Renal vascular anatomy of the toad (Bufo marinus)

The renal vasculature of the toad, Bufo marinus, was studied mainly by means of scanning electron microscopy of vascular corrosion casts. All arterial branches terminated in a glomerulus. Each glomerulus was supplied by only one afferent arteriole. No shunts between afferent and efferent arterioles were observed. The glomerular channels appeared to be permanent capillaries. No evidence supporting the theory of freely shifting glomerular blood channels was found. Efferent arterioles radiated out towards the dorsal surface of the kidney where they connected with peritubular vessels. The renal portal veins produced an anastomosing plexus on the dorsal surface of the kidney, giving rise to the peritubular vessels. Peritubular vessels ran radially toward the ventral surface of the kidney, where they formed the roots of the renal veins. Attention is drawn to the possibility of hairpin countercurrent exchange between the capillary-like efferent arterioles and the peritubular vessels in the dorsal kidney.     

Haematozoan parasites of the lizard Ameiva ameiva (Teiidae) from Amazonian Brazil: a preliminary note

Three different haematozoan parasites are described in the blood of the teiid lizard Ameiva ameiva Linn. from North Brazil: one in the monocytes and the other two in erythrocytes. The leucocytic parasite is probably a species of Lainsonia Landau, 1973 (Lankesterellidae) as suggested by the presence of sporogonic stages in the internal organs, morphology of the blood forms (sporozoites), and their survival and accumulation in macrophages of the liver. One of the erythrocytic parasites produces encapsulated, stain-resistant forms in the peripheral blood, very similar to gametocytes of Hemolivia Petit et al., 1990. The other is morphologically very different and characteristically adheres to the host-cell nucleus. None of the parasites underwent development in the mosquitoes Culex quinquefasciatus and Aedes aegypti and their behaviour in other haematophagous hosts is under investigation. Mixed infections of the parasites commonly occur and this often creates difficulties in relating the tissue stages in the internal organs to the forms seen in the blood. Concomitant infections with a Plasmodium tropiduri-like malaria parasite were seen and were sometimes extremely heavy.     

Microbodies (peroxisomes) in the toad,Bufo marinus

Summary Microbodies (peroxisomes), a group of cytoplasmic organelles enriched in catalase, are demonstrated in the toad, Bufo marinus, by light and electron microscopy by means of a cytochemical staining procedure that demonstrates the peroxidatic activity of catalase with diaminobenzidine (DAB). Amphibian microbodies are similar to those of other classes in their fine structure and localization in hepatocytes and kidney, where they are prominent in the proximal tubular cells. Nucleoids are present only in renal microbodies. In the proximal renal tubule an unusual group of large brown granules are identified as lysosomes by their acid phosphatase, -glucosaminidase and -glucuronidase activities.This work was supported by U.S. Public Health Service Grants Nos. NS-06856 and HD 00674. We wish to thank Dr. Richard M. Hays who generously supplied us with toads; Dr. Alex B. Novikoff for making available facilities for ultramicrotomy, Miss Betty De Prest for technical assistance; Miss Marianne Van Hooren for preparation of the photomicrographs.     

Innervation of the renal vasculature of the toad (Bufo marinus)

The innervation of the dorsal aorta and renal vasculature in the toad (Bufo marinus) has been studied with both fluorescence and ultrastructural histochemistry. The innervation consists primarily of a dense plexus of adrenergic nerves associated with all levels of the preglomerular vasculature. Non-adrenergic nerves are occasionally found in the renal artery, and even more rarely near the afferent arterioles. Many of the adrenergic nerve profiles in the dorsal aorta and renal vasculature are distinguished by high proportions of chromaffin-negative, large, filled vesicles. Close neuromuscular contacts are common in both the renal arteries and afferent arterioles. Possibly every smooth muscle cell in the afferent arterioles is multiply innervated. The glomerular capillaries and peritubular vessels are not innervated, and only 3-5% of efferent arterioles are accompanied by single adrenergic nerve fibres. Thus, nervous control of glomerular blood flow must be exerted primarily by adrenergic nerves acting on the preglomerular vasculature. The adrenergic innervation of the renal portal veins and efferent renal veins may play a role in regulating peritubular blood flow. In addition, glomerular and postglomerular control of renal blood flow could be achieved by circulating agents acting via contractile elements in the glomerular mesangial cells, and in the endothelial cells and pericytes of the efferent arterioles. Some adrenergic nerve profiles near afferent arterioles are as close as 70 nm to distal tubule cells, indicating that tubular function may be directly controlled by adrenergic nerves.     

Cytochemical and functional characterization of blood and inflammatory cells from the lizard Ameiva ameiva

The fine structure and differential cell count of blood and coelomic exudate leukocytes were studied with the aim to identify granulocytes from Ameiva ameiva, a lizard distributed in the tropical regions of the Americas. Blood leukocytes were separated with a Percoll cushion and coelomic exudate cells were obtained 24 h after intracoelomic thioglycollate injection. In the blood, erythrocytes, monocytes, thrombocytes, lymphocytes, plasma cells and four types of granulocytes were identified based on their morphology and cytochemistry. Types I and III granulocytes had round intracytoplasmic granules with the same basic morphology; however, type III granulocyte had a bilobued nucleus and higher amounts of heterochromatin suggesting an advance stage of maturation. Type II granulocytes had fusiformic granules and more mitochondria. Type IV granulocytes were classified as the basophil mammalian counterpart based on their morphology and relative number. Macrophages and granulocytes type III were found in the normal coelomic cavity. However, after the thioglycollate injection the number of type III granulocyte increased. Granulocytes found in the coelomic cavity were related to type III blood granulocyte based on the morphology and cytochemical localization of alkaline phosphatase and basic proteins in their intracytoplasmic granules. Differential blood leukocyte counts showed a predominance of type III granulocyte followed by lymphocyte, type I granulocyte, type II granulocyte, monocyte and type IV granulocyte. Taken together, these results indicate that types I and III granulocytes correspond to the mammalian neutrophils/heterophils and type II to the eosinophil granulocytes.     

Leptospires in the marine toad (Bufo marinus) on Barbados

Leptospires were isolated from the kidneys of four of 211 toads (Bufo marinus) caught on Barbados. Two of the isolates were identified as Leptospira interrogans serovar bim in the Autumnalis serogroup (the most common cause of leptospiral illness on Barbados), and two as possibly new serovars in the Australis serogroup. Sera from 198 of the toads were examined by the leptospire microscopic agglutination test. Forty-two (21%) were positive at titers of greater than or equal to 1:100, and 54 (27%) at greater than or equal to 1:50. The predominating serogroups were Australis (50%), Autumnalis (23%) and Panama (13%). The agglutination tests on the culture-positive toads showed that serologic studies alone may be of limited value in these animals. Bufo marinus can harbor pathogenic leptospires, and it may be a significant source of the Autumnalis serogroup infections in the Caribbean.     

Calcium in the toad (Bufo marinus) cornea: binding by the stroma

1. The Ca concentration in the toad (Bufo marinus) cornea was 2.6 mmol/kg wet wt compared at 1.0 mmol/l in the bathing aqueous humor and 2.8 mmol/kg wet wt in the separated corneal stromal layer. Cell Ca content was calculated to be about 1.8 mmol/kg wet wt. 2. About 80% of the total Ca appears to be sequestered or bound to tissue components most of which (68% of the total) is associated with the stroma (2.2 mmol/kg wet wt stroma). 3. About 85-90% of the Ca in the stroma is readily exchangeable with external 45Ca. 4. The loss of accumulated 45Ca from the stroma was measured in vitro. This efflux of the isotope was enhanced by multivalent ions and was greatest when Ca2+ or La3+ was present in the external media. Other alkaline earth metal ions were not as effective. The relative effectiveness of this displacement of 45Ca was Ca = La greater than Sr greater than Ba greater than Mg. 5. The results suggest that the Ca2+ is bound by the amphibian stroma at sites that have a preference or specificity for this divalent ion as compared to the other alkaline earth metals. 6. The possible functional role of this bound Ca is discussed.     

Concentrations of ketone bodies in the blood of the green lizard Ameiva ameiva (Teiidae) in different physiological situations

1. The concentrations of acetoacetate and 3-hydroxybutyrate have been determined in the blood of the green lizard Ameiva ameiva (Teiidae) in fed animals and in animals starved for periods from one week to about four months. 2. The concentrations of acetoacetate are low and unaltered in fed and starved animals, being in the range from 0.014 to 0.018 mM. 3. The concentrations of 3-hydroxybutyrate are high: 2.67 mM, in fed animals, falling during starvation down to 0.26 mM. 4. The 3-hydroxybutyrate/acetoacetate ratio is high, 151, in fed animals, falling down to 17. 5. The possible importance of ketone bodies in the metabolism of Ameiva ameiva is discussed.     

Morphology of the femoral glands in the lizard Ameiva ameiva (teiidae) and their possible role in semiochemical dispersion

Many lizards have epidermal glands in the cloacal or femoral region with semiochemical function related to sexual behavior and/or territorial demarcation. Externally, these glands are recognized as a row of pores, opening individually in the center of a modified scale. In many species the pores are used as systematic characters. They form a glandular cord or, in some species, a row of glandular beads below the dermis, and are connected to the exterior through the ducts, which continuously liberate a solid secretion. Dead cells, desquamated from the secretory epithelium, constitute the secretion, known as "a secretion plug." The present work focuses on the morphology of the femoral glands of the teiid lizard Ameiva ameiva, correlating it to the way in which the secretion is deposited in the environment. The results here obtained are compared to those available for other lizards and amphisbaenians. We observed that the diameter of the glandular pores did not show significant differences between males and females. The glands comprise germinative and secretory cells, which pass through at least three stages of differentiation, during which an accumulation of cytoplasmic granules, with a glycoprotein content, occurs. The cells eventually die and desquamate from the secretory epithelium, forming a secretory plug mostly constituted by juxtaposed nonfragmented secretory cells. Because of the arrangement of the rosette-like scales surrounding the femoral pores, we suggest that when the animal is in a resting position, with its femoral regions touching the ground, these scales may be involved in the breakage of their respective plugs, depositing tiny portions on the substrate. In this manner, it seems that the method for signal dispersion in this species involves specifically adapted structures and does not simply involve the chance breakage of the plug, as the gland secretes it. Signal dispersion must also be intimately associated with the animal's movement within its territory.     

Structure and function of ciliated peritoneal funnels in the toad kidney (Bufo marinus)

Scanning electron microscopy revealed 600-800 ciliated peritoneal funnels opening onto the ventral surface of each kidney in Bufo marinus. The size and configuration of funnel apertures vary greatly, but individuals course beneath the kidney surface before opening into peritubular blood vessels. Injections of India ink into the peritoneal cavity demonstrate that cilia lining the peritoneal funnels create a current carrying peritoneal fluid into the renal vasculature. Clearance of fluid by the funnels was dependent on pressure in the peritubular vessels, and was increased by arginine vasotocin. Ciliated peritoneal funnels may provide an important route for return of lymphatic fluid from the peritoneal cavity to the vasculature.     

Rapid expansion of the cane toad (Bufo marinus) invasion front in tropical Australia

Abstract Cane toads (Bufo marinus) are large toxic anurans that have spread through much of tropical Australia since their introduction in 1935. Our surveys of the location of the toad invasion front in 2001 to 2005, and radiotracking of toads at the front near Darwin in 2005, reveal much faster westwards expansion than was recorded in earlier stages of toad invasion through Queensland. Since reaching the wet‐dry tropics of the Northern Territory, the toads have progressed an average of approximately 55 km year⁻¹ (mean rate of advance 264 m night⁻¹ along a frequently monitored 55‐km road transect during the wet season of 2004–2005). Radiotracking suggests that this displacement is due to rapid locomotion by free‐ranging toads rather than human‐assisted dispersal; individual toads frequently moved >200 m in a single night. One radiotracked toad moved >21 800 m in a 30‐day period; the fastest rate of movement yet recorded for any anuran. Daily displacements of radiotracked toads varied with time and local weather conditions, and were highest early in the wet season on warm, wet and windy nights. The accelerated rate of expansion of the front may reflect either, or both: (i) evolved changes in toads or (ii) that toads have now entered an environment more favourable to spread. This accelerated rate of expansion means that toads will reach the Western Australian border and their maximal range in northern Australia sooner than previously predicted.     

Checklist of helminth parasites of the cane toad Bufo marinus (Anura: Bufonidae) from Mexico

Thirty-four adult cane toads Bufo marinus L. (12 males and 22 females) collected from 2 localities in Mexico (Cerro de Oro and Temascal Dams, Oaxaca) in September 2003 were examined for helminth parasites. In total, 14,749 helminths belonging to 14 taxa were collected. Included were 2 adult digeneans (Choledocystus hepaticus, Mesocoelium monas); 1 larval cestode (an unidentified pseudophyllidean); and 11 nematodes, including 3 species of larvae (Contracaecum sp., Physaloptera sp., Physocephalus sexalatus) and 8 species of adults (Aplectana itzocanensis, Cosmocerca sp., Cruzia morleyi, Ochoterenella digiticauda, Oswaldocruzia sp., Raillietnema sp., Rhabdias americanus, and Rhabdiasfuelleborni). Higher species richness was recorded in B. marinus from Cerro de Oro (12 taxa versus 9 in those from Temascal); hosts from both localities shared 7 taxa. There were 25 new locality records, and 2 taxa were registered in Mexico for the first time. To date, 112 helminth species have been recorded parasitizing B. marinus along its native and introduced range of distribution, with 40.5% of them reported from Mexico.     

The life-cycle and ultrastructure of Sarcocystis ameivamastigodryasi n. sp., in the lizard Ameiva ameiva (Teiidae) and the snake Mastigodryas bifossatus (Colubridae)

Sarcocysts in muscles of the teiid lizard Ameiva ameiva from north Brazil were fed to the colubrid snake Mastigodryas bifossatus, the faeces of which had been shown to be devoid of coccidial oocysts or sporocysts. When necropsied 16 days later the snake was shown to have developed a massive intestinal infection of Sarcocystis. Mature sporocysts from another, naturally infected M. bifossatus were fed to juvenile specimens of A. ameiva in which no sarcocysts could be detected in tail muscle biopsies. When examined 30 and 47 days later they had very large numbers of sarcocysts in their tail and tongue muscles. The parasite is given the name of Sarcocystis ameivamastigodryasi n. sp. An ultrastructural study has been made of the sarcocyst and of the parasite's sporulation in the lamina propria of the snake: the latter provides details of the wall formation process in developing sporocysts. Attempts to infect a specimen of the boid Boa constrictor constrictor by feeding it with infected Ameiva failed, suggesting that sporocysts previously recorded in genera of the family Boidae may be those of a different species of Sarcocystis.     

Inward rectification in muscle fibres of the toad Bufo marinus

Inward rectification of the resting potassium conductance was studied in skeletal muscle fibres of the toad Bufo marinus. This conductance was shown to be blocked by Ba and Cs and located both in the surface membrane and the membranes of the tubular system. Some differences were found between the properties of this conductance channel in Bufo marinus and those reported for various species of Rana. The possible adaptative value of these differences is pointed out.     

Transferrin endocytosis and the mechanism of iron uptake by reticulocytes in the toad (Bufo marinus)

Reticulocytosis was induced in toads (Bufo marinus) by treatment with phenylhydrazine. Iron and transferrin uptake and transferrin endocytosis and exocytosis by these cells were measured. The mean number of transferrin receptors per cell was found to be 4.5 X 10(5) and the affinity constant of transferrin to receptors was 0.2 X 10(7) M-1. Iron and transferrin uptake were temp.-dependent processes. An inflection point occurred at 15-16 degrees C in the Arrhenius plots of endocytosis and iron uptake. The activation energies of these two processes above and below the inflection temperature were 31 and 71 kJ/mol. It is concluded that iron uptake by immature toad erythroid cells occurs by receptor-mediated endocytosis which still functions at temps as low as 5 degrees C.     

An immunohistochemical study of the innervation of the large intestine of the toad (Bufo marinus)

The distribution of intrinsic enteric neurons and extrinsic autonomic and sensory neurons in the large intestine of the toad, Bufo marinus, was examined using immunohistochemistry and glyoxylic acid-induced fluoresecence. Three populations of extrinsic nerves were found: unipolar neurons with morphology and location typical of parasympathetic postganglionic neurons containing immunoreactivity to galanin, somatostatin and 5-hydroxytryptamine were present in longitudinally running nerve trunks in the posterior large intestine and projected to the muscle layers and myenteric plexus throughout the large intestine. Sympathetic adrenergic fibres supplied a dense innervation to the circular muscle layer, myenteric plexus and blood vessels. Axons containing colocalized calcitonin gene-related peptide immunoractivity and substance P immunoreactivity distributed to all layers of the large intestine and are thought to be axons of primary afferent neurons. Five populations of enteric neurons were found. These contained immunoreactivity to vasoactive intestinal peptide, which distributed to all layers of the large intestine; galanin/vasoactive intestinal peptide, which projected to the submucosa and mucosa; calcitonin gene-related peptide/vasoactive intestinal peptide, which supplied the circular muscle, submucosa and mucosa; galanin, which projected to the submucosa and mucosa; and enkephalin, which supplied the circular muscle layer.