斯洛维尼亚池塘中大蟾蜍的交配模式

为了解大蟾蜍( Bufo bufo)的配对成功是否与身体大小有关,在蟾蜍产卵之前,我们在斯洛文尼亚捕捉和测量了2 224只成体样本。在这些捕获的个体中, 1 772只为雄性, 452只为雌性,其中355对处于抱对状态。雌性的体长(从吻端到泄殖腔的距离)一般比雄性稍长。无论雄性还是雌性,抱对者的体长均大于未抱对者。抱对的雄性和雌性的体长具有显著的正相关。我们所发现的大小匹配的交配模式,与从其它普通蟾蜍种群得到的结果一致[动物学报51 (3) : 513 -515 , 2005]。     

The morphology of the juxtaglomerular apparatus in the toad,Bufo bufo

Summary In a light microscopic study the course of the tubule in the kidney of the toadBufo bufo was studied. The distal tubule returning to the glomerulus of its origin appears to enclose the afferent arteriole. In that area, from which a three dimensional graphic reconstruction is made, there is an intimate contact between tubular and vascular wall. The latter contains granulated media cells. In the part of the tubule adjacent to the afferent arteriole an accumulation of nuclei is present. It is suggested that this structure is similar to the macula densa of the mammalian juxtaglomerular apparatus. The functional significance of a stricture in the tubule distally from the macula densa-like structure is discussed.The authors wish to thank Mrs. Ineke van de Mee-Wienen and Miss Ans Rouwenhorst for their technical assistance and Mr. J. J. M. de Bekker for the realization of the graphic reconstruction.     

中华大蟾蜍卵母细胞质膜存在钙依赖性的氯离子通道

本文采用双微电极电压钳方法研究了中华大蟾蜍卵母细胞内源性电压门控型离子通道的成分及其生理特性。卵母细胞去极化至 -30 mV 及更正电压时,有一持续的电压依赖性外向电流出现。钾离子通道拮抗剂四乙基氯化氨(tetraethy-lammonium chloride, TEA, 10 mmol/L)和 4- 氨基吡啶(4-aminopyridine, 4-AP, 10 mmol/L)协同作用时,该电流只能被抑制到最大电流幅度的(23.4±0.72)%。但是,上述浓度的TEA和4-AP 与氯离子通道拮抗剂5- 硝基-2, 3- 苯酚丙胺苯甲酸盐 (5-nitro-2,3-phenypropylamino benzoate, NPPB, 30 μmol/L)、无钙 Ringer 氏液或钙离子通道拮抗剂维拉帕米(40 μmol/L)协同作用时,可分别将此外向电流抑制到最大电流幅度的(2.1±0.08)%、(2.2±0.04)% 和(3.1±0.15)%。结果表明,中华大蟾蜍卵母细胞质膜上除有钾离子电流之外,还存在钙依赖性的氯离子电流。     

DC electrical stimulation of the pretectal thalamus and its effects on the feeding behavior of the toad (Bufo bufo)

The feeding motivation of the common European common toad (Bufo bufo) can be quantified by the feeding sequence of arousal-orientation-approach-fixate-snap. Previous work has found that the optic tectum is an important structure responsible for the mediation of feeding behaviors, and combined electrical and visual stimulation of the optic tectum was found to increase the animals feeding behaviors. However, the pretectal thalamus has an inhibitory influence upon the optic tectum and its lesion results in disinhibited feeding behaviors. This suggests that feeding behavior of anurans is also subject to influence from the pretectal thalamus. Previous studies involving the application of DC stimulation to brain tissue has generated slow potential shifts and these shifts have been implicated in the modulation of the neural mechanisms associated with behavior. The current study investigated the application of DC stimulation to the diencephalon surface dorsal to the lateral posterodorsal pretectal thalamic nucleus in Bufo bufo, in order to assess effects on feeding motivation. The application of DC stimulation increased the incidence of avoidance behaviors to a visual prey stimulus while reducing the prey catching behavior component of approach, suggesting that the DC current applied to the pretectum increased the inhibition upon the feeding elements of the optic tectum. This can be explained by the generation of slow potential shifts.     

Impacts of climate and density on the duration of the tadpole stage of the common toad Bufo bufo

In an ongoing long-term study of a breeding population of common toads Bufo bufo at a pond in southern England, the dates of first spawning have been recorded since 1980, the dates of toadlet emergence since 1984, and the numbers of emergent toadlets estimated since 1988. The dates when spawn was first laid varied considerably between years from the earliest on 2 February 1993 (day 33) to the latest on 19 March 1996 (day 79). The duration of the tadpole stage was negatively correlated with the date of appearance of first spawn and was up to 30 days longer in early spawning years than in late ones. Despite this, toadlets still emerged from the natal pond up to 36 days earlier in early spawning years than in late ones. Significant positive correlations were found between the duration of the tadpole stage and both the proportion of days during the tadpole stage when the minimum ground temperature was at or below 0°C and the proportion of days when 10 mm or more rain fell. Tadpole mortality was positively correlated with the proportion of days during the tadpole stage when the minimum ground temperature was at or below 1.5°C. Evidence was also found to suggest that tadpole mortality was density-dependent, being proportionately higher when initial tadpole numbers were high than when they were low. Received: 7 May 1999 / Accepted: 19 July 1999     

Polymerase chain reaction primers for microsatellite loci in the Common Toad Bufo bufo

The Common Toad Bufo bufo is a wide‐ranging species, with a distribution encompassing much of Europe and Asia. Few molecular studies have been undertaken on this species, and only one polymorphic microsatellite locus has been identified. Therefore, little is known about the genetic variability within and between B. bufo populations. The value of such information is essential for monitoring the species and its environment. This paper reports the characterization of 15 B. bufo microsatellite loci using individuals from a Spanish and UK sample.     

The effect of winter temperatures on the timing of breeding activity in the common toad Bufo bufo

A 19-year study of a common toad population in south Dorset, UK, was carried out between 1980 and 1998. The daily arrival of sexually mature male and female toads at a breeding pond was recorded each year. The timing of the main arrival of toads at the breeding pond was highly correlated with the mean daily temperatures over the 40 days immediately preceding the main arrival. When the temperatures were higher than average, breeding occurred significantly earlier in the year than if they were either average or lower than average. During the study, the toad breeding seasons were early (2–13 February) in 5 years (1989, 1990, 1993, 1995, 1998), late (16–23 March) in 2 years (1986, 1996) and average (25 February–8 March) during the remaining 12 years. Evidence was found suggesting that common toads have a daylength threshold of about 9 h, below which the migration to the breeding pond does not occur. Evidence was also found indicating that common toads in southern England have a threshold temperature for activity of about 6°C and that the onset of breeding activity is highly correlated with the number of days during the 40 days prior to the main arrival at the breeding pond that were at or above this temperature. Predicting the start of the main breeding migration to a pond in any year may be possible by comparing the pattern of the 40-day running mean daily temperatures from 21 December the preceding year with those from previous years when the start of breeding activity is known. Although all five of the earliest recorded toad breeding years occurred during the last 10 years, and were associated with the occurrence of particularly mild winters, a significant trend towards earlier breeding in recent years compared with previous years was not found. Received: 16 July 1998 / Accepted: 14 September 1998     

Glow-worm larvae bioluminescence (Coleoptera: Lampyridae) operates as an aposematic signal upon toads (Bufo bufo)

It is an established fact that the spectacular bioluminescentdisplays of adult fireflies and glow-worms are used as courtshipsignals; however, the survival value of the glowing behaviorof their larvae remained the subject of speculation for manyyears. Our study is the first that demonstrates that lampyridlarvae use luminescence to signal unpalatability to nocturnal,visually guided predators. Wild-caught toads (Bufo bufo) weremore reluctant to attack luminescent artificial prey, and weshow that avoidance learning increased this reluctance. Afterbeing exposed to glow-worm larvae (Lampyris noctiluca), whichthe toads experienced as disagreeable, attack latencies to luminescentprey increased, but not those to nonglowing prey. Not all toadsshowed avoidance learning to the same extent, because of eitherdifferences in previous experience with glow-worms or differencesin memory.     

The atrial natriuretic peptide (ANP) system in the pronephros and mesonephros of Bufo bufo larvae

In this study on the excretory apparatus of the Bufo bufo larvae, the ultrastructural features and the atrial natriuretic peptide (ANP)-system were examined using cytochemical and immunocytochemical methods. The early embryonic kidney, the pronephros, is replaced by a later stage, the mesonephros. The pronephros degenerates at the time of metamorphosis and the mesonephros becomes the functional kidney in the adult. Both these organs are targets for ANP, demonstrated by the presence of the specific receptors, indirectly highlighted by the cytochemical localization of the guanylate cyclase in the presence of exogenous atrial natriuretic peptide. This study concluded that the mesonephros produces ANP and thus clusters of cells containing ANP-like granules, positive to the anti-α ANP immunolocalization, were present along the mesonephric proximal tubule. The atrial natriuretic peptide system carries out an important osmoregulatory role in the excretory apparatus.     

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.     

Histochemistry of the juxtaglomerular apparatus in the toad Bufo bufo

Summary An investigation regarding the question of whether there exists a macula densa as part of the juxtaglomerular apparatus in the kidney of amphibians has been carried out. With the aid of a histochemical reaction for glucose-6-phosphate dehydrogenase activity, the presence of a macula densa zone as a specialized part of the distal tubule in the toad Bufo bufo was demonstrated. The functional significance of the high glucose-6-phosphate dehydrogenase activity in the macula densa cells is discussed.     

铅对蟾蜍肝、肾过氧化物酶和酯酶同工酶的影响

以腹腔注射法对蟾蜍 (Bufobufogargarizans)给铅 ,处理 7d后 ,使用聚丙烯凝胶垂直平板电泳法 ,研究了不同浓度 (按铅计 1、2、4、8mg·kg-1 体重 )的铅对蟾蜍肝脏、肾脏过氧化物酶和酯酶同工酶的影响。结果表明 ,不同浓度的铅均可使肝、肾组织过氧化物酶同工酶带强弱发生明显变化 ;对肝、肾酯酶同工酶的影响表现出一定的组织差异性 ,且在一定范围内主要表现为应激性 ,即低剂量的铅可诱导酶活性的提高。     

Organogenesis and differentiation of the pancreas in the toad Bufo bufo L.

Summary In Bufo bufo at stage III₆ the first endocrine islets appear in the part of the pancreas corresponding to the dorsal anlage. At stage IV₂, 5 days later, the pancreatic duct develops and new islets arise by budding off from the ductal epithelium. The ultrastructural study of the secretory granules morphology of endocrine cells has distinguished four different cell types: B-cells (stage III₉), A-cells (stage IV₃), D-cells (stage IV₃) and a fourth type not yet identified (stage IV₃). By immunocytology insulin and corticotropin-releasing factor (CRF) cells have been demonstrated at stage III₉, and glucagon and somatostatin cells at stage IV₁. Lastly, endocrine islets can be homogeneous (predominantly containing insulin cells, rarely glucagon cells) or heterogeneous (insulin cells at the centre and glucagon or somatostatin cells at the periphery). Hypotheses are put forward for the origin and the constitution of the different generations of endocrine islets and isolated cells.     

Toxin depletion has no effect on antipredator responses in common toad (Bufo bufo) tadpoles

Antipredator responses often involve changes in several phenotypic traits and these changes interactively influence fitness. However, gaining insight into how the overall fitness effect of the overall response comes about is notoriously difficult. One promising avenue is to manipulate a single defensive trait and observe how that modifies fitness as well as the expression of other inducible responses. In chemically‐defended animals, toxins are likely to be costly to produce but it is still unknown how their depletion influences other characteristics. In the present study, we artificially depleted bufadienolide toxin stores in common toad (Bufo bufo) tadpoles, and assessed the effect of this with respect to the interaction with predator presence and limited food availability. We found that toxin depletion in tadpoles did not significantly affect any of the measured life‐history traits. Tadpoles in the predator treatment exhibited an elevated development rate, although this was only apparent when food availability was limited. Also, body mass at metamorphosis was lower in tadpoles exposed to chemical cues indicating a predation threat and when food availability was limited. These results provide evidence that, in larval common toads, the expression of inducible defences may incur fitness costs, whereas chemical defences are either expressed constitutively or, if inducible, elevated toxin production has negligible costs.     

Radial astrocytes and ependymocytes in the spinal cord of the adult toad (Bufo bufo L.)

Summary Immunohistochemical and ultrastructural techniques have been used to demonstrate glial fibrillary acidic protein (GFAP) immuno-positive cells in the adult toad spinal cord. Two types of GFAP-immunoreactive cells were observed: ependymocytes and radial astrocytes. GFAP-positive ependymocytes were scarce and contained the immunoreactive product in their processes. They showed intermediate filaments in the basal pole and in their processes when studied with the electron microscope. These immuno-positive ependymocytes represent the tanycytic form of ependymal cells because their processes ended at the subpial zone. The radial astrocytes showed a more intensive immunoreactive product in somata and processes when they were located far away from the ependymal layer. Cell bodies and processes were also associated with blood vessels, but most of the processes ended at the subpial zone forming a continuous subpial glia limitans. The GFAP-positive processes, which form this subpial glia limitans in the toad spinal cord, belong to both tanycytic ependymocytes and radial astrocytes, whose somata are located in the grey matter. These findings lead us to suggest that both types of GFAP-immunopositive cells might be the functional equivalents of mammalian astrocytes.     

Vascularization of the pars intermedia of the hypophysis in the toad,Bufo bufo (L.) (Amphibia,Anura)

The vascularization of the pars intermedia of the hypophysis of the toad, Bufo bufo (L.) was studied by injection of a mixture of India-ink and gelatine into the circulatory system of the head via the arteria carotis communis. Further methyl-methacrylate corrosion casts of brains were made and the hypophysial region of the corrosion casts was examined with the scanning electron microscope. The results showed that the vascularization of the pars intermedia of the toad hypophysis consists of a single-layered vascular network, which is located on the ventral surface of the pars intermedia. The network is formed by capillaries, which primarily run caudally in a fan-like manner and which show only a few cross-connections. In the rostral region of the pars intermedia this network lies rather superficially, while in the caudal region it slightly penetrates the parenchyma. The vascular network originates from vessels of the neural stalk and from wide capillaries of the rostro-ventral region of the neurointermediate junction. The venous drainage of the pars intermedia is exerted by veins, which leave the caudal region and drain into the veins leaving the venous pole of the pars distalis. The flat, wide meshed vascular net on the ventral side of the pars intermedia, demonstrated in this study, fits into the concept that the pars intermedia of the anuran hypophysis is under the control of nerve fibers coming from the hypothalamus.     

Vascularization of the pars distalis of the hypophysis in the toad,Bufo bufo (L.) (Amphibia,Anura)

Summary The vascularization of the pars distalis of the hypophysis of the toad, Bufo bufo (L.), was studied by the traditional method of injecting a mixture of India-ink and gelatine into the circulatory system of the head via the arteria carotis communis. Further, methyl-methacrylate corrosion casts of the brains were made; the hypothalamo-adenohypophysial region of these corrosion casts was studied with the scanning electron microscope. The results showed that the portal vessels which arise from the median eminence do not supply distinct areas in the pars distalis as is supposed by the point-to-point-hypothesis. The portal vessels enter the ventro-median region of the pars distalis and branch off into a three-dimensional network of the secondary capillary plexus of the pars distalis. The plexus is made up mostly by four- to six-sided meshes. This angioarchitecture guarantees an optimal supply of the glandular cells of the pars distalis with nutritional factors and releasing hormones, on the one hand, and facilitates the removal of the hormones which are released by these cells, on the other hand. The venous drainage of the pars distalis is exerted mainly by two large veins, which bilaterally leave the dorso-lateral region (venous pole) of the pars distalis and by a few small veins, which drain into the wide, sinus-like vessel, which curves around the dorso-caudal region of the pars distalis and joins bilaterally the vena hypophysea transversa.This work was supported by the Fonds zur Förderung der wissenschaftlichen Forschung (Projekt Nr. 2183/N 39) and by the Stiftungs- und Förderungsgesellschaft der Paris-Lodron-Universität SalzburgThe authors wish to thank Mag. Ursula Albrecht for excellent technical assistance and Mr. Gerhard Sulzer for photographic work