The gymnotid eels of tropical America.

Ellis, M. M.

doi:10.5962/bhl.title.12969

Cited by 53 publications

(66 citation statements)

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“…The second advantage is the potential to electrify most of a well-grounded animal (Movie S8). The latter result was reported by Sachs (18).…”

Section: Discussionsupporting

confidence: 76%

“…To illustrate this effect, sets of eel-powered LEDs were connected in series along separate strips of conductive tape attached, in turn, to a prosthetic limb, allowing direct observation of the increasing area of effect (Movie S7). An additional benefit from the leaping strategy might be gained for targets that have only a small portion of their body submerged but are grounded (5,18). Eel-powered LEDs were similarly used to illustrate this effect (Fig.…”

Section: The Author Declares No Conflict Of Interestmentioning

confidence: 99%

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Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses

Catania

2016

Proc. Natl. Acad. Sci. U.S.A.

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In March 1800, Alexander von Humboldt observed the extraordinary spectacle of native fisherman collecting electric eels (Electrophorus electricus) by "fishing with horses" [von Humboldt A (1807) Ann Phys 25: [34][35][36][37][38][39][40][41][42][43]. The strategy was to herd horses into a pool containing electric eels, provoking the eels to attack by pressing themselves against the horses while discharging. Once the eels were exhausted, they could be safely collected. This legendary tale of South American adventures helped propel Humboldt to fame and has been recounted and illustrated in many publications, but subsequent investigators have been skeptical, and no similar eel behavior has been reported in more than 200 years. Here I report a defensive eel behavior that supports Humboldt's account. The behavior consists of an approach and leap out of the water during which the eel presses its chin against a threatening conductor while discharging high-voltage volleys. The effect is to short-circuit the electric organ through the threat, with increasing power diverted to the threat as the eel attains greater height during the leap. Measurement of voltages and current during the behavior, and assessment of the equivalent circuit, reveal the effectiveness of the behavior and the basis for its natural selection.evolution | behavior | Humboldt | electroreception | neuroethology I n 1807, Alexander von Humboldt published his account of a battle between electric eels and horses (1). The stage for this event was set when Humboldt hired local fishermen to supply him with eels for research. Their method was to "fish with horses" (1). About 30 horses and mules were herded into a pool containing eels, which (according to Humboldt) emerged from the mud, swam to the surface, and attacked by pressing themselves against the horses while discharging. The fishermen kept the horses from escaping by surrounding the pool and climbing nearby trees with overhanging branches while crying out and waving reeds. Two horses drowned, and others stumbled from the pool and collapsed. Humboldt thought more horses would be killed, but the eels were exhausted before this happened. Five eels were then captured and Humboldt was able to conduct his experiments (2).This famous story has been illustrated and recounted many times (3-10) (Fig. 1A). However, some have doubted its accuracy (see ref. 8). Sachs (5) suggested the story was "poetically transfigured," Coates (11) flatly considered it "tommyrot," and Moller (8) [and Catania (12)] gently suggested Humboldt's accounts were "tales." The aggressive behavior of the eels, taking the offensive against horses, seems the most fantastic and questionable part of the story. Why would electric eels do this? No similar behavior has been reported since Humboldt's (1) publication.Here I report that electric eels attack large, moving, partially submerged conductors by leaping from the water while pressing themselves against the threat and discharging high-voltage volleys (Fig. 1B). This behavior appears to be ubiq...

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“…The second advantage is the potential to electrify most of a well-grounded animal (Movie S8). The latter result was reported by Sachs (18).…”

Section: Discussionsupporting

confidence: 76%

Section: The Author Declares No Conflict Of Interestmentioning

confidence: 99%

Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses

Catania

2016

Proc. Natl. Acad. Sci. U.S.A.

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“…A fossil gymnotiform was interpreted as having an adipose fin [55]; however, this interpretation has been challenged [56,57]. It has also been proposed that the 'dorsal filament' [58], an appendage found on the dorsal midline of some apteronotid gymnotiformes, which lacks a skeleton and musculature, is a transformed adipose fin. Assessment of this hypothesis yielded inconclusive results [59].…”

Section: (A) Adipose Fins Have Evolved Repeatedlymentioning

confidence: 99%

The origins of adipose fins: an analysis of homoplasy and the serial homology of vertebrate appendages

2014

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Adipose fins are appendages found on the dorsal midline between the dorsal and caudal fins in more than 6000 living species of teleost fishes. It has been consistently argued that adipose fins evolved once and have been lost repeatedly across teleosts owing to limited function. Here, we demonstrate that adipose fins originated repeatedly by using phylogenetic and anatomical evidence. This suggests that adipose fins are adaptive, although their function remains undetermined. To test for generalities in the evolution of form in de novo vertebrate fins, we studied the skeletal anatomy of adipose fins across 620 species belonging to 186 genera and 55 families. Adipose fins have repeatedly evolved endoskeletal plates, anterior dermal spines and fin rays. The repeated evolution of fin rays in adipose fins suggests that these fins can evolve new tissue types and increased structural complexity by expressing fin-associated developmental modules in these new territories. Patterns of skeletal elaboration differ between the various occurrences of adipose fins and challenge prevailing hypotheses for vertebrate fin origin. Adipose fins represent a powerful and, thus far, barely studied model for exploring the evolution of vertebrate limbs and the roles of adaptation and generative biases in morphological evolution.

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“…The oldest citation was by Ellis (1913), based on specimens identified as Hypopomus brevirostris (=Brachyhypopomus brevirostris) collected by Herman von Ihering in the laguna dos Patos drainage (Malabarba, 1989). Brachyhypopomus pinnicaudatus, B. beebei and an undescribed species have been quoted as widely distributed in cis-Andean South American basins by Sullivan (1997), including material from Rio Grande do Sul state.…”

Section: Introductionmentioning

confidence: 99%

Brachyhypopomus draco, a new sexually dimorphic species of Neotropical electric fish from southern South America (Gymnotiformes: Hypopomidae)

2008

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Brachyhypopomus draco, new species, is described from central, southern and coastal regions of Rio Grande do Sul state, Brazil, and Uruguay. It is diagnosed from congeners by, among other characters, the shape of the distal portion of the caudal filament in mature males, which during the reproductive period forms a distinct paddle shape structure.Brachyhypopomus draco, espécie nova, é descrita para as regiões central, sul e costeira do estado do Rio Grande do Sul, Brasil, e Uruguai. Ela é diagnosticada de seus congêneres, entre outros caracteres, pela porção final do filamento caudal de machos maduros, que adquire a forma de um remo durante o período reprodutivo, .

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The gymnotid eels of tropical America.

Abstract: No. 7. Catalog Eocene Fishes from Monte Bolea No. 4. Catalogof the Fishes of Formosa. Jordan^C arnegie Museum. By Charles R.

Cited by 53 publications

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Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses

Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses

The origins of adipose fins: an analysis of homoplasy and the serial homology of vertebrate appendages

Brachyhypopomus draco, a new sexually dimorphic species of Neotropical electric fish from southern South America (Gymnotiformes: Hypopomidae)

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