Nitrogen vacancy scattering in GaN grown by metal-organic vapor phase epitaxy

Electron mobility limited by nitrogen vacancy scattering was taken into account to evaluate the quality of n-type GaN grown by metal-organic vapor phase epitaxy. Two assumptions were made for this potential for the nitrogen vacancy (1) it acts in a short range, and (2) does not diverge at the vacancy core. According to the above assumptions, a general expression to describe the scattering potential U(r) = - U-0 exp[- (r/beta)(n)], (n = 1, 2,...,infinity) was constructed, where beta is the potential well width. The mobilities for n = 1, 2, and infinity were calculated based on this equation, corresponding to the simple exponential, Gaussian and square well scattering potentials, respectively. In the limiting case of kbeta << 1 (where k is the wave vector), all of the mobilities calculated for n = 1, 2, and infinity showed a same result but different prefactor. Such difference was discussed in terms of the potential tail and was found that all of the calculated mobilities have T-1/2 temperature and beta(-6) well width dependences. A mobility taking account of a spatially complicate scattering potential was studied and the same temperature dependence was also found. A best fit between the calculated results and experimental data was obtained by taking account of the nitrogen vacancy scattering. (C) 2002 Elsevier Science Ltd. All rights reserved.

Thermal redistribution of localized excitons and its effect on the luminescence band in InGaN ternary alloys

Temperature-dependent photoluminescence measurements have been carried out in zinc-blende InGaN epilayers grown on GaAs substrates by metalorganic vapor-phase epitaxy. An anomalous temperature dependence of the peak position of the luminescence band was observed. Considering thermal activation and the transfer of excitons localized at different potential minima, we employed a model to explain the observed behavior. A good agreement between the theory and the experiment is achieved. At high temperatures, the model can be approximated to the band-tail-state emission model proposed by Eliseev et al. [Appl. Phys. Lett. 71, 569 (1997)]. (C) 2001 American Institute of Physics.

Si doping effect on self-organized InAs/GaAs quantum dots

In situ ultra high vacuum scanning probe microscopy (SPM) and low-temperature :photoluminescence (PL) studies have been performed on Si-doped self-organized InAs/GaAs quantum dots samples to investigate the Si doping effects. Remarkably, when Si is doped in the sample, according to the SPM images, more small dots are formed when compared with images from undoped samples. On the PL spectra, high-energy band tail which correspond to the small dots appear, with increasing doping concentration, the integral intensity of the high-energy band tail account for the whole peak increase too. We relate this phenomenon to a model that takes the Si atom as the nucleation center for QDs formation. (C) 1999 Elsevier Science B.V. All rights reserved.

A 1Gb/s silicon photo-receiver in standard CMOS for 850-nm optical communication

A monolithic silicon CMOS optoelectronic integrated circuit (OEIC) was designed and fabricated with standard 0.6 mu m CMOS technology. This OEIC circuit consisted of an integrated double photodiode detector (DPD) and a preamplifier. The DPD detector exhibited high bandwidth by screening the bulk-generated diffusion carriers and suppressing the slow diffusion tail effect. The preamplifier exploited the regulated cascode (RGC) configuration as the input stage of receiver, thus isolating the influence of photodiode capacitance and input parasitic capacitance on bandwidth. Testing results showed that the bandwidth of OEIC was 700MHz, indicating the bit rate of 1Gb/s was achieved.

Micro-raman investigation of defects in a 4H-SiC homoepilayer

Three types of defects, namely defect I, defect 11, defect 111, in the 4H-SiC homoepilayer were investigated by micro-raman scattering measurement. These defects all originate from a certain core and are composed of (1) a wavy tail region, (11) two long tails, the so called comet and (111) three plaits. It was found that there are 3C-SiC inclusions in the cores of defect 11 and defect III and the shape of inclusion determines the type of defect II or defect III. If the core contains a triangle-shaped inclusion, the defect III would be formed; otherwise, the defect 11 was formed. No inclusion was observed in the core of the defect I. The mechanisms of these defects are discussed.

基于小规模尾字特征的中文命名实体识别研究

本文针对难度最大的两类命名实体(地名和机构名)在条件随机场框架下首次引入了小规模的常用尾字特征．实验表明，该特征与词类特征具有一定的互补性，联合使用可以以较小的训练代价显著提高专有名词的识别性能，特别是机构名的识别精度．该系统在我国863简体命名实体识别评测语料上专名(人名、地名和机构名)总体F1值达踞．76％，超过当年最佳系统8．63个百分点．在SIGHAN 2006命名实体识别语料上的结果也居于前列．

PBT/HIPS枘混体系的结构与性能及生物隆解聚合物结晶性能的研究

以过氧化二异丙苯(DCP)为引发剂，甲基丙烯酸缩水甘油醋(GMA)为活性单体对HIPS进行熔融接枝，制得了功能化的高抗冲苯乙烯(HIPS－g－GMA）。比较HIPS－g－GMA和纯的HIPS的红外谱图，可以看到在HIPS－g－GMA的谱图上出现了一个新的吸收峰，即1730cm~(-1)处的C=O的伸缩振动吸收峰，它为接枝的GMA中的醋基基团的特征峰，因此可以确定GMA己经接枝到HIPS上。能谱分析也提供了相似的结论。同时研究了单体浓度和DCP用量对产物接枝率的影响。用化学滴定方法测定了接枝物的接枝率。随着GMA量的增加，接枝率也随之增加，当GMA用量超过14％时，接枝率趋于平缓；接枝率随DCP量增加而增加。采用DSC、SEM, WAXD, DMA及力学性能等方法和手段研究PBTIHIPS和PBT/HIPS-g-GMA二元共混体系的结晶、形态结构、动态力学性能及力学性能随组成的变化。当PBT为分散相，在增容体系中的PBT出现了分级结晶现象，结晶温度降低，这是由于分散相更为精细的结果。DMA结果表明，在PBTIHIP S-g-GMA体系中由于发生了化学反应，有接枝共聚物生成，体系中两个聚合物的Tg松弛均出现了较明显的降低，增容后体系的力学性能有显著提高。采用DSC, SEM, DMA及力学性能等方法和手段研究PBT/HIPS/HIPS-g-GMA三元共混体系的结构与性能。结果表明PBT无论是分散相还是连续相，HIPS-g-GMA的作用表现为：（1）对PBTIHIPS体系的熔融和结晶行为产生了明显的影响，使PBT的结晶速率变慢，结晶度降低，结晶尺寸分布变宽，结晶完善性变差；（2）改善了共混体系的相容性。未增容体系的形态结构为锐型界面，分散相粒子同基材相连接处清晰缝隙表明两组分间界面粘接很差，为典型的不相容两相形态结构；而加入功能化接枝物的体系的分散相粒子明显变小且分布均匀，甚至难以分辨两相结构的界面；（3）提高了体系的力学性能。在多官能团单体存在下，辐照对PBTIHIPS产生影响。（1）对共混体系的熔融和结晶行为产生影响，使共混体系中的PBT的熔点降低，熔程变宽，结品度下降，结晶速率变慢，结晶尺寸分布变宽，结晶完善性变差；（2）辐射引发多官能团单体反应，使体系的两个Tg松弛发生内移，表明体系的相容性得到改善；（3）当PBT为连续相时，辐射引发的多官能团单体反应对体系的形态结构影响不如化学增溶剂HIPS-g-GMA的效果显著，含有TMPTA的体系的形态结构要好于TAIL o当PBT为分散相，体系的形态结构变化很大，分散相尺寸明显变下小，且分布均匀；（4）辐射改性能提高PBT为分散相的共混体系的力学性能。利用DSC研究了不同成核剂对生物降解聚合物PHBV的结晶性能的彩响。结果表明：（1)添加的成核剂均能影响PHBV的结晶和熔融行为，提高PHBV的结晶速率和使PHBV的结晶更加完美；（2）所有的成核剂均能降低PHBV的结晶自由能；（3）成核剂对PHBV的影响依次为BN, talc, Tb_2O_3和La_2O_3。

猕猴多潜能成体肝前体细胞及猕猴ES 定向分化为胆管上皮细胞的研究

为解决供体器官的不足，以细胞移植为基础的替代疗法已成为治疗不可逆肝 脏疾病新的希望。 肝前体（干）细胞（Hepatic progenitor cellS，HPCs）和 胚胎干细胞（embryoic stem cells, ES）由于其特殊的细胞特性已成为细胞替 代治疗理想的种源细胞。 然而一方面包括人在内的灵长类动物的正常成体肝来 源的HPCs 的分离依然是很困难的；另一方面，ES 细胞来源的肝细胞和胆管细胞 的生成效率依旧很低。因此有必要建立稳定的高效的灵长类动物HPCs 细胞分离 培养体系及ES 细胞的肝细胞或胆管细胞分化体系以满足供体细胞的不足；这种 体系的建立还有利于研究肝细胞生物学如分化机制、自我更新机制等方面的重要 基础问题。 本研究以猕猴为实验模型，研究了正常成体肝来源的猕猴HPCs 分离、纯化 的条件，系统地鉴定了猕猴HPCs 的细胞特性和体内、外分化潜能，并评价了体 内移植效果。 同时以rES 为材料，建立了rES 高效分化为限定性内胚层 （definitive endoderm cells, DE）和胆管上皮细胞的分化体系。主要实验结 果包括：1）： FBS、EGF、HGF 及rat tail collagen (鼠尾胶原)是分离培养正 常成体猕猴来源的肝上皮前体细胞(rhesus monkey liver epithelial progenitor cells, mLEPCs)所必需的，mLEPCs 在此培养体系中至少可以扩增20 代或5 个月以上，并仍然保持原有的细胞特性；mLEPCs 呈现典型的上皮细胞形 态，并表达HPCs 细胞特有的表达模式即同时表达肝细胞和胆管细胞相关基因 （ALB，APOH，CX43，IB4）或蛋白（CK7，CK8，CK18）；在适宜的分化体系下， mLEPCs 可分化为功能性的肝细胞，形成具有胆管上皮细胞的胆管样结构，并能 转分化形成肌肉样细胞、肌样成纤维细胞及少突样细胞；移植入肝损伤的免疫抑 制的小鼠体内后，mLEPCs 能参与受体肝组织的再生，并能分化成ALB 阳性的肝 细胞；体内定位发现mLEPCs 与胆管区的细胞有相似的免疫原性，提示mLEPCs 可能来源于胆管区。2）：rES 在高浓度的acitvin A（100ng/ml）和低浓度的血 清(1%)单层诱导体系下可定向分化得到高比率的限定性内胚层细胞（definitive endoderm cells，DE 细胞）(约80%)； 高比率的DE 细胞的得到还与rES 细胞的接种密度相关；BMP4 和FGF1 可诱导DE 细胞高效向胆管上皮细胞分化（约90%）， 但并不能得到肝细胞；而Notch 信号通路可维持DE 细胞的存活，并决定着DE 细胞向胆管细胞分化，在Notch 信号通路失活的情形下，即使存在BMP4 和FGF1 都不能促使DE 细胞向胆管细胞分化。 本实验首次成功建立了正常猕猴成体肝HPCs 分离培养体系，证实了分离得 到的猕猴肝上皮前体细胞不但具有正常HPCs 的增殖活力和参与受体肝组织的再 生能力，而且还具有三个胚层的分化潜能，这一结果将为以HPCs 为基础的细胞 替代治疗人类肝脏疾病的实现提供了可能，并首次证明了HPCs 也可以像某些少 数成体干细胞一样具有三个胚层得分化潜能。 此外，本研究建立了rES 高效定 向分化为DE 细胞和胆管细胞的分化体系，这一方法的建立将促进灵长类动物的 DE 细胞的发育机制研究，同时也可为高比率的内胚层功能细胞（如胰岛细胞、 肝细胞、肺细胞）的获得提供丰富的种源细胞和平台。

PHOTOEMISSION-STUDY ON THE SNO2/P A-SICX-H INTERFACE

Ultraviolet and X-ray photoemission spectroscopies (UPS and XPS) have been employed to SnO2 and its interface with P-type a-SiCx:H. The HeI valence band spectra of SnO2 show that the valence band maximum (VBM) shifts from 4.7 eV to 3.6 eV below the Fermi level (E(F)), and the valence band tail (VBT) extends up to the E(F), as a consequence of H-plasma treatments. The work function difference between SnO2 and P a-SiCx:H is found to decrease from 0.98 eV to 0.15 eV, owing to the increase of the work function of the treated SnO2. The reduction of SnO2 to metallic Sn is also observed by XPS profiling, and it is found that this leads to a wider interfacial region between the treated SnO2 and the successive growth of P a-SiCx:H.

METASTABLE DEFECT IN AMORPHOUS-SILICON SOLAR-CELLS INVESTIGATED BY JUNCTION RECOVERY TECHNIQUE

The effect of metastable defects caused by light soaking and carrier injection on the transport of carriers in undoped a-Si:H has been investigated by a junction recovery technique. The experiments show that after light soaking or carrier injection the product of mu-p-tau-p decreases, but no detectable change in the distribution of shallow valence band tail states was found.

PHOTOLUMINESCENCE OF ORDERED GA0.5IN0.5P GROWN BY METALORGANIC VAPOR-PHASE EPITAXY

Optical properties of ordered Ga0.5In0.5P epitaxial layers grown by metalorganic vapor phase epitaxy are investigated by photoluminescence (PL) in a temperature range of 10-200 K using excitation power densities between 0.35 W/cm(2) and 20 W/cm(2). It is found that the intensity of the highest-energy PL peak of the ordered Ga0.5In0.5P epilayer decreases first, then increases and finally goes down again with increasing temperature. A model of ordered Ga0.5In0.5P epitaxial layers is proposed, in which the ordered Ga0.5In0.5P epilayer is regarded as a type-II quantum well structure with band-tail states, and the dependence of PL spectra on the temperature and excitation intensity is reasonably explained. (C) 1995 American Institute of Physics.

棘蛙族(Tribe Paini)精子形态结构及精巢年周期研究

棘蛙族(Tribe Paini)隶两栖纲(Amphibia)、无尾目(Anura)、蛙科(Ranidae)、叉舌蛙亚科(Dicroglossinae)，由棘蛙属(Paa)、倭蛙属(Nanorana) 和沙巴蛙属(Chaparana)构成（Dubois,1992）。由于特殊的形态特征和染色体核型，棘蛙族受到国内外学者的广泛重视和研究，但是到目前为止，棘蛙族的系统发育关系尚未明晰，族下属种的分类和归属问题还有待进一步研究和新的证据出现。本文通过光学显微镜、电子显微镜和石蜡切片对棘蛙族10 物种的精子和精巢进行研究，旨在了解棘蛙族精子的形态、量度、超微结构特征及不同季节精巢结构的变化规律，同时为棘蛙族的系统研究提供新的依据，也为棘蛙族濒危物种的保护和经济物种的繁殖提供基础资料。研究结果表明：棘蛙族各属物种精子的形态基本相似，精子整体呈线形，由头部、中片和尾部构成。精子头部呈长条状，顶体呈锥状，位于头部顶端并向前伸出，中片较长，尾部波动弯曲。棘蛙族各属物种精子量度差异较大，将各属物种精子头部、中片、尾部、头宽、尾宽的量度数据进行聚类分析，结果表明棘蛙族10 物种可分为三类：第一类包括棘侧蛙、合江棘蛙、小棘蛙、棘腹蛙和棘胸蛙，特点是精子较短，全长在72.6～103.35µm 之间；第二类包括倭蛙、高山倭蛙、腹斑倭蛙，特点是精子较长，全长在107.74～129.75µm 之间；第三类包括隆肛蛙和双团棘胸蛙，特点是精子最长，全长在145.89～165.84µm 之间。棘蛙族各属精子超微结构基本相似：精子头部由顶体、细胞核构成；中片由中心粒、线粒体构成；尾部由单根轴丝构成。精子顶体横切呈圆环状，细胞核电子密度高；线粒体为卵圆形，呈环状围绕轴丝排列，线粒体数目较多，约30层；尾部轴丝为典型的9＋2结构，即由2根中央微管和9对外周微管组成。不同季节的倭蛙精巢结构变化表明倭蛙精巢每年只有一个生精周期，生精周期始于7 月，繁殖季节从5 月到6 月，生精高峰期为9 月；根据倭蛙不同季节精巢结构的变化，可将生精周期分为3 个阶段：第一阶段从7 月到9 月，为精子形成期；第二阶段从10 月到翌年4 月，为精子的贮存阶段，也即倭蛙的冬眠期；第三阶段从5 月到6 月，为精子的排放阶段，即倭蛙的繁殖期。不同季节的隆肛蛙精巢结构变化表明5 月为隆肛蛙的繁殖高峰期。根据棘蛙族各属精子的形态、量度和超微结构特征，结合已有的棘蛙族形态学、生态学、染色体核型及系统学研究成果，本文认为：1．基于精子数据对棘蛙族的划分和基于形态学及分子系统学数据对棘蛙族的划分均有相同之处，精子形态结构可为棘蛙族的系统研究提供新的证据。2． 棘蛙族各属精子的形态、量度及超微结构不仅与蛙科其他属种有明显差异，而且在无尾类中也较为特殊，精子学研究结果支持将棘蛙族从蛙科中分离出来，归隶于叉舌蛙科的叉舌蛙亚科的系统学修正。3. 精子的顶体、细胞核、中片的形态结构及量度可作为蛙科的分类指标。On the base of unique morphological and kyrotype characters, Dubois(1992)recognized three genera Paa, Narnorana, Chaparana as tribe Paini, which is amember of Dicroglossinae, Ranidae. In present study, the sperm shape, size andultrastructure of 10 paini species were investigated through the light and electronmicroscope, and testis structure of N. pleskei and F. quadrana was also studied. Wesuppose this study could offer some spermatological evidence to phylogeny andreproduction study of tribe Paini. The results were as follows:The sperm shape of tribe paini is homologically similar, the spermatozoa arefiliform, composed of elongate head, long mid-piece and waved tail. The acrosome isapically associated with the nucleus and extend anteriorly.The sperm length of tribe paini differ remarkably among genera. Cluster for thelength of sperm head, mid-piece, tail, total length, head-width, tail-width of ten painifrogs indicated the 10 species could be separated into three groups: GroupⅠcontainsP. shini, P. robertingeri, P. spinosa, P. exilispinosa, P. boulengeri, the spermatozoa ischaracterized with short in total length, ranging from 72.6µm to 103.35µm; GroupⅡcontains N. pleskei, N. parkeri, N. ventripunctata, the spermatozoa ischaracterized with relatively long in total length, ranging from 107.74µm to129.75µm; Group Ⅲ contains F. quadrana and P. yunnanensis, the spermatozoa is characterized with longest in total length, ranging from 145.89µm to 165.84µm. thethree groups based on spermatological data is partially match the classification basedon morphological and molecular data.The ultrastructure of spermatozoa in tribe paini is also basic similar, includingacrosome vescile, nuleus of the head proper, centriole, mitochondriol of themid-pieces, axoneme of the tail. The acrosome vescle is circle in TEM transversesection, the density of nucleus is high; The mitochondrions is oval, surrounding theaxial filament with about 30 layers of mitochondria; The axoneme has the typical 9+2pattern of microtubules.The seasonal changes in testis of N. pleskei indicates it has only onespermatogenesis circle, which begin in July, the reproduction season is from May toJune, the spermatogenesis is active in September. On the base of seasonal changes intestis, the spermatogenesis circle can be separated into three stages: In stageⅠfromJuly to September, spermatids are formed; In stage Ⅱ from October to April next year,the spermatozoa are stored in testis,which is the hibernated period; In stage Ⅲ fromMay to June, mature spermatozoa were released from the testis, which is thereproduction season of N. pleskei. As to F. quadrana, reproduction is active in May.With the previous study of morphology, ecology, karyotypes and phylogenyresearch of tribe Paini, the spermatological data in present study suggests:1. The spermatological classification of tribe paini is partially consistant with themorphological and molecular classification respectively.2.The sperm morphology and ultrustructure of tribe paini is unique not only inthe family Ranida but also in Anura, which suggest the tribe paini is monophyletic andmight be transfered from the family Ranida to the family Dicroglossidae based onmolecular evidence.3. The acrosome, nuleus, shape, length and ultrastructure of mid-piece can beused as an alternative taxonomic character in Anura.

角蟾科（Megophryidae; Anura）蝌蚪的形态多样性和生态适应

角蟾科（Megophryidae）是以角蟾属（Megophrys Kuhl and Van Hasselt, 1822）为模式属而建立的，隶于无尾目（Anura），变凹型亚目（Anomocoela）。角蟾科包括2 亚科11 属142 种，分布于东洋界，从巴基斯坦、中国西部向东直到菲律宾和苏达群岛；中国有9 属75 种分布于华中和华南地区。角蟾科被认为是原始的两栖动物之一，其分类学、系统学、生态学、动物地理学的研究均深受中外科学家的瞩目。近年来，通过形态学、古生物学、细胞学、生态学、支序系统学的研究，角蟾科的分类与系统学研究取得了较大进展。与成体形态和分子系统学研究结果相比较，蝌蚪的研究存在更多的问题和挑战，尚需深入研究：（1）角蟾科蝌蚪的形态多样性分析；（2）角蟾科的系统发育关系与蝌蚪的演化，以及口漏斗的起源；（3）角蟾科蝌蚪表型分化与栖息环境和觅食行为的适应演化。针对上述问题，本文对角蟾科9 属30 种蝌蚪的形态特征，包括外部宏观形态和口器外部结构特征、口器内部显微结构、唇齿和角质颌的亚显微结构作了深入细致、多层次的比较研究；通过12s rRNA 和cytochrome b 基因构建最大简约树，采用贝叶斯系统发育进行分析，蝌蚪型的演化采用祖先性状的重建方法分析；得到如下结论：1）初步将角蟾科蝌蚪分为4 种类型；并且建立了2 种新的角蟾科蝌蚪类型。A 型：拟髭蟾型蝌蚪，该型蝌蚪包括拟髭蟾属、髭蟾属、齿蟾属和齿突蟾属的物种；B 型：新类型，掌突蟾型蝌蚪，该型蝌蚪在本文中包括掌突蟾属、小臂蟾属的物种；C 型：新类型，短腿蟾型蝌蚪，一种特化类型，该型蝌蚪在本文中仅包括短腿蟾属的物种；D 型：角蟾型蝌蚪，该型蝌蚪在本文中包括无耳蟾属、小口拟角蟾属和异角蟾属的物种。2）对角蟾科的分类进行了修订：（1）支持角蟾科两个亚科的分类系统；（2）角蟾亚科包括拟角蟾属、异角蟾属、无耳蟾属和短腿蟾属；该亚科形态差异小，系统学关系比较复杂，暂不作族级分类的再划分；（3）拟髭蟾亚科分为2 个族：拟髭蟾族，该族物种具有类型A 的蝌蚪，包括4 个属：拟髭蟾属、髭蟾属、齿蟾属、齿突蟾属；掌突蟾族，该族物种具有类型B 的蝌蚪，包括2 个属：掌突蟾属和小臂蟾属。3）结合分子系统进化关系探讨了4 种蝌蚪类型的演化。（1）角蟾科蝌蚪的最近共同祖先来自于一类具有拟髭蟾型蝌蚪性状的蝌蚪；（2）掌突蟾型蝌蚪和角蟾亚科的蝌蚪是由具有拟髭蟾型蝌蚪性状的祖先蝌蚪分别演化而来；（3）短腿蟾型蝌蚪是角蟾型蝌蚪的一种特化类型；（4）外群蝌蚪具有与拟髭蟾型蝌蚪相似的性状，进一步印证了类拟髭蟾型蝌蚪是角蟾科蝌蚪的最近共同祖先的假说；（5）具有口漏斗的蝌蚪类型是由不具口漏斗的蝌蚪类型演化而来，在角蟾科中口漏斗是一种衍生性状。4）分析了角蟾科四种蝌蚪类型与栖息环境的适应演化。（1）角蟾科蝌蚪的口部和体形的变化反映了该科蝌蚪由缓流向类似静水生境的回水凼的渐变式适应，角蟾科蝌蚪的形态显示了多方面的适应变化；（2）随着蝌蚪类型由A 向D的演化，当水速较大时，拟髭蟾型的蝌蚪营流水攀吸型生活方式；当水速递减时，掌突蟾型蝌蚪营流水附着型生活方式；当水速进一步递减时，具有较小口漏斗的短腿蟾型蝌蚪和具有大漏斗的角蟾型蝌蚪营流水浮泳型生活。角蟾科蝌蚪对于水流递减的适应演化说明蝌蚪的生态学适应是具有进化意义的；（3）蝌蚪口器内部结构的分化揭示了蝌蚪和食性的适应关系，蝌蚪以口部的唇齿与角质颌刮取或吞吸水中的物质，然后，通过口乳突有选择地过滤进入口腔中食物。拟髭蟾亚科蝌蚪的唇齿多而窄，唇齿间距宽，颌鞘粗而稀，反映了其植食性为主的特点；它们的舌前乳突一般为指状，在口腔入口处所占面积小，其机械过滤的作用很多被唇齿和角质颌分担了；而角蟾亚科的蝌蚪，其角质颌弱，其舌前乳突一般为匙状，几乎填满了口腔入口处，因此舌前乳突起了主要的机械过滤作用。The family Megophryidae is the largest and most diverse families inArchaeobatrachia, and most of its species occur in India, Pakistan, and eastward intoChina, Southeast Asia, Borneo and the Philippines to the Sunda Islands. Currently thefamily includes 142 species have been grouped into two subfamilies, Megophryinaeand Leptobrachiinae. The mountains of central and southern China are rich in speciesof Megophryidae, 75 species belong to 9 genera and two subfamilies.The family was supposed to be ideal materials of studies in many fields of biology,such as taxonomy, evolution, systematics, ecology, and biogeography. Recently, therehave a great development in taxonomy and systematics of megophryids throughstudied by morphology, paleontology, cytology, ecology, and cladistics. However,larvae of megophryids were generally unknown, although the tadpoles might be veryimportant for above studies.In this paper, we examined the evolutionary scenario of the tadpoles’ morphologyin the context of a phylogenetic framework. Our objectives are (1) to evaluate thedivergence of larval body shape and oral discs in the family Megophryidae, (2) toexplore the evolutionary trends of the larvae in megophryidae, and test if thefunnel-shaped oral disc is apomorphic, and (3) to explore the relationship of the larvalstructure, diet and microhabitat.We examined larval morphology of 30 megophryid species, the larval body shape,oral discs, the buccopharyngeal cavity, and jaw sheaths and denticles of the Chinesemegophryid frogs were re-examined. We constructed a phylogeny of the species on thebasis of published mitochondrial cytochrome b and 16S rRNA gene segments usingpartitioned Bayesian analyses. Furthermore, hypothetical changes of larval morphologywere inferred using parsimony principle on the phylogeny. The results showed that:1) Four tadpole types in Megophryidae. The larval morphological charactersseries in Chinese megophryids fall into four general categories according to the bodyshape and oral discs: (A) Leptobrachiini type, species from genera Leptobrachium,Oreolalax, Scutiger and, Vibrissaphora share this type of tadpoles. (B) Leptolalax type,species of genus Leptolalax have this type of tadpoles. (C) Brachytarsophrys type,species of the genus Brachytarsophrys have this type of tadpoles. (D) Megophryinitype, species of the genera Atympanophrys, Ophryophryne, and Xenophrys share this type of tadpoles. Of which B and C are two novel types.2）Taxonomic implications. The present study leads us to reconsider the generalclassification of tribes attributed to members of Megophryidae. More specifically,concerning the phylogenetic relationships and the two novel tadpole types describedherein, we propose a provisional taxonomy for the family but suggest that further taxasampling of other megophryids be performed to confirm this taxonomic change. TheMegophryidae is composed of two subfamilies (Leptobrachiinae and Megophryinae).The Leptobrachiinae was recogonized the two tribes: (1) tribe Leptobrachiini sensuDubois, corresponding to the tadpole of type A, including four genera, i.e.,Leptobrachium, Oreolalax, Scutiger and, Vibrissaphora; (2) tribe Leptolalaxini,corresponding to the tadpole of novel type B, including two genera, i.e., Leptolalaxand Leptobrachella. However, the relationships among the genera of Megophryinaewere largely unresolved, they recognized no monophyletic groups above the generalevel. A more thorough sampling will likely foster a better taxonomic solution.3) The larval evolutionary scenario in Megophryidae.Type A is characteristicof normal-mouthed with multiple tooth rows, representing the tadpole type of theMRCA of Chinese megophryids. Type B is characteristic of normal-mouthed withreduced tooth rows, prolonging labium, and integumetary glands. Type C ischaracteristic of no labial teeth and smaller umbeliform oral disc. Type D ischaracteristic of no labial teeth, enlarged umbeliform oral disc, representing the tadpoleof the MRCA of subfamily Megophryinae. A previous hypothesis, referring tofunnel-shaped oral discs as an apomorphy, is supported.4) The larval adaptation to habitats in Megophryidae. Tadpoles generallyadhere to substrates using their mouths, and the microhabitat that the tadpoles occupyreflects the degree of adhesion and oral complexity. The morphological changes inmegophryid tadpoles virtually allow a progressive adaptation to a changing habitatfrom faster water to slower water. Within the tadpoles of Type A to type D, the TOTbecomes smaller and smaller, and the oral disc orientates from anteroventral toumbelliform upturned, and eye position orientates from dorsal to lateral, and the trunkis more and more depressed and tail becomes relatively longer and slender. Within therunning water, the normal-mouthed with multiple tooth rows of Leptobrachiini tadpoles are correlated with lotic-suctorial, benthic feeders with anteroventral oraldisc and the largest body. With the water’s velocity decreasing, the lotic-adherentfeeders of Leptolalax tadpoles have tube-shaped labium with reduced tooth rows andintegumetary glands. And then, the smaller umbeliform in Brachytarsophrys tadpolesand the enlarged umbeliform oral disc in the Megophryini tadpoles are inhabitmicrohabitats of non-flowing backwaters of rivers, indicative of adaptive traits oflotic-neustonic surface feeders. The scheme of megophryid tadpoles andmicrohabitats provided the first clear evidence which congruent with the hypothesis ofAltig and Johnston (1989). The ecological divergence plays a general role in thedivergence and evolution of megophrid larvae. There is a definite correlation amongthe buccopharyngeal cavity, diet and feeding mechanisms, the tadpole graze orswallow the food particles, then through papillae which like a sieve and sort out foodparticles to the oesophagus. The tadpole of Leptobrachiinae possess multiple toothrows, wide intertooth distance as well as thick and sparse jaw sheath, these tadpolesinhabit bottom of the streams and graze on epiphyton or major detritus of organicmatter on the substrates, their prelingual papillae like single finger, the mechanicalpurpose of papillae served share in by tooth and jaw. The tadpoles of Megophryinaeoccur near the water surface of small streams and are the filter feeder, their dietincludes plankton and organic debris floating on the water surface, those tadpolepossess weak jaw, their prelingual papillae like spoon, the mechanical purpose ofpapillae served mostly for sieve.