Flounder Specimens Research Articles

Larvae trypanorhynch (Cestoda) infecting the dusky flounder, Syacium papillosum (Paralichthyidae: Pleuronectiformes) in the continental shelf of the Yucatan Peninsula, Mexico.

Trypanorhynch cestode larvae were found parasitizing specimens of dusky flounder Syacium papillosum (Linnaeus, 1758) in the Southeastern Gulf of Mexico (s-GoM). Plerocercoids were recovered from a total of 194 flatfish, embedded in the intestine and stomach wall. Trypanorhynch were identified using morphology and a molecular phylogeny using newly sequenced partial 28S (region D1-D3) ribosomal DNA in combination with data derived from other species of trypanorhynchs available from GenBank. Larvae representing three genera of trypanorhynch cestodes, Nybelinia Poche, 1926; Kotorella Euzet & Radujkovic, 1989 and Oncomegas Dollfus, 1929 were found in dusky flounder specimens in the s-GoM. These plerocercoids represent six species: Nybelinia sp. 1, Nybelinia sp. 2, Nybelinia sp. 3, Nybelinia sp. 4, Kotorella pronosoma (Stossich, 1901) and Oncomegas wageneri (Linton, 1890) Dollfus, 1929. All cestode specimens in this study represent new locality records for their respective species.

Population Genetic Study on the European Flounder (Platichthys flesus) from the Southern Baltic Sea Using SNPs and Microsatellite Markers.

The European flounder (Platichthys flesus), which is closely related to the recently discovered Baltic flounder (Platichthys solemdali), is currently the third most commercially fished species in the Baltic Sea. According to the available data from the Polish Fisheries Monitoring Center and fishermen's observations, the body condition indices of the species in the Baltic Sea have declined in recent years. The aim of the present study was to obtain information on the current patterns of genetic variability and the population structure of the European flounder and to verify whether the Baltic flounder is present in the southern Baltic Sea. Moreover, we aimed to verify whether the observed decline in the body condition indices of the species in the Baltic Sea might be associated with adaptive alterations in its gene pool due to increased fishing pressure. For this purpose, 190 fish were collected from four locations along the central coastline of Poland, i.e., Mechelinki, Władysławowo, the Vistula Lagoon in 2018, and the Słupsk Bank in 2020. The fish were morphologically analyzed and then genetically screened by the application of nineteen microsatellite DNA and two diagnostic SNP markers. The examined European flounder specimens displayed a high level of genetic diversity (PIC = 0.832-0.903, I = 2.579-2.768). A lack of significant genetic differentiation (Fst = 0.004, p > 0.05) was observed in all the examined fish, indicating that the European flounder in the sampled area constitutes a single genetic cluster. A significant deficiency in heterozygotes (Fis = 0.093, p < 0.05) and overall deviations from Hardy-Weinberg expectations (H-WE) were only detected in fish sampled from the Słupsk Bank. The estimated effective population size (Ne) among the sampled fish groups varied from 712 (Słupsk Bank) to 10,115 (Władysławowo and Mechelinki). However, the recorded values of the Garza-Williamson indicator (M = 0.574-0.600) and the lack of significant (p > 0.05) differences in Heq > He under the SMM model did not support the species' population size changes in the past. The applied SNP markers did not detect the presence of the Baltic flounder among the fish sampled from the studied area. The analysis of an association between biological traits and patterns of genetic diversity did not detect any signs of directional selection or density-dependent adaptive changes in the gene pool of the examined fish that might be caused by increased fishing pressure.

Hemiurid and lecithasterid digenean trematodes and camallanid and cucullanid nematodes parasitizing flounders collected off the coast of Rio de Janeiro State, Brazil.

A total of 132 flounder specimens (60 Paralichthys isosceles, 36 Paralichthys patagonicus and 36 Xystreurys rasile) were collected off the coast of the state of Rio de Janeiro, Brazil. The fish were measured, necropsied, and had their organs investigated for hemiurid and lecithasterid digenean trematodes and camallanid and cucullanid nematodes. Taxonomic identification of the parasites was based on morphological and morphometric characters and was conducted using bright-field and scanning electron microscopies. The trematodes Lecithochirium monticellii and Aponurus laguncula were found parasitizing P. isosceles, P. patagonicus and X. rasile while the nematodes Procamallanus (Spirocamallanus) halitrophus and Cucullanus bonaerensis were found parasitizing P. isosceles and X. rasile and P. isosceles, P. patagonicus and X. rasile, respectively. Parasite indices of prevalence, mean intensity, mean abundance, and range of infection, as well as infection site, were evaluated for each parasite species. This study allowed to evidence the first occurrence of P. patagonicus by L. monticellii; X. rasile by A. laguncula and P. (S.) halitrophus; and P. isosceles and P. patagonicus by C. bonaerensis in the Western South Atlantic Ocean.

Kudoa ogawai (Myxosporea: Kudoidae) Infection in Cultured Olive Flounder Paralichthys olivaceus.

Since Kudoa septempuntata was identified as a causative agent of food poisoning associated with raw olive flounder Paralichthys olivaceus, interest and concern regarding the parasite have increased. However, there have been no investigations or reports of other Kudoa species infecting the fish (except for K. paralichthys, which infects the brain) in Korea. We found cysts filled with myxospores of Kudoa species in muscles of cultured olive flounder specimens and identified these to the species level. Mature spores were quadrate, measuring 8.7±0.5 μm in length, 9.2±0.4 μm in thickness, and 12.9±0.6 μm in width. The spores containing 4 polar capsules had a length of 2.1±0.2 μm and a width of 1.8±0.3 μm. The partial 18S and 28S rDNA of isolates showed 99–100% similarities with K. ogawai. Using these morphological and molecular analyses, the species was identified as K. ogawai. This study is the first report of K. ogawai infection in cultured olive flounder in Korea.

Isolation of Vibrio tapetis from two native fish species (Genypterus chilensis and Paralichthys adspersus) reared in Chile and description of Vibrio tapetis subsp. quintayensis subsp. nov.

A group of seven Chilean isolates presumptively belonging to Vibrio tapetis was isolated from diseased fine flounders (Paralichthys adspersus) and red conger eel (Genypterus chilensis) experimentally reared in Quintay (Chile). All isolates were confirmed as members of V. tapetis on the basis of matrix-assisted laser desorption ionization time-of-flight MS, 16S rRNA gene sequencing, DNA-DNA hybridization values and G+C content. The ERIC-PCR and REP-PCR patterns were homogeneous among those isolates recovered from the same host (red conger or fine flounders), but distinct from the type strains V. tapetis subsp. tapetis CECT 4600T and V. tapetis subsp. britannicus CECT 8161T. On the basis of atpA, rpoA, rpoD, recA and pyrH gene sequence similarities (99.7-100 %) and clustering in the phylogenetic trees, the red conger isolates (Q20, Q047, Q48 and Q50) were confirmed as representing V. tapetis subsp. tapetis. However, they differed from V. tapetis subsp. tapetis CECT 4600T in their lipase, alpha quimiotripsin and non-acid phosphatase production. On the other hand, the fine flounder isolates (QL-9T, QL-35 and QL-41) showed rpoD, recA and pyrH gene sequence similarities ranging from 91.6 to 97.7 % with the type strains of the two V. tapetis subspecies (CECT 4600T and CECT 8161T) and consistently clustered together as an independent phylogenetic line within V. tapetis. Moreover, they could be differentiated phenotypically from strains CECT 4600T and CECT 8161T by nine and three different biochemical tests, respectively. In conclusion, the presence of V. tapetis in diseased red conger eel and fine flounder was demonstrated, extending the known host range and geographical location for this pathogen. Furthermore, this study demonstrates that the three isolates from fine flounder represent a novel subdivision within V. tapetis, for which the name V. tapetis subsp. quintayensis subsp. nov. is proposed and with QL-9T (=CECT 8851T=LMG 28759T) as the type strain. Although QL-9T was isolated from kidney of diseased fine flounder specimens, the challenge assays showed that it was non-pathogenic for this species.

Can analysis of Platichthys flesus otoliths provide relevant data on historical metal pollution in estuaries? Experimental and in situ approaches

Despite recent efforts to manage them more efficiently, estuaries are natural sinks for a wide range of metal contaminants, many of which accumulate at potentially toxic concentrations for fish populations, posing a threat to recruitment and stocks. While analysis of metal concentrations in soft tissue and water samples calls for continuous and long-term sampling operations, the use of otoliths to study metal pollution may be one way of providing a historical record of pollutant exposure. In this study, we examine the potential use of otoliths as natural tracers of metal contamination. A “cocktail” of different metals (Cd, Pb and Ni) was used to test bio-accumulation in otoliths and tissue (liver, kidney, muscle and gills) extracted from juvenile flounder (Platichthys flesus). Assessment took place under controlled conditions over a three month period, with water exposure concentrations increasing every 3weeks. The concentrations used were natural (T1), X5 (T2), X10 (T3), and null (T4). Chemical analyses were carried out using an inductively coupled plasma optical emission spectrometer ICP-OES and atomic absorption spectrometer AAS for water and tissue, while otolith microchemistry analyses were performed using a femtosecond laser ablation-high resolution inductively coupled plasma mass spectrometer (fsLA-ICP-MS-HR). Significant differences between control and exposed individuals, as well as an increase in metal concentrations according to exposure level, were observed in all tissues except in muscle tissue. Significant increases in Pb were also detected in contaminated fish otoliths compared with control specimens, with the highest concentrations occurring in T3. Cartographies of Pb distribution in otoliths of both control and contaminated fish only showed high concentrations of Pb at the edge of contaminated fish otoliths, indicating an accumulation of metal during the experiment. Although the relationships between exposure level and Pb concentration in otoliths were complex, the concentrations were correlated with those in the water. Analysis of flounder specimens collected from 2007 to 2014 in the Gironde estuary (SW France) showed interannual variability in Pb concentrations, with higher values for fish otoliths from 2007 to 2010 than those from 2012 to 2014. This trend indicated a decrease in Pb in the Gironde estuary over the last decade, which is consistent with the results of other surveys on bivalves. Our study demonstrates that it is possible to use otolith microchemistry as a tool in assessing and retracing long-term metal pollution in estuarine systems.

The migration patterns of the European flounder Platichthys flesus (Linnaeus, 1758) (Pleuronectidae, Pisces) at the southern limit of its distribution range: Ecological implications and fishery management

This study aims to determine the diversity of migration patterns of the European flounder ( Platichthys flesus (Linnaeus, 1758)) present in the Minho estuary and in the adjacent coastal area (NW-Iberian Peninsula). Assessing the diversity of flounder migration patterns at the southern limit of its distribution allows the determination of characteristics of the species' ecology and provides useful information for fishery managers, since it is a regionally important estuarine fishery. An unexpected result of our study was that flounder appears to spawn in both estuarine and coastal areas and not just in coastal areas as was previously widely accepted. Our interpretation of otolith strontium distribution patterns from flounder specimens collected in the freshwater tidal area of the Minho estuary and in the lower estuary suggested that the flounders hatched in the estuary, while only 6.7% of those captured in the coastal area hatched in the coastal area. Ultimately, studies aimed at collecting larval stages and adult flounders must be made to confirm that flounders spawn in the estuary and to define new and better scientifically supported fishing policies, or simply to confirm the existing ones regarding temporal and spatial closures for each gear used in the Minho estuary.

미토콘드리아 DNA분석에 의한 자연산 및 양식산 넙치 집단의 유전적 다양성 변화

우리나라의 주요 양식 대상 종이며, 년간 총 생산량 1위를 점하고 있는 넙치를 모델로 하여 양식 집단의 유전적 다양성의 변화를 확인하였다. 이를 위해, 한국에서 서식하고 있는 자연산 및 양식산 넙치 각 29개체를 사용하여, hypervariation 영역으로 알려진 tRNA (<TEX>$tRNA^{Thr}$</TEX>, <TEX>$tRNA^{Pro}$</TEX>) 영역과 control region의 앞부분까지의 522 bp에 대한 염기서열의 특성을 분석하였다. 23개의 haplotype에서 522 bp의 염기 중 49곳(9.4%) 에서 변이가 나타났다. 대부분의 haplotype은 자연집단에서 유일하게 나타났으며, 오직 4개의 haplotype만이 양식집단에서 나타났다. 또한, 두 집단 사이에서는 유전적으로 유의한 집단분화가 발생하였다는 사실도 확인할 수 있었다. 따라서 미토콘드리아 DNA 염기서열 분석 기법은 집단의 유전적 다양성을 평가뿐만 아니라 양식집단의 유전적 모니터링에 사용 가능 할 것으로 판단된다. We sequenced a 522 bp fragment including the <TEX>$tRNA^{Thr}$</TEX>, <TEX>$tRNA^{Pro}$</TEX> gene and the first half of the control region from 29 wild and cultured olive flounder specimens from Korea. Out of 522 nucleotide sites, 49 (9.4%) were variable, 23 haplotypes being found. Most haplotypes are unique in the wild population and only four were shared by cultured specimins. The nucleotide diversity and differences between wild and cultured populations were <TEX>$0.025{\pm}0.013$</TEX> and <TEX>$0.015{\pm}0.008$</TEX>, and <TEX>$12.94{\pm}6.00$</TEX> and <TEX>$7.83{\pm}3.75$</TEX>, respectively. Haplotype diversity was <TEX>$0.98{\pm}0.02$</TEX> and <TEX>$0.49{\pm}0.09$</TEX> in the wild and cultured populations, respectively. These results show that marked reductions of genetic variability in the hatchery strains were observed in the number of mitochondrial DNA haplotypes and haplotype diversity when compared to the wild populations. Furthermore, we detected significant population differentiation between both populations. The mtDNA sequencing technique used to evaluate the genetic variability of hatchery strains compared to that of the wild population is potential for genetic monitoring of olive flounder hatchery stocks.

Environmental Genotoxicity Studies in Mussels and Fish from the Göteborg Area of the North Sea

The frequency of micronuclei (MN) was analysed in gill cells of 97 specimens of blue mussels (Mytilus edulis), in peripheral blood of 61 specimens of flounder (Platychthys flesus) and 40 specimens of wrasse (Symphodus melops), which were collected from seven study locations in the Goteborg area of the North Sea. The reference level of micronuclei was 0.04 MN/1,000 erythrocytes in flounder from the uncontaminated Nordre Alvsborg location and 0.05 MN/1,000 erythrocytes from the site at Fjallbacka. In mussels from the Stenungsund location, the reference level of micronuclei was 0.71 MN/1,000 cells. Ten times higher frequencies of micronuclei (0.45 MN/1,000 erythrocytes) were found in flounder collected from the contaminated zone at Jordhammarvik and eight times higher micronuclei levels (0.33 MN/1,000 erythrocytes) were recorded in fish from Nya Alvsborg, the inner part of the Goteborg harbour. In mussels, the highest response (a 2.8-fold increase compared to the reference level of MN) was established in spe...

Specific features of the external morphology of starry flounder Platichthys stellatus at atavism in the body color

An analysis of the morphology of starry flounder Platichthys stellatus, completely pigmented from both sides, was performed. It considerably differs from common individuals (pigmented from only one side) by several characters. The right eye in the atavistic specimen was located on the upper part of the head, and there was a deep notch between the eye and the dorsal fin. The differences between body proportions and sizes of fins in bilaterally pigmented and common flounder specimens were also detected. Based on an analysis of the data obtained, opinions concerning the causes of these morphological deviations in bilaterally pigmented flounder individuals are provided.

넙치와 조기의 원산지 판별을 위한 random amplified polymorphic DNA 패턴 연구

본 연구에서 넙치와 조기의 원산지를 판별하기 위한 도구로 RAPD PCR 방법의 가능성을 확인하였다. 넙치는 한국의 주문진 자연산, 통영 양식산, 거제 양식산 그리고 북한 자연산을 실험에 사용하였다. 조기는 한국산과 중국산을 사용하였다. 넙치의 RAPD 패턴에서는 뚜렷하고 일관성이 있는 진단용 띠들을 쉽게 찾을 수 있었다. 조기의 경우에는 유전적인 이질성으로 인하여 각 개체의 RAPD 패턴에서는 일관성이 있는 진단용 띠를 찾기 어려웠지만 각 원산지별로 얻은 RAPD 패턴에서는 가능성이 있는 진단용 띠들을 찾을 수 있었다. The random amplified polymorphic DNA (RAPD) technique was investigated as a potential tool for the origin identification of olive flounder (Paralichthys olivaceus) and redlip croaker (Pseudosciaena polyactis). Olive flounder specimens were collected from North Korea and several locations of South Korea (Jumunjin, Tongyoung and Geoje). Fishes obtained from Tongyeong and Geoje were cultured products. Redlip croaker specimens were collected from South Korea and China. Consistent and distinct diagnostic bands were easily identified in the RAPD patterns of the olive flounder specimens. Although consistent diagnostic bands rarely appeared in the RAPD pattern of redlip croaker specimens because of their genetic heterogeneity, we were able to find potential diagnostic bands in the average RAPD pattern of each origin.

Relationship between Sex Steroid and Vitellogenin Concentrations in Flounder ( Platichthys flesus ) Sampled from an Estuary Contaminated with Estrogenic Endocrine-Disrupting Compounds

High concentrations of vitellogenin (VTG; egg yolk protein) have previously been found in male flounder (Platichthys flesus) from several UK estuaries; these levels have been ascribed to the presence of estrogenic endocrine-disrupting compounds (EDCs). Gonadal abnormalities, including intersex, have also been recorded in these estuaries. However, there is no firm evidence to date that these two findings are causally linked or that the presence of estrogenic EDCs has any adverse population effects. In the present study, we examined the relationship between concentrations of VTG and sex steroids (11-oxotestosterone in males and 17β-estradiol in females) in specimens of flounder captured from the estuary of the River Mersey. We first questioned whether the high concentrations of VTG in male and immature female flounder were indeed caused by a direct effect of exogenous EDCs and not indirectly via the endogenous secretion of 17β-estradiol. The data favored the direct involvement of estrogenic EDCs. We then questioned whether the presence of estrogenic EDCs not only stimulated inappropriate VTG synthesis but whether it might also have had a negative effect on endogenous steroid secretion. It should be noted that the predicted consequences of a drop in steroid secretion include smaller gonads, smaller oocytes, fewer numbers of sperm, and depressed spawning behavior. This question was more difficult to answer because of the strong effect of the seasonal reproductive cycle and stage of maturation on steroid concentrations. However, matched by month of capture and stage of maturation, both 17β-estradiol in females and 11-keto-testosterone in males were in most cases significantly lower in those years when VTG concentrations were higher.

Occurrence of Listonella anguillarum in seed production environments of Japanese flounder Paralichthys olivaceus (Temminck et Schlegel)

The present study was undertaken to investigate the distribution of Listonella anguillarum in the rearing water, fish and diets (rotifers) of Japanese flounder (Paralichthys olivaceus). A total of 793 isolates were obtained from the seed production environment of Japanese flounder and 175 out of them were identified as L. anguillarum by biochemical characterization, polymerase chain reaction (PCR) detection for VAH1 haemolysin gene and phylogenetic analysis of 16S ribosomal deoxyribonucleic acids (rDNA) sequences. These results strongly suggested that L. anguillarum is rapidly and accurately identified by the combination of incubation on thiosulphate–citrate–bile salt–sucrose agar at 35°C overnight and PCR detection for the VAH1 haemolysin gene. All flounder specimens and all rotifer samples harboured L. anguillarum at high densities of 6.9 × 103–6.3 × 105 colony forming units (CFU) g−1 and 1.5 × 104–2.3 × 106 CFU g−1, respectively, while as low as 5.0 × 100–2.0 × 101 CFU mL−1 of L. aguillarum were detected in only two of 11 seawater samples, even though no vibriosis occurred in larval and juvenile flounder of tanks. This fact strongly suggests that L. anguillarum is an inhabitant in the seed production environments of Japanese flounder.

Proliferative and neoplastic conditions of flounder ( Platichthys flesus) in the northern Baltic Sea in relation to DNA-adducts

A disease survey off the Finnish sea coast of the Baltic Sea included 6644 specimens of flounder ( Platichthys flesus). The aim of the survey was to explore to what extent the quality of the coastal environment in the area is reflected in fish health parameters. As degenerative and proliferative conditions of fish liver have increasingly been recognized to be most closely correlated with chemical contaminants special attention was given to this organ. Some neoplastic conditions were recorded in other organs/tissues in the flounders and are reported too. On an average 3.0% of all flounders examined (>20 cm) were affected by preneoplastic/neoplastic liver lesions. The prevalence is significantly increasing with increasing size of fish. Of specimens >30 cm 10.1% were affected and, at one site the disease prevalence in female flounder >30 cm was 31.5%, which must be considered stikingly high. The site not immediately influenced by human activities but in closest contact with the main Baltic Sea, had the highest lesion prevalences. The levels of hydrophobic DNA-adducts in the liver of flounder in the area are low which indicates that, for example, polycyclic aromatic hydrocarbon compounds are not responsible for the high prevalences of proliferative lesions in flounder in this area.