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Bandara KA, Politis SN, Sørensen SR, Benini E, Tomkiewicz J, Vadstein O. Effect of Food Amounts on Larval Performance, Bacteriome and Molecular Immunologic Development during First-Feeding Culture of European Eel. Microorganisms 2024; 12:355. [PMID: 38399759 PMCID: PMC10892360 DOI: 10.3390/microorganisms12020355] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 01/24/2024] [Accepted: 01/26/2024] [Indexed: 02/25/2024] Open
Abstract
Production of European eel offspring has become a reality, but liquid diets during larval culture hold new challenges. This study focused on increasing food amounts without compromising well-being or healthy larvae-bacteria interactions. First-feeding larvae were fed two food amounts (Low = 0.5 mL food/L water vs. High = 1.5 mL food/L water) until 30 days post-hatch (dph). Results indicated that ~75% of larvae ingested the diet in both treatments, but upregulation of a stress/repair-related gene (hsp90) on 25 and 30 dph indicated nutritional inadequacy. Larvae fed a High amount of food were 3.68% bigger, while larvae in the Low-food group showed 45.2% lower gut fullness and upregulated expression of the gene encoding the "hunger hormone" ghrelin (ghrl), indicating signs of starvation. The High-food group larvae exhibited a healthier bacteriome with a higher abundance of potentially beneficial orders (Lactobacillales and Bacillales), whereas the Low-food group showed more potentially harmful orders (Vibrionales, Rhodobacterales, and Alteromonadales). While survival was initially lower in the High-food group, both treatments had comparable survival by the end of the experiment. In conclusion, feeding European eel larvae with High food amounts seemed beneficial, supported by increased gut fullness, reduced ghrl expression (no starvation), enhanced growth, and the presence of a healthier bacteriome.
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Affiliation(s)
- Kasun Anuruddha Bandara
- National Institute of Aquatic Resources, Technical University of Denmark, 2800 Kongens Lyngby, Denmark; (K.A.B.); (S.R.S.); (E.B.); (J.T.)
| | - Sebastian Nikitas Politis
- National Institute of Aquatic Resources, Technical University of Denmark, 2800 Kongens Lyngby, Denmark; (K.A.B.); (S.R.S.); (E.B.); (J.T.)
| | - Sune Riis Sørensen
- National Institute of Aquatic Resources, Technical University of Denmark, 2800 Kongens Lyngby, Denmark; (K.A.B.); (S.R.S.); (E.B.); (J.T.)
| | - Elisa Benini
- National Institute of Aquatic Resources, Technical University of Denmark, 2800 Kongens Lyngby, Denmark; (K.A.B.); (S.R.S.); (E.B.); (J.T.)
| | - Jonna Tomkiewicz
- National Institute of Aquatic Resources, Technical University of Denmark, 2800 Kongens Lyngby, Denmark; (K.A.B.); (S.R.S.); (E.B.); (J.T.)
| | - Olav Vadstein
- Department of Biotechnology and Food Science, NTNU—Norwegian University of Science and Technology, 7491 Trondheim, Norway
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Jaspers C, Hopcroft RR, Kiørboe T, Lombard F, López-Urrutia Á, Everett JD, Richardson AJ. Gelatinous larvacean zooplankton can enhance trophic transfer and carbon sequestration. Trends Ecol Evol 2023; 38:980-993. [PMID: 37277269 DOI: 10.1016/j.tree.2023.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 05/02/2023] [Accepted: 05/05/2023] [Indexed: 06/07/2023]
Abstract
Larvaceans are gelatinous zooplankton abundant throughout the ocean. Larvaceans have been overlooked in research because they are difficult to collect and are perceived as being unimportant in biogeochemical cycles and food-webs. We synthesise evidence that their unique biology enables larvaceans to transfer more carbon to higher trophic levels and deeper into the ocean than is commonly appreciated. Larvaceans could become even more important in the Anthropocene because they eat small phytoplankton that are predicted to become more prevalent under climate change, thus moderating projected future declines in ocean productivity and fisheries. We identify critical knowledge gaps and argue that larvaceans should be incorporated into ecosystem assessments and biogeochemical models to improve predictions of the future ocean.
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Affiliation(s)
- Cornelia Jaspers
- Centre for Gelatinous Plankton Ecology & Evolution, Technical University of Denmark, DTU Aqua, Kongens Lyngby, Denmark; Centre for Ocean Life, DTU Aqua, Technical University of Denmark, Kongens Lyngby, Denmark.
| | | | - Thomas Kiørboe
- Centre for Ocean Life, DTU Aqua, Technical University of Denmark, Kongens Lyngby, Denmark
| | - Fabien Lombard
- Sorbonne Université, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-Mer, France
| | - Ángel López-Urrutia
- Centro Oceanográfico de Gijón, Instituto Español de Oceanografia, IEO-CSIC, Gijón, Asturias, Spain
| | - Jason D Everett
- School of Environment, University of Queensland, Brisbane, QLD, Australia; CSIRO Environment, Queensland Biosciences Precinct, St Lucia, QLD, Australia; Centre for Marine Science and Innovation, School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Anthony J Richardson
- School of Environment, University of Queensland, Brisbane, QLD, Australia; CSIRO Environment, Queensland Biosciences Precinct, St Lucia, QLD, Australia
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Bandara KA, Benini E, Politis SN, Conceição LEC, Santos A, Sørensen SR, Tomkiewicz J, Vadstein O. Exploring bacterial community composition and immune gene expression of European eel larvae (Anguilla anguilla) in relation to first-feeding diets. PLoS One 2023; 18:e0288734. [PMID: 37498931 PMCID: PMC10373994 DOI: 10.1371/journal.pone.0288734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 07/04/2023] [Indexed: 07/29/2023] Open
Abstract
European eel (Anguilla anguilla) is a commercially important species for fisheries and aquaculture in Europe and the attempt to close the lifecycle in captivity is still at pioneering stage. The first feeding stage of this species is characterized by a critical period between 20 to 24 days post hatch (dph), which is associated with mortalities, indicating the point of no return. We hypothesized that this critical period might also be associated with larvae-bacterial interactions and the larval immune status. To test this, bacterial community composition and expression of immune and stress-related genes of hatchery-produced larvae were explored from the end of endogenous feeding (9 dph) until 28 dph, in response to three experimental first-feeding diets (Diet 1, Diet 2 and Diet 3). Changes in the water bacterial community composition were also followed. Results revealed that the larval stress/repair mechanism was activated during this critical period, marked by an upregulated expression of the hsp90 gene, independent of the diet fed. At the same time, a shift towards a potentially detrimental larval bacterial community was observed in all dietary groups. Here, a significant reduction in evenness of the larval bacterial community was observed, and several amplicon sequence variants belonging to potentially harmful bacterial genera were more abundant. This indicates that detrimental larvae-bacteria interactions were likely involved in the mortality observed. Beyond the critical period, the highest survival was registered for larvae fed Diet 3. Interestingly, genes encoding for pathogen recognition receptor TLR18 and complement component C1QC were upregulated in this group, potentially indicating a higher immunocompetency that facilitated a more successful handling of the harmful bacteria that dominated the bacterial community of larvae on 22 dph, ultimately leading to better survival, compared to the other two groups.
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Affiliation(s)
- Kasun A Bandara
- Technical University of Denmark, National Institute of Aquatic Resources, Lyngby, Denmark
- Department of Biotechnology and Food Science, NTNU-Norwegian University of Science and Technology, Trondheim, Norway
| | - Elisa Benini
- Technical University of Denmark, National Institute of Aquatic Resources, Lyngby, Denmark
| | - Sebastian N Politis
- Technical University of Denmark, National Institute of Aquatic Resources, Lyngby, Denmark
| | | | - André Santos
- SPAROS Lda, Área Empresarial de Marim, Lote C, Olhão, Portugal
| | - Sune Riis Sørensen
- Technical University of Denmark, National Institute of Aquatic Resources, Lyngby, Denmark
| | - Jonna Tomkiewicz
- Technical University of Denmark, National Institute of Aquatic Resources, Lyngby, Denmark
| | - Olav Vadstein
- Department of Biotechnology and Food Science, NTNU-Norwegian University of Science and Technology, Trondheim, Norway
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Shin MG, Ryu YW, Choi YH, Kim SK. Morphological and Allometric Changes in Anguilla japonica Larvae. BIOLOGY 2022; 11:biology11030407. [PMID: 35336781 PMCID: PMC8945780 DOI: 10.3390/biology11030407] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 02/27/2022] [Accepted: 03/04/2022] [Indexed: 11/18/2022]
Abstract
Simple Summary The freshwater eel Anguilla japonica is a commercially important in Northeast Asia. However, eels farming is entirely dependent on natural catches, and eel resources are declining. This study was conducted to provide baseline information on the development of mass seed production technology necessary for the conservation of species and the maintenance of aquaculture. This study was conducted for 200 days after hatching (DAH) and analyzed morphometry and allometry. In this study, cultured eel larvae stages were divided in size similar to wild eel larvae, but cultured eel differed from wild eel in growth rate and the number of preanal myomeres. In addition, as eel larvae rarely have mixed feeding periods, it is important to determine the optimal first feeding time. The eel larvae may need a change in diet type to prevent lower jaw deformity in the leptocephalus stage. As eel larvae changed to a willow leaf-like form, the relative growth pattern of the eel larval stages was unique. This growth pattern may reflect the early life history of long distance and diel vertical migration. Meanwhile, the inflection point in the body parts’ growth patterns showed only before 30 DAH and was similar to the period of mass mortality. Therefore, future studies should focus on developing an optimal feeding and rearing protocol from the first feeding to 30 DAH. Abstract The freshwater eel Anguilla japonica is rapidly decreasing in number and has not yet been successfully mass produced. This may be at least partially attributable to the unique and long early life history of the eel. Therefore, we investigated its ontogeny of morphometry and growth pattern in larval stages to provide baseline information for understanding the early life history and improving seed rearing technology. This study was conducted for 200 days after hatching (DAH) and analyzed morphometry and allometry for eel larvae. The following cultured eel larval stages were identified: the yolk sac larvae stage (0–6 DAH, 3.23–6.85 mm total length (TL)), the pre-leptocephalus stage (7–30 DAH, 6.85–15.31 mm TL), and the leptocephalus stage (50–200 DAH, 15.31–60.06 mm TL). Cultured and wild eel larvae could be divided into characteristic larval stages at similar sizes. However, compared to wild eels, cultured eels had a slower growth rate and fewer preanal myomeres. Meanwhile, cultured eel larvae rarely had a mixed feeding period as the absorption of endogenous reserves was completed by 7 DAH. The lower jaw of eel larvae was significantly longer than the upper jaw from 50 DAH. In the pre-leptocephalus and leptocephalus stages, eel larvae showed continuous positive allometric growth at trunk height and tail muscle height with change to the willow leaf-like form. These growth characteristics may be the result of adaptation to the migration over long distances and to a diel vertical migration. The inflection point in the body parts growth patterns showed only before 30 DAH, and mass mortality appeared at this period. Therefore, to improve the growth and survival rates of cultured eel seed, it is necessary to focus on improving the feeding and rearing protocol until 30 DAH.
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Affiliation(s)
- Min-Gyu Shin
- Aquaculture Research Division, National Institute of Fisheries Science, 216, Gijanghaean-ro, Gijang-eup, Gijang-gun, Busan 46083, Korea; (M.-G.S.); (Y.-W.R.)
- Department of Fisheries Biology, Pukyong National University, Busan 48513, Korea
| | - Yong-Woon Ryu
- Aquaculture Research Division, National Institute of Fisheries Science, 216, Gijanghaean-ro, Gijang-eup, Gijang-gun, Busan 46083, Korea; (M.-G.S.); (Y.-W.R.)
| | - Youn-Hee Choi
- Department of Fisheries Biology, Pukyong National University, Busan 48513, Korea
- Department of Marine Bio-Materials & Aquaculture, Pukyong National University, Busan 48513, Korea
- Correspondence: (Y.-H.C.); (S.-K.K.); Tel.: +82-51-629-5915 (Y.-H.C.); +82-51-720-2421 (S.-K.K.)
| | - Shin-Kwon Kim
- Aquaculture Research Division, National Institute of Fisheries Science, 216, Gijanghaean-ro, Gijang-eup, Gijang-gun, Busan 46083, Korea; (M.-G.S.); (Y.-W.R.)
- Correspondence: (Y.-H.C.); (S.-K.K.); Tel.: +82-51-629-5915 (Y.-H.C.); +82-51-720-2421 (S.-K.K.)
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18S rRNA gene sequences of leptocephalus gut contents, particulate organic matter, and biological oceanographic conditions in the western North Pacific. Sci Rep 2021; 11:5488. [PMID: 33658626 PMCID: PMC7930194 DOI: 10.1038/s41598-021-84532-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Accepted: 02/15/2021] [Indexed: 11/09/2022] Open
Abstract
Eel larvae apparently feed on marine snow, but many aspects of their feeding ecology remain unknown. The eukaryotic 18S rRNA gene sequence compositions in the gut contents of four taxa of anguilliform eel larvae were compared with the sequence compositions of vertically sampled seawater particulate organic matter (POM) in the oligotrophic western North Pacific Ocean. Both gut contents and POM were mainly composed of dinoflagellates as well as other phytoplankton (cryptophytes and diatoms) and zooplankton (ciliophoran and copepod) sequences. Gut contents also contained cryptophyte and ciliophoran genera and a few other taxa. Dinoflagellates (family Gymnodiniaceae) may be an important food source and these phytoplankton were predominant in gut contents and POM as evidenced by DNA analysis and phytoplankton cell counting. The compositions of the gut contents were not specific to the species of eel larvae or the different sampling areas, and they were most similar to POM at the chlorophyll maximum in the upper part of the thermocline (mean depth: 112 m). Our results are consistent with eel larvae feeding on marine snow at a low trophic level, and feeding may frequently occur in the chlorophyll maximum in the western North Pacific.
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Chow S, Inaba N, Nagai S, Kurogi H, Nakamura Y, Yanagimoto T, Tanaka H, Hasegawa D, Asakura T, Kikuchi J, Tomoda T, Kodama T. Molecular diet analysis of Anguilliformes leptocephalus larvae collected in the western North Pacific. PLoS One 2019; 14:e0225610. [PMID: 31774866 PMCID: PMC6881025 DOI: 10.1371/journal.pone.0225610] [Citation(s) in RCA: 14] [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: 07/10/2019] [Accepted: 11/07/2019] [Indexed: 11/18/2022] Open
Abstract
Natural diets of leptocephalus larvae have been enigmatic. In this study, we collected DNA samples from the gut contents and body surface of leptocephali belonging to the five Anguilliform families (Anguillidae, Chlopsidae, Congridae, Muraenidae, and Serrivomeridae) from the northwest Pacific and performed next-generation 18S rDNA sequencing. Wide variety of eukaryotes was detected in both samples, from which eight eukaryotic groups (jellyfish, conoid parasite, tunicate, copepod, krill, segmented worm, fungi, and dinoflagellate) were selected on the basis of abundance. All groups except conoid parasites were common in both the samples. Cnidarian 18S rDNA reads were the most abundant in both the samples; however, the number of samples having cnidarian reads and the read counts were significantly higher in the body surface scraping samples than in the gut content samples, regardless of careful rinsing of the body surface. These results indicate that the cnidarian DNAs are most likely found because of cross contamination from the body surface and/or environment. 18S rDNA read counts of copepod and tunicate in the gut contents were greater than or comparable with those in the body surface scraping samples, which may correspond to the previous observations of fecal pellets and larvacean houses in the leptocephali gut. Thus, the present study supports previous implications that leptocephali utilize detritus materials, so called marine snow.
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Affiliation(s)
- Seinen Chow
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
- * E-mail:
| | - Nobuharu Inaba
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
- Civil Engineering Research Institute for Cold Region, Public Works Research Institute, Sapporo, Hokkaido, Japan
| | - Satoshi Nagai
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
| | - Hiroaki Kurogi
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
| | - Yoji Nakamura
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
| | - Takashi Yanagimoto
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
| | - Hideki Tanaka
- Aquaculture Research Institute, Kindai University, Higashimuro, Wakayama, Japan
| | - Daisuke Hasegawa
- Tohoku National Fisheries Research Institute, Japan Fisheries Research and Education Agency, Shiogama, Miyagi, Japan
| | - Taiga Asakura
- RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Japan
| | - Jun Kikuchi
- RIKEN Center for Sustainable Resource Science, Tsurumi, Yokohama, Japan
| | - Tsutomu Tomoda
- Shibushi Station, National Research Institute of Aquaculture, Japan Fisheries Research and Education Agency, Shibushi, Kagoshima, Japan
| | - Taketoshi Kodama
- National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Kanazawa, Yokohama, Japan
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