Hoplias Aimara Research Articles

Genomic resources for the monitoring and management of Tometes trilobatus, Hoplias aimara and Myloplus rhomboidalis, three exploited freshwater fish species in French Guiana

The Neotropical region, hosts a quarter of all freshwater fish species, while providing important food resources for local human populations. The management of neotropical freshwater ecosystems is thus of primary importance for both biodiversity conservation and local human sustainability. Recent technological advances in the field of genomics offer new tools for managers and practitioners to monitor entire fish assemblages using environmental DNA (eDNA) metabarcoding, or to detect specific species or populations using targeted eDNA. The availability of species genomics information is thus crucial to implement eDNA monitoring methods. Nevertheless, specific primers allowing species-centred approaches are lacking for most species. In French Guiana, only 18 mitochondrial genomes of freshwater fishes have been published out of more than 400 species known from French Guiana. In this study, we provide genomic resources for Myloplus rhomboidalis (locally called Koumarou), Hoplias aimara (Aimara) and Tometes trilobatus (Pakou), three exploited fish species in French Guiana. We provide complete mitochondrial genomes and tools for the detection of the three fish species by developing a targeted species approach using digital PCR (dPCR) for each species.

Ectoparasite crustaceans of ten fish species from the upper Araguari River in northern Brazil.

Fish parasites are an important part of aquatic biodiversity and knowing these species and their interactions with their hosts helps in monitoring the aquatic biota. The present study investigated the ectoparasite crustacean fauna of ten fish species from the upper Araguari River, in the state of Amapá, northern Brazil. A total of 508 fish were collected and analyzed from July to November 2014, of which 82.6% (109) were parasitized by one or more crustacean ectoparasite species. In the ten host fish species, a total of 308 ectoparasite specimens were collected, from 12 taxa, such as Argulus multicolor Stekhoven, 1937, Argulus spinulosus Silva, 1980, Argulus sp.1, Argulus sp.2, Argulus sp.3, Dipteropeltis sp., Dipteropeltis hirundo Calman, 1912, Dolops bidentata Bouvier, 1899, Dolops striata Bouvier, 1899 (Argulidae), Braga fluviatilis Richardson, 1911, Braga amapaensis Thatcher, 1996 (Cymothoidae) and Excorallana berbicensis Boone, 1918 (Corallanidae). Higher levels of prevalence and abundance were recorded for Hoplias aimara (Valenciennes, 1847) and Tometes trilobatus Valenciennes, 1850, respectively. These ectoparasites were found in the fins, integument, mouth, and anus of the host fish. Argulus sp.2 and D. bidentata were the most abundant parasites (65.1%), and had the highest species richness. This study registered 36 novel host-parasite interactions, and thus represents a new record for all host species here examined.

Hepatozoon parasites (Apicomplexa: Hepatozoidae) in fish Hoplias aimara (Characiformes, Erythrinidae) from the Eastern Amazon, Brazil.

This study reports the occurrence of parasites belonging to the Hepatozoon genus in fish Hoplias aimara from the Eastern Amazon. Fish (n = 54) were sampled from the Falsino River, located in the Amapá National Forest (FLONA), in the state of Amapá, northern Brazil. Fresh liver preparations were examined in the field between a slide and a coverslip under a light microscope. Cysts containing Hepatozoon cystozoites were observed in the liver of 5 (9%) out of 54 H. aimara individuals. The cysts were ovoid (mean dimensions 10.28 × 9.8μm), presenting up to four elongated cystozoites (mean dimensions 11.04 × 1.68μm), containing 1 to 4 residual bodies of different sizes. A single liver sample containing cysts was submitted to DNA extraction and PCR analyses based on a fragment of the 18S rRNA gene. The sequencing revealed a 465bp fragment exhibiting 99% query coverage, 0.0 E-value, and 98.7% identity with Hepatozoon caimani (MF322538 and MF322539), detected in caimans (Caiman yacare) from Brazil. This is the first report of the occurrence of cysts containing Hepatozoon cystozoites in free-living fishes.

Bioaccumulation of mercury in predatory fish from Amapá State, Brazil.

Bioaccumulation of Hg in aquatic systems varies considerably according to the food chain structure and age of fish. As fishes are an important food resource in the Amazon region, common species of carnivorous and piscivorous fish in Amapa State were analyzed for contamination by Mercury. Specifically, the influence of standard length and weight of individuals on the observed Hg concentrations was investigated and used to evaluate whether bioaccumulation rates vary among different species. The fishes were collected from five locations in Amapa State between August 2017 and May 2018. We measured the total mercury content in 204 specimens representing nine carnivorous/piscivorous species of fishes: Serrasalmus rhombeus, Plagioscion squamosissimus, Megalops atlanticus, Hoplias malabaricus, Cichla monoculus, Brachyplatystoma vaillantii, Boulengerella cuvieri, Ageneiosus inermis and Hoplias aimara. All fishes had some level of Hg contamination and the potential for bioaccumulation of this contaminant varied among species. A positive relationship between weight and/or length and the total body Hg concentration was observed only for Serrasalmus rhombeus, Hoplias malabaricus, Cichla monoculus and Brachyplatystoma vaillantii.

High Genetic Diversity despite Conserved Karyotype Organization in the Giant Trahiras from Genus Hoplias (Characiformes, Erythrinidae).

In the fish genus Hoplias, two major general groups can be found, one of which is formed by the “common trahiras” (Hoplias malabaricus group) and the other by the “giant trahiras” (Hoplias lacerdae group, in addition to Hoplias aimara), which usually comprises specimens of larger body size. Previous investigations from the giant trahiras group recovered 2n = 50 meta/submetacentric chromosomes and no sex chromosome differentiation, indicating a probable conservative pattern for their karyotype organization. Here, we conducted comparative cytogenetic studies in six giant trahiras species, two of them for the first time. We employed standard and advanced molecular cytogenetics procedures, including comparative genomic hybridization (CGH), as well as genomic assessments of diversity levels and phylogenetic relationships among them. The results strongly suggest that the giant trahiras have a particular and differentiated evolutionary pathway inside the Hoplias genus. While these species share the same 2n and karyotypes, their congeneric species of the H. malabaricus group show a notable chromosomal diversity in number, morphology, and sex chromosome systems. However, at the same time, significant changes were characterized at their inner chromosomal level, as well as in their genetic diversity, highlighting their current relationships resulting from different evolutionary histories.

Caribbean Consortium for Research in Environmental and Occupational Health (CCREOH) Cohort Study: influences of complex environmental exposures on maternal and child health in Suriname.

PurposeThe Caribbean Consortium for Research in Environmental and Occupational Health prospective environmental epidemiologic cohort study addresses the impact of chemical and non-chemical environmental exposures on mother/child dyads in Suriname. The study determines associations between levels of environmental elements and toxicants in pregnant women, and birth outcomes and neurodevelopment in their children.ParticipantsPregnant women (N=1143) were enrolled from December 2016 to July 2019 from three regions of Suriname: Paramaribo (N=738), Nickerie (N=204) and the tropical rainforest interior (N=201). Infants (N=992) were enrolled at birth. Follow-up will take place until children are 48 months old.Findings to dateBiospecimens and questionnaire data on physiological and psychosocial health in pregnant women have been analysed. 39.1% had hair mercury (Hg) levels exceeding values considered safe by international standards. Median hair Hg concentrations in women from Paramaribo (N=522) were 0.64 µg/g hair (IQRs 0.36–1.09; range 0.00–7.12), from Nickerie (N=176) 0.73 µg/g (IQR 0.45–1.05; range 0.00–5.79) and the interior (N=178) 3.48 µg/g (IQR 1.92–7.39; range 0.38–18.20). 96.1% of women ate fish, respective consumption of the three most consumed carnivorous species, Hoplias aimara, Serrasalmus rhombeus and Cichla ocellaris, known to have high Hg levels, was 44.4%, 19.3% and 26.3%, respectively, and was greater among the interior subcohort. 89% frequently consumed the vegetable tannia, samples of which showed presence of worldwide banned pesticides. 24.9% of pregnant women had Edinburgh Depression Scale scores indicative of probable depression.Future plansFish consumption advisories are in development, especially relevant to interior women for whom fish consumption is likely to be the primary source of Hg exposure. Effects of potentially beneficial neuroprotective factors in fish that may counter neurotoxic effects of Hg are being examined. A pesticide literacy assessment in pregnant women is in progress. Neurodevelopmental assessments and telomere length measurements of the children to evaluate long-term effects of prenatal exposures to toxicant mixtures are ongoing.

Analysis of inorganic contaminants in Hoplias aimara Valenciennes 1846 (Trairão) explored by the fishing activity in the high Rio Araguari, Amapá, Brazil

This study aims to evaluate the concentration of inorganic contaminants in Hoplias aimara Valenciennes 1846, coming from the upper Rio Araguari, State of Amapa.

Application of the European Water Framework Directive: Identification of reference sites and bioindicator fish species for mercury in tropical freshwater ecosystems (French Guiana)

Abstract Mercury (Hg) is a toxic metal subject to several international regulations. The European Water Framework Directive (WFD) established in 2008 an Environmental Quality Standard for biota (EQSbiota) at 0.02 µg.g−1 fresh weight. This standard is not always adapted, such as in French Guiana subjected to high natural background Hg levels and intensive illegal gold mining. Therefore, this study focuses on how to apply the WFD for the definition of good chemical status (i.e., EQSbiota) in a context of strong and generalized natural and anthropic Hg contamination. Based on Hg concentrations measured in 6208 fish over >200 sites between 2004 and 2015, we first aimed at discriminating the natural or anthropogenic influences at each site. Then, as WFD recommends considering only high trophic level fish species as bioindicator species, we selected carnivorous/piscivorous fish species able to significantly accumulate Hg and discriminate reference sites from gold mining polluted sites. Total Hg concentrations measured in fish muscle were mostly above the EQSbiota (100% for creeks and 84% for rivers), confirming the unsuitability of the direct application of this standard in French Guiana. Among the studied sites, few potential reference sites were identified: eight sites spread over six different watersheds for creeks, and only two areas (group of sites) both on the Oyapock watershed for rivers. Several relevant bioindicators fish species are proposed: ten species (over 35 species tested) belonging to seven genera on creeks (Moenkhausia oligolepis, Gymnotus carapo, Sternopygus macrurus, Jupiaba [abramoides + keithi], Pimelodella [cristata + geryi + macturki], Copella carsevennensis, Pyrrhulina filamentosa.), and four species (over 21 species tested) belonging to three genera on rivers (Acestrorhyncus [micropelis + falcatus], Hoplias aimara, Ageneiosus inermis). In order to facilitate field sampling, difficult in such remote hydrosystems, and to improve results interpretation, we tested the possibility to group some of these species. Our results indicate that only Jupiaba, Moenkhausia, Pimelodella and Pyrrhulina on creeks could be grouped; and the three bioindicators species proposed on rivers could be pooled. Finally, this work proposes in situ-based reference Hg concentrations for selected bioindicator fish species from French Guiana as an alternative to detect Hg-impacted sites and help the application of the WFD in tropical systems.

Mercury contamination levels in the bioindicator piscivorous fish Hoplias aïmara in French Guiana rivers: mapping for risk assessment.

In French Guiana, native populations present high level of mercury contamination, which has been linked to the consumption of contaminated fishes. The goal of this study is to undertake a cartography of mercury contamination levels in fishes from the six main Guiana rivers. The selected species for this study is the ubiquitous piscivorous fish Hoplias aimara. A total number of 575 fishes from 134 discrete fishing sites are regrouped into 51 river sectors. Results from this study permits to rank the six main Guiana rivers by their mean level of contamination: Oyapock (0.548mgkg-1), Comté (0.624mgkg-1), Maroni (0.671mgkg-1), Approuague (0.684mgkg-1), Mana (0.675mgkg-1), and Sinnamary (1.025mgkg-1). The contamination is however not spatially homogenous along each river, and a map of the different levels of mercury contamination in fishes is provided. Sectors of low mean Hg contamination are observed both upstream (0.471mgkg-1) and downstream (0.424mgkg-1), corresponding to areas without any influence of gold mining activities and areas under the influence of estuarine dilution, respectively. Anoxia and gold mining activities are found to be the two main factors responsible for the high mercury concentration in fish muscles. While mean levels of mercury contaminations are higher in anoxia areas (1.029mgkg-1), contaminations induced by gold mining activities (0.717mgkg-1) present the most harmful consequences to human populations. No significant differences in Hg concentrations are observed between 2005 and 2014 for neither a pristine nor a gold mining area, while Hg concentration differences are observed between former (0.550mgkg-1) and current gold mining sites (0.717mgkg-1).

First Record in Brazil of <i> Epistylis </i> sp. (Ciliophora) Adhered to <i> Argulus </i> sp. (Argulidae), a Parasite of <i> Hoplias aimara </i> (Eritrhinidae)

This paper records the first occurrence of Epistylis sp. on the body surface of Argulus sp. parasitizing Hoplias aimara from the upper Araguari River, in the eastern Amazon region, in the north of Brazil. Of the 16 specimens of H. aimara examined, 93.7% had their pelvic, caudal and pectoral fins and tegument infested by Argulus sp. (n = 73), which in turn were infested by Epistylis sp. The specimens of Epistylis sp. from the body surface of Argulus sp. were analyzed using Scanning Electron Microscopy (SEM). The present study also identified a widening of the geographic distribution of these two species of ectoparasites to the eastern Amazon region of Brazil.

First data on the parasites of Hoplias aimara (Characiformes): description of two new species of gill monogeneans (Dactylogyridae).

The first data on the parasites of the giant trahira, Hoplias aimara (Characiformes: Erythrinidae), a little known, but popular fish for sport angling, are provided. In H. aimara from the Xingu River in Brazil, two new species of gill monogeneans of the family Dactylogyridae were found and their description is provided herein. Urocleidoides aimarai n. sp. differs from all 18 congeners by the presence of a large accessory piece of the male copulatory organ and based by morphology of anchors. Urocleidoides xinguensis n. sp. is distinguished by unique combination of copulatory complex and haptoral structures.

Confirmation of sexual dimorphism in Hoplias aimara (Valenciennes, 1847) (Erythrinidae: Characiformes) proposed by local expertise in Amapá, Brazil.

Fishes may show sexual dimorphism according to their reproductive strategies. In some species, this differentiation is already well known. However, with the findings obtained from recent studies, the number of species for which sex can be determined without dissection has increased. Thus far, the presence of external secondary sexual characteristics in Hoplias aimara, a very well-studied species, has not been reported. Traditional knowledge evidenced through riparian people observations indicated the possibility of sexual dimorphism in this species, which was studied in 2 conservation units, Sustainable Development Reserve of Iratapuru River and Tumucumaque Mountains National Park, in the state of Amapá, Brazil. Fishes were captured, and their anal fins were examined when they were still fresh; the sex of the fishes was confirmed by dissection. The same procedure was used for formalin-fixed fishes. By assessing the shape of the anal fin in fresh or fixed fishes, it was possible to determine the sex of the fish, which was then confirmed by dissection. H. aimara shows sexual dimorphism expressed in the morphology of their anal fin. Thus, the sex of fishes deposited in collections can be identified without any dissection, thereby providing important biological information about the specimens.

Effects of Methylmercury Contained in a Diet Mimicking the Wayana Amerindians Contamination through Fish Consumption: Mercury Accumulation, Metallothionein Induction, Gene Expression Variations, and Role of the Chemokine CCL2

Methylmercury (MeHg) is a potent neurotoxin, and human beings are mainly exposed to this pollutant through fish consumption. We addressed the question of whether a diet mimicking the fish consumption of Wayanas Amerindians from French Guiana could result in observable adverse effects in mice. Wayanas adult men are subjected to a mean mercurial dose of 7 g Hg/week/kg of body weight. We decided to supplement a vegetarian-based mice diet with 0.1% of lyophilized Hoplias aimara fish, which Wayanas are fond of and equivalent to the same dose as that afflicting the Wayanas Amerindians. Total mercury contents were 1.4 ± 0.2 and 5.4 ± 0.5 ng Hg/g of food pellets for the control and aimara diets, respectively. After 14 months of exposure, the body parts and tissues displaying the highest mercury concentration on a dry weight (dw) basis were hair (733 ng/g) and kidney (511 ng/g), followed by the liver (77 ng/g). Surprisingly, despite the fact that MeHg is a neurotoxic compound, the brain accumulated low levels of mercury (35 ng/g in the cortex). The metallothionein (MT) protein concentration only increased in those tissues (kidney, muscles) in which MeHg demethylation had occurred. This can be taken as a molecular sign of divalent mercurial contamination since only Hg2+ has been reported yet to induce MT accumulation in contaminated tissues. The suppression of the synthesis of the chemokine CCL2 in the corresponding knockout (KO) mice resulted in important changes in gene expression patterns in the liver and brain. After three months of exposure to an aimara-containing diet, eight of 10 genes selected (Sdhb, Cytb, Cox1, Sod1, Sod2, Mt2, Mdr1a and Bax) were repressed in wild-type mice liver whereas none presented a differential expression in KO Ccl2−/− mice. In the wild-type mice brain, six of 12 genes selected (Cytb, Cox1, Sod1, Sod2, Mdr1a and Bax) presented a stimulated expression, whereas all remained at the basal level of expression in KO Ccl2−/− mice. In the liver of aimara-fed mice, histological alterations were observed for an accumulated mercury concentration as low as 32 ng/g, dw, and metal deposits were observed within the cytoplasm of hepatic cells.

Comparative Cytogenetics of Giant Trahiras Hoplias aimara and H. intermedius (Characiformes, Erythrinidae): Chromosomal Characteristics of Minor and Major Ribosomal DNA and Cross-Species Repetitive Centromeric Sequences Mapping Differ among Morphologically Identical Karyotypes

Karyotype and cytogenetic characteristics of 2 species of giant trahiras, Hopliasintermedius, São Francisco river basin, and Hopliasaimara, Arinos river (Amazon basin), were examined by conventional (C-banding, Ag-NOR, DAPI/CMA₃ double-staining) and fluorescent in situ hybridization (FISH) with 5S, 18S rDNA probes and cross-species Cot-1 DNA probing. Both species invariably had diploid chromosome number 2n = 50 and identical karyotypes composed of 10 pairs of metacentric and 15 pairs of submetacentric chromosomes. On the other hand, staining with base-specific fluorochromes (CMA₃, DAPI) and FISH mapping of repetitive DNA sequences showed extensive interspecific differences: while the genome of H. aimara had one submetacentric pair bearing CMA₃-positive (DAPI-negative) sites, that of H. intermedius had 4 such pairs; while FISH with a 5S rDNA probe showed one (likely homologous) signal-bearing pair, that with 18S rDNA displayed one signal-bearing pair in H. intermedius and 2 such pairs in H. aimara. Cross-species FISH probing with Cot-1 DNA prepared from total DNA of both species showed no signals of Cot-1 DNA from H. aimara on chromosomes of H. intermedius but reciprocally (Cot-1 DNA from H. intermedius on chromosomes of H. aimara) displayed signals on at least 4 chromosome pairs. Present findings indicate (i) different composition of repetitive sequences around centromeres, (ii) different NOR phenotypes and (iii) distinct taxonomic status of both giant trahira species.

Taxonomic Study of Hoplias Aimara (Valenciennes, 1846) and Hoplias macrophthalmus (Pellegrin, 1907) (Ostariophysi, Characiformes, Erythrinidae)

The taxonomy of the nominal species of giant trahiras Hoplias aimara (Valenciennes, 1846) and Hoplias macrophthalmus (Pellegrin, 1907), both described from Cayenne (French Guiana), was evaluated to determine whether they constitute distinct forms and to determine the geographic distribution of the recognized species. A total of 200 specimens were examined (30–624 mm standard length). Analysis of meristic and morphometric data resulted in the recognition of a single species. Study of the type-specimens revealed that both species names, H. aimara and H. macrophthalmus, refer to the same taxon. According to the Principle of Priority of the International Code of Zoological Nomenclature the name Hoplias aimara has precedence. This species is distinguished from congeners by the presence of a vertically-elongate dark spot on the median portion of the opercular membrane and by the absence of the accessory ectopterygoid. Hoplias aimara occurs in the drainages of Rio Tocantins, Rio Xingu, Rio Tapajós, Rio Jarí, and Rio Trombetas, in coastal drainages of the Guyanas, Suriname, and state of Amapá, Brazil. In the Río Orinoco basin, the species occurs only in the Río Caroní and rivers to the east of this drainage. Literature records of Hoplias aimara for the Rio Purus and upper Río Orinoco were based on misidentifications. This pattern of geographic distribution of Hoplias aimara in rivers of the Guyanas and Brazilian Shields also occurs in other Neotropical species of fishes.

Goldmining and mercury contamination of the piscivorous fish Hoplias aimara in French Guiana (Amazon basin)

Mercury contamination of 35 freshwater fish species collected from the upper part of the Petit-Saut hydroelectric reservoir (French Guiana) was analyzed in relation to their food regimes. Results showed marked biomagnification: the ratio between extreme Hg concentrations in the muscle from piscivorous species (14.3μg/g, dry weight (dw) for Acestrorhynchus guianensis) and herbivorous species (0.02μg/g, dw for Myleus ternetzi) was 715. The piscivorous species Hoplias aimara was selected to define the relationships between biometric criteria and Hg accumulation. The probability of catching a H. aimara exceeding the WHO safety limit (2.5μgHg/g, dw) was computed from the kernel density estimator of mercury concentrations in the muscle: for fish weighing over 1kg (fish usually consumed), the probability was 0.93. From these results, H. aimara could be considered an indicator of mercury biomagnification in the foodwebs and a potential risk to human populations that include this fish in their diet.

Movements of Hoplias aimara during the filling phase of the Petit‐Saut dam, French Guyana

Twenty Hoplias aimara were tagged intraperitoneally with radio‐transmitters in the Sinnamary River, French Guyana. In November 1993, 13 tagged fish were released in an area which would be flooded by the Petit‐Saut reservoir impoundment in mid‐1994. Seven other tagged fish were released in January 1994, 20 km upstream of the upper limit of the reservoir. Hoplias aimara showed site fidelity: 75% of fish returned to their capture site before the test area was inundated. The remaining fish stayed close to the release area. Monitoring during three 24‐h cycles before reservoir filling showed that H. aimara has a limited home range, which is less marked in unconstrained reaches during the wet season (April to August) than in constrained reaches during the dry season (September to November). In natural conditions, H. aimara has a wider home range in unconstrained river reaches than in constrained river reaches. After closure of the dam, in September and October 1994 (dry season, low water) more than half of the total H. aimara tagged in the flooded zone migrated upstream following the rise of water.