Guillaume, O. 2000. The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). I. Female. —Acta Zoologica (Stockholm) 81: 213–221
Cloacae of female Proteus ...anguinus were examined by light and electron microscopy. Females possess spermathecae and anterior ventral glands such as Necturus females. However, female P. anguinus possess new additional cloacal glands of unknown homology. These tubular glands secrete on the ventral epidermis of the cloacal area. Considering these characteristics, it is proposed that they will be called the ventral skin glands.
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Since thyroid hormones play a pivotal role in amphibian metamorphosis we used PCR to amplify DNA fragments corresponding to a portion of the ligand-binding domain of the thyroid hormone receptor (TR) ...genes in several neotenic amphibians: the obligatory neotenic members of the family Proteidea the mudpuppy Necturus maculosus and Proteus anguinus as well as two members of the facultative neotenic Ambystoma genus: the axolotl Ambystoma mexicanum and the tiger salamander Ambystoma tigrinum. In addition, we looked for TR genes in the genome of an apode Typhlonectes compressicaudus. TR genes were found in all these species including the obligatory neotenic ones. The PCR fragments obtained encompass both the C and E domains and correspond to alpha and beta genes. Their sequences appear to be normal, suggesting that there is no acceleration of evolutionary rates in the TR genes of neotenic amphibians. This result is not surprising for Ambystomatidae, which are known to respond to T3 (3,3',5-triiodothyronine) but is not in agreement with biochemical and biological data showing that Proteidea cannot respond to thyroid hormones. Interestingly, by RT-PCR analysis we observed a high expression levels of TRalpha in gills, intestine, and muscles of Necturus as well as in the liver of Ambystoma mexicanum, whereas TRbeta expression was only detected in Ambystoma mexicanum but not in Necturus. Such a differential expression pattern of TRalpha and TRbeta may explain the neoteny in Proteidea. The cloning of thyroid-hormone-receptor gene fragments from these species will allow the molecular study of their failure to undergo metamorphosis.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Guillaume, O. 2000. The ventral skin glands, new additional cloacal glands in Proteus anguinus (Caudata, Proteidae). II. Male. —Acta Zoologica (Stockholm) 81: 223–234
Cloacae from male Proteus ...anguinus were examined for the first time by light and electron microscopy. Male P. anguinus possess anterior and posterior ventral glands, dorsal and lateral pelvic glands, vent glands and Kingsbury’s glands as do Necturus males. However, male P. anguinus also possess the new additional cloacal glands found in females and which the author has called the ventral skin glands. Furthermore, the number, the length and the diameter of these tubular glands are higher in males. Therefore the inference is that these glands are sexually dimorphic glands.
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A phylogenetic analysis of partial 12S rRNA mitochondrial gene sequences from representatives of salamandroid families provided moderate support for the monophyly of the family Proteidae, comprising ...the North American genus Necturus and the European blind cave salamander Proteus.
The blind cave salamander's (Proteus anguinus L.) sensitivity for electrical fields was determined by recordings from afferent fibers coming from ampullary electroreceptors. The animals were ...stimulated with single rectangular or continuous sinusoidal electrical signals passed through the cave water in the experimental tank. Best threshold sensitivities of the fibers for both kinds of signals were in the same range (0.1-0.5 mV/cm = 30-150 nA/cm2). The fibers showed phase-locked responses to rostrally cathodic phases of rectangular or sinusoidal stimuli and suppression to anodal phases. Units were tuned to 'best frequencies' (B.F., sine waves) between 20 and 40 Hz. Any functional, i.e. phase-related, firing or suppression of firing occurs in a total frequency range of less than 0.1 to around 100 Hz. This frequency range of tuning in the primary fibers was the same as found in the behavior, and this therefore reflects the peripheral sensory properties. Electrical sensitivity might be of special value for these cave dwelling animals, as they may detect and recognize prey animals by means of the prey's electrical field spreading into the surroundings, i.e. its electromyogram.
Life and development in complete darkness for a strictly cavernicolous Urodele species such as
Proteus raises the problem of orientation and environmental perception. An experimental study of ...olfaction in
Proteus anguinus was undertaken on two complementary aspects: (a) a anatomical and ultrastructural aspect (photon and electron microscopy); and (b) a behavioural aspect, by testing
Proteus’ sensitivity to decreasing amounts of dead prey (chironomid larvae) in a choice chamber. The results show that: (a)
Proteus’ olfactory epithelium clearly belonged to the general model established for all vertebrates, with a pseudo-stratified structure mainly composed of the three classical cell types (sensory cells, supporting cells and basal cells). With the unusual thickness of the epithelium common to the Proteidae, a fourth cell type is observed in
Proteus; and (b)
Proteus shows a well-developed olfactive sense: the sensitivity threshold occurs around 1 g of prey (in a 250 cm
3/min water current). This relatively low detection threshold implies the use of an outstanding sense of smell probably due to the particular necessities of the subterranean environment. The experiments also emphasize the effects of environmental factors on
Proteus’ response to experiments, and the role of thigmotactism.
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IJS, IMTLJ, KILJ, KISLJ, NUK, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In the urodeles Proteus anguinus and Euproctus asper, thresholds of an overt avoidance response to weak electrical field stimuli (continuous sine-waves) were measured as a function of frequency. ...Thresholds down to 0.1 mV/cm (30 nA/cm2) were found in P. anguinus and 2 mV/cm (600 nA/cm2) in E. asper at 'best frequencies' (B.F.) of 20-30 Hz, but sensitivity covered a total frequency range of below 0.1 Hz to 1-2 kHz, with up to 70 dB higher thresholds. Average thresholds of 1 mV/cm in P. anguinus and 40 mV/cm in E. asper were more than 30 dB apart and significantly different. Both species were sensitive to galvanic DC-pulses, clicks, and noise bursts with intensities of about the same order of magnitude. Specimens of the transparent catfish, Kryptopterus (Siluridae) reacted in the same frequency range as found for Proteus and Euproctus, and had still lower thresholds, down to 0.02 mV/cm (1.5 nA/cm2). The biological significance and possibly still ongoing evolution of the electrical sense in urodeles is interpreted in terms of comparative sensory physiology and more recent, still speculative, evolutionary diversification during and since the Pleistocene.
Thyroid hormone has long been known to induce metamorphosis in amphibians. The understanding of the molecular steps controlling the completion of metamorphosis has nevertheless been hampered by the ...complexity of this event. The comparison of organisms in which metamorphosis does or does not occur, may provide clues into the molecular cascade that control it. Up to now the available data suggest that perennibranchiate amphibians retain their larval characters mainly because their tissues do not respond to thyroid hormones. In such a context the recent identification of a thyroid hormone receptor alpha in the perennibranchiate Proteus anguinus is provocative (Ho Huynh et al., Int. J. Dev. Biol. 40:537-543, 1996). In the present paper, we provide evidences that this recently described sequence is in fact a sequence from Xenopus laevis. Indeed, we identified the authentic thyroid hormone receptors of both alpha and beta types in two perennibranchiate species Necturus maculosus and Proteus anguinus. The various controls required to ascertain the authenticity of a developmental gene cloned by PCR or RT-PCR analysis are presented. The results reported in the present paper are relevant with phylogenetical analysis. This induces our team to conclude that the Proteus TR alpha sequence reported by Ho Huynh et al. (1996) reflects a contamination of the RT-PCR by Xenopus laevis material.
The ultrastructural characteristics of melanosomes and premelanosomes observed during the biogenesis of melanosomes in liver pigment cells of the neotenic cave salamander Proteus anguinus (Proteidae) ...are described. It is well known that amphibian liver pigment cells, also known as Kupffer cells (KC), contain melanosomes and are able to synthesize melanin. Liver pigment cells of P. anguinus contain numerous siderosomes and melanosomes. The melanosomes are grouped together within single-membrane-bounded bodies, named as 'clusters of melanosomes' or 'melanosomogenesis centers'. Inside such clusters, different structures are present: (1) filament-like structures, characteristic of the initial stage of melanosome biogenesis, (2) medium electron-dense melanosomes in different stages of melanization, (3) melanosomes with an electron-dense cortical area and a less electron-dense medullar area, and (4) uniformly highly electron-dense mature melanosomes or melanin granules. Histochemical and cytochemical dihydroxyphenylalanine (DOPA) oxidase reactions in pigment cells were positive. Our results confirm the ability of amphibian KC to synthesize melanin and contribute to this little known subject.
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We demonstrated the presence of thyroid hormone receptor alpha mRNAs in tissues of the perennibranchiate amphibian Proteus anguinus, which is insensitive to thyroid hormone. From P. anguinus muscle ...we cloned and sequenced the 3' coding and untranslated region of a cDNA corresponding to a thyroid hormone receptor alpha 1. Using cDNA-PCR and in situ hybridization, we showed a tissue-specific expression of thyroid hormone receptor alpha genes, which was not upregulated by thyroid hormone as opposed to that observed in the TH-sensitive species, Xenopus laevis.
