Plasticity of animal genome architecture unmasked by rapid evolution of a pelagic tunicate

Genomes of animals as different as sponges and humans show conservation of global architecture. Here we show that multiple genomic features including transposon diversity, developmental gene repertoire, physical gene order, and intron-exon organization are shattered in the tunicate Oikopleura, belonging to the sister group of vertebrates and retaining chordate morphology. Ancestral architecture of animal genomes can be deeply modified and may therefore be largely nonadaptive. This rapidly evolving animal lineage thus offers unique perspectives on the level of genome plasticity. It also illuminates issues as fundamental as the mechanisms of intron gain.     

Interocean differences in size and nutrition of coral reef sponge populations

Sponges consume an order of magnitude more organic matter on Caribbean coral reefs than on the Great Barrier Reef. This rate of consumption is attributed to Caribbean sponge biomass being five to six times greater than that on the Great Barrier Reef, on average, and to the absence in the Caribbean of phototrophic sponges, which are a feature of clean water regions of the Great Barrier Reef. The long temporal and spatial separation of the Atlantic and Pacific oceans has resulted in the evolution of dissimilar sponge faunas, with Caribbean sponges being heterotrophic, whereas many Great Barrier Reef sponges rely on nutritional input from photosynthetic symbionts.     

A catastrophic death assemblage and paleoclimatic implications of pliocene seabirds of Florida

A deposit of fossil seabirds from the late Pliocene of Florida includes more than 130 skeletons of an extinct cormorant that is related phylogenetically to Recent species currently restricted to the eastern north Pacific. Evidence suggests the birds died in a single catastrophic event, perhaps a red tide. The fossil cormorant, along with other extinct seabirds and marine mammals, supports molluscan evidence for cold-water upwelling along the Florida Gulf Coast during the Pliocene. A decline in species richness of marine vertebrates throughout the Pliocene of Florida coincides with cessation of upwelling after emergences of the Panamanian Land Bridge.     

Putative skeletal neural crest cells in early late ordovician vertebrates from colorado

Two vertebrates from the Colorado Formation are known to have acellular bone and dentine, tissues found in heterostracan fishes and proposed as the primitive exoskeleton. High-resolution optical microscopy and scanning electron microscopy indicate that a third vertebrate is represented by a quite distinct exoskeleton of denticles, with many cell and cell process spaces throughout, tissue that resembles that of osteostracans more than heterostracans. Cellular bone coexists with cellular dentine in this Ordovician vertebrate, demonstrating that these skeletal tissues are as old as acellular bone. Both are proposed to come from neural crest because denticles are considered homologous with teeth.     

海洋无脊椎动物多不饱和脂肪酸合成代谢机理研究进展

近年来,人们对水产品质量安全、优质的动物蛋白以及脂肪来源的关注度越来越高。海洋无脊椎动物不仅是优质食物蛋白的重要来源,也是人体获取多不饱和脂肪酸（polyunsaturated fatty acids,PUFA）的主要食物来源。研究表明,几乎所有的PUFA都来自于水生生态系统中的初级生产者,海洋中主要初级生产者微藻生产出PUFA进入食物链后,较高营养级生物可通过生物转化或修饰产生新的PUFA。关于初级生产者和脊椎动物中PUFA合成代谢的研究较多,但位于两者之间无脊椎动物PUFA的生物合成代谢途径却知之甚少。因此,本文对五类海洋无脊椎动物（多孔动物、刺胞动物、软体动物、甲壳动物和棘皮动物）PUFA的合成代谢途径以及参与其过程中重要酶和关键基因的研究进展进行了总结,以期为更深入地理解海洋无脊椎动物PUFA的合成代谢与调控体系提供有价值的参考资料。     

Peafowl lactate dehydrogenase: problem of isoenzyme identification

Peafowl, like other vertebrates, contain multiple forms of lactate dehydrogenase. The electrophoretic properties of the peafowl isoenzymes are unusual in that the isoenzyme from heart tissue can be either more or less anodic than that of muscle, depending on the pH. This finding focuses attention on the problem of isoenzyme identification. It is suggested that isoenzymes be identified on the basis of properties that are chemically and biologically more significant than electrophoretic mobility.     

Leg patterning driven by proximal-distal interactions and EGFR signaling

wingless and decapentaplegic signaling establishes the proximal-distal axis of Drosophila legs by activating the expression of genes such as Distalless and dachshund in broad proximal-distal domains during early leg development. However, here we show that wingless and decapentaplegic are not required throughout all of proximal-distal development. The tarsus, which has been proposed to be an ancestral structure, is instead defined by the activity of Distalless, dachshund, and a distal gradient of epidermal growth factor receptor (EGFR)-Ras signaling. Our results uncover a mechanism for appendage patterning directed by genes expressed in proximal-distal domains and possibly conserved in other arthropods and vertebrates.     

输变电工程对陆生脊椎动物的影响和保护措施

对四川雅安至安徽皖南1 000 kV交流特高压输变电工程项目沿线的陆生脊椎动物进行实地调查,分析了输变电工程的建设期和运营期对陆生脊椎动物的影响,并提出了相应的保护措施和建议。结果表明,在工程区域范围内共记录陆生脊椎动物4纲32目89科,502种;输变电工程建设、营运过程中会破坏动物的栖息地,造成陆生脊椎动物的直接死亡,使得大部分陆生脊椎动物迁移到其他地方,远离施工区范围。同时,对动物的觅食、生殖等活动都构成不同程度的影响。通过实行有效的保护措施以及陆生脊椎动物自身的调节能力能将影响降至最小。     

Retention of potential to differentiate in long-term cultures of tooth germs

When tooth germs derived from 14-day mouse embryos were cultured on gelatin sponges in vitro for 37 days, they lost their characteristic morphology, appearing as a layer of undifferentiated epithelium on the sponge surface, with the mesenchymal cells scattered throughout the interstices. These cultures were then transplanted subcutaneously into isologous, newborn recipients and, over a period of 56 days, developed into incisor teeth that were almost perfect in shape and structure.     

Genomic insights into the immune system of the sea urchin

Comparative analysis of the sea urchin genome has broad implications for the primitive state of deuterostome host defense and the genetic underpinnings of immunity in vertebrates. The sea urchin has an unprecedented complexity of innate immune recognition receptors relative to other animal species yet characterized. These receptor genes include a vast repertoire of 222 Toll-like receptors, a superfamily of more than 200 NACHT domain-leucine-rich repeat proteins (similar to nucleotide-binding and oligomerization domain (NOD) and NALP proteins of vertebrates), and a large family of scavenger receptor cysteine-rich proteins. More typical numbers of genes encode other immune recognition factors. Homologs of important immune and hematopoietic regulators, many of which have previously been identified only from chordates, as well as genes that are critical in adaptive immunity of jawed vertebrates, also are present. The findings serve to underscore the dynamic utilization of receptors and the complexity of immune recognition that may be basal for deuterostomes and predicts features of the ancestral bilaterian form.     

Thermophysiology of Tyrannosaurus rex: Evidence from Oxygen Isotopes

The oxygen isotopic composition of vertebrate bone phosphate (delta(p)) is related to ingested water and to the body temperature at which the bone forms. The delta(p) is in equilibrium with the individual's body water, which is at a physiological steady state throughout the body. Therefore, intrabone temperature variation and the mean interbone temperature differences of well-preserved fossil vertebrates can be determined from the deltap variation. Values of delta(p) from a well-preserved Tyrannosaurus rex suggest that this species maintained homeothermy with less than 4 degrees C of variability in body temperature. Maintenance of homeothermy implies a relatively high metabolic rate that is similar to that of endotherms.     

Neural crest and the origin of vertebrates: a new head

Most of the morphological and functional differences between vertebrates and other chordates occur in the head and are derived embryologically from muscularized hypomere, neural crest, and epidermal (neurogenic) placodes. In the head, the neural crest functions as mesoderm and forms connective, skeletal, and muscular tissue. Both the neural crest and the epidermal placodes form special sense organs and other neural structures. These structures may be homologous to portions of the epidermal nerve plexus of protochordates. The transition to vertebrates apparently was associated with a shift from a passive to an active mode of predation, so that many of the features occurring only in vertebrates became concentrated in the head.     

A Reassessment of Astraspis desiderata, the Oldest North American Vertebrate

The fossil evidence for the early evolution of vertebrates consists of the remains of agnathans, jawless vertebrates, from the Ordovician of Australia, North America, and Bolivia. Because of the fragmentary nature of the material, it has not been possible to reconstruct these animals sufficiently well to understand their relation to each other and to later vertebrates. Though two genera have been known from the Harding Sandstone of North America since 1892, there are still only three articulated specimens known, two of Astraspis desiderata and one of Eriptychius americanus. The most recently found specimen of Astraspis was reexamined and found to show the orbit, a series of eight branchial openings and a complete tail, structures hitherto undescribed in any Ordovician vertebrate. A reconstruction ofAstraspis shows, on the basis of the series of branchial openings, that it is a primitive craniate and not a heterostracan as previously thought.     

海绵共附生放线菌的分离鉴定与抑菌活性分析

为了探究海南海绵共附生放线菌资源的多样性及潜在的药用价值，采用 4 种分离培养基分离海南文昌海域海绵的共附生放线菌，利用 16S rRNA序列分析对分离的放线菌进行鉴定，采用滤纸片扩散法对分离放线菌的发酵产物进行抗菌活性分析。结果表明，从4种海绵中共获得50株放线菌，所分离菌株归属于5 个亚目、6个科和 7 个属，包括链霉菌属、小单孢菌属、红球菌属、糖多孢菌、栖白蚁菌属、分枝杆菌属和Krasilnikoviella属，其中Krasilnikoviella为首次从海绵中分离得到，4株海洋放线菌为潜在的新物种。抗菌活性测试显示48%的分离菌株呈现抗细菌活性，24%的分离菌株呈现抗植物丝状病原真菌活性。本研究结果初步揭示了海南文昌海域海绵共附生放线菌的可培养物种多样性及其发酵产物的抑菌活性。     

Near extinction of a large, widely distributed fish

Are extinctions of marine vertebrates as rare and unlikely as current data indicate? Long-term research surveys on the continental shelf between the Grand Banks of Newfoundland and southern New England reveal that one of the largest skates in the northwest Atlantic, the barndoor skate (Raja laevis), is close to extinction. Forty-five years ago, research surveys on St. Pierre Bank (off southern Newfoundland) recorded barndoor skates in 10% of their tows; in the last 20 years, none has been caught, and this pattern of decline is similar throughout the range of the species.     

State-dependent learned valuation drives choice in an invertebrate

Humans and other vertebrates occasionally show a preference for items remembered to be costly or experienced when the subject was in a poor condition (this is known as a sunk-costs fallacy or state-dependent valuation). Whether these mechanisms shared across vertebrates are the result of convergence toward an adaptive solution or evolutionary relicts reflecting common ancestral traits is unknown. Here we show that state-dependent valuation also occurs in an invertebrate, the desert locust Schistocerca gregaria (Orthoptera: Acrididae). Given the latter's phylogenetic and neurobiological distance from those groups in which the phenomenon was already known, we suggest that state-dependent valuation mechanisms are probably ecologically rational solutions to widespread problems of choice.     

Temperature as a universal resetting cue for mammalian circadian oscillators

Environmental temperature cycles are a universal entraining cue for all circadian systems at the organismal level with the exception of homeothermic vertebrates. We report here that resistance to temperature entrainment is a property of the suprachiasmatic nucleus (SCN) network and is not a cell-autonomous property of mammalian clocks. This differential sensitivity to temperature allows the SCN to drive circadian rhythms in body temperature, which can then act as a universal cue for the entrainment of cell-autonomous oscillators throughout the body. Pharmacological experiments show that network interactions in the SCN are required for temperature resistance and that the heat shock pathway is integral to temperature resetting and temperature compensation in mammalian cells. These results suggest that the evolutionarily ancient temperature resetting response can be used in homeothermic animals to enhance internal circadian synchronization.     

Neurobiological bases of rhythmic motor acts in vertebrates

The general principles governing the nervous control of innate motor acts in vertebrates are discussed. Particular consideration is given to the control of locomotion in both mammals and lower vertebrates. One in vitro model of the lamprey central nervous system has been developed. It can be maintained in vitro for several days and the motor pattern underlying locomotion can be elicited in isolated sections of the spinal cord. These findings now allow a detailed analysis of the underlying neural mechanisms. The hypothesis that different parts of the network controlling locomotion can be used in a variety of other motor acts, including learned ones, is reviewed.     

Evolution of a vertebrate social decision-making network

Animals evaluate and respond to their social environment with adaptive decisions. Revealing the neural mechanisms of such decisions is a major goal in biology. We analyzed expression profiles for 10 neurochemical genes across 12 brain regions important for decision-making in 88 species representing five vertebrate lineages. We found that behaviorally relevant brain regions are remarkably conserved over 450 million years of evolution. We also find evidence that different brain regions have experienced different selection pressures, because spatial distribution of neuroendocrine ligands are more flexible than their receptors across vertebrates. Our analysis suggests that the diversity of social behavior in vertebrates can be explained, in part, by variations on a theme of conserved neural and gene expression networks.     

Pregnancy-stimulated neurogenesis in the adult female forebrain mediated by prolactin

Neurogenesis occurs in the olfactory system of the adult brain throughout life, in both invertebrates and vertebrates, but its physiological regulation is not understood. We show that the production of neuronal progenitors is stimulated in the forebrain subventricular zone of female mice during pregnancy and that this effect is mediated by the hormone prolactin. The progenitors then migrate to produce new olfactory interneurons, a process likely to be important for maternal behavior, because olfactory discrimination is critical for recognition and rearing of offspring. Neurogenesis occurs even in females that mate with sterile males. These findings imply that forebrain olfactory neurogenesis may contribute to adaptive behaviors in mating and pregnancy.