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Vinatea L, Carbó R, Andree KB, Gisbert E, Estévez A. Rearing European Eel ( Anguilla anguilla) Elvers in a Biofloc System. Animals (Basel) 2023; 13:3234. [PMID: 37893957 PMCID: PMC10603747 DOI: 10.3390/ani13203234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 10/13/2023] [Accepted: 10/15/2023] [Indexed: 10/29/2023] Open
Abstract
European eel (Anguilla anguilla) elvers (initial body weight (BW) = 3 g) were raised in triplicate for 60 days in a biofloc system (BFT) at 21 °C. Data from the current first study evaluating this farming technology indicated that European eel elvers adapted well to BFT systems as data on growth performance (specific growth rate = 1.48% ± 0.13 BW/day and FCR = 1.05 ± 0.09) indicated, with production costs using BFT being lower than conventional RAS units. The most critical issues associated with this aquaculture system were the maintenance of the biofloc in tanks by the regular addition of refined sugar (46% C) to keep a relationship for C:N of 20:1, and the prevention of emergence of opportunistic pathogens like the monogenean Pseudodactylogyrus sp. The overall results of this study in terms of elvers' performance and quality and the composition of the biofloc material and its microbial composition indicated that BFT, which is considered to be one of the most cost-effective, sustainable, and environmentally friendly farming systems due to its zero water exchange and improvement of feed conversion ratio by the dietary contribution of bioflocs, may be satisfactorily used for farming European eels elvers at a density of 2 kg/m3. However, further studies are needed to test this technology with older eel stages.
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Affiliation(s)
- Luis Vinatea
- Departamento de Acuicultura, Universidade Federal de Santa Catarina (UFSC), Florianópolis 88061-600, SC, Brazil
| | - Ricard Carbó
- Aquaculture Program, Centre de la Ràpita, Institut de Recerca i Tecnología Agroalimentàries (IRTA), Ctra. Poble Nou, km 5.5, 43540 Sant Carles de la Rapita, Spain; (R.C.); (K.B.A.); (A.E.)
| | - Karl B. Andree
- Aquaculture Program, Centre de la Ràpita, Institut de Recerca i Tecnología Agroalimentàries (IRTA), Ctra. Poble Nou, km 5.5, 43540 Sant Carles de la Rapita, Spain; (R.C.); (K.B.A.); (A.E.)
| | - Enric Gisbert
- Aquaculture Program, Centre de la Ràpita, Institut de Recerca i Tecnología Agroalimentàries (IRTA), Ctra. Poble Nou, km 5.5, 43540 Sant Carles de la Rapita, Spain; (R.C.); (K.B.A.); (A.E.)
| | - Alicia Estévez
- Aquaculture Program, Centre de la Ràpita, Institut de Recerca i Tecnología Agroalimentàries (IRTA), Ctra. Poble Nou, km 5.5, 43540 Sant Carles de la Rapita, Spain; (R.C.); (K.B.A.); (A.E.)
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Lai XJ, Peng S, Wang YL. Dynamic transcriptome analysis of ovarian follicles in artificial maturing Japanese eel (Anguilla japonica). Theriogenology 2021; 180:176-188. [PMID: 34990963 DOI: 10.1016/j.theriogenology.2021.12.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2021] [Revised: 12/18/2021] [Accepted: 12/27/2021] [Indexed: 12/29/2022]
Abstract
Inducing maturation of the ovaries to enable the production of good-quality eggs is critical for the successful artificial breeding of Anguilla japonica. During the spawning season, however, the ovaries of A. japonica have been found to develop into asynchronous clutches, impeding the success of artificial breeding on a commercial scale. The dynamic molecular regulation of follicular development in the same individual was assessed by transcriptome analysis of the five stages of follicles, the pre-vitellogenic, early vitellogenic, midvitellogenic, late vitellogenic, and migratory nucleus stages in artificial maturing A. japonica. Comparisons across these developmental stages identified a total of 19,298 differentially expressed transcripts (DETs). Short time-series expression miner analysis across these DETs revealed four significant expression profiles. Gene Ontology function and Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses found that some of the significantly enriched biological processes and metabolic pathways included those related to steroid hormone biosynthesis (cyp11a1, cyp17a1, cyp17a2, hsd17b1, and hsd17b12), cargo receptor activity (vtgr and vldlr), meiosis and ovulation (pgrs and mPRγ), hydration (cts and aqp1), and egg coat formation (zp). These genes and pathways were associated with serum 17β-estradiol concentrations and morphological changes. The levels of hsd17b12 and mPRγ mRNAs were much higher during the migratory nucleus stage, suggesting their respective involvement in the biosynthesis and functional pathway of the maturation-inducing steroid 17α,20β-dihydroxy-4-pregnen-3-one. The gene subtypes aqp1b and ctsd may regulate water influx into oocytes and yolk protein proteolysis, respectively. To our knowledge, the present study is the first to describe combined transcriptome profiling of asynchronously developing follicles in the same individual. The findings suggest that steroid hormone synthesis and nutrient absorption in follicular somatic cells play important roles during follicular development and maturation, despite the same external physiological surroundings.
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Affiliation(s)
- Xiao Jian Lai
- Fisheries College, Jimei University, Xiamen, 361021, China; Engineering Research Center of the Modern Technology for Eel Industry, Ministry of Education, Xiamen, 361021, China; Key Laboratory of Cultivation and High-value Utilization of Marine Organisms in Fujian Province, Xiamen, 361013, China.
| | - Shuai Peng
- Fisheries College, Jimei University, Xiamen, 361021, China; Engineering Research Center of the Modern Technology for Eel Industry, Ministry of Education, Xiamen, 361021, China
| | - Yi Lei Wang
- Fisheries College, Jimei University, Xiamen, 361021, China.
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Kottmann JS, Jørgensen MGP, Bertolini F, Loh A, Tomkiewicz J. Differential impacts of carp and salmon pituitary extracts on induced oogenesis, egg quality, molecular ontogeny and embryonic developmental competence in European eel. PLoS One 2020; 15:e0235617. [PMID: 32634160 PMCID: PMC7340298 DOI: 10.1371/journal.pone.0235617] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2020] [Accepted: 06/19/2020] [Indexed: 12/26/2022] Open
Abstract
Low egg quality and embryonic survival are critical challenges in aquaculture, where assisted reproduction procedures and other factors may impact egg quality. This includes European eel (Anguilla anguilla), where pituitary extract from carp (CPE) or salmon (SPE) is applied to override a dopaminergic inhibition of the neuroendocrine system, preventing gonadotropin secretion and gonadal development. The present study used either CPE or SPE to induce vitellogenesis in female European eel and compared impacts on egg quality and offspring developmental competence with emphasis on the maternal-to-zygotic transition (MZT). Females treated with SPE produced significantly higher proportions of floating eggs with fewer cleavage abnormalities and higher embryonic survival. These findings related successful embryogenesis to higher abundance of mRNA transcripts of genes involved in cell adhesion, activation of MZT, and immune response (dcbld1, epcam, oct4, igm) throughout embryonic development. The abundance of mRNA transcripts of cldnd, foxr1, cea, ccna1, ccnb1, ccnb2, zar1, oct4, and npm2 was relatively stable during the first eight hours, followed by a drop during MZT and low levels thereafter, indicating transfer and subsequent clearance of maternal mRNA. mRNA abundance of zar1, epcam, and dicer1 was associated with cleavage abnormalities, while mRNA abundance of zar1, sox2, foxr1, cldnd, phb2, neurod4, and neurog1 (before MZT) was associated with subsequent embryonic survival. In a second pattern, low initial mRNA abundance with an increase during MZT and higher levels persisting thereafter indicating the activation of zygotic transcription. mRNA abundance of ccna1, npm2, oct4, neurod4, and neurog1 during later embryonic development was associated with hatch success. A deviating pattern was observed for dcbld1, which mRNA levels followed the maternal-effect gene pattern but only for embryos from SPE treated females. Together, the differences in offspring production and performance reported in this study show that PE composition impacts egg quality and embryogenesis and in particular, the transition from initial maternal transcripts to zygotic transcription.
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Affiliation(s)
- Johanna S. Kottmann
- National Institute of Aquatic Resources, Technical University of Denmark, Kgs. Lyngby, Denmark
- * E-mail:
| | | | - Francesca Bertolini
- National Institute of Aquatic Resources, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Adrian Loh
- School of Science, University of Greenwich, Chatham Maritime, Kent, United Kingdom
| | - Jonna Tomkiewicz
- National Institute of Aquatic Resources, Technical University of Denmark, Kgs. Lyngby, Denmark
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Estimation of the spawning time of Japanese eels in the open ocean. Sci Rep 2020; 10:4172. [PMID: 32144285 PMCID: PMC7060335 DOI: 10.1038/s41598-020-61029-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Accepted: 01/31/2020] [Indexed: 12/01/2022] Open
Abstract
To understand the spawning ecology of the Japanese eel, the spawning time of this species was estimated based on measurements of the ascending speed of eggs and previously obtained data. Two types of water temperature parameters were calculated assuming an arbitrary spawning time. The ‘incubation temperature’ of 53 eggs collected in the spawning area was estimated based on the developmental stage of each egg and experimentally determined relationships between water temperature and incubation duration. The ‘experienced temperature’ of eggs ascending in the water column after spawning was estimated based on an ascending egg speed of 3.69 m/h and spawning depth of 230 m determined from a pop-up satellite archival tag release experiment on silver eels conducted in the same area. The incubation and experienced temperatures of the eggs coincided only at 20:20–22:30 h, 3 days prior to the new moon. This period is only a few hours after the diel vertical migration of Japanese eels in the evening, when adults move up from a depth of ~800 m (approximately 5 °C) to shallower waters of 200–250 m depth (approximately 20 °C). Our findings will facilitate improvements in aquaculture techniques and the detection of eel spawning events in the open ocean.
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Hagihara S, Aoyama J, Sudo R, Limbong D, Ijiri S, Adachi S, Tsukamoto K. Reproductive physiological characteristics of tropical Celebes eels Anguilla celebesensis in relation to downstream migration and ovarian development. JOURNAL OF FISH BIOLOGY 2020; 96:558-569. [PMID: 31837014 DOI: 10.1111/jfb.14231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Accepted: 12/11/2019] [Indexed: 06/10/2023]
Abstract
Downstream-migrating (n = 64) and non-migrating (n = 21) female Celebes eels Anguilla celebesensis were captured from the Poso Lake-River system on Sulawesi Island, Indonesia, and their reproductive physiological characteristics were examined. A histological observation of the ovaries revealed that most non-migrating eels were at the perinucleolus (43%) or oil-droplet (48%) stage, whereas most migrating eels were at the early vitellogenic (36%) or midvitellogenic (61%) stage. Transcript levels of gonadotropin genes (fshb, lhb) in the pituitary gland and concentrations of sex steroids [11-ketotestosterone (11-KT), testosterone, 17β-oestradiol (E2 )] in blood plasma of migrating eels were significantly higher than those of non-migrating eels. The fshb messenger (m)RNA levels were lower in perinucleolus and oil-droplet stages and then significantly increased in the early vitellogenic stage. The lhb mRNA levels in vitellogenic-stage eels were significantly higher than those in perinucleolus- and oil-droplet-stage eels. The 11-KT levels of eels at the oil-droplet and vitellogenic stages were significantly higher than those of eels at the perinucleolus stage. The E2 levels at the vitellogenic stage were significantly higher than those at the perinucleolus and oil-droplet stages. These dynamics of the reproductive hormones represented the physiological background of oogenesis in A. celebesensis that has remarkably well-developed oocytes just before downstream migration.
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Affiliation(s)
- Seishi Hagihara
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| | - Jun Aoyama
- International Coastal Research Center, Atmosphere and Ocean Research Institute, The University of Tokyo, Tokyo, Iwate, Japan
| | - Ryusuke Sudo
- Minami-izu Laboratory, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Shizuoka, Japan
| | | | - Shigeho Ijiri
- Graduate School of Fisheries Sciences, Hokkaido University, Hokkaido, Japan
| | - Shinji Adachi
- Graduate School of Fisheries Sciences, Hokkaido University, Hokkaido, Japan
| | - Katsumi Tsukamoto
- Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
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6
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Damsteegt EL, Thomson-Laing G, Wylie MJ, Lokman PM. Effects of estradiol and 11-ketotestosterone pre-treatment on artificial induction of maturation in silver female shortfinned eels (Anguilla australis). PLoS One 2020; 15:e0229391. [PMID: 32092110 PMCID: PMC7039463 DOI: 10.1371/journal.pone.0229391] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2019] [Accepted: 02/05/2020] [Indexed: 11/29/2022] Open
Abstract
Our previous work documented significant advancements in steroid-induced progression of oogenesis, demonstrating that co-treatment of female eels with 11-ketotestosterone (11KT) and estradiol-17β (E2) successfully induced uptake of vitellogenin by oocytes. Here we evaluate the effects of this steroid co-treatment on subsequent time to ovulation and egg quality in shortfinned eels artificially matured by hypophysation. Co-treatment with 11KT (1 mg) and E2 (0.2 or 2 mg) significantly reduced time to ovulation and therefore, the amount of pituitary homogenate required, without any detrimental effects on gonadosomatic index, oocyte diameter or the total weight of stripped eggs. E2 treatment resulted in promising increases in fertilization rates. These indicators suggest that co-treatment with 11KT and E2 holds promise for future artificial maturation practices in terms of minimising fish handling and stress, and of reducing the need for expensive pituitary preparations.
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Affiliation(s)
- Erin L. Damsteegt
- Department of Zoology, University of Otago, Dunedin, New Zealand
- * E-mail:
| | | | - Matthew J. Wylie
- Department of Zoology, University of Otago, Dunedin, New Zealand
| | - P. Mark Lokman
- Department of Zoology, University of Otago, Dunedin, New Zealand
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Herranz-Jusdado JG, Gallego V, Morini M, Rozenfeld C, Pérez L, Müller T, Horváth Á, Ohta H, Asturiano JF. Eel sperm cryopreservation: An overview. Theriogenology 2020; 133:210-215. [PMID: 31155036 DOI: 10.1016/j.theriogenology.2019.03.033] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 03/30/2019] [Indexed: 10/26/2022]
Abstract
The eels are teleost fishes from the order Anguilliformes that includes several species with high commercial value. Due to the high interest for aquaculture production of some eel species and for the need to restore eel species that are endangered, several research groups have directed their research toward developing protocols to cryopreserve the spermatozoa of Japanese eel (Anguilla japonica) and European eel (Anguilla anguilla). In this review, we provide an overview on the different protocols that have been developed so far. The first developed protocols used DMSO as cryoprotectant in both species with good success, obtaining sperm motilities of over 45% in Japanese eel and over 35% in European eel. Moreover, sperm cryopreserved using DMSO was successfully used in fertilization trials, although with low fertilization rates. However, recent studies show that DMSO produce epigenetic changes in eel sperm and therefore, the last developed protocols used methanol as cryoprotectant instead. Cryopreservation protocols using methanol as cryoprotectant, showed improved motility values in both Japanese and European eel. In addition, the latest protocols have been adapted to cryopreserve larger volumes of sperm of up to 5 mL, which is useful for larger scale fertilization trials. The present study introduces the state of the art and future perspectives of the eel sperm cryopreservation to be applied in aquaculture and biological conservation programs.
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Affiliation(s)
- Juan German Herranz-Jusdado
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Victor Gallego
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Marina Morini
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Christoffer Rozenfeld
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Luz Pérez
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain
| | - Tamás Müller
- Department of Aquaculture, Szent István University, 2100, Gödöllő, Páter K. U. 1., Hungary
| | - Ákos Horváth
- Department of Aquaculture, Szent István University, 2100, Gödöllő, Páter K. U. 1., Hungary
| | - Hiromi Ohta
- Department of Fisheries, Graduate School of Agriculture, Kindai University, Nara, 631-8505, Japan
| | - Juan F Asturiano
- Grupo de Acuicultura y Biodiversidad, Instituto de Ciencia y Tecnología Animal, Universitat Politècnica de València, Camino de Vera s/n, 46022 Valencia, Spain.
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Politis SN, Mazurais D, Servili A, Zambonino-Infante JL, Miest JJ, Tomkiewicz J, Butts IAE. Salinity reduction benefits European eel larvae: Insights at the morphological and molecular level. PLoS One 2018; 13:e0198294. [PMID: 29897966 PMCID: PMC5999099 DOI: 10.1371/journal.pone.0198294] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 05/16/2018] [Indexed: 11/23/2022] Open
Abstract
European eel (Anguilla anguilla) is a euryhaline species, that has adapted to cope with both, hyper- and hypo-osmotic environments. This study investigates the effect of salinity, from a morphological and molecular point of view on European eel larvae reared from 0 to 12 days post hatch (dph). Offspring reared in 36 practical salinity units (psu; control), were compared with larvae reared in six scenarios, where salinity was decreased on 0 or 3 dph and in rates of 1, 2 or 4 psu/day, towards iso-osmotic conditions. Results showed that several genes relating to osmoregulation (nkcc2α, nkcc2β, aqp1dup, aqpe), stress response (hsp70, hsp90), and thyroid metabolism (thrαA, thrαB, thrβB, dio1, dio2, dio3) were differentially expressed throughout larval development, while nkcc1α, nkcc2β, aqp3, aqp1dup, aqpe, hsp90, thrαA and dio3 showed lower expression in response to the salinity reduction. Moreover, larvae were able to keep energy metabolism related gene expression (atp6, cox1) at stable levels, irrespective of the salinity reduction. As such, when reducing salinity, an energy surplus associated to reduced osmoregulation demands and stress (lower nkcc, aqp and hsp expression), likely facilitated the observed increased survival, improved biometry and enhanced growth efficiency. Additionally, the salinity reduction decreased the amount of severe deformities such as spinal curvature and emaciation but also induced an edematous state of the larval heart, resulting in the most balanced mortality/deformity ratio when salinity was decreased on 3 dph and at 2 psu/day. However, the persistency of the pericardial edema and if or how it represents an obstacle in further larval development needs to be further clarified. In conclusion, this study clearly showed that salinity reduction regimes towards iso-osmotic conditions facilitated the European eel pre-leptocephalus development and revealed the existence of highly sensitive and regulated osmoregulation processes at such early life stage of this species.
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Affiliation(s)
- Sebastian N. Politis
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
- * E-mail:
| | - David Mazurais
- Ifremer, Marine Environmental Science Laboratory UMR 6539, Plouzané, France
| | - Arianna Servili
- Ifremer, Marine Environmental Science Laboratory UMR 6539, Plouzané, France
| | | | | | - Jonna Tomkiewicz
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
| | - Ian A. E. Butts
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
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Politis SN, Mazurais D, Servili A, Zambonino-Infante JL, Miest JJ, Sørensen SR, Tomkiewicz J, Butts IAE. Temperature effects on gene expression and morphological development of European eel, Anguilla anguilla larvae. PLoS One 2017; 12:e0182726. [PMID: 28806748 PMCID: PMC5555698 DOI: 10.1371/journal.pone.0182726] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2017] [Accepted: 07/24/2017] [Indexed: 12/02/2022] Open
Abstract
Temperature is important for optimization of rearing conditions in aquaculture, especially during the critical early life history stages of fish. Here, we experimentally investigated the impact of temperature (16, 18, 20, 22 and 24°C) on thermally induced phenotypic variability, from larval hatch to first-feeding, and the linked expression of targeted genes [heat shock proteins (hsp), growth hormone (gh) and insulin-like growth factors (igf)] associated to larval performance of European eel, Anguilla anguilla. Temperature effects on larval morphology and gene expression were investigated throughout early larval development (in real time from 0 to 18 days post hatch) and at specific developmental stages (hatch, jaw/teeth formation, and first-feeding). Results showed that hatch success, yolk utilization efficiency, survival, deformities, yolk utilization, and growth rates were all significantly affected by temperature. In real time, increasing temperature from 16 to 22°C accelerated larval development, while larval gene expression patterns (hsp70, hsp90, gh and igf-1) were delayed at cold temperatures (16°C) or accelerated at warm temperatures (20–22°C). All targeted genes (hsp70, hsp90, gh, igf-1, igf-2a, igf-2b) were differentially expressed during larval development. Moreover, expression of gh was highest at 16°C during the jaw/teeth formation, and the first-feeding developmental stages, while expression of hsp90 was highest at 22°C, suggesting thermal stress. Furthermore, 24°C was shown to be deleterious (resulting in 100% mortality), while 16°C and 22°C (~50 and 90% deformities respectively) represent the lower and upper thermal tolerance limits. In conclusion, the high survival, lowest incidence of deformities at hatch, high yolk utilization efficiency, high gh and low hsp expression, suggest 18°C as the optimal temperature for offspring of European eel. Furthermore, our results suggest that the still enigmatic early life history stages of European eel may inhabit the deeper layer of the Sargasso Sea and indicate vulnerability of this critically endangered species to increasing ocean temperature.
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Affiliation(s)
- Sebastian N. Politis
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
- * E-mail:
| | - David Mazurais
- Ifremer, Marine Environmental Science Laboratory UMR 6539, Plouzané, France
| | - Arianna Servili
- Ifremer, Marine Environmental Science Laboratory UMR 6539, Plouzané, France
| | | | | | - Sune R. Sørensen
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
| | - Jonna Tomkiewicz
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
| | - Ian A. E. Butts
- National Institute of Aquatic Resources, Technical University of Denmark, DTU, Lyngby, Denmark
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10
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Freese M, Sühring R, Marohn L, Pohlmann JD, Wolschke H, Byer JD, Alaee M, Ebinghaus R, Hanel R. Maternal transfer of dioxin-like compounds in artificially matured European eels. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 227:348-356. [PMID: 28482314 DOI: 10.1016/j.envpol.2017.04.096] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 04/24/2017] [Accepted: 04/30/2017] [Indexed: 06/07/2023]
Abstract
Several eel species of the genus Anguilla are considered endangered due to a severe decline in recruitment. Up to now, the reasons for this threatening development are not fully understood. The eel's highly specialized biology can lead to explicitly high accumulation of globally distributed organic lipophilic contaminants during its continental life. Because of this and due the particular toxicological sensitivity of early life stages of oviparous organisms towards dioxin-like compounds, it is crucial to improve our understanding concerning toxicokinetics and maternal transfer of organic contaminants in eels. This study presents analytical data on maternal transfer of dioxin-like (dl) compounds in relevant tissue samples taken from artificially matured and non-matured European silver eels (Anguilla anguilla) from German inland waters using gas chromatography coupled with mass spectrometry (GC/MS) and high-resolution mass spectrometry (GC/HRMS). Detected concentrations revealed a lipid-driven transfer of targeted compounds from muscle-fat-reserves to gonads and eggs respectively, with no distinct preferences concerning the chlorination degree of targeted compounds. Dl-PCBs were shown to contribute the major share of toxicity equivalents found in analysed eel tissues. Maternal muscle tissue to egg concentration ratios in wet weight-based samples had a mean of 6.95 ± 1.49 in accordance with the differences in total lipid content in the respective body matrices. Dioxins and furans in analysed samples were (from a toxicological point of view) of less relevance. Furthermore it was shown that muscle concentrations in silver eels could be used in future assessments to make conservative predictions for expected egg concentrations in female eels.
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Affiliation(s)
- Marko Freese
- Thünen Institute of Fisheries Ecology, Palmaille 9, 22767 Hamburg, Germany.
| | - Roxana Sühring
- Centre for Environment, Fisheries and Aquaculture Science (Cefas), Lowestoft, Suffolk NR33 0HT, United Kingdom
| | - Lasse Marohn
- Thünen Institute of Fisheries Ecology, Palmaille 9, 22767 Hamburg, Germany
| | - Jan-Dag Pohlmann
- Thünen Institute of Fisheries Ecology, Palmaille 9, 22767 Hamburg, Germany
| | - Hendrik Wolschke
- Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research, Institute of Coastal Research, Department for Environmental Chemistry, Max-Planck-Straße 1, 21502 Geesthacht, Germany
| | - Jonathan D Byer
- Life Science and Chemical Analysis, LECO Corporation, St. Joseph, MI, United States
| | - Mehran Alaee
- Water Science and Technology Directorate, Environment Canada, Burlington, Ontario L7R4A6, Canada
| | - Ralf Ebinghaus
- Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research, Institute of Coastal Research, Department for Environmental Chemistry, Max-Planck-Straße 1, 21502 Geesthacht, Germany
| | - Reinhold Hanel
- Thünen Institute of Fisheries Ecology, Palmaille 9, 22767 Hamburg, Germany
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11
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Balk L, Hägerroth PÅ, Gustavsson H, Sigg L, Åkerman G, Ruiz Muñoz Y, Honeyfield DC, Tjärnlund U, Oliveira K, Ström K, McCormick SD, Karlsson S, Ström M, van Manen M, Berg AL, Halldórsson HP, Strömquist J, Collier TK, Börjeson H, Mörner T, Hansson T. Widespread episodic thiamine deficiency in Northern Hemisphere wildlife. Sci Rep 2016; 6:38821. [PMID: 27958327 PMCID: PMC5153840 DOI: 10.1038/srep38821] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 11/14/2016] [Indexed: 11/09/2022] Open
Abstract
Many wildlife populations are declining at rates higher than can be explained by known threats to biodiversity. Recently, thiamine (vitamin B1) deficiency has emerged as a possible contributing cause. Here, thiamine status was systematically investigated in three animal classes: bivalves, ray-finned fishes, and birds. Thiamine diphosphate is required as a cofactor in at least five life-sustaining enzymes that are required for basic cellular metabolism. Analysis of different phosphorylated forms of thiamine, as well as of activities and amount of holoenzyme and apoenzyme forms of thiamine-dependent enzymes, revealed episodically occurring thiamine deficiency in all three animal classes. These biochemical effects were also linked to secondary effects on growth, condition, liver size, blood chemistry and composition, histopathology, swimming behaviour and endurance, parasite infestation, and reproduction. It is unlikely that the thiamine deficiency is caused by impaired phosphorylation within the cells. Rather, the results point towards insufficient amounts of thiamine in the food. By investigating a large geographic area, by extending the focus from lethal to sublethal thiamine deficiency, and by linking biochemical alterations to secondary effects, we demonstrate that the problem of thiamine deficiency is considerably more widespread and severe than previously reported.
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Affiliation(s)
- Lennart Balk
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Per-Åke Hägerroth
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Hanna Gustavsson
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Lisa Sigg
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Gun Åkerman
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Yolanda Ruiz Muñoz
- Department of Biochemistry, Genetics and Immunology, University of Vigo, Lagoas-Marcosende, ES-36310 Vigo, Spain
| | - Dale C. Honeyfield
- Leetown Science Center, Northern Appalachian Research Laboratory, U.S. Geological Survey (USGS), Wellsboro, Pennsylvania 16901, USA
| | - Ulla Tjärnlund
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Kenneth Oliveira
- Department of Biology, University of Massachusetts Dartmouth, Dartmouth, Massachusetts 02747, USA
| | - Karin Ström
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
| | - Stephen D. McCormick
- Leetown Science Center, Conte Anadromous Fish Research Laboratory, U.S. Geological Survey (USGS), Turners Falls, Massachusetts 01376, USA
| | - Simon Karlsson
- River Ecology and Management, Karlstad University, SE-65188 Karlstad, Sweden
- Department of Aquatic Resources, Institute of Freshwater Research, Swedish University of Agricultural Sciences (SLU), SE-17893 Drottningholm, Sweden
| | - Marika Ström
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
- Department of Medicine Solna and Center for Molecular Medicine, Karolinska Institutet, SE-17176 Stockholm, Sweden
| | - Mathijs van Manen
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
- Institute for Risk Assessment Sciences (IRAS), Utrecht University, NL-3508 TD Utrecht, the Netherlands
| | - Anna-Lena Berg
- Medical Products Agency, Box 26, SE-75103 Uppsala, Sweden
| | | | - Jennie Strömquist
- Department of Aquatic Resources, Institute of Freshwater Research, Swedish University of Agricultural Sciences (SLU), SE-17893 Drottningholm, Sweden
| | - Tracy K. Collier
- NOAA Fisheries, Northwest Fisheries Science Center, Seattle, Washington 98112, USA
| | - Hans Börjeson
- Department of Aquatic Resources, Fisheries Research Station, Swedish University of Agricultural Sciences (SLU), Brobacken, SE-81494 Älvkarleby, Sweden
| | - Torsten Mörner
- Department of Disease Control and Epidemiology, National Veterinary Institute (SVA), SE-75189 Uppsala, Sweden
| | - Tomas Hansson
- Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, SE-10691 Stockholm, Sweden
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12
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Rigaud C, Couillard CM, Pellerin J, Légaré B, Byer JD, Alaee M, Lebeuf M, Casselman JM, Hodson PV. Temporal variations in embryotoxicity of Lake Ontario American eel (Anguilla rostrata) extracts to developing Fundulus heteroclitus. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 541:765-775. [PMID: 26433333 DOI: 10.1016/j.scitotenv.2015.09.049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Revised: 09/10/2015] [Accepted: 09/10/2015] [Indexed: 06/05/2023]
Abstract
The recruitment of American eel (Anguilla rostrata) juveniles to Lake Ontario (LO), Canada has declined significantly since the 1980s. To investigate the possible contribution of maternally-transferred persistent organic pollutants (POPs) to this decline, this study measured temporal variations in the toxicity of complex organic mixtures extracted from LO American eels captured in 1988, 1998 and 2008 to developing Fundulus heteroclitus exposed by intravitelline (IVi) injection. The 1988 and 1998 eel extracts were most toxic, causing a pattern of sublethal embryotoxic responses similar to those previously reported in F. heteroclitus embryos exposed to single dioxin-like compounds (DLCs): stunted growth, craniofacial deformities, EROD activity induction, and reduced predatory capacities. The potency of extracts declined over time; the only significant effect of the 2008 eel extracts was EROD induction. The chemically-derived TCDD-TEQs of eel extracts, calculated using measured concentrations of some DLCs and their relative potencies for F. heteroclitus, overestimated their potency to induce EROD activity possibly due to interactions among POPs. Other POPs measured in eel extracts (non-dioxin-like PCBs, PBDEs and organochlorinated pesticides) did not appear to be important agonistic contributors to the observed toxicity. The toxicity of the complex mixtures of POPs measured in LO eels may have been underestimated as a result of several factors, including the loss of POPs during extracts preparation and a focus only on short-term effects. Based on the model species examined, our results support the hypothesis that contamination of LO with DLCs may have represented a threat to the American eel population through ecologically-relevant effects such as altered larval prey capture ability. These results prioritize the need to assess early life stage (ELS) toxicity of DLCs in Anguilla species, to investigate long-term effects of complex eel extracts to ELS of fish, and to develop biomarkers for potential effects in eel ELS sampled in the field.
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Affiliation(s)
- Cyril Rigaud
- Institut des Sciences de la Mer, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada; Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada.
| | - Catherine M Couillard
- Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada.
| | - Jocelyne Pellerin
- Institut des Sciences de la Mer, Université du Québec à Rimouski, 310 Allée des Ursulines, Rimouski, Québec G5L 3A1, Canada
| | - Benoît Légaré
- Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada
| | - Jonathan D Byer
- Environment Canada, 867 Lakeshore Road, Burlington, Ontario L7R 4A6, Canada; Queen's University, 99 University Avenue, Kingston, Ontario K7L 3N6, Canada
| | - Mehran Alaee
- Environment Canada, 867 Lakeshore Road, Burlington, Ontario L7R 4A6, Canada
| | - Michel Lebeuf
- Fisheries and Oceans Canada, Maurice Lamontagne Institute, P.O. Box 1000, Mont-Joli, Québec G5H 3Z4, Canada
| | - John M Casselman
- Queen's University, 99 University Avenue, Kingston, Ontario K7L 3N6, Canada
| | - Peter V Hodson
- Queen's University, 99 University Avenue, Kingston, Ontario K7L 3N6, Canada
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13
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Burgerhout E, Minegishi Y, Brittijn SA, de Wijze DL, Henkel CV, Jansen HJ, Spaink HP, Dirks RP, van den Thillart GEEJM. Changes in ovarian gene expression profiles and plasma hormone levels in maturing European eel (Anguilla anguilla); Biomarkers for broodstock selection. Gen Comp Endocrinol 2016; 225:185-196. [PMID: 26255685 DOI: 10.1016/j.ygcen.2015.08.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Revised: 06/29/2015] [Accepted: 08/05/2015] [Indexed: 01/08/2023]
Abstract
Complete sexual maturation of European eels (Anguilla anguilla) in captivity can only be achieved via injections with gonadotropins. For female eels this procedure takes 4-6months and the response ranges from "unresponsive" to final maturation and ovulation. Reproductive success could be significantly increased via early selection of responders based on predictive markers and minimally invasive sampling methods. To get a better understanding of the genetic background of ovarian maturation of the European eel we performed a pilot deep-sequencing transcriptome analysis of ovarian tissue derived from a yellow eel, a prepubertal silver eel and a post-spawning matured eel. Two key players in steroidogenesis were strongly correlated with advanced sexual maturation, namely P450c17 and liver receptor homolog-1, suggesting that blood plasma steroids might qualify as minimally invasive markers for early detection of responders. Since the predictive value of plasma sex steroid levels for final maturation of the European eel had not yet been carefully examined, we performed an extensive artificial maturation trial. Farmed silver eels were treated with pituitary extracts and sampled at multiple time intervals. Expression of steroidogenesis-related genes in ovarian tissue of responding and non-responding eels after four weekly injections with pituitary extract was compared using a custom-built microarray and RNAseq. Increased expression of 17β-hsd1 was strongly linked to sexual maturation. Blood plasma levels of sex steroids were measured using ELISAs. We show that a 2.5-fold increase in blood-plasma estradiol level after 4 weekly pituitary extract injections is a strong predictor of final sexual maturation of female European eel.
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Affiliation(s)
- Erik Burgerhout
- Institute of Biology, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands.
| | - Yuki Minegishi
- Institute of Biology, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands.
| | | | - Danielle L de Wijze
- Institute of Biology, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands.
| | | | - Hans J Jansen
- ZF-screens B.V., J.H. Oortweg 19, 2333 CH Leiden, The Netherlands.
| | - Herman P Spaink
- Institute of Biology, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands.
| | - Ron P Dirks
- ZF-screens B.V., J.H. Oortweg 19, 2333 CH Leiden, The Netherlands.
| | - Guido E E J M van den Thillart
- Institute of Biology, Leiden University, P.O. Box 9505, 2300 RA Leiden, The Netherlands; ZF-screens B.V., J.H. Oortweg 19, 2333 CH Leiden, The Netherlands.
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14
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Miller MJ, Bonhommeau S, Munk P, Castonguay M, Hanel R, McCleave JD. A century of research on the larval distributions of the Atlantic eels: a re-examination of the data. Biol Rev Camb Philos Soc 2014; 90:1035-64. [PMID: 25291986 DOI: 10.1111/brv.12144] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Revised: 07/25/2014] [Accepted: 08/15/2014] [Indexed: 11/28/2022]
Abstract
The spawning areas of the Atlantic freshwater eels were discovered about a century ago by the Danish scientist Johannes Schmidt who after years of searching found newly hatched larvae of the European eel, Anguilla anguilla, and the American eel, Anguilla rostrata, in the southern Sargasso Sea. The discovery showed that anguillid eels migrate thousands of kilometers to offshore spawning areas for reproduction, and that their larvae, called leptocephali, are transported equally long distances by ocean currents to their continental recruitment areas. The spawning sites were found to be related to oceanographic conditions several decades later by German and American surveys from 1979 to 1989 and by a Danish survey in 2007 and a German survey in 2011. All these later surveys showed that spawning occurred within a restricted latitudinal range, between temperature fronts within the Subtropical Convergence Zone of the Sargasso Sea. New data and re-examinations of Schmidt's data confirmed his original conclusions about the two species having some overlap in spawning areas. Although there have been additional collections of leptocephali in various parts of the North Atlantic, and both otolith research and transport modelling studies have subsequently been carried out, there is still a range of unresolved questions about the routes of larval transport and durations of migration. This paper reviews the history and basic findings of surveys for anguillid leptocephali in the North Atlantic and analyses a new comprehensive database that includes 22612 A. anguilla and 9634 A. rostrata leptocephali, which provides a detailed view of the spatial and temporal distributions and size of the larvae across the Atlantic basin and in the Mediterranean Sea. The differences in distributions, maximum sizes, and growth rates of the two species of larvae are likely linked to the contrasting migration distances to their recruitment areas on each side of the basin. Anguilla rostrata leptocephali originate from a more western spawning area, grow faster, and metamorphose at smaller sizes of <70 mm than the larvae of A. anguilla, which mostly are spawned further east and can reach sizes of almost 90 mm. The larvae of A. rostrata spread west and northwest from the spawning area as they grow larger, with some being present in the western Caribbean and eastern Gulf of Mexico. Larvae of A. anguilla appear to be able to reach Europe by entering the Gulf Stream system or by being entrained into frontal countercurrents that transport them directly northeastward. The larval duration of A. anguilla is suggested to be quite variable, but gaps in sampling effort prevent firm conclusions. Although knowledge about larval behaviour is lacking, some influences of directional swimming are implicated by the temporal distributions of the largest larvae. Ocean-atmosphere changes have been hypothesized to affect the survival of the larvae and cause reduced recruitment, so even after about a century following the discovery of their spawning areas, mysteries still remain about the marine life histories of the Atlantic eels.
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Affiliation(s)
- Michael J Miller
- Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan
| | | | - Peter Munk
- National Institute of Aquatic Resources, Technical University of Denmark, Charlottenlund, Denmark
| | - Martin Castonguay
- Maurice-Lamontagne Institute, Fisheries and Oceans Canada, Mont-Joli, Québec G5H 3Z4, Canada
| | | | - James D McCleave
- School of Marine Sciences, University of Maine, Orono, ME, U.S.A
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15
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Côté CL, Castonguay M, Kalujnaia MS, Cramb G, Bernatchez L. In absence of local adaptation, plasticity and spatially varying selection rule: a view from genomic reaction norms in a panmictic species (Anguilla rostrata). BMC Genomics 2014; 15:403. [PMID: 24884429 PMCID: PMC4229938 DOI: 10.1186/1471-2164-15-403] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Accepted: 05/07/2014] [Indexed: 01/24/2023] Open
Abstract
Background American eel (Anguilla rostrata) is one of the few species for which panmixia has been demonstrated at the scale of the entire species. As such, the development of long term local adaptation is impossible. However, both plasticity and spatially varying selection have been invoked in explaining how American eel may cope with an unusual broad scope of environmental conditions. Here, we address this question through transcriptomic analyses and genomic reaction norms of eels from two geographic origins reared in controlled environments. Results The null hypothesis of no difference in gene expression between eels from the two origins was rejected. Many unique transcripts and two out of seven gene clusters showed significant difference in expression, both at time of capture and after three months of common rearing. Differences in expression were observed at numerous genes representing many functional groups when comparing eels from a same origin reared under different salinity conditions. Plastic response to different rearing conditions varied among gene clusters with three clusters showing significant origin-environment interactions translating into differential genomic norms of reaction. Most genes and functional categories showing differences between origins were previously shown to be differentially expressed in a study comparing transcription profiles between adult European eels acclimated to different salinities. Conclusions These results emphasize that while plasticity in expression may be important, there is also a role for local genetic (and/or epigenetic) differences in explaining differences in gene expression between eels from different geographic origins. Such differences match those reported in genetically distinct populations in other fishes, both in terms of the proportion of genes that are differentially expressed and the diversity of biological functions involved. We thus propose that genetic differences between glass eels of different origins caused by spatially varying selection due to local environmental conditions translates into transcriptomic differences (including different genomic norms of reaction) which may in turn explain part of the phenotypic variance observed between different habitats colonized by eels.
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Affiliation(s)
| | | | | | | | - Louis Bernatchez
- Institut de Biologie Intégrative et des Systèmes (IBIS), Université Laval, Québec G1V 0A6, Canada.
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16
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Miller MJ, Casselman JM. The American Eel: A Fish of Mystery and Sustenance for Humans. EELS AND HUMANS 2014. [DOI: 10.1007/978-4-431-54529-3_11] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
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17
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Henkel CV, Dirks RP, de Wijze DL, Minegishi Y, Aoyama J, Jansen HJ, Turner B, Knudsen B, Bundgaard M, Hvam KL, Boetzer M, Pirovano W, Weltzien FA, Dufour S, Tsukamoto K, Spaink HP, van den Thillart GE. First draft genome sequence of the Japanese eel, Anguilla japonica. Gene 2012; 511:195-201. [DOI: 10.1016/j.gene.2012.09.064] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Accepted: 09/11/2012] [Indexed: 10/27/2022]
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18
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Minegishi Y, Henkel CV, Dirks RP, van den Thillart GEEJM. Genomics in eels--towards aquaculture and biology. MARINE BIOTECHNOLOGY (NEW YORK, N.Y.) 2012; 14:583-590. [PMID: 22527267 PMCID: PMC3419832 DOI: 10.1007/s10126-012-9444-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 03/23/2012] [Indexed: 05/31/2023]
Abstract
Freshwater eels (genus Anguilla), especially the species inhabiting the temperate areas such as the European, American and Japanese eels, are important aquaculture species. Although artificial reproduction has been attempted since the 1930s and large numbers of studies have been conducted, it has not yet fully succeeded. Problems in eel artificial breeding are highly diverse, for instance, lack of basic information about reproduction in nature, no appropriate food for larvae, high mortality, and high individual variation in adults in response to maturation induction. Over the last decade, genomic data have been obtained for a variety of aquatic organisms. Recent technological advances in sequencing and computation now enable the accumulation of genomic information even for non-model species. The draft genome of the European eel Anguilla anguilla has been recently determined using Illumina technology and transcriptomic data based on next generation sequencing have been emerging. Extensive genomic information will facilitate many aspects of the artificial reproduction of eels. Here, we review the progress in genome-wide studies of eels, including additional analysis of the European eel genome data, and discuss future directions and implications of genomic data for aquaculture.
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Affiliation(s)
- Yuki Minegishi
- Institute of Biology-Leiden, Leiden University, Leiden, The Netherlands.
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19
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Minegishi Y, Dirks RP, de Wijze DL, Brittijn SA, Burgerhout E, Spaink HP, van den Thillart GEEJM. Quantitative bioassays for measuring biologically functional gonadotropins based on eel gonadotropic receptors. Gen Comp Endocrinol 2012; 178:145-52. [PMID: 22580328 DOI: 10.1016/j.ygcen.2012.04.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2011] [Revised: 03/12/2012] [Accepted: 04/27/2012] [Indexed: 02/07/2023]
Abstract
Significant declines in eel stocks have been noted in many parts of the world. Because eel aquaculture is dependent on wild-caught juveniles, there is a need to achieve artificial reproduction. Adult eel maturation is currently induced by repeated injections of purified gonadotropin (human chorionic gonadotropin [hCG]) or pituitary extract. Thus the determination of the biological efficacy and quantification of internal levels of gonadotropic hormones is important for optimizing artificial reproduction protocols. To quantify the plasma levels of biologically functional gonadotropic hormones, we developed a bioassay for luteinizing hormone (LH) and follicle-stimulating hormone (FSH) based on the stable expression of receptors in HEK293 cells of the Japanese eel Anguilla japonica LH (ajLHR) and the European eel Anguilla anguilla FSH (aaFSHR), respectively. Such cells also contain a firefly luciferase reporter gene driven by a cAMP-responsive element (CRE-Luc). We found that the obtained stable cells, with ajLHR, responded linearly to a more than 100,000-fold concentration range of hCG diluted in saline. The cells with aaFSHR showed a linear response to a 1000-fold concentration range of salmon pituitary extract mixed with saline. The biological functionality of the LH and FSH bioassays was validated using hCG, human FSH, and pituitary extracts from salmon, carp and eel. Since the toxins in eel plasma damaged the HEK293 cells, the protocol was adapted to selectively inactivate the toxins by heating at 37°C for 24h. This process successfully enabled the monitoring of hormone levels in blood plasma sampled from hCG-injected eels. In this paper, we describe the development of gonadotropin bioassays that will be useful for improving reproduction protocols in eel aquaculture.
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Affiliation(s)
- Y Minegishi
- Institute of Biology Leiden, Sylvius Laboratory, Leiden University, Leiden, The Netherlands.
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20
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Henkel CV, Burgerhout E, de Wijze DL, Dirks RP, Minegishi Y, Jansen HJ, Spaink HP, Dufour S, Weltzien FA, Tsukamoto K, van den Thillart GEEJM. Primitive duplicate Hox clusters in the European eel's genome. PLoS One 2012; 7:e32231. [PMID: 22384188 PMCID: PMC3286462 DOI: 10.1371/journal.pone.0032231] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 01/25/2012] [Indexed: 11/18/2022] Open
Abstract
The enigmatic life cycle and elongated body of the European eel (Anguilla anguilla L., 1758) have long motivated scientific enquiry. Recently, eel research has gained in urgency, as the population has dwindled to the point of critical endangerment. We have assembled a draft genome in order to facilitate advances in all provinces of eel biology. Here, we use the genome to investigate the eel's complement of the Hox developmental transcription factors. We show that unlike any other teleost fish, the eel retains fully populated, duplicate Hox clusters, which originated at the teleost-specific genome duplication. Using mRNA-sequencing and in situ hybridizations, we demonstrate that all copies are expressed in early embryos. Theories of vertebrate evolution predict that the retention of functional, duplicate Hox genes can give rise to additional developmental complexity, which is not immediately apparent in the adult. However, the key morphological innovation elsewhere in the eel's life history coincides with the evolutionary origin of its Hox repertoire.
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