Fiber‐type composition in the perivertebral musculature of lizards: Implications for the evolution of the diapsid trunk muscles

The perivertebral musculature of lizards is critical for the stabilization and the mobilization of the trunk during locomotion. Some trunk muscles are also involved in ventilation. This dual function of trunk muscles in locomotion and ventilation leads to a biomechanical conflict in many lizards and constrains their ability to breathe while running (“axial constraint”) which likely is reflected by their high anaerobic scope. Furthermore, different foraging and predator‐escape strategies were shown to correlate with the metabolic profile of locomotor muscles in lizards. Because knowledge of muscle's fiber‐type composition may help to reveal a muscle's functional properties, we investigated the distribution pattern of muscle fiber types in the perivertebral musculature in two small lizard species with a generalized body shape and subjected to the axial constraint (Dipsosaurus dorsalis, Acanthodactylus maculatus) and one species that circumvents the axial constraint by means of gular pumping (Varanus exanthematicus). Additionally, these species differ in their predator‐escape and foraging behaviors. Using refined enzyme‐histochemical protocols, muscle fiber types were differentiated in serial cross‐sections through the trunk, maintaining the anatomical relationships between the skeleton and the musculature. The fiber composition in Dipsosaurus and Acanthodactylus showed a highly glycolytic profile, consistent with their intermittent locomotor style and reliance on anaerobic metabolism during activity. Because early representatives of diapsids resemble these two species in several postcranial characters, we suggest that this glycolytic profile represents the plesiomorphic condition for diapsids. In Varanus, we found a high proportion of oxidative fibers in all muscles, which is in accordance with its high aerobic scope and capability of sustained locomotion. J. Morphol., 2013. © 2012 Wiley Periodicals, Inc.     

三种蜘蛛酯酶同工酶的比较研究

应用聚丙烯酰胺凝胶电泳对狼蛛科的拟水狼蛛、蟹蛛科的三突花蛛和肖蛸科的鳞纹肖蛸3种蜘蛛的酯酶同工酶进行了比较研究。结果表明,不同科的蜘蛛酯酶同工酶种问差异性大并有着明显的种簇特异性,推测它们的酯酶同工酶酶谱中的区带组受不同的基因位点控制,且各自的基因位点数不等;同种蜘蛛的雌蛛和雄蛛之间也有各自的酯酶同工酶谱型,但差异小,其控制基因位点大体相同。这样,我们从分子的水平上讨论了酯酶同工酶的差异性可以用来作为识别物种的附加指标。     

Microhabitat Variation Explains Local‐scale Distribution of Terrestrial Amazonian Lizards in Rondônia,Western Brazil

We investigate the role of ecology and phylogeny in the association between lizard abundance and microhabitat variables in an Amazon rain forest site. Using pitfall trap arrays, we collected data from 349 individuals belonging to 23 lizard species. After accounting for spatial autocorrelation and using a canonical correspondence analysis (CCA), we found that lizard captures were significantly associated with microhabitat variables, which accounted for 48 percent of the observed variation. Furthermore, a canonical phylogenetic ordination (CPO) indicated that microhabitat variables are more important in determining the distribution of lizard species than phylogenetic relationships among species. Termite nests, canopy openness, and tree circumference were strongly associated with the number of captures of certain lizard species. Our results confirm autecology studies of individual lizard species for which data are available. We suggest that maintaining heterogeneous forested microhabitats should be a central goal for sustaining a high lizard biodiversity in Amazon rain forests.     

Developmental staging table of the green iguana

Embryonic staging tables provide information to standardize embryological investigations and to subsidize discussions about evolution. We have established a developmental staging table for Iguana iguana iguana. The sample was composed of 142 embryos, incubated at a constant temperature and collected at regular intervals. Morphological features as pharyngeal arches, craniofacial structures, eyes, limbs, claws, pigmentation, scales and egg tooth were evaluated to determine development stages. The normal staging table includes 17 stages from oviposition to hatching, based on chronology and morphological external features. Stages from 1 to 27 occur before oviposition. Stage 28 was the first described, because all embryos presented limb bud anlage, key feature of the previous stage. We used pharyngeal arches and limb buds to describe the first stages; claws, genital papilla and scales to describe the middle stages; and pigmentation, size and egg tooth to describe the last stages. Incubation lasted approximately 2 months in a controlled environment. The results were similar to the data from other lizards, confirming the embryonic conservative pattern of the group.     

The anatomy of the upper cretaceous snake Najash rionegrina Apesteguía & Zaher, 2006, and the evolution of limblessness in snakes

Najash rionegrina Apesteguía & Zaher, 2006 , a terrestrial fossil snake from the Upper Cretaceous of Argentina, represents the first known snake with a sacrum associated with robust, well‐developed hind limbs. Najash rionegrina documents an important gap in the evolutionary development towards limblessness, because its phylogenetic affinities suggest that it is the sister group of all modern snakes, including the limbed Tethyan snakes Pachyrhachis, Haasiophis, and Eupodophis. The latter three limbed marine fossil snakes are shown to be more derived morphologically, because they lack a sacrum, but have articulated lymphapophyses, and their appendicular skeleton is enclosed by the rib cage, as in modern snakes.     

极度濒危植物五针白皮松的保护遗传学研究

用随机扩增多态(RAPD)方法对极度濒危植物五针白皮松(Pinus squamata X.W.Li)的遗传多样性和居群遗传结构进行了研究。14个随机引物共获得93条RAPD谱带,其中6条为多态带,多态位点百分率仅为6．45％,遗传多样性极低。Shannon指数I和Nei指数h在种内也只有0．020和0．030,两个亚居群间(半阴坡亚居群与半阳坡亚居群)遗传分化程度不高,遗传分化系数Gst只有0．110,与大多数松科植物近似,居群每代迁移数为4．032。五针白皮松极低的遗传多样性可能是由于它在演化过程中遭受过严重的灾害,造成严重的瓶颈效应,丧失其大部分遗传变异。在随后的演化过程中由于遗传漂变、自交衰退等小种群现象,导致遗传多样性的进一步丧失。另外,阔叶树种对其生存的挤压和人类的干扰也是导致五针白皮松遗传多样性降低的因素之一。本文最后对该结果的保护生物学意义进行了评价。     

由5个DNA片段推断极度濒危植物五针白皮松的系统位置

五针白皮松(Pinus squamata X. W. Li)是上世纪90年代描述的一种中国特有松树,目前野外只有立木32株,处于极度濒危状态.前人认为这个种可能是白松亚属(subgen. Strobus)的白皮松(P. bungeana Zucc. ex Endl.)与松亚属(subgen. Pinus)的云南松(P. yunnanensis Franch.)的过渡类型,并将其归入白皮松组狐尾松亚组(subsect. Balfourianae).本文试图在前人分子系统学工作的基础上,检测五针白皮松5个DNA片段,叶绿体基因rbcL、matK、rpl20-rps18间隔区和trnV 内含子以及核糖体ITS,将五针白皮松放在整个松属中探讨其系统位置.4个叶绿体基因单独分析结果和它们的联合数据分析结果以及根据ITS得到的系统树均表明,五针白皮松是白皮松亚组(subsect. Gerardianae)的一个稳定成员,其可能的姐妹群是西藏白皮松(P. gerardiana Wall.).对白皮松亚组的地理分布作了初步探讨.     

Photoinhibition by solar radiation in the Mediterranean alga Peyssonnelia squamata measured on site

Photoinhibition of photosynthesis, defined as reversible decrease in the effective photosynthetic quantum yield, was measured in the Mediterranean red alga, Peyssonnelia squamata, using pulse amplitude modulation (PAM) chlorophyll fluorescence and oxygen production on site. This alga is adapted to very low fluence rates of solar radiation and is easily inhibited by exposure to excessive radiation. At high solar angles its photosynthetic capacity is impaired even in its natural habitat, in the protective shade of overhanging rocks. Oxygen production was maximal at 5 m depth and decreased to almost zero at the surface. When exposed at the surface oxygen production ceased within 16 min. The optimal photosynthetic quantum yield, defined as Fv/Fm, was about 0.45 in dark-adapted specimens. After 30 min of exposure to unattenuated solar radiation the (effective, Fv/Fm) quantum yield decreased to below 0.1. Removing solar UV (especially UV-B) significantly reduced photoinhibition: the quantum yield of a sample exposed under a UV-B cut-off filter was double that of a sample exposed to full solar radiation after 30 min exposure. Recovery from photoinhibition took several hours and was not complete after prolonged exposure (1.5 h) to direct solar radiation. The degree of photoinhibition depended on the depth at which the thalli were exposed. Recovery from photoinhibition was complete within 2 h except when the algae were exposed at the surface. When measured over the whole day, the effective photosynthetic quantum yield significantly decreased by about 25% from initially high values toward early afternoon and rose again towards evening. The data indicate that this alga is adapted to very low irradiances and is easily inhibited by excessive solar radiation; solar UV contributes substantially to the observed photoinhibition.     

The kinds of traits involved in male--male competition: a comparison of plumage, behavior, and body size in quail

I compared the role of ornate plumage, behavior, and body sizeduring male—male competition in two species of New Worldquail. Gambel's quail (Callipepla gambelii) is a highly ornateand dichromatic species, whereas scaled quail (C. squamata)is unornamented and monochromatic. During paired contests betweenunfamiliar males, high rates of testosterone-mediated behaviors(tidbitting, calling) and large body size (mass, tarsus, andtail length) corresponded to winners. In the highly ornate Gambel's quail, male head plumes also influenced the outcomeof contests. Plume enhancement made Gambel's quail more likelyto win contests, whereas plume removal made males more likelyto lose. Plume position also reflected male status. Winningmales erected plumes, whereas losers frequently flattened them.Some plumage ornaments, such as belly patches, did not playa primary role during male contests. Unlike static ornaments,head plumes are highly modifiable and likely signal immediateinformation regarding a male's intent, similar to a coverablebadge. Combined, intrasexual selection favored dynamic traits(fast display rates, modifiable ornaments) and static traits(body size) as indicators of male condition or motivation.In scaled quail only, male size was favored both by male—malecompetition and female choice. Accordingly, the degree of sizedimorphism (tarsus length) is greater in scaled than in Gambel'squail. The frequency of overt aggression (chases, pecks, displacement)also differed between species. Gambel's quail were very aggressive,and subordinates often challenged their opponents. In contrast, scaled quail were less aggressive, and subordinates rarely disputedrank. Interspecific comparison indicated differences in themaintenance of male status and possibly in the honesty of signaling.Both appear to be related to differences in social system.