V. The electric organ of the skate : observations on the structure, relations, progressive development, and growth of the electric organ of the skate

Ewart, J. C.

doi:10.1098/rspl.1891.0063

Cited by 3 publications

(7 citation statements)

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“…These characters may be synapomorphies of the clade thus supporting McEachran and Miyake (1990a (Ewart, 1888a(Ewart, , 1892. Raja (Dipturus) is distinguished from the other taxa of Rajini in possessing relatively greatly expanded electrocytes.…”

Section: Discussionmentioning

confidence: 84%

“…The electrocytes were classified as cup-shape, modified cup-shape, intermediate-shape, or discshape. The four shape classifications were treated as a transformation series because disc-shaped electrocytes pass through cupshaped, modified cup-shaped, and intermediate-shaped stages before assuming the discshape (Ewart, 1888a(Ewart, , 1892 (Ewart, 1888a(Ewart, , 1892). Ewart's (1888a) terminology for the cytoplasmic layers and other structures of the electrocytes was accepted in the present study, except that the alveolar and cortical layers were considered to be synonymous.…”

Section: Methodsmentioning

confidence: 99%

“…The ontogeny of the electrocytes of skates, as described by Ewart (1888aEwart ( , 1892, was used to polarize the electrocytes for the phylogenetic analysis because electric organs were not present in the outgroups. The electrocytes were classified as cup-shape, modified cup-shape, intermediate-shape, or discshape.…”

Section: Methodsmentioning

confidence: 99%

“…Also, all electric organs were tail-positive, with the electric motor plate (=electroplate), site of nervous innervation, anteriorly located. The electrocytes were arranged, as previously stated by Stark (1844) and Ewart (1892), into horizontal columns divided by transverse septa into many individual units. The columns had a concentric arrangement forming hollow cones one within the another and were continuous with the muscular cones of the lateral muscle bundle.…”

Section: Generalmentioning

confidence: 99%

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Electric organs in skates: Variation and phylogenetic significance (Chondrichthyes: Rajoidei)

Jacob

McEachran

Lyons

1994

Journal of Morphology

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A total of 63 species of skates (Chondrichthyes: Rajoidei) were surveyed, along with three species of the outgroup (Chondrichtyes: Rhinobatoidei) for electric organs along the sides of the tail. All skate specimens examined possessed what appeared to be functional electric organs, and the three species of the outgroup lacked evidence of electric organs. The electric organs were tail-positive and arranged into horizontal columns divided by transverse septa. The electrocytes varied considerably within and among supraspecific taxa (subgenera and genera), but they could be broadly classified into cup-shape, modified cup-shape, intermediate-shape, and disc-shape cells, provided that the distinction was partially based on position of the electrocytes within their connective tissue chambers. The survey, in part, corroborates a phylogenetic hypothesis of skates and in some respects further resolves the hypothesis. The supraspecific taxa Atlantoraja and Rioraja have similar derived-type electrocytes, as do the five supraspecific taxa of Rajini, and Cruriraja and Anacanthobatis, and to a lesser extent the supraspecific taxa Arhynchobatis, Psammobatis, and Sympterygia, and the supraspecific taxa Notoraja, Pavoraja, and Pseudoraja, corroborating the hypothesis. The supraspecific taxa Amblyraja, Rajella, Leucoraja, Breviraja, and Dactylobatus were unresolved in the phylogenetic hypothesis, but the electrocyte survey suggested that Leucoraja, Breviraja, and Dactylobatus were derived with respect to Amblyraja and Rajella. © 1994 Wiley-Liss, Inc.

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Section: Discussionmentioning

confidence: 84%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Generalmentioning

confidence: 99%

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Electric organs in skates: Variation and phylogenetic significance (Chondrichthyes: Rajoidei)

Jacob

McEachran

Lyons

1994

Journal of Morphology

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“…It is not surprising, however, that nearly all these works have suffered greatly on account of paucity of embryonic material. Nevertheless, a considerable body of information has been accumulated to show that the source of origin of electric organs is striated muscle tissue for teleostean fishes also, as for elasmobranch fishes (Ewart, 1893;Engelmann, 1894;Ogneff, 1897). But for this fact, inadequacy of our knowledge on other developmental aspects is apparent.…”

mentioning

confidence: 98%

Development of electric organs of Gymnarchus niloticus (Fam. Gymnarchidae): I. Origin and histogenesis of electroplates

Srivastava

Szabo

1972

Journal of Morphology

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The development of the electric organs of Gymnarchus niloticus has been studied and the origin and histogenesis of a n electroplate worked out. A segmental origin of the electroplate is reported for the first time for this fish. Light has been thrown on many hitherto obscure phenomena, viz., growth of core girth, loss of transverse striations on the myofibrillar elements, differentiation of electroplate polarities, shortening in length of the electroplate etc. The transverse striations of the myofibrillar bundle of the electroplate primordium progressively disappear with development owing to splitting apart of the constituent myofilaments and consequent loss of their parallel order, and not to degeneration of the myofibrillar bundle. The excessive growth of the core girth of the electroplates is caused by the deposition of some kind of interfibrillar substance probably secreted by the peripheral cytoplasm.

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Morphological variation in the electric organ of the little skate (Leucoraja erinacea) and its possible role in communication during courtship

Morson

Morrissey

Developments in Environmental Biology of Fishes 27

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Skates discharge an electrical current too weak to be used for predation or defense, and too infrequent and irregular to be used for electrolocation. Additionally, skates possess a specialized sensory system that can detect electrical stimuli at the same strength at which they discharge their organs. These two factors are suggestive of a communicative role for the electric organ in skates, a role that has been demonstrated in similarly weakly electric teleosts (e.g., mormyrids and gymnotiforms). There is evidence that the sexual and ontogenetic variations in the electric organ discharge (EOD) in these other weakly electric fishes are linked to morphological variations in electric organs and the electrogenerating cells of the organs, the electrocytes. Little work has been done to examine possible sexual and ontogenetic variations in skate EODs or variations in the electrocytes responsible for those discharges. Electric organs and electrocyte morphology of male and female, and mature and immature little skates, Leucoraja erinacea, are characterized here. Female electric organs were bigger than male electric organs. This is suggestive of a sexually dimorphic EOD waveform or amplitude, which might be used as a sex-specific identification signal during courtship. The shapes of electrocytes that make up the organ were found to be significantly different between mature and immature individuals and, in some cases, posterior membrane surface area of the electrocytes increased at the onset of maturity due to the formation of membrane surface invaginations and papillae. This is evidence that the EOD of skates may differ in its waveform or amplitude or frequency between mature and immature skates, and act as a signal for readiness to mate. This study supports a communicative role during courtship for the weak electric organs of little skates, but studies that characterize skate EOD dimorphisms are needed to corroborate this speculation before conclusions can be drawn about the role the electric organ plays in communication during courtship.

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V. The electric organ of the skate : observations on the structure, relations, progressive development, and growth of the electric organ of the skate

Cited by 3 publications

References 0 publications

Electric organs in skates: Variation and phylogenetic significance (Chondrichthyes: Rajoidei)

Electric organs in skates: Variation and phylogenetic significance (Chondrichthyes: Rajoidei)

Development of electric organs of Gymnarchus niloticus (Fam. Gymnarchidae): I. Origin and histogenesis of electroplates

Morphological variation in the electric organ of the little skate (Leucoraja erinacea) and its possible role in communication during courtship

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