scholarly journals Modeling the drift of European (Anguilla anguilla) and American (Anguilla rostrata) eel larvae during the year of spawning

2018 ◽  
Vol 75 (2) ◽  
pp. 224-234 ◽  
Author(s):  
Håkan Westerberg ◽  
Selma Pacariz ◽  
Lasse Marohn ◽  
Vilhelm Fagerström ◽  
Klaus Wysujack ◽  
...  
Keyword(s):  
Climatic Factors ◽  
Anguilla Anguilla ◽  
Alternative Interpretation ◽  
Current Data ◽  
Anguilla Rostrata ◽  
Sargasso Sea ◽  
Spawning Period ◽  
Highly Sensitive ◽  
Leptocephalus Larvae ◽  
Individual Larva

The distribution of the leptocephalus larvae of European (Anguilla anguilla) and American (Anguilla rostrata) eels collected during recent Sargasso Sea surveys was used to model larval drift. The drift trajectories of individual larva were back-calculated to the estimated time of spawning, using current data from two global oceanographic assimilation models. The results of both models give the same overall result; widespread spawning extended in time from December to March. The drift was also calculated forwards for approximately 1 year. The forward drift modelling showed that most leptocephali remained in the area south of the Subtropical Frontal Zone. One conclusion is that the majority of leptocephali remain trapped and possibly die in the retention area. A small proportion of leptocephali are entrained into the Gulf Stream system. An implication is that the spawning success may be highly sensitive to oceanographic and climatic factors that alter the dispersion of leptocephali out from the retention area. An alternative interpretation is that the surveys were made too late after the peak spawning period and that the core spawning area was missed.

scholarly journals Digestive Tract and the Muscular Pharynx/Esophagus in Wild Leptocephalus Larvae of European Eel (Anguilla anguilla)

2021 ◽  
Vol 8 ◽  
Author(s):  
Helene Rønquist Knutsen ◽  
Sune Riis Sørensen ◽  
Peter Munk ◽  
Tora Bardal ◽  
Elin Kjørsvik
Keyword(s):  
Digestive Tract ◽  
Striated Muscle ◽  
Feeding Strategy ◽  
Posterior Part ◽  
Anguilla Anguilla ◽  
Pancreatic Tissue ◽  
European Eel ◽  
Sargasso Sea ◽  
Larval Body ◽  
Leptocephalus Larvae

Several aspects of the biology of European eel (Anguilla anguilla) larvae are still unknown; particularly, information about their functional development and feeding is sparse. In the present study, we histologically characterize the digestive system of wild caught specimens of European eel leptocephalus larvae. The aim was to provide more understanding about how food may be ingested and mechanically processed in the leptocephalus larvae, and to discuss this in the context of its hypothesized feeding strategy. Larvae were caught in the Sargasso Sea during the “Danish Eel Expedition 2014” with the Danish research vessel Dana. The larval sizes ranged from 7.0 to 23.3 mm standard length (SL) at catch. We found that the mouth/pharynx, especially the anterior esophagus, was surrounded by a multi-layered striated muscle tissue and that the epithelium in the mouth/pharynx had a rough filamentous surface, followed by epithelial columnar cells with multiple cilia in the anterior esophagus. This suggests an expandable pharynx/esophagus, well-suited for the transportation of ingested food and likely with a food-crushing or grinding function. The digestive tract of the larvae consisted of a straight esophagus and intestine ventrally aligned within the larval body, and its length was linearly correlated to the larval length (SL). The length of the intestinal part constituted up to 63% of the total length of the digestive tract. The intestinal epithelium had a typical absorptive epithelium structure, with a brush border and a well-developed villi structure. Some cilia were observed in the intestine, but any surrounding muscularis was not observed. The liver was observed along the posterior part of the esophagus, and pancreatic tissue was located anterior to the intestine. Our findings support the hypothesis that the eel leptocephalus may ingest easily digestible gelatinous plankton and/or marine snow aggregates. The muscular esophagus and the ciliated epithelium appear sufficient to ensure nutrient transport and absorption of the ingested food through the digestive tract.

Artificial maturation, fertilization, and early development of the American eel (Anguilla rostrata)

2010 ◽  
Vol 88 (11) ◽  
pp. 1121-1128 ◽  
Author(s):  
K. Oliveira ◽  
W. E. Hable
Keyword(s):  
Early Development ◽  
Anguilla Rostrata ◽  
Sargasso Sea ◽  
American Eel ◽  
Important Species ◽  
Vitro Fertilization ◽  
Commercially Important ◽  
Elusive Species ◽  
American Eels

Spawning for the American eel ( Anguilla rostrata (Le Sueur, 1817)) takes place in secretive locations within the Sargasso Sea, which has thus far prevented investigations of gametogenesis and early development in this ecologically and commercially important species. Attempts to induce maturation and reproduction in this species have been few and have produced limited results, with a single report of the production of gastrula-stage embryos. Here we report the successful maturation of female American eels. Maturation occurred within 13 weeks and ovulation was induced with a single injection of 17α,20β-dihydroxy-4-pregnen-3-one (DHP). Following in vitro fertilization, embryogenesis through hatching was observed and larvae were maintained for up to 6 days. We show that a crucial factor for successful fertilization is the stage of the oocyte at the time of induced ovulation. Oocytes that had not reached the migratory nucleus stage, or had passed this stage, were not successfully fertilized. These findings demonstrate that American eel can reproduce in the laboratory and previously untestable hypotheses pertaining to the developmental biology of this elusive species can now be explored.

scholarly journals Gelatinous plankton is important in the diet of European eel (Anguilla anguilla) larvae in the Sargasso Sea

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Daniel J. Ayala ◽  
Peter Munk ◽  
Regitze B. C. Lundgreen ◽  
Sachia J. Traving ◽  
Cornelia Jaspers ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
European Eel ◽  
Sargasso Sea

scholarly journals Glass eels (Anguilla anguilla) imprint the magnetic direction of tidal currents from their juvenile estuaries

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Alessandro Cresci ◽  
Caroline M. Durif ◽  
Claire B. Paris ◽  
Steven D. Shema ◽  
Anne Berit Skiftesvik ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
Magnetic Compass ◽  
European Eel ◽  
Sargasso Sea ◽  
North African ◽  
Compass Direction ◽  
Tidal Flows ◽  
Glass Eels ◽  
Cardinal Directions ◽  
Magnetic North

Abstract The European eel (Anguilla anguilla) hatches in the Sargasso Sea and migrates to European and North African freshwater. As glass eels, they reach estuaries where they become pigmented. Glass eels use a tidal phase-dependent magnetic compass for orientation, but whether their magnetic direction is innate or imprinted during migration is unknown. We tested the hypothesis that glass eels imprint their tidal-dependent magnetic compass direction at the estuaries where they recruit. We collected 222 glass eels from estuaries flowing in different cardinal directions in Austevoll, Norway. We observed the orientation of the glass eels in a magnetic laboratory where the magnetic North was rotated. Glass eels oriented towards the magnetic direction of the prevailing tidal current occurring at their recruitment estuary. Glass eels use their magnetic compass to memorize the magnetic direction of tidal flows. This mechanism could help them to maintain their position in an estuary and to migrate upstream.

Isolation and characterization of two different 5S rDNA in Anguilla anguilla and in Anguilla rostrata: possible markers of evolutionary divergence

2006 ◽  
Vol 6 (3) ◽  
pp. 638-641 ◽  
Author(s):  
GIUSEPPINA PICHIRI ◽  
MARIELLA NIEDDU ◽  
SARA MANCONI ◽  
CINZIA CASU ◽  
PIERPAOLO CONI ◽  
...  
Keyword(s):  
5S Rdna ◽  
Anguilla Anguilla ◽  
Anguilla Rostrata ◽  
Evolutionary Divergence ◽  
Isolation And Characterization

Do Leptocephali of the European Eel Swim to Reach Continental Waters? Status of the Question

1998 ◽  
Vol 78 (1) ◽  
pp. 285-306 ◽  
Author(s):  
J.D. McCleave ◽  
P.J. Brickley ◽  
K.M. O'Brien ◽  
D.A. Kistner ◽  
M.W. Wong ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Anguilla Anguilla ◽  
Late Winter ◽  
European Eel ◽  
Sargasso Sea ◽  
North East ◽  
Nutritional Mode ◽  
Mid Atlantic Ridge ◽  
One Year ◽  
European Coast

We examined recent arguments that leptocephali of the European eel,Anguilla anguilla, swim in an oriented manner, rather than drift, to reach the continental shelf of Europe and the Mediterranean Sea. There is a cline of increasing body length of leptocephali from south to north and from west to east from the Mid-Atlantic Ridge (30°W) to the continental shelf, which could represent migration from south-west to north-east, transport eastward at all latitudes, or increased growth rate with latitude. Evidence that this cline is a trend in age of arriving glass eels along the European coast, and that the duration of migration is less than one year, is weak. Ages reported in the literature for specimens from Morocco to The Netherlands were based on the unvalidated assumption that rings in otoliths were deposited daily. The assumption is unwarranted because of low metabolic rate and uncertainty of nutritional mode of leptocephali. If the assumption were accepted, calculated hatching dates of eels arriving at the European coast imply year-round spawning. Lengths of leptocephali in the Sargasso Sea at various times imply that eels spawn only in late winter and spring. Leptocephali contain tiny amounts of muscle, especially aerobic muscle for sustained swimming. They probably have insufficient capability to swim across the Atlantic in the less than 1–2 y reported by others.

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