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The untold story of the caudal skeleton in the electric eel (ostariophysi: gymnotiformes: electrophorus).

de Santana CD, Vari RP, Wosiacki WB - PLoS ONE (2013)

Bottom Line: The confluence of the two fins is proposed as an additional autapomorphy for the genus.Under all alternative proposed hypotheses of relationships within the order Gymnotiformes, the presence of a caudal fin in Electrophorus optimized as being independent of the occurence of the morphologically equivalent structure in the Apteronotidae.Possible functional advantages to the presence of a caudal fin in the genus are discussed.

View Article: PubMed Central - PubMed

Affiliation: Division of Fishes, Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D. C., United States of America. apteronotidae@ig.com.br

ABSTRACT
Alternative hypotheses had been advanced as to the components forming the elongate fin coursing along the ventral margin of much of the body and tail from behind the abdominal region to the posterior margin of the tail in the Electric Eel, Electrophorus electricus. Although the original species description indicated that this fin was a composite of the caudal fin plus the elongate anal fin characteristic of other genera of the Gymnotiformes, subsequent researchers proposed that the posterior region of the fin was formed by the extension of the anal fin posteriorly to the tip of the tail, thereby forming a "false caudal fin." Examination of ontogenetic series of the genus reveal that Electrophorus possesses a true caudal fin formed of a terminal centrum, hypural plate and a low number of caudal-fin rays. The confluence of the two fins is proposed as an additional autapomorphy for the genus. Under all alternative proposed hypotheses of relationships within the order Gymnotiformes, the presence of a caudal fin in Electrophorus optimized as being independent of the occurence of the morphologically equivalent structure in the Apteronotidae. Possible functional advantages to the presence of a caudal fin in the genus are discussed.

Show MeSH
Phylogenetic relationships in Gymnotiformes based on [1], [17], [25] illustrating most parsimonious hypothesis for origins of caudal skeleton.Electrophorus + Gymnotus  = Gymnotidae; arrows indicate presence of caudal fin complex in Apteronotidae and Electrophorus.
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pone-0068719-g007: Phylogenetic relationships in Gymnotiformes based on [1], [17], [25] illustrating most parsimonious hypothesis for origins of caudal skeleton.Electrophorus + Gymnotus  = Gymnotidae; arrows indicate presence of caudal fin complex in Apteronotidae and Electrophorus.

Mentions: The second major phylogenetic hypothesis of relationships for the Gymnotiformes, this based on morphological data, alternatively has the Gymnotidae (Electrophorus plus Gymnotus) as the sister clade to the remainder of the order [1], [17], [25] (Fig. 7). Under that scenario the Apteronotidae is a crown group within the Gymnotiformes separated by four nodes from Electrophorus. Within this phylogenetic scheme, the presence of a caudal fin in those taxa again optimizes as separate events, with two alternative equally parsimonious explanations. Under one, the presence of the caudal fin in the Apteronotidae and Electrophorus represents separate acquisitions post the presumed loss of the complex in the ancestor of the Gymnotiformes. The second scheme involves the loss of the fin in Gymnotus (the sister group to Electrophorus) in the Gymnotidae and in the ancestor of the Rhamphichthyidae, Hypopomidae, Sternopygidae and Apteronotidae and the reacquistion of the fin in the Apteronotidae (Fig. 7).


The untold story of the caudal skeleton in the electric eel (ostariophysi: gymnotiformes: electrophorus).

de Santana CD, Vari RP, Wosiacki WB - PLoS ONE (2013)

Phylogenetic relationships in Gymnotiformes based on [1], [17], [25] illustrating most parsimonious hypothesis for origins of caudal skeleton.Electrophorus + Gymnotus  = Gymnotidae; arrows indicate presence of caudal fin complex in Apteronotidae and Electrophorus.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3722192&req=5

pone-0068719-g007: Phylogenetic relationships in Gymnotiformes based on [1], [17], [25] illustrating most parsimonious hypothesis for origins of caudal skeleton.Electrophorus + Gymnotus  = Gymnotidae; arrows indicate presence of caudal fin complex in Apteronotidae and Electrophorus.
Mentions: The second major phylogenetic hypothesis of relationships for the Gymnotiformes, this based on morphological data, alternatively has the Gymnotidae (Electrophorus plus Gymnotus) as the sister clade to the remainder of the order [1], [17], [25] (Fig. 7). Under that scenario the Apteronotidae is a crown group within the Gymnotiformes separated by four nodes from Electrophorus. Within this phylogenetic scheme, the presence of a caudal fin in those taxa again optimizes as separate events, with two alternative equally parsimonious explanations. Under one, the presence of the caudal fin in the Apteronotidae and Electrophorus represents separate acquisitions post the presumed loss of the complex in the ancestor of the Gymnotiformes. The second scheme involves the loss of the fin in Gymnotus (the sister group to Electrophorus) in the Gymnotidae and in the ancestor of the Rhamphichthyidae, Hypopomidae, Sternopygidae and Apteronotidae and the reacquistion of the fin in the Apteronotidae (Fig. 7).

Bottom Line: The confluence of the two fins is proposed as an additional autapomorphy for the genus.Under all alternative proposed hypotheses of relationships within the order Gymnotiformes, the presence of a caudal fin in Electrophorus optimized as being independent of the occurence of the morphologically equivalent structure in the Apteronotidae.Possible functional advantages to the presence of a caudal fin in the genus are discussed.

View Article: PubMed Central - PubMed

Affiliation: Division of Fishes, Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D. C., United States of America. apteronotidae@ig.com.br

ABSTRACT
Alternative hypotheses had been advanced as to the components forming the elongate fin coursing along the ventral margin of much of the body and tail from behind the abdominal region to the posterior margin of the tail in the Electric Eel, Electrophorus electricus. Although the original species description indicated that this fin was a composite of the caudal fin plus the elongate anal fin characteristic of other genera of the Gymnotiformes, subsequent researchers proposed that the posterior region of the fin was formed by the extension of the anal fin posteriorly to the tip of the tail, thereby forming a "false caudal fin." Examination of ontogenetic series of the genus reveal that Electrophorus possesses a true caudal fin formed of a terminal centrum, hypural plate and a low number of caudal-fin rays. The confluence of the two fins is proposed as an additional autapomorphy for the genus. Under all alternative proposed hypotheses of relationships within the order Gymnotiformes, the presence of a caudal fin in Electrophorus optimized as being independent of the occurence of the morphologically equivalent structure in the Apteronotidae. Possible functional advantages to the presence of a caudal fin in the genus are discussed.

Show MeSH