Polymorphism and Geographic Variation in the Feeding Behavior of the Garter Snake Thamnophis elegans

Geographic variation in behaviors that influence resource utilization is a key component in current ecological theory, but the phenomenon has been poorly documented. Propensity to attack slugs varies geographically in a western garter snake, Thamnophis elegans. Many naive, newborn snakes from inland localities in California refuse to eat slugs. In contrast, virtually all naive young from coastal localities eat slugs. There is, however, no demonstrable polymorphism or geographic variation for propensity to eat anurans. Both coastal and inland snakes consistently eat anurans.     

Coral snake mimicry: does it occur?

Field observations and experimental evidence refute previous objections to the coral snake mimicry hypothesis. Concordant color pattern variation spanning hundreds of miles and several presumed venomous models strongly suggests that several harmless or mildly venomous colubrid snakes are indeed mimics of highly venomous elapids.     

The role of social groups in the persistence of learned fear

Classical fear conditioning investigates how animals learn to associate environmental stimuli with an aversive event. We examined how the mechanisms of fear conditioning apply when humans learn to associate social ingroup and outgroup members with a fearful event, with the goal of advancing our understanding of basic learning theory and social group interaction. Primates more readily associate stimuli from certain fear-relevant natural categories, such as snakes, with a negative outcome relative to stimuli from fear-irrelevant categories, such as birds. We assessed whether this bias in fear conditioning extends to social groups defined by race. Our results indicate that individuals from a racial group other than one's own are more readily associated with an aversive stimulus than individuals of one's own race, among both white and black Americans. This prepared fear response might be reduced by close, positive interracial contact.     

Sex pheromones in snakes

The majority of pheromones identified to date are insect pheromones, which are volatile in nature. Identification of nonvolatile pheromones have been relatively rare, especially in vertebrates. Male and female garter snakes use pheromones to mediate sexual behavior. The female sex attractiveness pheromone of the Canadian red-sided garter snake, Thamnophis sirtalis parietalis, consists of a novel series of nonvolatile saturated and monounsaturated long-chain methyl ketones, whereas the male sex recognition pheromone contains squalene. These compounds were isolated, identified, and partially synthesized, and field tests show them to be biologically active.     

不同种动物心电图波形的比较

参照测定人体心电图的标准Ⅱ导联,研究了鲤、蛙、龟、蛇、鸡、马、驴、西门塔尔牛、湖羊、细毛羊、梅花鹿、驼、猪、犬、猫、小白鼠、家兔和人等五大类17种具有代表意义的动物心电图,对其P波、QRS波、T波的形态学进行了比较分析,其结果表明:鲤、蛇的P波形态变异较大,且鲤P波与人类P波形态相反,有50％呈负向,其余动物的P渡与人类P波的形态相似,呈现以正向为主,鲫、蛙、龟、蛇的QRS波以R波为主波,其中鲤以QR波为主,蛙为RS波,龟、蛇以Rs波为主,鸡52％呈RS型,42％呈rS型,其余动物和人类均属于以R波为主的QRS波,同一种动物的QRS波可有各种形态出现,主要为QR、qR,qRs、Rs,RS、R波的QRS波型,蛙、蛇、猫、兔、猪、驴、驼等动物的T波与人类相似、呈现以直立为主,其他动物的形态则变异较大。     

滑鼠蛇出生至50日龄身体大小和免疫功能的变化

为探究滑鼠蛇（Ptyas mucosus）生后发育不同阶段身体大小和免疫功能的变化,在室温为（30±1）℃、相对湿度为70%~75%条件下,监测了3、10、20、30、40和50日龄滑鼠蛇身体大小及各型白细胞的百分比、嗜中性粒细胞与淋巴细胞的比值（N/L）和血清杀菌能力的变化。体重、体全长、重长比和尺度化的质量指数3至20日龄增长缓慢,之后陡增,50日龄最高（P<0.05）;淋巴细胞和嗜中性粒细胞的百分比居前两位,但两者的百分比、N/L的比值和血清杀菌能力均无组间差异（P>0.05）;嗜碱性粒细胞的百分比10日龄组与3日龄组接近,但高于其他日龄组（P<0.05）;50日龄内,滑鼠蛇的身体大小开口前增长缓慢,开口后增加迅速,蜕皮后嗜碱性粒细胞的百分比显著提升,建议可根据体重和嗜碱性粒细胞百分比的变化来预判蛇场内幼蛇的健康状态。     

Lipid barrier to water exchange in reptile epidermis

Extraction of lipids from the shed epidermis of the terrestrial snake Elaphe obsoleta obsoleta increases cutaneous water loss in vitro as much as 15-fold. Partial denaturation of epidermal keratin without lipid extraction increases cutaneous water loss only twofold. Histological observations and thin-layer and gas-liquid chromatography of the lipid extracts indicate a complex mixture of polar and neutral lipids predominantly in the mesos layer of the cornified epidermis. Comparative measurements of cutaneous water loss in other species of snakes and a lizard show that permeabilities differ naturally but are essentially identical after lipid extraction. These findings establish the importance of lipids in the permeability barrier of reptilian skin and suggest that keratin or scale morphology are of nominal importance in limiting water exchange.     

Lizard Tail Autotomy: Function and Energetics of Postautotomy Tail Movement in Scincella lateralis

Handling of autotomized, thrashing and autotomized, exhausted tails of the lizard Scincella lateralis by mammals and snakes was tested to examine the function of postautotomy tail movement. Tail movement attracted a mammal's attack to the tail, permitting the lizard to escape and increased the time required for a snake to subdue a tail before swallowing it, increasing the lizard's escape time by 40 percent. Lactate concentrations of autotomized tails after movement were compared to those of intact tails after rest in S. lateralis, a species with a high rate of autotomized tail thrashing, and Anolis carolinensis, a species with a low rate of thrashing. Postautotomy movement increased tail lactate concentration in both species, but mean tail lactate concentration in S. lateralis was 60 percent higher than that in A. carolinensis, and a third higher than that reportedfor whole-body lactate content of the very mobile lizard Dipsosaurus dorsalis.     

Pulmonary blood flow regulation in an aquatic snake

Regulation of pulmonary blood flow was studied during voluntary diving in the aquatic file snake, Acrochordus granulatus. Measurements of pressure and blood flow in pulmonary and systemic vessels indicate that blood flow completely bypasses the lung for significant periods during prolonged and quiescent submergence (greater than 30 minutes). When the lung is ventilated, pulmonary blood flow increases to 36 milliliters per minute per kilogram of body mass (measured in the anterior pulmonary artery), and the cardiac output largely bypasses the systemic circulation. These reciprocating patterns of preferential blood flow reflect inverse relations between flow and vascular resistance, with the result that systemic and pulmonary arterial pressures remain virtually constant throughout repetitive dive cycles. Neuropharmacological studies of freely diving snakes and isolated, perfused lung preparations show that pulmonary blood flow is regulated by an interplay of adrenergic vasodilatation and cholinergic vasoconstriction within the densely innervated lung vasculature. The patterns of blood circulation shown by diving Acrochordus reflect an unusual lability of intracardiac shunts.     

Collective behavior in an early Cambrian arthropod

Examples that indicate collective behavior in the fossil record are rare. A group association of specimens that belong to a previously unknown arthropod from the Chengjiang Lagerst?tte, China, provides evidence that such behavior was present in the early Cambrian (about 525 million years ago), coincident with the earliest extensive diversification of the Metazoa, the so-called Cambrian explosion event. The chainlike form of these specimens is unique for any arthropod, fossil or living, and most likely represents behavior associated with migration.     

广东地质发展简史及植物区系溯源

广东植物区系的发展由来已久，现代的广东植物是晚白垩世或早第三世的孑遗物，地层中存在磊量的古植物化石。如本内苏铁，银杏，苏铁等极为丰富，种子特别是大羽羊齿尤为突出，而且在白垩纪晚期至第三纪的广东地层中，存在着丰富的现代植物的化石或化石孢粉组合，如朴树，桦木、鹅耳枥及松、冷杉、雪松等，还有其它阔叶树和针叶树，所有这些都与广东复杂的地质发展史密切相关，它预示着广东植物区系可能起源于亚带山地，而且广东无颖     

Chemical-cue preferences of newborn snakes: influence of prenatal maternal experience

Newborn garter snakes (Thamnophis sirtalis) responded similarly to worm and fish surface extracts regardless of whether the mothers were fed exclusively on fish or worms during the gestation period. Worm extract was the more effective. This result is in contrast with the easy modifiability of chemical-cue preferences in young snakes after birth. The initial stimulus control of the attack response in newborn snakes thus seems relatively unmodifiable.     

Crystal axes in recent and fossil adult echinoids indicate trophic mode in larval development

The type of larval development in echinoids (Phylum Echinodermata) was found to determine crystal patterns in adult apical skeletal plates. This relation between larvae and adults will allow fossil species to be examined to determine the effects of developmental mode on evolutionary patterns, such as species longevity and speciation rate. Independent tests of hypotheses of such patterns now shown among fossil mollusks with and without feeding larvae can thus be performed.     

Upper eocene gilled mushroom from the dominican republic

Coprinites dominicana gen.nov., spec.nov. (Coprinaceae) found in amber from the Dominican Republic is the earliest known gilled mushroom, the first fossil fleshy agaric determinable, and the only kiiown fossil "mushroom" (Agaricales) from the tropics. This find is of significance with respect to the evolutionary development of the Basidiomycetes. Because the appearance of this fossil is quite modern, it suggests that mushrooms as a group probably arose much earlier than the early to mid-Tertiary.     

An ostracode crustacean with soft parts from the Lower Silurian

An exceptionally well-preserved ostracode from the Silurian of Herefordshire, United Kingdom, provides a rare view of the fossilized soft-part anatomy of this important group of living crustaceans and confirms that Ostracoda were extant in the Paleozoic. The fossil has striking similarity to the extant myodocopid family Cylindroleberididae, to which it is assigned, and demonstrates remarkable evolutionary stasis over 425 million years. The fossil is identified as a male on the basis of its copulatory organ.     

应用电导率法及Logistic方程测试蛇皮果抗寒性研究

对4个蛇皮果品种Bali、Pondoh、Galing和M9进行了不同低温胁迫处理,结果显示4个品种的抗寒性依次为Pon-doh>Gad ing>M9>Bali;相对电导率随着处理温度的递减而增加;叶片伤害率在5℃以下明显增大,其变化强度为:Bali>M9>Gad ing>Pondoh。在5%显著水平上,Bali与M9的相对电导率差异不显著,与Pondoh、Gad ing的差异显著;M9、Pondoh和Gad ing的差异不显著。在叶片伤害率上,Bali与M9间差异不显著,这两个品种与Pondoh、Gad ing的差异显著。蛇皮果叶片半致死温度(LT50)范围在4.0~6.0℃。结果表明用电导率评价蛇皮果的抗寒性效果较好,结合Logistic方程可以推算出蛇皮果可耐受的最低温度,为蛇皮果抗寒性栽培和我国泛热带地区引种提供理论依据。     

Ingestion of petroleum by seabirds can serve as a monitor of water quality

The ingestion by seabirds of fossil fuel hydrocarbons and other pollutants has been of great interest. This paper reports that storm-petrels ingest petroleum at sea and that residues can be detected in their stomach oil. The incidence of gut samples containing fossil fuel hydrocarbons (dirty samples) increased significantly after oil spills, and significantly more birds regurgitated dirty samples after large nearby spills than small distant ones. This appears to be one of the first reported instances where individuals of a natural population of marine birds have been shown to ingest sublethal doses of oil from sources of low-level, long-term pollution or from oil spills. Because of certain natural traits, Procellariiformes could serve as monitors of pollutants in the marine environment.     

Chondrites: a trace fossil indicator of anoxia in sediments

The trace fossil Chondrites, a highly branched burrow system of unknown endobenthic deposit feeders, occurs in all types of sediment, including those deposited under anaerobic conditions. In some cases, such as the Jurassic Posidonienschiefer Formation of Germany, Chondrites occurs in black, laminated, carbonaceous sediment that was deposited in chemically reducing conditions. In other cases, such as numerous oxic clastic and carbonate units throughout the geologic column, Chondrites typically represents the last trace fossil in a biotutbation sequence. This indicates that the burrow system was produced deep within the sediment in the anaerobic zone below the surficial oxidized zone that was characterized by freely circulating and oxidizing pore waters.     

Hinged teeth in snakes: an adaptation for swallowing hard-bodied prey

Six genera of snakes, representing at least three lineages, possess teeth that fold backward against the jaws rather than being firmly ankylosed. This condition, effected by a connective tissue hinge at the base of each tooth, is associated with suites of cephalic modifications that enable the snakes to grasp and to swallow hard-bodied prey.     

Regional specialization of reptilian scale surfaces: relation of texture and biologic role

The iridescent body scales of the fossorial uropeltid snakes produce these interference colors by keratinous ridges spaced at 2500 A. The pattern inhibits wetting of the surface and adhesion of soil particles and thus reduces friction between the snake's trunk and walls of its tunnel. The epidermal scales of the blunt tail show a sharply defined pattern of spines and ridges with convergent flutings. Dirt caught here forms a plug that protects the snake's caudal end. The sharp transition of surface textures suggests (i) that selection for each of the two roles is great, and (ii) that the interference colors of many fossorial snakes indicate that friction as well as dirt adhesion are being reduced.