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综 论2008040144低 PH 值 对 Ammonia beccarii 实 验 变 形 的 影响 - 用 实 验 变 形 作 为 污 染 指 示 物 的 意 义 =Low pH effects on Ammonia beccarii test deformation:implications for using test deformationsas a pollution indicator. ( 英 文 ). Valérie LeCadre; Debenay J P; Lesourd M. Journal of ForaminiferalResearch, 2003, 33(1): 1-9 3 图 版 .The use of foraminifers as bioindicators ofpollution in coastal and paralic environments hasundergone a very fast development. Amongvarious criteria, morphological abnormalities aresometimes considered as pollution indicators.However, responses to pollutants have not alwaysbeen distinguished from responses to naturalenvironmental parameters. In particular,endopelic foraminifers often live in changing pHconditions that may induce test deformation.To study pH effects, cultures with pH rangingfrom normal marine down to ph 7 were preparedusing hydrochloric acid to lower the pH. Ammoniabeccarii was collected and introduced intothese different cultures. Under neutral pH (7.0)conditions, pseudopodial emission was reducedor stopped. Then the test became opaque as aresult of superficial alteration, which is the firststage of test decalcification. Decalcification progressivelyextended over the whole test, firstdestroying the last chambers, which are thinner.After 15 days, only interlocular walls were preserved,giving the test a star-shape characteristicof an advanced stage of decalcification. If aspecimen was maintained in low pH conditions,the test was sometimes entirely destroyed andonly the cytoplasm, covered with the Inner OrganicLayer, remained. On the other hand, if aspecimen with a partially dissolved test wasplaced in a solution with normal pH, it was ableto rebuild its test. Recalcification was somewhatdifferent from the original calcification and wasaccompanied, in most cases, by morphologicalabnormalities (e.g., abnormal expansions, irregularchamber sizes, wall with concave form).These observations show that temporary acidificationof the environment, causing partial decalcificationof the test, is able to induce morphologicalabnormalities of foraminiferal tests duringrecalcification. This acidification may becaused by anthropogenic impact or a naturalcause. In both cases, deformation of foraminiferaltests yields information on environmentalcharacteristics of the area.2008040145埃 迪 卡 拉 期 两 侧 动 物 的 出 现 : 基 因 和 地 质 的 化石 记 录 的 一 致 性 = The Ediacaran emergence ofbilaterians: congruence between the genetic andthe geological fossil records. ( 英 文 ). Kevin J.Peterson1; James A. Cotton; James G Gehling;Davide Pisani. Philosophical Transactions of theRoyal Society B: Biological Sciences, 2008,363(1496): 1435-1443Unravelling the timing of the metazoan radiationis crucial for elucidating the macroevolutionaryprocesses associated with the Cambrianexplosion. Because estimates of metazoan divergencetimes derived from molecular clocksrange from quite shallow (Ediacaran) to verydeep (Mesoproterozoic), it has been difficult toascertain whether there is concordance or quitedramatic discordance between the genetic andgeological fossil records. Here, we show using arange of molecular clock methods that the majorpulse of metazoan divergence times was duringthe Ediacaran, which is consistent with a synopticreading of the Ediacaran macrobiota. Theseestimates are robust to changes in priors, and arereturned with or without the inclusion of a palaeontologicallyderived maximal calibrationpoint. Therefore, the two historical records oflife both suggest that although the cradle ofMetazoa lies in the Cryogenian, and despite theexplosion of ecology that occurs in the Cambrian,it is the emergence of bilaterian taxa in the Ediacaranthat sets the tempo and mode of macroevolutionfor the remainder of geological time.2008040146其 他 后 生 动 物 躯 体 造 型 的 起 源 : 幼 虫 形 式 的演 化 = Origins of the other metazoan body plans:the evolution of larval forms. ( 英 文 ). Raff R A.Philosophical Transactions of the Royal SocietyB: Biological Sciences, 2008, 363(1496): 1473-1479Bilaterian animal body plan origins are notsolely about adult forms. Most animals have larvaewith body plans, ontogenies and ecologiesdistinct from adults. There are two primary hypothesesfor larval origins. The first hypothesissuggests that the first animals were small pelagicforms similar to modern larvae, with adult bilaterianbody plans evolved subsequently. The secondhypothesis suggests that adult bilaterianbody plans evolved first and that larval bodyplans arose by interpolation of features into direct-developingontogenies. The two hypotheseshave different consequences for understandingparsimony in evolution of larvae and of developmentalgenetic mechanisms. If primitivemetazoans were like modern larvae and distinctadult forms evolved independently, there shouldbe little commonality of patterning genes amongadult body plans. However, sharing of patterninggenes is observed. If larvae arose by co-option ofadult bilaterian-expressed genes into independentlyevolved larval forms, larvae may showmorphological convergence, but with distinctpatterning genes, and this is observed. Thus,44