Electric Organs and Their Control

Caputi, Ángel A.; Carlson, Bruce A.; Macadar, O.

doi:10.1007/0-387-28275-0_14

Cited by 73 publications

(103 citation statements)

References 97 publications

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“…Species specificity of the EOD is provided by the evolution of different electromotor control mechanisms and effectors responsible for this control (Bennett and Grundfest, 1959;Bennett, 1971;Bass, 1986;Caputi, 1999;Caputi et al, 2005). While the EOD waveform of African electric fish (Mormyridae) is characteristic of the responses of a homogeneous population of synchronously activated electrogenic units (Hopkins, 1999), American electric fish (Gymnotiforms) show a combination of strategies yielding more complex EOD waveforms.…”

Section: Introductionmentioning

confidence: 99%

Waveform diversity of electric organ discharges: the role of electric organ auto-excitability inGymnotusspp.

Rodríguez-Cattáneo

Caputi

2009

Journal of Experimental Biology

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SUMMARYThis article shows that differences in the waveforms of the electric organ discharges (EODs) from two taxa are due to the different responsiveness of their electric organs (EOs) to their previous activity (auto-excitability). We compared Gymnotus omarorum endemic to Uruguay (35°South, near a big estuary), which has four components in the head to tail electric field (V 1 to V 4 ), with Gymnotus sp. endemic to the south of Brazil, Paraguay and Argentinean Mesopotamia (25°South, inland), which shows a fifth component in addition to the others (V 5 ). We found that: (a) the innervation pattern of the electrocytes, (b) the three earlier, neurally driven, EOD components (V 1 to V 3 ), and (c) their remnants after curarisation were almost identical in the two taxa. The equivalent electromotive forces of late components (V 4 and V 5 ) increased consistently as a function of the external current associated with the preceding component and were abolished by partial curarisation in both taxa. Taken together these data suggest that these components are originated in the responses of the electrocytes to longitudinal currents through the EO. By using a differential load procedure we showed that V 4 in G. omarorum responded to experimental changes in its excitation current with larger amplitude variations than V 4 in Gymnotus sp. We conclude that the differences in the EOD phenotype of the two studied taxa are due to the different EO auto-excitability. This, in turn, is caused either by the different expression of a genetic repertoire of conductance in the electrocyte membrane or in the wall of the tubes forming the EO.

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Section: Introductionmentioning

confidence: 99%

Waveform diversity of electric organ discharges: the role of electric organ auto-excitability inGymnotusspp.

Rodríguez-Cattáneo

Caputi

2009

Journal of Experimental Biology

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“…These fishes, like other members of the order Gymnotiformes, exhibit the unusual ability to generate electric fields from a specialized electric organ (EO) controlled by the nervous system (Lissmann, 1958;Caputi et al, 2005;Caputi, 2011). The field generated by the electric organ discharge (EOD) is affected by the presence of nearby objects.…”

Section: Introductionmentioning

confidence: 99%

“…It has been proposed (Bennett and Grundfest, 1959;Bennett, 1971;Macadar, 1993;Caputi, 1994;Caputi, 1999;Caputi et al, 2005;Rodríguez-Cattáneo, 2009) that the structure and specificity of the EOD field waveform in pulse fish depends on variation in six different factors. Three of these, occurring at the cellular level of organization, determine the locally generated waveforms: (1) the geometry and channel repertoire of myogenic electrocytes; (2) the localization of the synaptic contacts on electrocytes surface; and (3) the synchronous activity of a large bundle of electromotor axons preceding the discharge of electrocytes.…”

Section: Introductionmentioning

confidence: 99%

Electric organ discharge diversity in the genusGymnotus: functional groups and electrogenic mechanisms

Rodríguez-Cattáneo

Aguilera

Cilleruelo

et al. 2012

Journal of Experimental Biology

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SUMMARYPrevious studies describe six factors accounting for interspecific diversity of electric organ discharge (EOD) waveforms in Gymnotus. At the cellular level, three factors determine the locally generated waveforms: (1) electrocyte geometry and channel repertoire; (2) the localization of synaptic contacts on electrocyte surfaces; and (3) electric activity of electromotor axons preceding the discharge of electrocytes. At the organismic level, three factors determine the integration of the EOD as a behavioral unit: (4) the distribution of different types of electrocytes and specialized passive tissue forming the electric organ (EO); (5) the neural mechanisms of electrocyte discharge coordination; and (6) post-effector mechanisms. Here, we reconfirm the importance of the first five of these factors based on comparative studies of a wider diversity of Gymnotus than previously investigated. Additionally, we report a hitherto unseen aspect of EOD diversity in Gymnotus. The central region of the EO (which has the largest weight on the conspecific-received field) usually exhibits a negative-positive-negative pattern where the delay between the early negative and positive peaks (determined by neural coordination mechanisms) matches the delay between the positive and late negative peaks (determined by electrocyte responsiveness). Because delays between peaks typically determine the peak power frequency, this matching implies a co-evolution of neural and myogenic coordination mechanisms in determining the spectral specificity of the intraspecific communication channel. Finally, we define four functional species groups based on EO/EOD structure. The first three exhibit a heterogeneous EO in which doubly innervated electrocytes are responsible for a main triphasic complex. Group I species exhibit a characteristic cephalic extension of the EO. Group II species exhibit an early positive component of putative neural origin, and strong EO auto-excitability. Group III species exhibit an early, slow, negative wave of abdominal origin, and variation in EO auto-excitability. Representatives of Group IV generate a unique waveform comprising a main positive peak followed by a small, load-dependent negative component.

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“…In G. carapo different phases of the waveform are generated by distinct parts of the electric organ; the abdominal and central portion of the electric organ have doubly innervated electrocytes allowing it to produce an EOD waveform with four faces (Caputi et al, 2005;Trujilo-Cenoz and Echague, 1989). In several gymnotids, S. elegans (Hypopomidae) and rhamphichthyds (Rhamphichthyidae) accessory organs contribute additional phases to the waveforms (Crampton and Albert, 2006).…”

Section: Proximate Differences In Signal Production May Account For Dmentioning

confidence: 99%

“…The EOD is produced by the summation of action potentials generated by electrocytes, electrically excitable cells of the electric organ properties of the electrocytes , the innervation patterns and the presence of excitable faces of the individual electrocytes, as well as presence and location of accessory electric organs (Caputi et al, 2005;Kirschbaum and Schwassmann, 2008).…”

Section: Acknowledgementsmentioning

confidence: 99%

Endocrine Regulation of Dynamic Communication Signals in Gymnotiform Fish

Goldina¹

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between an inconspicuous signal that evades predators and an extravagant signal preferred by females. Such a signal has been described in the gymnotiform electric fish, Brachyhypopomus gauderio, which produces a sexually dimorphic electric organ discharge (EOD). The EOD varies on a circadian rhythm and in response to social cues. This signal plasticity is mediated by the slow action of androgens and rapid action of melanocortins.My dissertation research tested the hypotheses that (1) signal plasticity is related to sociality levels in gymnotiform species, and (2) differences in signal plasticity are regulated by differential sensitivity to androgen and melanocortin hormones. To assess the breadth of dynamic signaling within the order Gymnotiformes, I sampled 13 species from the five gymnotiform families. I recorded EODs to observe spontaneous signal oscillations after which I injected melanocortin hormones, saline control, or presented the fish with a conspecific. I showed that through the co-option of the ancient melanocortin vii pathway, gymnotiforms dynamically regulate EOD amplitude, spectral frequency, both, or neither.To investigate whether observed EOD plasticities are related to species-specific sociality I tested four species; two territorial, highly aggressive species, Gymnotus carapo and Apteronotus leptorhynchus, a highly gregarious species, Eigenmannia cf. virescens, and an intermediate short-lived species with a fluid social system, Brachyhypopomus gauderio. I examined the relationship between the androgens testosterone and 11-ketotestosterone, the melanocortin α-MSH, and their roles in regulating EOD waveform.

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Electric Organs and Their Control

Cited by 73 publications

References 97 publications

Waveform diversity of electric organ discharges: the role of electric organ auto-excitability inGymnotusspp.

Waveform diversity of electric organ discharges: the role of electric organ auto-excitability inGymnotusspp.

Electric organ discharge diversity in the genusGymnotus: functional groups and electrogenic mechanisms

Endocrine Regulation of Dynamic Communication Signals in Gymnotiform Fish

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