariae clearly separates them into three species. These findings suggest that consistent differences in the transverse nerves of digenean metacercariae could enable the differentiation of metacercariae to the species level in the absence of molecular techniques. This, however, might require further testing on a larger number of species of digenean metacercariae. [ABSTRACT FROM AUTHOR]

Mitochondrial cytochrome C Oxidase I (COI) sequence variation among the clariid fishes of India (Clarias magur, C. dussumieriandC. gariepinus) and their relationship with other representative clariids was studied in this work. Three species were sampled and together with 23 COI sequences from GenBank were used to reconstruct phylogenetic relationships in the family Clariidae. The study revealed two clades: one consisting of the African species withC. dussumieri, and the other of Asian species suggesting the prevalence of intra-continental diversification of catfishes. This study further revealed that the genusClariasis monophyletic. For theCOIgene, the interspecies genetic divergence ranged from 0.056 to 0.182. The mean genetic difference betweenC. dussumieriand other selected African species in this study is 12.1%. It was also observed that the morphological similarity ofC. dussumieriandC. magurwas not replicated in the genetic level.Clarias dussumieriwas more close to African catfishC. gariepinusthus indicating the utility of COI phylogeny to identify the well-known African-Asian relationships within catfishes. The results also showed thatC. magurandC. batrachusare genetically distinct from each other. [ABSTRACT FROM AUTHOR]

Clariidae is a group that includes many species that have great economic importance in both fisheries and fish culture. Monogenean parasites of fishes assigned to this family have been studied in Cameroon, but there have been no studies on Clarias submarginatus Peter, 1882, a fish that is traditionally consumed by the local people. The examination of 43 specimens identified as C. submarginatus from Lake Ossa (first record of this fish species in the Sanaga basin), revealed that some of them belong to Quadriacanthus and are new. Their identification was made based on the morphology and the size of sclerotized parts of the haptor and the male and female copulatory complexes. Quadriacanthus macruncus Bahanak, Nack & Pariselle sp. nov. and Quadriacanthus submarginati Bahanak, Nack & Pariselle sp. nov. are characterized by the morphology of their accessory piece, pointed, slightly curved and wider at medium level, equipped with two subterminal, symmetrical and similar spines for Q. macruncus sp. nov. and made up of one long tip flanked by a short spine and a bulb for Q. submarginati sp. nov., while Quadriacanthus ossaensis Bahanak, Nack & Pariselle sp. nov. is distinguished by the unique morphology of the penis, ending in a fork. The new species of Quadriacanthus are herein described and their host specificity is discussed. [ABSTRACT FROM AUTHOR]

Present study was aimed to examine the role of exogenous melatonin on air-breathing activity rhythm in under constant light, LL and constant dark, DD. The actiity pattern emerged from actograms depicted occurrence of synchronized 24-h rhythm with the timings of light on/off in air-breathing activity (activity elevated during dark and declined during light hours) under LD 12:12 regime. However, such activity rhythm free runs under LL and DD. In addition, reappearance of entrained rhythm (atleast with the initiation of subjective dark hour) has been noticed after administration of melatonin. [ABSTRACT FROM AUTHOR]

We evaluated the role of the first pair of gill arches in the control of cardiorespiratory responses to normoxia and hypoxia in the air-breathing catfish, Clarias gariepinus . An intact group (IG) and an experimental group (EG, bilateral excision of first gill arch) were submitted to graded hypoxia, with and without access to air. The first pair of gill arches ablations reduced respiratory surface area and removed innervation by cranial nerve IX. In graded hypoxia without access to air, both groups displayed bradycardia and increased ventilatory stroke volume ( V T ), and the IG showed a significant increase in breathing frequency ( f R ). The EG exhibited very high f R in normoxia that did not increase further in hypoxia, this was linked to reduced O 2 extraction from the ventilatory current ( E O 2 ) and a significantly higher critical O 2 tension ( P cO 2 ) than the IG. In hypoxia with access to air, only the IG showed increased air-breathing, indicating that the first pair of gill arches excision severely attenuated air-breathing responses. Both groups exhibited bradycardia before and tachycardia after air-breaths. The f H and gill ventilation amplitude ( V AMP ) in the EG were overall higher than the IG. External and internal NaCN injections revealed that O 2 chemoreceptors mediating ventilatory hypoxic responses ( f R and V T ) are internally oriented. The NaCN injections indicated that f R responses were mediated by receptors predominantly in the first pair of gill arches but V T responses by receptors on all gill arches. Receptors eliciting cardiac responses were both internally and externally oriented and distributed on all gill arches or extra-branchially. Air-breathing responses were predominantly mediated by receptors in the first pair of gill arches. In conclusion, the role of the first pair of gill arches is related to: (a) an elevated E O 2 providing an adequate O 2 uptake to maintain the aerobic metabolism during normoxia; (b) a significant bradycardia and increased f AB elicited by externally oriented O 2 chemoreceptors; (c) increase in the ventilatory variables ( f R and V AMP ) stimulated by internally oriented O 2 chemoreceptors. [ABSTRACT FROM AUTHOR]

This study was conducted to assess the effect of the water quality of Ogun River, on the African catfish Clarias gariepinus haematological indices. Samples of water and C. gariepinus were collected from Ogun River (Station I, Opeji and Station II, Lafenwa) to determine and compare effects of possible differences of water quality on hematological parameters of C. gariepinus. The results showed that higher values were recorded at the station II than Station I for almost all the physicochemical parameters and only sulphate values from Stations I and II were statistically significant (P < 0.05). [ABSTRACT FROM AUTHOR]

The structure and physiology of enteric system are very similar in all classes of vertebrates, although they have been investigated only occasionally in non-mammalian vertebrates. Very little is known about the distribution of the neurotransmitters in the gut of actinopterygian fishes. Anatomical and physiological studies of enteric nervous systems in the spotted gar ( Lepisosteus oculatus) and airbreathing catfish ( Clarias batrachus), a non-teleost and teleost actinopterygian, respectively, have not been undertaken. This study provides the first comprehensive characterization of the range of neurochemical coding in the enteric nervous system of these two species, including the chemical diversity of the mucosal endocrine cells in the pyloric stomach of Clarias. Autonomic innervation of the secretory glands is also described and reported herein for the first time for fishes. We also report splanchnic (spinal) innervation of the stomach, submucosal ganglia (that also colocalize with nNOS) and caudal intestine of Clarias. In both fish species, numerous 5 HT, Ch AT, n NOS and TH-positive nerve fibres have been observed. These discoveries demonstrate that much more physiological and pharmacological data are needed before a comprehensive model of enteric nervous system control in vertebrates can be developed. [ABSTRACT FROM AUTHOR]

Taste preferences to classical taste substances and L-isomers of free amino acids and feeding behavior are analyzed in clariids Clarias gariepinus, C. macrocephalus, and C. batrachus and the hybrid between C. macrocephalus (female) and C. gariepinus (male). It is found that citric acid (0.26 M) is palatable for all studied clariids, and the presence of this acid in agar-agar pellets considerably increases their consumption by fish. The stimulating effect of citric acid on C. gariepinus and C. macrocephalus is greater than the effect of water extracts of organisms consumed by these species or of artificial foods. Sucrose (0.29 M) is palatable for both species. The palatability of sodium chloride (1.73 M) and calcium chloride (0.9 M) is the same for C. gariepinus and the hybrid but different for C. macrocephalus ( p < 0.05), indicating the patroclinous type of taste preference inheritance. Of the 21 free amino acids (0.1-0.001 M), 17 are palatable for C. gariepinus (methionine, alanine, glutamine, cysteine, histidine, etc.) and four are indifferent (arginine, leucine, isoleucine, and tryptophan). No amino acid is found to be deterrent for the studied fishes. All studied fishes typically consume or reject pellets after a single intraoral testing; repeated grasping of pellets is extremely rare. The total time clariids spend on intraoral testing and consumption or rejection of one pellet is at most 3-5 s. Clariids captured in their natural environments ( C. macrocephalus and C. batrachus) require considerably more time for acclimation to aquarium conditions than clariids taken from the aquaculture ( C. gariepinus and the hybrid): at least one month and several days, respectively. The stress response to handling in wild fish includes the release of large amounts of skin mucus. [ABSTRACT FROM AUTHOR]

Growth and feed conversion were monitored in triplicate groups of the African catfishHeterobranchus longifilis(mean weight 11 ± 1.8 g) fed small (2.5–5.54 cm) tilapia (Oreochromis niloticus) and artificial feeds at various rates (treatments 1, 2, and 3), and tilapia or artificial feed (treatments 4 and 5, respectively). Artificial feed was a 42% crude protein commercial pellet. LiveO. niloticuswere fed at a rate of 4 g live tilapia/catfish/day. Pelleted feeding rate was 2%, 1%, 0.5%, and 1% of body weight thrice daily in treatments 1, 2, 3, and 5, respectively. After 70 days, mean weight was 180 ± 9.5 g, 157 ± 15.7 g, 147 ± 2.6 g, 77 ± 10.9 g, and 74 ± 10 g, in treatments 1, 2, 3, 4, and 5, respectively. Treatment significantly affected SGR (% day−1) (P < 0.03) and pelleted feed conversion ratio (P < 0.0003). FCR was 1.09 ± 0.01, 0.63 ± 0.08, 0.42 ± 0.11, and 1.12 ± 0.13 in treatments 1, 2, 3, and 5, respectively. Profit was highest (P < 0.01) in treatment 2. Tilapia consumption seems to improve utilization of artificial feed and may be a way for some catfish farmers to save money. [ABSTRACT FROM AUTHOR]