Chromatophoromas in a pine snake

Iridophoroma and melanophoroma were diagnosed in an adult male pine snake. Light microscopic examination of irregularly thickened white and black portions of abnormal scales demonstrated two distinctive populations of pigment-containing cells. Pigment cells within abnormal-appearing white scales had needle-shaped granules that were dark amber in color while black portions were composed of pigment cells typical of melanophores, with dark black, round granules. Both populations of cells showed junctional activity, and clusters of both neoplastic pigment cell types were found in adjoining areas of the epidermis. By electron microscopy, the pigment cell with amber-colored granules contained reflecting platelet profiles typical of iridophores while pigment cells with dark round granules contained melanosomes. At a junctional area between abnormal white and black scales, mosaic chromatophores containing reflecting platelet profiles and melanosomes were observed. At 1 1/2 years following initial diagnosis, the snake died and neoplastic iridophores were found at multiple visceral sites; there was no evidence of metastases of melanophores to any organ. The two pigment cell tumors are believed to have developed from either stem cells destined to become iridophores and melanophores or from prexisting iridophores and melanophores in the dermis.     

On making measurements in silo-stored grain

A sectional tubular steel sampler has been designed, with which samples of grain have regularly been obtained at 1 m. intervals to depths of 15 m. in normal grain. A new form of this sampler permits re-closing of the sampling ports after filling, so that contamination of the samples can be avoided. Associated records of the grain temperatures and samples of the intergranular gases have been obtained at similar depths. Certain precautions to be observed in sampling from silo bins are emphasized. Observations are reviewed which show the extensive effects of granular segregation during movement. Material, such as extraneous seeds, holed grains, etc., segregates so that ( a ) it is delayed in the outfall whilst emptying bins, ( b ) it is more concentrated in the central column of the bin after filling, ( c ) in direct sampling it is scarcer in the first part of the sample to fall into the container, with the implication that the sample as whole is deficient in such material. Larger objects settle at the surface of the grain on a moving belt, whilst smaller ones sink between the grains. The consistency of the results suggests strong reasons for a reconsideration of the principles of sampling, either direct or indirect. Meanwhile, samples obtained by any one method are likely to prove fairly consistent inter se.     

“精制多价抗海蛇血清”的制作

目的　海蛇均为前沟牙毒蛇 ,分布于太平洋及印度洋沿岸 ,大西洋没有海蛇。中国产海蛇 1 6种 ,分布于北起辽宁、南至海南及广西沿海 ,分布较广、数量较多及蛇伤发病率较高的海蛇为青环海蛇( H ydrophis cyanocinctus)和平颏海蛇( Laticauda semifasciata)。调查结果表明 ,被海蛇咬伤如不及时处理 ,通常有 50 %的患者死亡。在中国广西北海市每年均有被海蛇咬伤中毒致死的病例。为研制中国、日本及东南亚沿海国家主要有毒海蛇青环海蛇和平颏海蛇咬伤的有效治疗药“多价抗海蛇毒血清”,填补急救医学空白。　　方法　从中国北部湾产青环海蛇和平…     

Soft epidermis of a scaleless snake lacks beta-keratin

Beta-keratins are responsible for the mechanical resistance of scales in reptiles. In a scaleless crotalus snake (Crotalus atrox), large areas of the skin are completely devoid of scales, and the skin appears delicate and wrinkled. The epidermis of this snake has been assessed for the presence of beta-keratin by immunocytochemistry and immunoblotting using an antibody against chicken scale beta-keratin. This antibody recognizes beta-keratins in normal snake scales with molecular weights of 15-18 kDa and isoelectric points at 6.8, 7.5, 8.3 and 9.4. This indicates that beta-keratins of the stratum corneum are mainly basic proteins, so may interact with cytokeratins of the epidermis, most of which appear acidic (isoelectric points 4.5-5.5). A beta-layer and beta-keratin immunoreactivity are completely absent in moults of the scaleless mutant, and the corneous layer comprises a multi-layered alpha-layer covered by a flat oberhautchen. In conclusion, the present study shows that a lack of beta-keratins is correlated with the loss of scales and mechanical protection in the skin of this mutant snake.     

Aerobic metabolism during predation by a boid snake

We quantified the oxygen uptake rates (VO(2)) and time spent, during the constriction, inspection, and ingestion of prey of different relative sizes, by the prey-constricting boid snake Boa constrictor amarali. Time spent in prey constriction varied from 7.6 to 16.3 min, and VO(2) during prey constriction increased 6.8-fold above resting values. This was the most energy expensive predation phase but neither time spent nor metabolic rate during this phase were correlated with prey size. Similarly, prey size did not affect the VO(2) or duration of prey inspection. Prey ingestion time, on the other hand, increased linearly with prey size although VO(2) during this phase, which increased 4.9-fold above resting levels, was not affected by prey size. The increase in mechanical difficulty of ingesting larger prey, therefore, was associated with longer ingestion times rather than proportional increases in the level of metabolic effort. The data indicate that prey constriction and ingestion are largely sustained by glycolysis and the intervening phase of prey inspection may allow recovery between these two predatory phases with high metabolic demands. The total amount of energy spent by B. c. amarali to constrict, inspect, and ingest prey of sizes varying from 5 to 40% of snake body mass varied inversely from 0.21 to 0.11% of the energy assimilated from the prey, respectively. Thus, prey size was not limited by the energetic cost of predation. On the contrary, snakes feeding on larger prey were rewarded with larger energetic returns, in accordance with explanations of the evolution of snake feeding specializations.     

Long-term population dynamics in a Mediterranean aquatic snake

A review of several long-term studies has recently suggested that snakes might be declining in large parts of the world. Additional data from other long-term studies are therefore urgently needed in order to assess the generalities of such suggested declines. Based on a 20-year study, we analyzed demographic data on adult dice snakes (Natrix tessellata) studied in central Italy between 1985 and 2004. Both male and female dice snakes were relatively long-lived, with no significant differences in longevity between the sexes. Individual males and females were observed over a maximum of 10 and 14 years, respectively. However, the among-year recapture rates between the year the snakes were initially captured and the subsequent year (i.e., year 1 to year 2) was significantly lower (45%) than the among-year recapture rates during subsequent years (74%; i.e., year 2 to year 3), suggesting that a large proportion of the snakes at first capture were in fact not resident within our study area, and hence many snakes were migrating in and out of our 2-km stream study site, with no inter-sexual difference in dispersal rates. Sex ratio was virtually equal if we consider the study period as a whole. Significant annual fluctuations were, however, observed through the study. In 1985–1990, 1993–1995, 1998 and 1999 the sex ratio was male-biased, whereas in 2000–2004 female-biased. In terms of both survival and recapture probabilities, model selection showed that Akaike’s information criterion favored the model incorporating body size, with the model incorporating year having an intermediate likelihood, and the model with sex included being the most disfavored. Total population number estimates suggest an average 86 adult individuals along the 2 km of stream with only minor annual variations. However, a significant decrease in the number of males occurred during the last 6 years of our study. Thus, further monitoring of this population is warranted in light of the decline of snake populations reported recently.     

Retinal projections in a snake, Thamnophis sirtalis

The retinofugal projections of the snake Thamnophis sirtalis were studied by the method of experimentally induced Wallerian degeneration stained by the Fink-Heimer method. The retinal ganglion cells project to all parts of the contralateral lateral geniculate complex, nucleus lentiformis mesencephali, nucleus geniculatus pretectalis, nucleus posterodorsalis, basal optic nucleus and superficial layers of the optic tectum. In addition, the retinofugal projections were observed terminating in portions of the ipsilateral lateral geniculate complex and nucleus posterodorsalis. Examination of the morphology of the retinal terminal areas stained for Nissl substance with cresyl violet led to the conclusion that these regions are well differentiated and should not be considered poorly developed when compared with other reptilian forms such as turtles.     

Evidence for heterogeneous forms of the snake venom metalloproteinase jararhagin: a factor contributing to snake venom variability

The reprolysin subfamily of metalloproteinases includes snake venom metalloproteinases (SVMP) and mammalian disintegrin/metalloproteinase. These proteins are synthesized as zymogens and undergo proteolytic processing resulting in a variety of multifunctional proteins. Jararhagin is a P-III SVMP isolated from the venom of Bothrops jararaca. In crude venom, two forms of jararhagin are typically found, full-length jararhagin and jararhagin-C, a proteolytically processed form of jararhagin that is composed of the disintegrin-like and cysteine-rich domains of jararhagin. To better understand the structural and mechanistic bases for these forms of jararhagin in the venom of B. jararaca and the source of venom complexity in general, we have examined the jararhagin forms isolated from venom and the autolysis of isolated jararhagin under the conditions of varying pH, calcium ion concentration, and reducing agents. From our results, jararhagin isolated from venom appears as two forms: a predominant form that is stable to in vitro autolysis and a minor form that is susceptible to autolysis under a variety of conditions including alkaline pH, low calcium ion concentrations, or reducing agent. The autolysis site for production of jararhagin-C from isolated jararhagin was different from that observed for jararhagin-C as isolated from crude venom. Taken together, these data lead us to the conclusion that during the biosynthesis of jararhagin in the venom gland at least three forms are present: one form which is rapidly processed to give rise to jararhagin-C, one form which is resistant to processing in the venom and autolysis in vitro, and one minor form which is susceptible to autolysis under conditions that promote destabilization of its structure. The presence of these different forms of jararhagin contributes to greater structural and functional complexity of the venom and may be a common feature among all snake venoms. The biological and biochemical features in the venom gland responsible for these jararhagin isoforms are currently under investigation.     

Body condition threshold for breeding in a viviparous snake

One major goal of physiological ecology is to seek links between life history traits. Identification of a body condition threshold for breeding (e.g. critical level of body reserves) provides a link between the physiological process involved in storage of body reserves and the ability to reproduce. One hundred and twenty-nine freeranging adult female Vipera aspis, a viviparous snake, were marked with electronic identification tags and/or by scale clipping, weighed, and measured at the onset of vitellogenesis, and immediately released in the field in western central France (47°03N; 02°00W). The 129 snakes were recaptured 2–6 months later between ovulation and parturition, and individual reproductive status was then determined. Eighty-four females (65%) captured at the onset of vitellogenesis became vitellogenic, 45 did not. There was no difference in mean body length between reproductive and non-reproductive females. Initial body condition influenced reproductive outcome: we found a precise threshold in body condition necessary for the induction of vitellogenesis. Almost all females (88%) with a body condition greater than the observed threshold became vitellogenic, 12% did not, and no female with a body condition under the threshold became vitellogenic. Body reserves were estimated in the 129 living females using data gathered on 69 autopsied females. Females which became vitellogenic had large body reserves, but females which did not were not particularly emaciated (whilst postparturiant females had few body reserves remaining). This precise condition threshold for breeding is discussed in terms of the reproductive ecology of this species.     

Gliding flight in Chrysopelea: turning a snake into a wing

Although many cylindrical animals swim through water, flying snakes of the genus Chrysopelea are the only limbless animals that glide through air. Despite a lack of limbs, these snakes can actively launch by jumping, maintain a stable glide path without obvious control surfaces, maneuver, and safely land without injury. Jumping takeoffs employ vertically looped kinematics that seem to be different than any other behavior in limbless vertebrates, and their presence in a closely related genus suggests that gap-crossing may have been a behavioral precursor to the evolution of gliding in snakes. Change in shape of the body by dorsoventral flattening and high-amplitude aerial undulation comprise two key features of snakes' gliding behavior. As the snake becomes airborne, the body flattens sequentially from head to vent, forming a cross-sectional shape that is roughly triangular, with a flat surface and lateral "lips" that protrude ventrally on each side of the body; these may diminish toward the vent. This shape likely provides the snake with lift coefficients that peak at high angles of attack and gentle stall characteristics. A glide trajectory is initiated with the snake falling at a steep angle. As the snake rotates in the pitch axis, it forms a wide "S" shape and begins undulating in a complex three-dimensional pattern, with the body angled upward relative to the glide path. The head moves side-to-side, sending traveling waves posteriorly toward the tail, while the body (most prominently, the posterior end) oscillates in the vertical axis. These active movements while gliding are substantially different and more dynamic than those used by any other animal glider. As the snake gains forward speed, the glide path becomes less steep, reaching minimally recorded glide angles of 13°. In general, smaller snakes appear to be more proficient gliders. Chrysopelea paradisi can also maneuver and land either on the ground or on vegetation, but these locomotor behaviors have not been studied in detail. Future work aims to understand the mechanisms of production and control of force in takeoff, gliding, and landing, and to identify the musculoskeletal adaptations that enable this unique form of locomotion.