Aldosterone regulation of active sodium chloride transport in the lizard colon (Gallotia galloti)

Summary Bioelectrical parameters and unidirectional sodium and chloride fluxes were measured under voltageclamp conditions in groups of lizards submitted to single or chronic aldosterone treatment. Both acute (AT) and chronic (CT) treatment induced significant increases in the short-circuit current (I _sc), as well as in the mucosa-to-serosa (J _m-s ^Na ) and net sodium flux (J _net ^Na ). In AT tissues, aldosterone did not change net chloride flux (J _net ^Cl ) but did so in CT tissues. Amiloride reduced the aldosterone-increased I _sc in AT and CT tissues, inhibited J _net ^Na in AT tissues and abolished it in CT colons. J _net ^Cl was also reduced by the diuretic in the group of AT colons, whereas no changes were observed in the CT tissues. Addition of luminal DIDS reduced Na⁺ absorption and totally inhibited Cl^- absorption in the AT tissues, but did not change I _sc. However, in CT tissues neither Na⁺ nor Cl^- transport were affected by DIDS. A good relationship between I _sc and J _m-s ^Na was apparent after DIDS treatment in AT tissues. In this group, simultaneous addition of DIDS and amiloride totally abolished J _net ^Na and reduced I _sc to untreated control values. Addition of serosal ouabain abolished I _sc and Na⁺ absorption in AT and CT colons, but Cl^- absorption was only altered in AT tissues. These results support the hypothesis that aldosterone induces an electrogenic, amiloride-sensitive sodium absorption, and in a dose-dependent fashion suppresses electroneutral NaCl absorption in the lizard colon.Abbreviations AT acutely treated - CT chronically treated animals - DIDS 4-4-diisothiocyanatostibene-2-2-disulfonic acid - DMSO dimethylsulphoxide - G _t tissue conductance - I _sc short circuit current - PD transepithelial potential difference - SITS 4-acetamido-4-isothiocyanatostilbene-2-2-disulfonic acid - UC untreated controls Preliminary results of this paper were presented at the X ^th meeting of the European Intestinal Transport Group (EITG), Askov Hojskole, Denmark, 16–19 September 1990     

Neuronal typology of the thalamic area triangularis of Gallotia galloti (reptilia,sauria)

In a Golgi study of the area triangularis (AT), a rostral nucleus of the ventral thalamus of Gallotia galloti, we have identified four major neuronal types on the basis of their morphological characteristics: medium-sized fusiforms with two processes, medium-sized fusiforms with three or four processes, small bipolars, and small and medium-sized multipolars. These neurons are characterized by a simple morphology and radial arrangement. Cell size varies from small to medium, and all axons project laterally. These characteristics distinguish AT neurons from those of neighboring nuclei. In addition, we found some evidence of differential topographic distribution of each neuronal type within the nucleus. Medium-sized fusiform neurons with two processes are located in the most ventral part, where they constitute the ventral nuclear limit. Small multipolar neurons prevail in the dorsal and ventromedial parts, and in the rest of the nucleus medium-sized neurons, including both fusiform with three or four processes and multipolar types, are normally found. Finally, we discuss a putative homology of the reptilian AT with a part of the mammalian zona incerta.     

Diencephalic neuronal populations projecting axons into the basal plate in a lizard (Gallotia galloti).

Lizard diencephalic populations sending axons into the basal plate were studied by the in vitro HRP technique in the lizard Gallotia. Retrograde labeled cells were concentrated in distinct neuronal groups within alar plates of prosomeres p1 and p3, whereas the alar plate of p2 was poorly labeled. Efferent fibers from alar p1 and p3 populations entered the basal plate of the diencephalon along topologically dorsoventral courses, bifurcating thereafter into longitudinal ascending (rostral) and descending (caudal) trajectories. Thus, diencephalic segments p1 and p3 have alar cell populations contributing to the longitudinal premotor connectivity of the neural axis , whereas the alar p2 segment projects via the fasciculus retroflexus, the efferent tract of the epithalamus. However, the axons from the habenular complex bifurcate within or adjacent to the floor plate and not within the basal plate.     

Proximate causes of intraspecific variation in locomotor performance in the lizard Gallotia galloti.

To understand the evolution of biological traits, information on the degree and origins of intraspecific variation is essential. Because adaptation can take place only if the trait shows heritable variation, it is important to know whether (at least) part of the trait variation is genetically based. We describe intra- and interindividual variation in three performance measures (sprint speed, climbing, and clambering speed) in juvenile Gallotia galloti lizards from three populations and examine how genetic, environmental (incubation temperature), and ontogenetic (age, size) effects interact to cause performance variation. Moreover, we test whether the three performance traits are intercorrelated phenotypically and genetically. Sprint speed is highest in juveniles incubated at the lowest temperature (26 degrees C) irrespective of population. Climbing speed differs among populations, and the differences persist at least until the lizards are 30 wk old. This suggests that the three populations experience different selective pressures. Moreover, mass, snout-vent length, and hindlimb length seem to affect climbing performance differently in the three populations. The variation in sprinting and climbing ability appears to be genetically based. Moreover, the two performance traits are intercorrelated and thus will not evolve independently from each other. Clambering speed (i.e., capacity to climb up an inclined mesh) varies among individuals, but the origin of this variation remains obscure.     

New Eimeriid Coccidia from the Canarian Lizard, Gallotia galloti Oudart, 1839

One species of Eimeria and one species of Isospora have been discovered in several specimens of the Canarian lizard, Gallotia galloti , collected on Tenerife, Canary Islands, and are described herein as new. The oocysts of Eimeria gallotiae n. sp. are elongate-ellipsoidal and measure 30.6 (29.1–32.6) by 16.0 (14.0–17.9) μm. Micropyle, oocyst residuum, and polar granule are absent. Oocysts each contain four ellipsoidal sporocysts measuring 14.6 (12.2–17.3) by 9.2 (8.2–11.2) μm. Sporocysts have sporocyst residuum but not a Stieda body. The majority of oocysts are fully sporulated when shed. Few oocysts are excreted unsporulated or in the beginning phase of sporulation. The oocysts of Isopora gallotiae n. sp. are spherical and 16.5 (15.3–17.6) μm in diameter. Micropyle, oocyst residuum, and polar granule are absent. Each oocyst has two lemon-shaped sporocysts, 11.5 (10.2–12.2) by 7.3 (6.6–8.2) μm, which take up almost the entire space of the oocyst. A sporocyst residuum is present as well as a knob-like Stieda body and a substieda body. Most oocysts are in the beginning phase of sporulation when excreted and have two spherical sporoblasts. Sporulation is completed within 24 to 28 h at 21 ± 2°C.     

Development of astroglial cells in the encephalon of Gallotia galloti: A Golgi technique study

Some variants of the Golgi techniques have been used to study the possible origin and developmental sequence of astroglial cells in the lizard Gallotia galloti. the developmental sequence consists of progressive transformations of astroglial cells originating either from radial glia or from glioblasts. The so-called displaced radial glia, an intermediate cellular type between radial glia and astrocytes, indicate the radial glia/astrocytes transformation. Apparently, glioblasts also evolve into astroblasts that, in turn could develop into immature protoplasmic or fibrous astrocytes, precursors of mature protoplasmic and fibrous astrocytes, respectively. The present study confirms our previous ultrastructural and immunohistochemical studies on the same animal. © 1995 Wiley-Liss, Inc.     

Relationship between cortical electrical and cardiac autonomic activities in the awake lizard, Gallotia galloti

ECG and EEG signals were simultaneously recorded in lizards, Gallotia galloti, both in control conditions and under autonomic nervous system (ANS) blockade, in order to evaluate possible relationships between the ANS control of heart rate and the integrated central nervous system activity in reptiles. The ANS blockers used were prazosin, propranolol, and atropine. Time-domain summary statistics were derived from the series of consecutive R-R intervals (RRI) of the ECG to measure beat-to-beat heart rate variability (HRV), and spectral analysis techniques were applied to the EEG activity to assess its frequency content. Both prazosin and atropine did not alter the power spectral density (PSD) of the EEG low frequency (LF: 0.5-7.5 Hz) and high frequency (HF: 7.6-30 Hz) bands, whereas propranolol decreased the PSD in these bands. These findings suggest that central beta-adrenergic receptor mechanisms could mediate the reptilian waking EEG activity without taking part any alpha(1)-adrenergic and/or cholinergic receptor systems. In 55% of the lizards in control conditions, and in approximately 43% of the lizards under prazosin and atropine, a negative correlation between the coefficient of variation of the series of RRI value (CV(RRI)) and the mean power frequency (MPF) of the EEG spectra was found, but not under propranolol. Consequently, the lizards' HRV-EEG-activity relationship appears to be independent of alpha(1)-adrenergic and cholinergic receptor systems and mediated by beta-adrenergic receptor mechanisms.     

S100 immunoreactive glial cells in the forebrain and midbrain of the lizard Gallotia galloti during ontogeny

We identified S100 immunoreactive cells in the brain of the lizard Gallotia galloti during ontogeny using immunohistochemical techniques for light and electron microscopy. In double labeling experiments with antibodies specific for S100A1 and S100B (anti-S100) and proliferative cell nuclear antigen (anti-PCNA), myelin basic protein (anti-MBP), phosphorylated neurofilaments (SMI-31), glial fibrillary acidic protein (anti-GFAP), or glutamine synthetase (anti-GS), we detected S100-like immunoreactivity in glial cells but never in neurons. Restricted areas of the ventricular zone were stained in the hypothalamus from E32 to postnatal stages, and in the telencephalon at E35, E36, and in adults. S100 immunoreactivity was observed predominantly in scattered PCNA-negative cells that increased in number from E35 to the adult stage in the myelinated tracts of the brain and had the appearance of oligodendrocytes. Quantitative analysis revealed that all of the S100-positive glial cells were GFAP-negative, whereas most of the S100-positive glial cells were GS-positive. Ultrastructurally, most of these S100-positive/GS-positive glial cells resembled oligodendrocytes of light and medium electron density. In adult lizards, a small subpopulation of astrocyte-like cells was also stained in the pretectum. We conclude that in the lizard S100 can be considered a marker of a subpopulation of oligodendrocytes rather than of astrocytes, as is the case in mammals. The S100-positive subpopulation of oligodendrocytes in the lizard could represent cells actively involved in the process of myelination during development and in the maintenance of myelin sheaths in the adult.     

Geological history and within-island diversity: a debris avalanche and the Tenerife lizard Gallotia galloti

Several processes have been described that could explain geographical variation and speciation within small islands, including fragmentation of populations through volcanic eruptions. Massive landslides, or debris avalanches, could cause similar effects. Here we analyse the potential impact of the 0.8 million-year-ago (Ma) Güimar valley debris avalanche on the phylogeography of the lizard Gallotia galloti on the Canary Island of Tenerife. Distributions of mitochondrial DNA lineages (based on cytochrome b sequences) were analysed on a 60-km southeastern coast transect centred on this area. Three main clades were detected, which can be divided into northern (one clade) and southern (two clades) groups that introgress across the valley. Maximum-likelihood estimates of migration rates (scaled for mutation rate) revealed highly asymmetric patterns, indicating that long-term gene flow into this region from both the northern and the southern populations greatly exceeded that in the opposite directions, consistent with recolonization of the area. The ancestral Tenerife node on the G. galloti tree is estimated at 0.80 Ma, matching closely with the geological estimate for the debris avalanche. Morphological variation (body dimensions and scalation) was also analysed and indicated a stepped cline in female scalation across the valley, although the patterns for male scalation and male and female body dimensions were not as clear. Together these findings provide support for the hypothesis that the debris avalanche has shaped the phylogeography of G. galloti and may even have been a primary cause of the within-island cladogenesis through population fragmentation and isolation. Current estimates of timing of island unification mean that the original hypothesis that within-island diversity is explained by the secondary contact of populations from the two ancient precursor islands of Teno and Anaga is less plausible for this and some other Tenerife species. Large-scale landslides have occurred on many volcanic islands, and so may have been instrumental in shaping within-island diversities.     

Sexual dimorphism of head size in Gallotia galloti: testing the niche divergence hypothesis by functional analyses

1. Two often cited hypotheses explaining sexual head size dimorphism in lizards are: sexual selection acting on structures important in intrasexual competition, and reduction of intersexual competition through food niche separation.
2. In this study some implicit assumptions of the latter hypothesis were tested, namely that an increase in gape distance and bite force should accompany the observed increase in head size. These assumptions are tested by recording bite forces, in vivo , for lizards of the species Gallotia galloti . In this species, male lizards have significantly larger heads than female conspecifics of similar snout–vent length.
3. Additionally, the average force needed to crush several potential prey species was determined experimentally and compared with the bite force data. This comparison clearly illustrates that animals of both sexes can bite much harder than required for most insect food items, which does not support the niche divergence hypothesis. The apparent 'excess' bite force in both sexes might be related to the partially herbivorous diet of the animals.
4. To unravel the origin of differences between sexes in bite capacity, the crushing phase of biting was modelled. The results of this model show different strategies in allocation of muscle tissue between both sexes. The origin of this difference is discussed and a possible evolutionary pathway of the development of the sexual dimorphism in the species is provided.     

Population evolution of western Canary Island lizards (Gallotia galloti): 4-base endonuclease restriction fragment length polymorphisms of mitochondrial DNA

The mitochondrial DNA evolution of the western Canary Island lacertid, Galloti galloti , was studied using six restriction enzymes ( Hae III, Mva I, Hin fl, Taq I, Msp I and Dsa V). The population phytogeny ( G. stehlini , from the adjacent island of Gran Canada, was used as an outgroup) based on 56 restriction fragments from the first two enzymes indicates two distinct lineages; a 'northern' lineage of La Palma, north Tenerife and south Tenerife populations and a 'southern' lineage of populations from Gomera and Hierro. The relationships within the northern lineage are also supported by an additional analysis of 132 restriction fragments from the remaining four enzymes. This molecular phylogeny argues for the recognition of two subspecies corresponding to the two main lineages and against the recognition of the six current subspecies which are based on inadequate 'conventional' criteria.     

Pineal Gland and Circadian Locomotor Activity Rhythm in the Lacertid Gallotia galloti eisentrauti: Pinealectomy Induces Arrhythmicity

In order to contribute to a comparative view on lacertids, the effect of pinealectomy on the freerunning activity displayed under constant darkness and temperature (27.5°C ± 0.5) has been studied in the lizard Gallotia galloti eisentrauti . Animals showed an entrained motor activity rhythm under an initial light-dark (12:12 hours) routine and freerunning circadian periods ranging between 24.1 and 25.5 h during constant darkness (periodograms obtained by Sokolove & Bushell's method). After pinealectomy, most animals showed no significant circadian rhythm, their locomotor activity becoming diffuse throughout the whole 24 h period. Thus, the pineal gland seems to play an important role as a main pacemaker regulating the endogenous activity rhythm under constant conditions. This result contrasts with that found in Podarcis sicula where after pinealectomy only changes in length of the freerunning period were found.     

Nonlinearity and fractality in the variability of cardiac period in the lizard, Gallotia galloti: effects of autonomic blockade

Both nonlinear and fractal properties of beat-to-beat R-R interval variability signal (RRV) of freely moving lizards (Gallotia galloti) were studied in baseline and under autonomic nervous system blockade. Nonlinear techniques allowed us to study the complexity, chaotic behavior, nonlinearity, stationarity, and regularity over time of RRV. Scaling behavior of RRV was studied by means of fractal techniques. The autonomic nervous system blockers used were atropine, propranolol, prazosin, and yohimbine. The nature of RRV was linear in baseline and under beta-, alpha(1)- and alpha(2)-adrenoceptor blockades. Atropine changed the linear nature of RRV to nonlinear and increased its stationarity, regularity and fractality. Propranolol increased the complexity and chaotic behavior, and decreased the stationarity, regularity, and fractality of RRV. Both prazosin and yohimbine did not change any of the nonlinear and fractal properties of RRV. It is suggested that 1) the use of both nonlinear and fractal analysis is an appropriate approach for studying cardiac period variability in reptiles; 2) the cholinergic activity, which seems to make the alpha(1)-, alpha(2)- and beta-adrenergic activity interaction unnecessary, determines the linear behavior in basal RRV; 3) fractality, as well as both RRV regularity and stationarity over time, may result from the balance between cholinergic and beta-adrenergic activities opposing actions; 4) beta-adrenergic activity may buffer both the complexity and chaotic behavior of RRV, and 5) neither the alpha(1)- nor the alpha(2)-adrenergic activity seem to be involved in the mediation of either nonlinear or fractal components of RRV.     

Autonomic mediation in the interdependences between cardiocortical activity time variations and between cardiorespiratory activity time variations in the lizard, Gallotia galloti

Multivariate nonlinear analysis methods were applied to variability time series extracted from electrocardiographic, electrocorticographic and respiratory activities of Gallotia galloti lizards, to study interdependences between cardio-cortical activity time variations, and between cardio-respiratory activity time variations. Autonomic nervous system involvement in the mediation of such interdependences was investigated through pharmacological blockade. Cardiac variability was evaluated from the R-R intervals of the electrocardiogram (RRIv). Cortical (CORTv) and respiratory (RESPv) activity time variations were evaluated from power-data signals derived from both electrocorticogram and respiratory signal segments obtained within each R-R interval, respectively. A nonlinear index N to measure interdependence between the signals, and a surrogate data test to measure the significance and nature of the interdependences were used. A nonlinear dependence of RRIv vs. CORTv and of RRIv vs. RESPv was found. Both dependences seem to be unconnected with the functioning of both alpha(1)-adrenoceptor and cholinoceptor systems, but appear to be mediated by beta-adrenoceptor mechanisms. A linear dependence of CORTv vs. RRIv and of RESPv vs. RRIv was also found. Both dependences seem to be unconnected with the operation of alpha(1)-adrenoceptor, beta-adrenoceptor and cholinoceptor systems. It is suggested that both the cardiocortical and cardiorespiratory synchronizations studied seem to be mediated by beta-adrenoceptor mechanisms.     

Helminth infracommunities of Gallotia caesaris caesaris and Gallotia caesaris gomerae (Sauria: Lacertidae) from the Canary Islands (Eastern Atlantic)

A survey of gastrointestinal helminth communities of Gallotia caesaris caesaris (Lehrs, 1914) and G. c. gomerae (Boettger and MUller, 1914), from the islands of El Hierro and La Gomera, respectively, in the Canary Archipelago, Spain, was conducted to determine the prevalence, intensity, and diversity of intestinal parasites of these lacertid lizards. Larval forms of cestodes, nematodes, and acanthocephalans were found in the body cavity of G. c. caesaris; this lizard is the intermediate or paratenic host in the life cycle of these helminths. Pharyngodonid nematodes were the most common intestinal helminths in both hosts, 4 of them being Gallotia spp. specialists. Helminth infracommunities of both hosts were depauperate and isolationist, according to the low values of helminth diversity.     

Autonomic mediation in the interdependences between cardiocortical activity time variations and between cardiorespiratory activity time variations in the lizard, Gallotia galloti.

Multivariate nonlinear analysis methods were applied to variability time series extracted from electrocardiographic, electrocorticographic and respiratory activities of Gallotia galloti lizards, to study interdependences between cardio-cortical activity time variations, and between cardio-respiratory activity time variations. Autonomic nervous system involvement in the mediation of such interdependences was investigated through pharmacological blockade. Cardiac variability was evaluated from the R-R intervals of the electrocardiogram (RRIv). Cortical (CORTv) and respiratory (RESPv) activity time variations were evaluated from power-data signals derived from both electrocorticogram and respiratory signal segments obtained within each R-R interval, respectively. A nonlinear index N to measure interdependence between the signals, and a surrogate data test to measure the significance and nature of the interdependences were used. A nonlinear dependence of RRIv vs. CORTv and of RRIv vs. RESPv was found. Both dependences seem to be unconnected with the functioning of both alpha(1)-adrenoceptor and cholinoceptor systems, but appear to be mediated by beta-adrenoceptor mechanisms. A linear dependence of CORTv vs. RRIv and of RESPv vs. RRIv was also found. Both dependences seem to be unconnected with the operation of alpha(1)-adrenoceptor, beta-adrenoceptor and cholinoceptor systems. It is suggested that both the cardiocortical and cardiorespiratory synchronizations studied seem to be mediated by beta-adrenoceptor mechanisms.