鲁西地区蛇类的分布格局

以山东聊城分布的7种蛇类作为研究对象,探讨了鲁西平原区蛇类的群落结构和分布格局.结果 表明,该区蛇类平均分布密度较高的是白条锦蛇Elaphe dione、赤链蛇Dinodon rufozonatum和虎斑颈槽蛇大陆亚种Rhabdophis tigrina lateralis.多数蛇类倾向于选择湿地周边、边缘富有灌草丛的农田区以及有丰富草被的居民区等为栖息地,该区蛇类的栖息地选择有着显著的不重叠性.     

Transcriptional Instability during Evolving Sepsis May Limit Biomarker Based Risk Stratification

Background

Sepsis causes extensive morbidity and mortality in children worldwide. Prompt recognition and timely treatment of sepsis is critical in reducing morbidity and mortality. Genomic approaches are used to discover novel pathways, therapeutic targets and biomarkers. These may facilitate diagnosis and risk stratification to tailor treatment strategies.

Objective

To investigate the temporal gene expression during the evolution of sepsis induced multi-organ failure in response to a single organism, Neisseria meningitidis, in previously healthy children.

Method

RNA was extracted from serial blood samples (6 time points over 48 hours from presentation) from five critically ill children with meningococcal sepsis. Extracted RNA was hybridized to Affymetrix arrays. The RNA underwent strict quality control and standardized quantitation. Gene expression results were analyzed using GeneSpring software and Ingenuity Pathway Analysis.

Result

A marked variability in differential gene expression was observed between time points and between patients revealing dynamic expression changes during the evolution of sepsis. While there was evidence of time-dependent changes in expected gene networks including those involving immune responses and inflammatory pathways, temporal variation was also evident in specific “biomarkers” that have been proposed for diagnostic and risk stratification functions. The extent and nature of this variability was not readily explained by clinical phenotype.

Conclusion

This is the first study of its kind detailing extensive expression changes in children during the evolution of sepsis. This highlights a limitation of static or single time point biomarker estimation. Serial estimations or more comprehensive network approaches may be required to optimize risk stratification in complex, time-critical conditions such as evolving sepsis.     

Communication and Displays of Snakes

With limitations imposed by the lack of appendages and elongatemorphology, snakes exhibit a variety of unique ritualistic behaviorsin the contexts of agonistic encounters and courtship and mating.During male combat rituals, actions involve high vertical displaystances (crotaline) to horizontal stances (colubrid) with eithermale attempting to force the other's head down. Superior positionappears to be important during these encounters. Dominant andsubordinate actions and postures are recognized. Courting snakesexhibit a variety of positions and movements, performed primarilyby the male, which appear to passify the female and induce herreceptivity. Actions involved may be chin rubbing, body jerksor caudocephalic waves, cephalocaudal waves, tail searching,pushing, nudging, biting, and tail raising. Sequences and phasesof the actions used vary with the species. Significant featuresof these behaviors are the different actions taking place separatelyor simultaneously along the elongate cylindrical snake. Visual,tactile, and olfactory communication each play a role.     

Early Embryonic Chromosome Instability Results in Stable Mosaic Pattern in Human Tissues

The discovery of copy number variations (CNV) in the human genome opened new perspectives on the study of the genetic causes of inherited disorders and the aetiology of common diseases. Here, a single-cell-level investigation of CNV in different human tissues led us to uncover the phenomenon of mitotically derived genomic mosaicism, which is stable in different cell types of one individual. The CNV mosaic ratios were different between the 10 individuals studied. However, they were stable in the T lymphocytes, immortalized B lymphoblastoid cells, and skin fibroblasts analyzed in each individual. Because these cell types have a common origin in the connective tissues, we suggest that mitotic changes in CNV regions may happen early during embryonic development and occur only once, after which the stable mosaic ratio is maintained throughout the differentiated tissues. This concept is further supported by a unique study of immortalized B lymphoblastoid cell lines obtained with 20 year difference from two subjects. We provide the first evidence of somatic mosaicism for CNV, with stable variation ratios in different cell types of one individual leading to the hypothesis of early embryonic chromosome instability resulting in stable mosaic pattern in human tissues. This concept has the potential to open new perspectives in personalized genetic diagnostics and can explain genetic phenomena like diminished penetrance in autosomal dominant diseases. We propose that further genomic studies should focus on the single-cell level, to better understand the aetiology of aging and diseases mediated by somatic mutations.     

Evolutionary Patterns in Advanced Snakes

One prevalent view of phylogenetic events in advanced snakesholds that the fangs evolved along at least two pathways one(e.g. elapids) from ancestors with enlarged anterior and theother (e.g. viperids) from ancestors with enlarged posteriormaxillary teeth. Selective forces driving these changes arepresumed to arise from the increasing advantages of teeth andglands in venom injection. In this paper another plausible viewof these events is proposed. First fangs of both elapids and viperids likely evolved fromreal maxillary teeth. In non-venomous snakes, differences intooth morphology and function suggest that there may be somedivision of labor among anterior and posterior maxillary teeth.Anterior maxillary teeth, residing forward in the mouth likelyserve the biological role of snaring and impaling prey duringthe strike. They are also conical frequently recurved and lacka secretion groove. On the other hand posterior teeth becauseof their geometric position on the maxilla and mechanical advantages,tend to serve as aids in preingestion manipulation and swallowingof prey. They are often blade shaped and occasionally bear asecretion groove along their sides. Although both front andrear maxillary teeth of nonvenomous snakes may be elongatedthis is likely to serve these different functional roles andhence they evolved under different selective pressures. Whenfangs evolved they did so several times independently but fromrear maxillary teeth. In support one notes a) the similar positionpostorbital of venom and Duvernoy s glands b) similar embryonicdevelopment of fangs and rear maxillary teeth c) secretion groovewhen present, is found only on rear teeth and d) similar biologicalroles of some rear teeth and fangs. For ease in clearance ofthe prey during the strike the fangs are positioned forwardin the mouth accomplished in viperid snakes by forward rotationof the maxilla and elapids by rostral anatomical migration tothe front of the maxilla. Second, the adaptive advantage first favoring initial rear toothenlargement likely centered not on their role in venom injectionbut rather on their role in preingestion manipulation and swallowing.However once enlarged, teeth would be preadapted for later modificationinto fangs under selection pressures arising from advantagesof venom introduction. This has implications for the function and evolution of associatedstructures. Besides possibly subduring or even killing of preythe secretion of Duvernoy's gland may be involved in digestionor in neutralizing noxious or fouling products of the prey.The presence or absence of constriction need not be functionallytied to absence or presence of venom injection. The phylogeneticpathways outlined herein were likely traveled several timesindependently in advanced snakes.     

Dietary Correlates of the Origin and Radiation of Snakes

Stomach analyses of living families and of a fossil containingprey were used to address possible dietary correlates of thehistory of snakes. Aniliids, morphologically primitive amongliving snakes, feed on relatively heavy, elongate vertebrates.Large aniliids eat larger prey than do small individuals but,as in advanced snakes, they also take small items. Living boids,structurally intermediate between aniliids and advanced snakes,feed on relatively heavy prey of a much greater variety of shapesthan do aniliids. An Eocene fossil that might be a boid containsa relatively large crocodilian in its gut. These findings, previousstudies, and morphological considerations suggest that veryearly snakes used constriction and powerful jaws to feed onelongate, heavy prey. This would have permitted a shift fromfeeding often on small items to feeding rarely on heavy items,without initially requiring major changes in jaw structure relativeto a lizard-like ancestor. Subsequent morphological changescould then have allowed boids to utilize a broad range of preytypes, including many of those currently eaten by advanced snakes.More recent dietary themes include the consumption of even heavierprey by highly venomous elapids and viperids, and frequent feedingon relatively small items by some other advanced snakes.     

Scaling of Cardiovascular Physiology in Snakes

The elongate body form of snakes and the wide diversity of habitatsinto which they have radiated have affected the form and functionof the cardiovascular system. Heart position is strongly correlatedwith habitat. The heart is located 15–25% of the bodylength from the head in terrestrial and arboreal species, but25–45% in totally aquatic species. Semi-aquatic and fossorialspecies are intermediate. The viperids are exceptional, withgenerally more posterior hearts but arboreal species have heartscloser to the head. An anterior heartis favored when snakesclimb because it reduces the hydrostatic pressure of the bloodcolumn above the heart and tends to stabilize cephalic bloodpressure. In water, where hydrostatic bloodpressure is not aproblem, a more centrally located heart is favored because theheart does less work perfusing the body. In terrestrial species,head-heart distance increases linearly with body length andthe increased hydrostatic pressure is matched by higher restingarterial blood pressure in longer animals. Unlike mammals andbirds, snakes have blood pressures that increasewith body mass.The added stress on the ventricle wall in larger snakes is correlatedwith ventricles that are larger than predicted by other reptiles.Heart mass scales with body mass to the 0.95 power in snakesbut only 0.77–0.91 in other reptiles that are not as subjectto the hydrostatic effects of gravity. The spongy hearts ofreptiles do not conform well to the Principle of Laplace.     

Development of Antipredator Responses in Snakes

Individual and litter differences in the number of attacks directed by Mexican garter snakes (Thamnophis melanogaster) at a threatening stimulus were studied over the first year of life. Newborn snakes born to wildcaught females from the same population were tested the day after they were born and at 7, 16, 31, and 54 weeks of age on reactivity to a potent nonmoving and moving stimulus (a human finger). There were significant individual and interlitter differences in number of strikes directed at both stimuli but no significant effect of sex. Intercorrelations among the strike scores of individuals across test days averaged .54 for the nonmoving stimulus presentations and .63 for trials with the moving stimulus. Strike scores to the moving and nonmoving stimuli were significantly correlated at each age, however, attack responses to the moving stimulus declined over the year while those to the nonmoving stimulus remained constant. Measures of concordance showed that both individual strike scores and litter means were highly consistent, whereas consistency within litters was reduced. The results indicate that litter and individual differences among newborn snakes in the tendency to engage in antipredator behavior (“defensive temperament”) remain relatively stable from the first day after birth throughout the first year of life.     

Phylogeny of Courtship and Male-Male Combat Behavior in Snakes

Background

Behaviors involved in courtship and male-male combat have been recorded in a taxonomically broad sample (76 species in five families) of snakes in the clade Boidae + Colubroidea, but before now no one has attempted to find phylogenetic patterns in such behaviors. Here, we present a study of phylogenetic patterns in such behaviors in snakes.

Methodology/Principal Findings

From the literature on courtship and male-male combat in snakes we chose 33 behaviors to analyze. We plotted the 33 behaviors onto a phylogenetic tree to determine whether phylogenetic patterns were discernible. We found that phylogenetic patterns are discernible for some behaviors but not for others. For behaviors with discernible phylogenetic patterns, we used the fossil record to determine minimum ages for the addition of each behavior to the courtship and combat behavioral repertoire of each snake clade.

Conclusions/Significance

The phylogenetic patterns of behavior reveal that male-male combat in the Late Cretaceous common ancestors of Boidae and Colubridae involved combatants raising the head and neck and attempting to topple each other. Poking with spurs was added in Boidae. In Lampropeltini the toppling behavior was replaced by coiling without neck-raising, and body-bridging was added. Phylogenetic patterns reveal that courtship ancestrally involved rubbing with spurs in Boidae. In Colubroidea, courtship ancestrally involved chin-rubbing and head- or body-jerking. Various colubroid clades subsequently added other behaviors, e.g. moving undulations in Natricinae and Lampropeltini, coital neck biting in the Eurasian ratsnake clade, and tail quivering in Pantherophis. The appearance of each group in the fossil record provides a minimum age of the addition of each behavior to combat and courtship repertoires. Although many gaps in the story of the evolution of courtship and combat in snakes remain, this study is an important first step in the reconstruction of the evolution of these behaviors in snakes.     

lntracortical Connections in the Snakes Natrix sipedon and Thamnophis sirtalis

The association and commissural connections between the four cortical areas in water (Natrix sipedon) and garter (Thamnophis sirtalis) snakes were studied by placing lesions on the cortical surface and studying the resulting degeneration in Fink-Heimer preparations. Lateral cortex projects to the outer one third of layer 1 of ipsilateral medial cortex. Dorsal cortex projects to the middle third of layer 1 of ipsilateral medial cortex. Dorsomedial cortex projects bilaterally to the inner third of layer 1 and to layer 3 of me dial cortex. It also projects to layer 1 of contralateral dorsomedial cortex. Medial cortex projects ipsilaterally to each of the other cortical areas. With the apparent exception of the projection of medial cortex to lateral cortex, each projection is organized such that each rostrocaudal segment of a cortical area projects to all segments of the target area lying at the same or more caudal levels.     

Specializations of the Body Form and Food Habits of Snakes

Viperid snakes have stouter bodies, larger heads, and longerjaws than snakes in other families; there are no major differencesbetween the two subfamilies of vipers in these features. A suiteof morphological characters that facilitates swallowing largeprey finds its greatest expression among vipers, but certainelapid and colubrid snakes have converged upon the same bodyform. The number of jaw movements required to swallow prey islinearly related to the size of a prey item when shape is heldconstant. Very small and very large prey are not disproportionatelydifficult for a snake to ingest. Vipers swallow their prey withfewer jaw movements than do colubrids or boids and can swallowprey that is nearly three times larger in relation to theirown size. Proteolytic venom assists in digestion of prey, andmelanin deposits shield the venom glands from light that woulddegrade the venom stores. Ancillary effects of the morphologicalfeatures of vipers, plus the ability to ingest a very largequantity of food in one meal, should produce quantitative andqualitative differences in the ecology and behavior of vipersand other snakes.     

The Cochlear Duct of Lizards and Snakes

The gross morphology of the cochlear ducts of approximatelyhalf (150) of the living genera of lizards and a third (130)of the living genera of snakes have been studied. The differencesin the structure of the cochlear duct are related to both theacoustical capacities and the taxonomic relationships of certainlizards and snakes. The cochlear duct of lizards consists offairly well joined lagenar and limbic portions. By contrast,the cochlear duct of snakes consists of a lagenar sac somewhatconstricted from the limbus. Each family of lizards has a morphologicallycharacteristic cochlear duct, but taxonomic relationships areindicated by certain anatomical similarities. The cochlear ductof snakes is more primitive than that of lizards, and, unlikelizards, does not exhibit marked specializations of its variousparts. Differences in morphology of the cochlear duct in snakesare much more related to habitat than family. The limbus andpapilla basilaris of snakes regardless of family, are most elongatedin bin rowing species, are only moderately elongated or ovoidin terrestrial species, and are small or reduced in certainarboreal and aquatic species.     

Mineralized Tissues and Exercise Physiology of Snakes

Previous studies indicate a tight correlation of predatory modes,morphology, and activity physiology in snakes. Active foragerslike the coachwhip (Masticophis flagellum) exhibit great staminaand high rates of aerobiosis and anaerobiosis during intenseexercise. The western rattlesnake (Crotalus viridis), a sit-and-waitpredator, is capable of bouts of intense activity for limitedperiods of time before exhaustion. During maximal activity therattlesnake has moderate powers of anaerobiosis and limitedpowers of aerobiosis. Superior blood buffering capacity in thecoachwhip seems at least partially responsible for its stamina.New evidence presented here indicates that low endurance inthe rattlesnake may be associated with exercise-related bonedissolution, resulting in hypercalcemia. Such hypercalcemiamay function to further debilitate the already poorly developedblood buffering capacity of the rattlesnake.     

钝头蛇类系统学研究进展

钝头蛇类不同类群在外形、色斑及鳞被特征上有很高的相似度,关于其种属划分长期以来一直存在争议。本文根据已有文献资料及笔者自己的研究成果,主要从形态学和分子系统学方面叙述了钝头蛇类分类学的研究进展,从属以上、属级以及种级分类阶元叙述其研究历史及成果,主要进展如下:1整个亚洲食螺蛇类(钝头蛇类)构成一个科,即钝头蛇科(Pareatidae),而非隶属于游蛇科(Colubridae)的钝头蛇亚科(Pareatinae);2单楯蛇属(Aplopeltura)和弱钝头蛇属(Asthenodipsas)为有效属,最大的钝头蛇属(Pareas)理论上可进一步分为两个属,但需要更充分的分子系统学与形态学资料验证;3分子系统学研究结果提示台湾钝头蛇(P.formosensis)与中国钝头蛇(P.chinensis)不构成单系,应恢复后者的有效性;4综合分类学研究恢复了Asthenodipsas tropidonotus的有效性,并设立新种A.lasgalenensis。本文同时提出了钝头蛇类分类学研究中存在的主要问题,即中国钝头蛇种组(Pareas chinensis species group)的内部分类关系需进一步厘定。