川东獐牙菜(龙胆科)的胚胎学研究

利用石蜡切片技术,对川东獐牙菜(Swertia davidii)的胚胎发育过程进行显微观察,并根据现有资料,对獐牙菜属的几种植物进行了比较胚胎学研究。结果表明:川东獐牙菜花药四室,药壁发育为基本型,绒毡层异型起源,为腺质绒毡层,发育后期药室内观察到的绒毡层核是早期该层细胞有丝分裂凸入药室并原位退化形成的,中层细胞3层,药室内壁退化,花药壁表皮宿存,细胞柱状伸长,纤维状加厚;小孢母细胞减数分裂为同时型,四分体排列方式主要为四面体形和左右对称型,少数为"T"形和十字交叉形,成熟花粉为2-细胞类型;子房2心皮、1室,侧膜胎座;薄珠心,单珠被,倒弯生胚珠,大孢子母细胞减数分裂形成4个大孢子直线形排列,合点端的大孢子具功能,雄配子体发育为蓼型;2个极核在受精前融合为1次生核,合点端3个反足细胞宿存,每个细胞均多核和异常膨大,形成明显的反足吸器,并在胚乳之外形成染色较深的类似"外胚乳"结构;珠孔受精,受精作用属于有丝分裂前类型;胚乳发育为核型,胚胎发育为茄型;果实成熟时,种子发育至心形胚阶段;反足细胞在龙胆科一些短命植物中的宿存与分裂具有重要的生殖适应与进化意义。     

獐牙菜的胚胎发生

对獐牙菜大孢子发生、雌配子体形成、受精、胚及胚乳发育过程进行了研究。主要结果如下：子房2心皮,1室,4列胚珠,侧膜胎座;薄珠心,单珠被,倒弯生胚珠。大孢子母细胞减数分裂形成4个大孢子直线形排列,合点端的大孢子具功能,胚囊发育为蓼型。3个反足细胞宿存,每个细胞均多核和异常膨大,反足吸器明显,并在胚乳之外形成染色较深的类似“外胚乳”的结构。珠孔受精,受精作用属于有丝分裂前类型。胚乳发育为核型;胚胎发育为茄型。果实成熟时,种子发育至球形胚阶段。反足细胞在龙胆科一些短命植物中的宿存与分裂具有重要的生殖适应与进化意义。     

喉毛花的胚胎学研究

本文首次系统地记载了喉毛花属的胚胎发育过程,并以此为依据讨论了该属的分类等级和系统位置。喉毛花花药四室;药壁发育属双子叶型;绒毡层单型起源,细胞具单核,属腺质绒毡层;一层中层细胞;花药壁表皮层宿存,纤维状加厚和膨大;药室内壁减缩。小孢子母细胞减数分裂为同时型,四分体的排列为四面体型;成熟花粉为3-细胞型。子房为2心皮、l室,典型的侧膜胎座,胚珠8列,胚珠胎座靠近两心皮腹缝线。薄珠心,单珠被,倒生胚珠。大孢子母细胞减数分裂形成的4个大孢子呈直列式排列,其中合点端的大孢子具功能。胚囊发育为蓼型。极核在受精前融合为次生核。反足细胞宿存、分裂为8～12个,每个细胞均多核和异常膨大,反足细胞形成的吸器明显。异花传粉,珠孔受精。花粉管通过破坏一助细胞进入胚囊。受精作用属于有丝分裂前配子体融合类型。胚乳发育为核型,每核含2～3核仁。胚胎发育为茄型酸浆I变型,成熟种子胚只发育至球形胚阶段。反足细胞在合子分裂之后才开始退化,在胚的发育过程中反足细胞在胚乳层之外形成一层染色深、类似“外胚乳”的结构。比较喉毛花、龙胆属、假龙胆属以及肋柱花属的胚胎学特征表明喉毛花与假龙胆属的亲缘关系最近,在分类等级上作为一个独立的属较为合适,在系统位置上它比假龙胆属更为原始。     

小蓬草的胚胎学研究

对小蓬草（Conyzacanadensis）大小孢子发生、雌雄配子体形成、受精、胚及胚乳发育过程进行了研究,主要结果如下：花药四室,药壁由表皮、药室内壁、中层和绒毡层组成。表皮退化;药室内壁宿存,细胞柱状伸长,纤维状加厚;中层细胞退化较早,在小孢子母细胞减数分裂开始时仅存残迹;绒毡层于小孢子母细胞减数第一次分裂前期开始原位变形退化,属于腺质型绒毡层;小孢子母细胞减数分裂为同时型,四分体的排列方式主要为四面体形和左右对称形;成熟花粉粒多为3-细胞花粉粒,偶见2-细胞花粉粒。子房下位,2心皮,1室,单胚珠,基生胎座;单珠被,薄珠心,倒生胚珠,具发达的珠被绒毡层。珠心表皮下分化出大孢子孢原细胞,孢原细胞直接发育为大孢子母细胞,大孢子母细胞减数分裂形成4个大孢子直线形排列,仅合点端的大孢子发育成功能大孢子母细胞,胚囊发育为蓼型。两个极核在受精前融合为次生核,珠孔受精。胚乳发育属于核型,胚胎发育为紫菀型;具胚乳吸器。     

高山红景天胚胎学研究

高山红景天(Rhodiola sachalinensis A.Bor.)具8个雄蕊,每个雄蕊有4个花粉囊。小孢子母细胞减数分裂时,胞质分裂为同时型。形成的四分体为四面体形。花药壁由表皮、药室内壁、二层中层和绒毡层五层细胞组成,其发育方式为基本型。腺质型绒毡层,有些绒毡层细胞分裂形成不规则双层,少数细胞双核。二细胞型花粉。雌蕊由4心皮组成。边缘胎座,倒生胚珠,双珠被,厚珠心,胚珠发育中形成珠心喙。大孢子四分体线形或T -形,合点大孢子具功能。胚囊发育为蓼型。成熟胚囊中,卵细胞核、助细胞核均位于细胞的合点端,珠孔端具液泡;极核融合为次生核,并位于卵细胞合点端附近; 3个反足细胞退化。双受精属于有丝分裂前配子融合类型。胚的发育为石竹型;基细胞侵入珠孔端,形成囊状吸器。细胞型胚乳;初生胚乳核分裂形成两个细胞,其珠孔端的细胞发育成胚乳本体,合点端的细胞直接发育成具一单核的合点吸器。     

小蓬草的胚胎学研究

对小蓬草(Conyza canadensis)大小孢子发生、雌雄配子体形成、受精、胚及胚乳发育过程进行了研究,主要结果如下:花药四室,药壁由表皮、药室内壁、中层和绒毡层组成.表皮退化;药室内壁宿存,细胞柱状伸长,纤维状加厚;中层细胞退化较早,在小孢子母细胞减数分裂开始时仅存残迹;绒毡层于小孢子母细胞减数第一次分裂前期开始原位变形退化,属于腺质型绒毡层;小孢子母细胞减数分裂为同时型,四分体的排列方式主要为四面体形和左右对称形;成熟花粉粒多为3细-胞花粉粒,偶见2细-胞花粉粒.子房下位,2心皮,1室,单胚珠,基生胎座;单珠被,薄珠心,倒生胚珠,具发达的珠被绒毡层.珠心表皮下分化出大孢子孢原细胞,孢原细胞直接发育为大孢子母细胞,大孢子母细胞减数分裂形成4个大孢子直线形排列,仅合点端的大孢子发育成功能大孢子母细胞,胚囊发育为蓼型.两个极核在受精前融合为次生核,珠孔受精.胚乳发育属于核型,胚胎发育为紫菀型;具胚乳吸器.     

湖北双蝴蝶的胚胎发生

对湖北双蝴蝶大孢子发生、雌配子体形成、受精、胚及胚乳发育过程进行了解剖学观察研究.结果显示:(1)子房2心皮,1室-侧膜胎座,薄珠心,单珠被,倒生胚珠,胚珠列数为4列;大孢子母细胞减数分裂形成的4个大孢子多呈直线形排列,少数为"T"形四分体,合点端的大孢子具功能;胚囊发育为蓼型;3个反足细胞宿存至8-细胞原胚.(2)珠孔受精;胚乳发育为核型;胚发育为茄型.(3)果实成熟时,种子发育至球形胚阶段.     

红直獐牙菜的胚胎学

首次报道了红直獐牙菜大小孢子发生,雌雄配子体形成和胚胎发育过程。主要结果如下：花药四室,药壁发育为双子叶型,绒毡层异型起源,接近腺质绒毡层,中层３层,花药壁表皮宿存,细胞柱状伸长,纤维状加厚,药室内壁退化,小孢子母细胞减数分裂为同时型,四分体的排列方式为四面体形;成熟花粉为３－细胞;子房２心皮,１室,１２列胚珠,侧膜胎座,薄珠心,单珠被,倒生胚珠,蓼型胚囊,反足细胞３个,宿存时间短,胚乳发育为核型     

黄檗的胚胎学研究

黄檗(PhellodendronamurenseRupr.)为雌雄异株植物,雌花中有退化的雄蕊原基,雄花中有退化的心皮。黄檗花药壁发育为基本型。腺质绒毡层,细胞双核或多核。小孢子母细胞减数分裂为同时型。小孢子四分体为四面体型排列,成熟花粉有2-细胞和3-细胞型2种。子房5室,中轴胎座、倒生胚珠、具珠柄珠孔塞、双珠被、厚珠心和多孢原细胞。大孢子四分体为直线型、少数为“T”型排列,合点端的一个为功能性大孢子。蓼型胚囊,双受精属于有丝分裂前配子融合类型。胚的发育为藜型,核型胚乳。后期胚乳组织外层形成“次生胚乳”,原胚乳细胞逐渐退化解体。     

南方山荷叶大、小孢子发生与雌、雄配子体发育

首次报道了南方山荷叶大、小孢子发生和雌、雄配子体形成。主要结果如下:花药4室,花药壁发育为基本型,由7层细胞组成,由外到内依次为表皮、药室内壁、3层中层和2层绒毡层;药室内壁有带状加厚现象,绒毡层细胞多具双核,为腺质型绒毡层;多孢原,发生于表皮下;小孢子母细胞减数分裂为同时型,小孢子四分体多为四面体型,少数为十字交叉形、直线形、左右对称形或"T"形;成熟花粉粒为2-细胞型,偶见3-细胞型;成熟花粉粒呈圆形,具单萌发孔。雌蕊1枚,子房单心皮,纵切面呈瓶状;1室,边缘胎座,具4～5枚发育不同步的横生胚珠。胚珠具双珠被,厚珠心;珠孔由两层珠被共同形成,在一直线上或呈"之"字形。多孢原,位于珠心表皮下。直线形四分体,合点端的1个大孢子发育为功能大孢子,胚囊发育为蓼型。成熟胚囊中,3个反足细胞大而明显,但宿存时间短,较早退化。     

Phylogeny of cardinalfishes (Teleostei: Gobiiformes: Apogonidae) and the evolution of visceral bioluminescence

The cardinalfishes (Apogonidae) are a diverse clade of small, mostly reef-dwelling fishes, for which a variety of morphological data have not yielded a consistent phylogeny. We use DNA sequence to hypothesize phylogenetic relationships within Apogonidae and among apogonids and other acanthomorph families, to examine patterns of evolution including the distribution of a visceral bioluminescence system. In conformance with previous studies, Apogonidae is placed in a clade with Pempheridae, Kurtidae, Leiognathidae, and Gobioidei. The apogonid genus Pseudamia is recovered outside the remainder of the family, not as sister to the superficially similar genus Gymnapogon. Species sampled from the Caribbean and Western Atlantic (Phaeoptyx, Astrapogon, and some Apogon species) form a clade, as do the larger-bodied Glossamia and Cheilodipterus. Incidence of visceral bioluminescence is found scattered throughout the phylogeny, independently for each group in which it is present. Examination of the fine structure of the visceral bioluminescence system through histology shows that light organs exhibit a range of morphologies, with some composed of complex masses of tubules (Siphamia, Pempheris, Parapriacanthus) and others lacking tubules but containing chambers formed by folds of the visceral epithelium (Acropoma, Archamia, Jaydia, and Rhabdamia). Light organs in Siphamia, Acropoma, Pempheris and Parapriacanthus are distinct from but connected to the gut; those in Archamia, Jaydia, and Rhabdamia are simply portions of the intestinal tract, and are little differentiated from the surrounding tissues. The presence or absence of symbiotic luminescent bacteria does not correlate with light organ structure; the tubular light organs of Siphamia and chambered tubes of Acropoma house bacteria, those in Pempheridae and the other Apogonidae do not.     

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

Scirtothrips perseae Nakahara was discovered attacking avocados in California, USA, in 1996. Host plant surveys in California indicated that S. perseae has a highly restricted host range with larvae being found only on avocados, while adults were collected from 11 different plant species. As part of a management program for this pest, a “classical” biological control program was initiated and foreign exploration was conducted to delineate the home range of S. perseae, to survey for associated natural enemies and inventory other species of phytophagous thrips on avocados grown in Mexico, Guatemala, Costa Rica, the Dominican Republic, Trinidad, and Brazil. Foreign exploration efforts indicate that S. perseae occurs on avocados grown at high altitudes (>1500 m) from Uruapan in Mexico south to areas around Guatemala City in Guatemala. In Costa Rica, S. perseae is replaced by an undescribed congener as the dominant phytophagous thrips on avocados grown at high altitudes (>1300 m). No species of Scirtothrips were found on avocados in the Dominican Republic, Trinidad, or Brazil. In total, 2136 phytophagous thrips were collected and identified, representing over 47 identified species from at least 19 genera. The significance of these species records is discussed. Of collected material 4% were potential thrips biological control agents. Natural enemies were dominated by six genera of predatory thrips (Aeolothrips, Aleurodothrips, Franklinothrips, Leptothrips, Scolothrips, and Karnyothrips). One genus each of parasitoid (Ceranisus) and predatory mite (Balaustium) were found. Based on the results of our sampling techniques, prospects for the importation of thrips natural enemies for use in a “classical” biological control program in California against S. perseae are not promising.     

Molecular phylogeny of Phebalium (Rutaceae: Boronieae) and related genera based on the nrDNA regions ITS 1+2

Parsimony analyses of the internal transcribed spacer regions of nuclear ribosomal DNA (ITS 1 & ITS 2) for 38 taxa sampled from the Phebalium group (Rutaceae: Boronieae) and two outgroups confirm that, with the exception of Phebalium sensu stricto and Rhadinothamnus, six of the currently recognised genera within the group are monophyletic. The data indicate that Phebaliums. str. is paraphyletic with respect to Microcybe, and Rhadinothamnus is paraphyletic with respect to Chorilaena. Rhadinothamnus and Chorilaena together are the sister group to Nematolepis. Drummondita, included as an outgroup taxon, clustered within the ingroup as sister to Muiriantha and related to Asterolasia.The phylogeny suggests that the evolution of major clades within a number of these genera (e.g. Phebalium) relates to vicariance events between eastern and south-western Australia. Leionema is an eastern genus, with the most basal taxon being the morphologically distinct Leionema ellipticum from northern Queensland. Leionema also includes one species from New Zealand, but this species (as with some others) proved difficult to sequence and its phylogenetic position remains unknown. Taxonomic changes at the generic level are recommended.The authors wish to thank Paul G.Wilson, PERTH, for advice and discussion, and Paul Forster, BRI, for collecting and providing material of Leionema ellipticum. The project was supported by a Melbourne University Postgraduate Award (to BM), the Australian Biological Resources Study (ABRS), Australian Systematic Botany Society and Wolf Den (Australia) Investments.     

Molecular identification of Taenia spp. in wolves (Canis lupus), brown bears (Ursus arctos) and cervids from North Europe and Alaska

Taenia tapeworms of Finnish and Swedish wolves (Canis lupus) and Finnish brown bears (Ursus arctos), and muscle cysticerci of Svalbard reindeer (Rangifer tarandus platyrhynchus), Alaskan Grant's caribou (Rangifer tarandus granti) and Alaskan moose (Alces americanus) were identified on the basis of the nucleotide sequence of a 396 bp region of the mitochondrial cytochrome c oxidase subunit 1 gene. Two species were found from wolves: Taenia hydatigena and Taenia krabbei. The cysticerci of reindeer, caribou and one moose also represented T. krabbei. Most of the cysticercal specimens from Alaskan moose, however, belonged to an unknown T. krabbei-like species, which had been reported previously from Eurasian elks (Alces alces) from Finland. Strobilate stages from two bears belonged to this species as well. The present results suggest that this novel Taenia sp. has a Holarctic distribution and uses Alces spp. as intermediate and ursids as final hosts.     

Planting densities and bird and rodent absence affect size distributions of four dicots in synthetic tallgrass communities

Variability in the size distributions of populations is usually studied in monocultures or in mixed plantings of two species. Variability of size distributions of populations in more complex communities has been neglected. The effects of seeding density (35 or 350 seeds/species/m²) and presence of small vertebrates on the variability of size distributions were studied for a total of 1,920 individuals of 4 species in replicated synthetic communities of 18 species in northern Illinois. End-of season height and above-ground biomass were measured for prairie perennials Dalea purpurea (purple prairie clover), Echinacea purpurea (purple coneflower), Desmanthus illinoensis (Illinois bundleflower) and Heliopsis helianthoides (early sunflower). Variability in biomass distribution of the four target species was twice as great at low than at high densities when small vertebrates were excluded. Our results suggest that inter- and intraspecific competition may affect all individuals more under high-density conditions, thereby reducing the variability in their biomass distributions within this community. This result, a consequence of plant-plant interaction, is obscured when small birds or mammals are present, presumably because either or both add variance that overwhelms the pattern.     

Phylogeny and Megasystematics of Phagotrophic Heterokonts (Kingdom Chromista)

Heterokonts are evolutionarily important as the most nutritionally diverse eukaryote supergroup and the most species-rich branch of the eukaryotic kingdom Chromista. Ancestrally photosynthetic/phagotrophic algae (mixotrophs), they include several ecologically important purely heterotrophic lineages, all grossly understudied phylogenetically and of uncertain relationships. We sequenced 18S rRNA genes from 14 phagotrophic non-photosynthetic heterokonts and a probable Ochromonas, performed phylogenetic analysis of 210–430 Heterokonta, and revised higher classification of Heterokonta and its three phyla: the predominantly photosynthetic Ochrophyta; the non-photosynthetic Pseudofungi; and Bigyra (now comprising subphyla Opalozoa, Bicoecia, Sagenista). The deepest heterokont divergence is apparently between Bigyra, as revised here, and Ochrophyta/Pseudofungi. We found a third universal heterokont signature sequence, and deduce three independent losses of ciliary hairs, several of 1-2 cilia, 10 of photosynthesis, but perhaps only two plastid losses. In Ochrophyta, heterotrophic Oikomonas is sister to the photosynthetic Chrysamoeba, whilst the abundant freshwater predator Spumella is biphyletic; neither clade is specifically related to Paraphysomonas, indicating four losses of photosynthesis by chrysomonads. Sister to Chrysomonadea (Chrysophyceae) is Picophagea cl. nov. (Picophagus, Chlamydomyxa). The diatom-parasite Pirsonia belongs in Pseudofungi. Heliozoan-like actinophryids (e.g. Actinosphaerium) are Opalozoa, not related to pedinellids within Hypogyristea cl. nov. of Ochrophyta as once thought. The zooflagellate class Bicoecea (perhaps the ancestral phenotype of Bigyra) is unexpectedly diverse and a major focus of our study. We describe four new biciliate bicoecean genera and five new species: Nerada mexicana, Labromonas fenchelii (=Pseudobodo tremulans sensu Fenchel), Boroka karpovii (=P. tremulans sensu Karpov), Anoeca atlantica and Cafeteria mylnikovii; several cultures were previously misidentified as Pseudobodo tremulans. Nerada and the uniciliate Paramonas are related to Siluania and Adriamonas; this clade (Pseudodendromonadales emend.) is probably sister to Bicosoeca. Genetically diverse Caecitellus is probably related to Anoeca, Symbiomonas and Cafeteria (collectively Anoecales emend.). Boroka is sister to Pseudodendromonadales/Bicoecales/Anoecales. Placidiales are probably divergent bicoeceans (the GenBank Placidia sequence is a basidiomycete/heterokont chimaera). Two GenBank ‘opalinid’ sequences are fungal; Pseudopirsonia is cercozoan; two previous GenBank ‘Caecitellus’ sequences are Adriamonas. Electronic Supplementary Material Electronic Supplementary material is available for this article at and accessible for authorised users. [Reviewing Editior: Patnck J. Keeling]     

Seven new calochroid and fulvoid species of Cortinarius

We describe seven new European species of Cortinarius. All species are based on analyses of morphological and DNA sequence data. They all belong to a well-supported clade comprising most species traditionally treated in Cortinarius subgenus Phlegmacium sections Fulvi and Calochroi (i.e. the/Calochroi clade). All taxa are either fulvoid (containing anthraquinoid pigments) or calochroid (without these pigments). Morphological and ecological data are presented for all species and compared with similar species. A dichotomous key is presented for C. calochrous and similar species, including all six newly described calochroid species. The calochroid species C. albertii, C. chailluzii, C. cisticola, C. sancti-felicis, C. selandicus and C. vesterholtii spp. nov., and the fulvoid species C. langeorum sp. nov. are described.     

New geographical distribution and host records of rust fungi from northern Thailand

Ten species of rust fungi (Crossopsora 2, Maravalia 1, Pileolaria 1, Puccinia 1, Ravenelia 1, Sphaerophragmium 1, Uredo 2, and Uromyces 1) are newly recorded together with six new host plants in Thailand.Contribution no. 194, Laboratory of Plant Parasitic Mycology, Graduate School of Life and Environmental Sciences, University of Tsukuba, Japan     

The hernandez and fernandez genes of Drosophila specify eye and antenna

The formation of different structures in Drosophila depends on the combined activities of selector genes and signaling pathways. For instance, the antenna requires the selector gene homothorax, which distinguishes between the leg and the antenna and can specify distal antenna if expressed ectopically. Similarly, the eye is formed by a group of "eye-specifying" genes, among them eyeless, which can direct eye development ectopically. We report here the characterization of the hernandez and fernandez genes, expressed in the antennal and eye primordia of the eye-antenna imaginal disc. The predicted proteins encoded by these two genes have 27% common amino acids and include a Pipsqueak domain. Reduced expression of either hernandez or fernandez mildly affects antenna and eye development, while the inactivation of both genes partially transforms distal antenna into leg. Ectopic expression of either of the two genes results in two different phenotypes: it can form distal antenna, activating genes like homothorax, spineless, and spalt, and it can promote eye development and activates eyeless. Reciprocally, eyeless can induce hernandez and fernandez expression, and homothorax and spineless can activate both hernandez and fernandez when ectopically expressed. The formation of eye by these genes seems to require Notch signaling, since the induction of ectopic eyes and the activation of eyeless by the hernandez gene are suppressed when the Notch function is compromised. Our results show that the hernandez and fernandez genes are required for antennal and eye development and are also able to specify eye or antenna ectopically.