Lizard Agama Research Articles

Ultrastructural study ofPirhemocytonvirus in lizard erythrocytes

Ultrastructural study of Pirhemocyton infection in the lizard Agama impalearis, and the geckoes Tarentola mauritanica, Ptyodactylus hasselquistii, Gehyra australis and Heteronotia binoei confirmed is viral nature. Despite the apparent structural similarity, being all icosahedral iridovirus-like, virions from the diverse saurian hosts differed in size, nucleoid morphology and cytopathic effects on the erythocytes of their respective hosts. Virions from gecko infections were altogether larger than those found in A. impalearis. In the latter there was also no vacuole formation. The gecko infections are very different from one another in the pattern of their cytoplasmic membranes and the nature of their vacuoles. In P. hasselquistii virions became associated with the vacuole binding membrane. In the other geckoes the vacuole was an unbound inclusion of osmiophilic substance, very different from that found in the vacuole of P. hasselquistii.

Ultrastructural studies on oocysts, sporulation and sporozoites of Schellackia cf. agamae from the intestine of the starred lizard Agama stellio

Young intracellular oocysts of Schellackia cf. agamae in the gut epithelium of Agama stellio were bound by several fine membranes. Later-stage oocysts and sporoblasts in the lamina propria were intercellular and were bound by a thin but firm tri-layered wall. Oocysts had a large central refractile body which, during sporulation, sent extensions into the developing sporozoites. Sporozoites escaped into the gut tissue, leaving a large oocyst residuum with the remains of a refractile body. These sporozoites invaded a variety of connective tissue cells, endothelial cells and circulatory leucocytes in the lamina propria. Sporozoites caused lysis of the host cell cytoplasm at their perimeter and multiple sporozoite infections led to complete degradation of the host cell.

Activity of sarafotoxin/endothelin peptides in the heart and brain of lower vertebrates

The effects of sarafotoxin-b (SRTX-b) and endothelin-1 (ET-1) were tested in the fish tilapia ( Ore niloticus × O. aureus hybrids) and torpedo ( Torpedo ocellata), the toad ( Bufo viridis), the agama lizard ( Agama stellio) and water snake ( Natrix tessellata). In isolated heart preparations of the fish and agama, peptide doses of 0.05–0.5 μg/ml induced positive inotropic effects, reduction of the contraction rate and arrhythmia, leading to cardiac arrest. In the toad, a negative inotropic effect and a reduction of the contraction rate were observed, whereas the water snake was hardly affected by either SRTX-b or ET-1. In the agama, an i.v. injection of 15 μg of SRTX-b caused changes in the ECG, culminating in A-V block that led to cardiac arrest, while in the toad an injection of 45 μg induced only transient disturbances in the ECG. Binding studies with 125I-SRTX-b revealed specific binding sites for SRTX-b and ET-1 in the heart and brain preparations of fish (tilapia and torpedo) and agama, whereas no specific binding could be demonstrated in the toad or in the snake. These results suggest that most vertebrates tested are sensitive to SRTX/ET, while the snake may possess receptors that are of a different structure.

Kinematics of prey capture and chewing in the lizard Agama agama (squamata: Agamidae).

High speed video recordings (200 fields per second) of prey capture and food processing in Agama agama permit the identification of strikes, chews and transport movements. Ten variables from strike movements and seven variables from chewing sequences are digitized; transport movements are inspected only. Univariate and multivariate statistical analyses disclose significant interindividual differences for three variables (maximum gape distance, maximum head angle, and maximum throat distance); but neither these nor principal components analysis show differences between strikes and chews for any of the gape change and hyoid depression variables. However, strikes and chews obviously differ in tongue protrusion and body movements. Chewing may be divided into four stages, comparable to those of transport cycles of other lizards and the generalized tetrapod model. Transport differs from chewing by having a shorter power stroke and relatively more cranial and less jaw movement. The kinematics of feeding in Agama agama are compared with those of other lizards studied previously.

Food consumption of the lizard Agama stellio stellio

Food consumption in the lizard Agama stellio stellio was measured by calibrated production of faeces and urates. There was no difference between daily food consumption in spring and in summer. This non-seasonal pattern in A. stellio from a temperate arid habitat thus falls between the spring/summer pattern found in other lizards from warm temperature climates, and the wet/dry season pattern found in arid environments. Estimated consumption was close to that predicted for a 66 g lizard, and slightly higher than that of the tropical Agama agama. Occupation of a temperate climate has not reduced energy intake in A. stellio, but may have consequences for its time budget.

Life cycle and transmission of Schellackia cf. agamae, a parasite of the starred lizard Agama stellio

Patent infections with Schellackia cf. agamae were established in the starred lizard Agama stellio by feeding blood or liver or by injection of blood from A. stellio infected with sporozoite stages. Mosquitoes, Aedes aegypti and Culex molestus, and larval ticks of Hyalomma aegyptium were fed on sporozoite infected A. stellio and themselves gave rise to patent infections after ingestion by uninfected A. stellio. Merogony in the duodenal epithelium usually lasted to the 14th day post-infection (d.p.i.), while in some lizards it persisted until 18 d.p.i. Microgamonts, macrogamonts and zygotes occurred 11–14 d.p.i. Oocysts migrated into the lamina propria before sporulation. Sporulation had terminated by 18 d.p.i., when sporozoites first appeared in the liver and the blood. Small, young sporozoites invaded hepatocytes and liver macrophages, while a few occurred in the erythrocytes. Sporozoites which occurred from 25 d.p.i. were larger and had invaded erythrocytes and aggregated in melanin-containing liver macrophages. Parasitaemias of medium and high levels as well as hepatic sporozoites persisted in some experimentally infected lizards for 357–370 d.p.i. Lizards could not be reinfected while a parasitaemia was detectable in them. Reptiles other than A. stellio could not be infected with S. cf. agamae.

Demonstration of prostaglandin activity in longs of the rainbow lizard (Agama agama) by bioassay

Extracts and perfusate effluents of lungs of the rainbow lizard (Agama agama) were assayed for prostaglandin-like activity. Results of differential bioassay and thin-layer chromatography suggested that the prostanoid was predominantly PGE2-like. The mean PGE2-like content of 10 lizard lung extracts was 2.9 micrograms g-1 wet weight compared with 146 ng g-1 in rat lungs. Mechanical pressure applied to the lung during perfusion through the pulmonary vasculature provoked the release of large quantities of PGE2-like material. This release was blocked by fatty acid cyclooxygenase inhibitors. Compared with guinea-pig and rat lungs, lizard lungs exhibited a markedly low capacity for inactivating PGE2. In view of an apparently high prostaglandin-forming and a low inactivating capacity, we speculate that under certain circumstances, lizard lungs may release vasoactive substances into the circulation.

Ultrastructural studies on sporozoite stages of Schellackia cf. agamae from liver and blood of the starred lizard agama stellio

Ultrastructural studies on sporozoite stages of Schellackia cf. agamae from liver and blood of the starred lizard Agama stellio. International Journal for Parasitology 19: 13–19. Sporozoite stage infection of Schellackia cf. agamae (Laveran & Petitt, 1909, Bulletin de la Société de Pathologie Éxotique 2: 511–512) was studied in naturally and experimentally infected Agama stellio. Infection in the liver coincided with infection in erythrocytes. In the liver sporozoites occurred in hepatocytes as well as in macrophages. Infection resulted in extreme vacuolization of the host cell, parasites were located in a common large enclave formed by the collapse of individual parasitophorous vacuoles. Sporozoites aggregated in melanin-containing macrophages in the liver in advanced stage of infection were causing only limited damage to the host cell cytoplasm. Progressive erosion of the cytoplasm also characterized infected erythrocytes.

Responses of the isolated rectum of the rainbow lizard (Agama agama) to sympathomimetics

The relaxant effects of isoprenaline, noradrenaline, and adrenaline on the isolated rectum of the rainbow lizard (Agama agama) were studied. Responses were measured as a reduction of carbachol-induced contractions for each sympathomimetic agent. Isoprenaline, adrenaline, noradrenaline produced a dose-dependent relaxation of this preparation and the order of potency was as given. The pD2 value of 8.15 +/- 1.88 obtained for isoprenaline was significantly different (p less than 0.05) from those for adrenaline (5.80 +/- 0.90) and noradrenaline (5.25 +/- 1.18). H35/25, propranolol, and practolol competitively antagonized the relaxant effects of isoprenaline on the isolated lizard rectum. The pA2 values for these beta-adrenoceptor antagonists did not differ significantly (at p less than 0.05). alpha-Adrenoceptor antagonists, phentolamine and phenoxybenzamine, failed to alter the relaxant responses of these sympathometics to any appreciable extent. These results are interpreted to suggest that the relaxant effect produced by these sympathomimetics are mediated predominantly by beta-adrenoceptors that are not significantly differentiated into subtypes. alpha-Adrenoceptors in this preparation contribute minimally to the observed inhibitory response following sympathomimetic stimulation.

Observations on the lipids of Oochoristica agamae (Cestoda).

An investigation of the lipids of Oochoristica agamae, an anoplocephalid cestode of the Agama lizard, was undertaken. Total lipids of the parasite accounted for 8.4% of the fresh weight; neutral lipids comprised 82.98% of the total, glycolipids, 5.01%, and phospholipids, 12.03%. The major lipid classes in O. agamae include triglycerides, cholesterol, phosphatidyl choline, and phosphatidyl ethanolamine. The 16- and 18-carbon fatty acids were predominant in the parasite. Hexadecenoic acid, usually found at low concentrations in the lipids of helminth parasites, was the most abundant of the 16-carbon fatty acids of O. agamae (notably in the neutral lipid fraction). Although octadecatrienoic acid occurred only in trace amounts in the intestinal contents of the host, significant amounts of this fatty acid were detected in the parasite. A lack of 20-carbon fatty acids was determined in the lipids of the host's intestinal contents and the neutral lipid fraction of the parasite. O. agamae is suspected to be capable of modifying fatty acids obtained from dietary sources by chain elongation.

Comparative studies on the lipid composition of some parasitic nematodes of the Agama lizard

Aisien S.O. and Onyeari F. 1988. Comparative studies on the lipid composition of some parasitic nematodes of the Agama lizard. International Journal for Parasitoiogy 18: 553–555. Lipid composition of three nematodes inhabiting different microenvironments within the Agama lizard were investigated. Total lipids of Strongyluris brevicaudata and Ophidascaris larvae accounted for 3.24% and 3.31% of the fresh weight, respectively. The major lipid classes of the two nematodes were triglycerides, phosphatidyl choline and phosphatidyl ethanolamine. Lipid classes of Foleyella agamae, Strongyluris brevicaudata and Ophidascaris larvae were similar to those obtained from the microenvironments occupied within the host. Fatty acids of F. agamae and Ophidascaris larvae lipids were both qualitatively and quantitatively similar to those of the host plasma lipids. Lipids from the caecal contents of the Agama lizard contained fatty acids varying in chain length from 10 to 18 carbon atoms. S. brevicaudata residing within this microenvironment contained fatty acids with up to 20 carbon atoms. S. brevicaudata may be capable of modifying host fatty acids by chain elongation.

Le Regime Alientaire du Lezard Tropical African Agama Cyanogaster Ruppell, 1835 dans la Region de Lwiro, est du Zaire

The analysis of stomach contents of thc African tropical lizard Agama cyallogaster RUppell. 1835 shows that the diet is exclusively composed of invertebrates (90 %) wherc insects are predominant (81.75 %). Plants makc up only about 10 % of the diet. The male eats more plant matters (14.58 ~;,;) than the female (5.69 %). The dict is largely dependent on the annual variation of the rainfall. Thc relative importancc of insects eatcn is in the following order: Hymcnoptcra (33.50%), Lepidoptera (22.71/;,,), Orthoptera (17.90%). Coleoptera (15.49%) and the other groups (10/;,,).

Studies on the chromosomes of the rainbow lizard Agama agama agama (L.) with notes on polypoidy in the spermatocytes.

The chromosomes of the Rainbow lizard, A. agama agama have been studied from bone marrow and testis preparations. The animal has a diploid chromosome complement of 44 with a fundamental number of 46. The karyotype bears very close relationship to that of A. atra from South Aftrica. Several spermatocytes in diakinesis and metaphase I show polyploidy which may be regular or apparent. The incidence of the regular polyploids varies from one animal to the other, although averagely about 4.8% of all cells in diakinesis are of the tetraploid origin while other ploidy levels account for 0.4%. Quadrivalents were not found in these polyploid cells and a process of endoreduplication of chromosomes without separation of sister chromatids is suggested for their origin.

Lipid Storage and Utilization in the Lizard Agama stellio stellio

Lipid Storage and Utilization in the Lizard Agama stellio stellio

Some physiological observations on ketamine hydrochloride anaesthesia in the agamid lizard.

Some physiological parameters of the agamid lizard (Agama agama agama) were studied after intramuscular injection of diazepam. Heart rates and electrocardiograms were recorded. Respiratory rates were also monitored before and during anaesthesia. The study showed that ketamine given at a dose of 20-30 mg/kg body weight intramuscularly provides optimal anaesthesia for surgical procedures on the agamid lizard.

On the Role of Colour Display in the Social and Spatial

AbstractA population of rainbow lizards (Agama agama) was studied in central Kenya. Rainbow lizards are able to rapidly change their colours. Dominant territorial males usually exhibited intensive bright colours. Dominant males were less intensively coloured when close to their territory border than in its center. Dominant males tolerated subordinate adult males in their territories. The colours of subordinate adult males were less intensive when these males were close to dominant males than when far from them. We interpret our findings in light of theories of sexual selection.

The tail of the lizard Agama stellio stellio: Energetics, significance and comments on its regeneration

AbstractThe percentage of Agama s. stellio with broken tails is low compared to other lizards, and is higher in males than in females. The tail has a low energy content. Agama s. stellio has a tail retention adaptation as do other lizards which use the tail for climbing. The tail regenerates little or not at all, possibly because breaks occur intervertebrally, intravertebral fracture planes not being present.

Effect of environmental temperature on some metabolic aspects of the desert lizard Agama stellio (L)

The lizard Agama stellio (L) of the Western Desert of Egypt has lower blood glucose concentration, higher glycogen content of the liver and gastrocnemius muscle, and higher serum esterified fatty acids in winter than in summer. The increase in the muscle glycogen content is not significant. There is no significant difference in total serum protein, serum glutamic oxaloacetic transaminase (SGOT) and serum glutamic pyruvic transaminase (SGPT) between lizards in summer and in winter. It is concluded that in winter, when food is scarce, energy is obtained from fat reserves.

Activity metabolism of the lizard Agama stellio stellio

1. 1. Oxygen consumption and lactate production above resting levels, and selected body temperatures, were measured in the lizard Agama stellio. 2. 2. Active and resting V ̇ O 2 have low Q 10 (1.7, 2.0) in the activity range 30–37°C and higher 4.0) below this. 3. 3. A correlation was found between published resting and active V ̇ O 2 of lizards, and between V ̇ O 2 and lifestyle. Four types were recognized, in order of increasing V ̇ O 2 : (a) fossorial; (b) sit-and-wait (in A. stellio): (c) cruising, and (d) widely foraging. 4. 4. A. stellio has a high capacity for lactate production, correlated with its short but rapid bursts of activity. This accounts for 80–90% of the energy used during 30 sec maximal activity.

Effect of adenosine 5′-triphosphate (ATP) on the isolated rectum of the rainbow lizard Agama agama

1. 1. ATP but not adenosine contracts lizard isolated rectal muscles. Theophylline, quinidine, nifedipine and lack of Ca 2+ inhibited ATP contractions, but dipyridamole, indomethacin, atropine, d-tubocurarine, phentolamine, l-propranolol, cimetidine, mepyramine and methysergide did not significantly modify the contractions. 2. 2. ATP inhibited Ca 2+-induced contractions in Na +-free, high K + media. In normal Ringer, it relaxed carbachol-contracted muscles and inhibited KCl contractions. 3. 3. The results suggest that ATP contractions are dependent upon external Ca 2+, and are probably associated with extracellular Ca 2+ influx. The contractions appear to have occurred independently of receptor activation and may have been mediated by a depolarising action of the nucleotide. The relaxant effect of ATP possibly occurred as a consequence of inhibition of Ca 2+ influx into carbachol or K +-depolarised muscles.