Observations on the peristome and systematic position of Tetrastichium fontanum (Musci)

Abstract

The peristome of the monotypic hookeriaceous genus Tetrastichium is described from a specimen of T. fontanum from La Palma (Canary Is.). The peristome is similar to that of two other members of the family, Rhynchostegiopsis and Leucomium. The precise systematic position of the species is discussed and it is maintained, pending further evaluation of the structure of the peristome, near Hookeria.     

藓类蒴齿的发育、结构与功能研究进展

藓类的蒴齿生于藓类植物孢蒴口部,由蒴周层3层细胞或细胞壁发育而成,结构较为复杂。其主要功能是主导和保护藓类孢子的散发,同时也是分类和判定藓类系统发育地位的一个重要依据。藓类蒴齿的结构多样性、功能多样性和分子生物学层面的研究目前在国内还较薄弱。该文对近年来国内外有关藓类蒴齿的发育、结构和功能的相关研究进展进行了综述。     

贵州喀斯特高原金发藓原变种(Polytrichum commune Hedw.var.commune)蒴齿水湿运动研究

为探究线齿藓类植物在水湿运动中蒴齿结构的变化及对孢子散发的影响,选取贵州喀斯特高原金发藓原变种(Polytrichum commune Hedw.var.commune)为研究对象,通过观察湿度变化下蒴齿结构差异及孢子释放规律,拟揭示水湿运动对孢子释放的影响和功能。结果显示:①湿度增加引起蒴齿间距及盖膜面积的显著增大,并在干燥时恢复。其中齿间距从8.33μm显著增加到11.53μm,同时盖膜面积扩大20%。②在连续风吹试验中,水湿运动初期孢子释放量显著提高,随蒴齿结构的恢复呈下降趋势,并最终保持在极低的孢子释放数量。同时发现,湿度增加导致孢子释放中簇孢占比的提高,并随孢子释放量的减少呈上升趋势,并在蒴齿结构恢复时达到显著差异。③通过单独对干燥期、水湿运动初期及蒴齿结构恢复期进行风吹试验发现,水湿运动初期孢子释放量显著高于干燥期和蒴齿结构再恢复期。当蒴齿结构恢复时,由于簇孢占比的提高,孢子的释放数量仍能显著高于干燥期。本研究表明在水湿运动中金发藓原变种蒴齿结构发生改变,进而显著提高孢子的释放量,并在蒴齿结构恢复时仍能保持高于干燥时的孢子释放能力,这对该物种的传播及繁衍具有积极的意义。     

喀斯特天坑内孔雀藓属蒴齿亚显微结构研究

喀斯特天坑微环境对植物结构特征有显著的影响。采用扫描电子显微镜，探究孔雀藓属蒴齿在喀斯特天坑内的亚显微结构，旨在为微环境下藓类植物蒴齿结构特征研究提供参考。研究结果表明：①基于蒴齿的亚显微形态研究，孔雀藓属两个种，即黄边孔雀藓（Hypopterygium flavo-limbatum C.Muell）、东亚孔雀藓（Hypopterygium japonicum Mitt）蒴齿双齿层，内外齿层数均为16枚，外齿层背面均具"Z"字形的中脊，齿片形态、曲向、外齿层背侧脊纹、齿条腹侧横纹以及是否具节瘤具有明显的差异，属于稳定性特征，可作为系统分类的依据；而齿片长度、宽度、节片数、横脊数、中脊数，属于可变性特征，受环境因子的影响，在运用藓类植物蒴齿作为系统分类依据时应作性状的筛选。②光照度、空气温度、空气湿度以及海拔是影响天坑内黄边孔雀藓（H.flavo-limbatum）蒴齿形态结构发育生长的主要环境因子，空气湿度、光照度以及人为干扰度是影响天坑内东亚孔雀藓（H.japonicum）蒴齿形态结构发育生长的主要环境因子。两种孔雀藓属植物蒴齿结构受湿度的影响最大，其生境多为湿度大、土壤含水量丰富的环境。     

Floristic study of <Emphasis Type="Italic">Geastrum</Emphasis> in Japan: three new records for Japanese mycobiota and reexamination of the authentic specimen of <Emphasis Type="Italic">Geastrum minus</Emphasis> reported by Sanshi Imai

Geastrum berkeleyi, G. fornicatum, and G. minimum are newly recorded from Japan. A peristome of G. fornicatum has hitherto been described as indistinct, whereas the Japanese specimens have a well-delimited, fibrillose peristome. Geastrum minus, reported for the first time from Japan by Sanshi Imai, represents G. quadrifidum. Macroscopic and microscopic features of those four taxa are described and illustrated based on Japanese specimens.     

Correlation of Ciliary and Nuclear Development in the Life Cycle of Euplotes

SYNOPSIS. Kinetosomal changes, as indicative of cytoplasmic reorganization in binary fission and during and after conjugation, were followed in a zoochlorellae-bearing species of Euplotes. The preconjugant peristome, designated the first generation peristome, breaks down partially after the conjugants have paired; the basal section, comprising the shorter adoral membranelles and the undulating, membrane, is resorbed. A new peristome, the second generation peristome, arises as a small pit near the left ventral margin, in midline, at the time when the micronuclei are in the first meiotic prophase. By the time of the second meiotic division a single set of new cirri, the second generation cirri, has formed in each conjugant. This second set is not perfect, lacking one of the frontals. Neither the second generation peristome nor cirri develop very far, or migrate, until after separation of the conjugants. Then the new peristome replaces the old one and the new cirri become functional. However, the new peristome lacks an undulating membrane and does not complete its development, bearing only a fraction of the normal number of membranelles. At its posterior termination, at the time of condensation of the macronuclear anlage, another peristome, the third generation peristome, is formed and develops as a granular, and later striated, invagination extending posteriorly. It appears to integrate with its predecessor and, as its constituent membranelles develop, a third generation single set of new cirri arises. These replace the imperfect previous set, all of the cirri being represented. In anticipation of the first postconjugant fission, all of the cirral apparatus is discarded again and two new sets (fourth generation cirri) originate; the old (combination second and third generation) peristome is retained by the proter while a new one is provided for the opisthe. It is evident, therefore, that a rather far-reaching cytoplasmic reorganization accompanies the nuclear changes of conjugation, seeming, for the most part, to follow the nuclear changes. The old macronuclear fragments have been found not to fuse with the macronuclear anlage.     

PERISTOME DEVELOPMENT IN MOSSES IN RELATION TO SYSTEMATICS AND EVOLUTION. II. TETRAPHIS PELLUCIDA (TETRAPHIDACEAE)

The Tetraphidae is a small subclass of mosses with a nematodontous peristome that has frequently been interpreted as primitive among the true mosses. The developmental cell sequence leading to the formation of the four peristome teeth of Tetraphis pellucida is described for the first time. Comparisons are made with sequences known for other nematodontous and arthrodontous mosses. Peristome development in T. pellucida is more like that described previously for arthrodontous peristomes than to published developmental sequences for nematodontous peristomes of species in the Polytrichaceae. On the other hand, our observations confirm a basic uniformity of the earliest developmental stages in all mosses studied thus far, regardless of their systematic position.     

Harmless nectar source or deadly trap: Nepenthes pitchers are activated by rain, condensation and nectar

The leaves of Nepenthes pitcher plants are specialized pitfall traps which capture and digest arthropod prey. In many species, insects become trapped by 'aquaplaning' on the wet pitcher rim (peristome). Here we investigate the ecological implications of this capture mechanism in Nepenthes rafflesiana var. typica. We combine meteorological data and continuous field measurements of peristome wetness using electrical conductance with experimental assessments of the pitchers' capture efficiency. Our results demonstrate that pitchers can be highly effective traps with capture rates as high as 80% but completely ineffective at other times. These dramatic changes are due to the wetting condition of the peristome. Variation of peristome wetness and capture efficiency was perfectly synchronous, and caused by rain, condensation and nectar secreted from peristome nectaries. The presence of nectar on the peristome increased surface wetness mainly indirectly by its hygroscopic properties. Experiments confirmed that pitchers with removed peristome nectaries remained generally drier and captured prey less efficiently than untreated controls. This role of nectar in prey capture represents a novel function of plant nectar. We propose that the intermittent and unpredictable activation of Nepenthes pitcher traps facilitates ant recruitment and constitutes a strategy to maximize prey capture.     

16种丛藓科（Pottiaceae）植物蒴齿形态特征及其系统学意义

通过扫描电镜（SEM）观察了16种国产丛藓科（Pottiaceae）植物蒴齿的形态特征,结果表明：丛藓科植物的蒴齿为单齿类,齿条1~3回左旋或直立,多具基膜,并密被疣,这些共同特征说明了丛藓科植物蒴齿具有一定的相似性;但在齿条形状和旋转情况及基膜特征等方面又有区别,明显分为3种类型,显示了不同属、种间的遗传分化。最后,本文还讨论了蒴齿特征与干旱环境的适应。     

Two new species of Ulota (Orthotrichaceae,Bryopsida) with multicellular spores,from the Hengduan Mountains,Southwestern China

Abstract

Two new species, Ulota yunnanensis and Ulota gigantospora, are described from Yunnan and Sichuan Provinces, China. Both have multicellular spores, a relatively uncommon character in the genus. Differences between the species include growth form and habit, leaf areolation, capsule shape, peristome structure and ornamentation, operculum shape and colour, as well as vaginula and calyptra hairiness. These characters and those discriminating the new species from other ones with similar spore type are discussed and illustrated.     

乌兰坝紫萼藓(紫萼藓科)成熟孢子体的发现（英文）

最近在中国内蒙古发现了乌兰坝紫萼藓(Grimmia ulaandamana J. Mu?oz, C. Feng, X.L. Bai&J. Kou)的可育植株,介绍了乌兰坝紫萼藓成熟孢子体、雌株和雄株的特征。孢子体的孢蒴长于蒴柄,蒴柄弯曲,蒴壶表面具纵褶,蒴壁中部表皮细胞厚壁,环带细胞方形或短长方形,蒴盖有喙;蒴齿具疣并在上部分叉,蒴齿在基部分开,蒴齿基部低于蒴壶口,蒴壁表皮细胞和蒴齿之间存在一层小型细胞,蒴齿骨小梁在基部1/3处强烈凸出;蒴帽基部完整。最内侧雌苞叶较茎叶大。乌兰坝紫萼藓具有重要的形态特征变异,可育植株与相似种直叶紫萼藓(G. elatior)易于区分。对乌兰坝紫萼藓进行了全面的描述并配显微图,探讨了孢子体对确定其系统发育位置的重要性。     

Comparative analysis of the structure and thermal stability of sea urchin peristome and rat tail tendon collagen

We have purified collagen from two distinct sources; the vertebrate, rat tail tendon and an invertebrate, sea urchin adult tissue, the peristome. The collagenous nature of the purification products was confirmed by amino acid compositional analysis. Both preparations had high contents of glycine and proline residues and hydroxyproline was also present. The total pyrrolidine (proline+hydroxyproline) content decreased from 17.9 mole% in rat tail collagen to 12.9 mole% in peristome collagen. Distinctly different circular dichroic spectra were measured for these collagens. Analyses of spectra, measured as a function of temperature, revealed distinct thermal denaturation profiles. The melting temperature for rat tail collagen was 38.5 degrees C, while the corresponding value for peristome collagen was significantly lower at 27 degrees C. A similar thermal denaturation profile was obtained for rat tail collagen in digestion experiments using a 41-kDa gelatinase activity, isolated from sea urchin eggs. These results identify structural differences between a typical, vertebrate type I fibrillar collagen and an echinoderm collagen which serves as a constituent of a mutable connective tissue. These differences may relate to the functional roles played by collagen in these distinctly different tissues.     

The insect-trapping rim of Nepenthes pitchers: Surface structure and function

Carnivorous pitcher plants of the genus Nepenthes capture prey with a pitfall trap that relies on a micro-structured, slippery surface. The upper pitcher rim (peristome) is fully wettable and causes insects to slip by aquaplaning on a thin water film. The high wettability of the peristome is probably achieved by a combination of hydrophilic surface chemistry, surface roughness and the presence of hygroscopic nectar. Insect foot attachment could be prevented by the delayed drainage of the thin water film between the adhesive pad and the surface. Drainage should be faster for insects with a hairy adhesive system; however, they slip equally on the wet peristome. Therefore the stability of the water film against dewetting appears to be the key factor for aquaplaning. New experimental techniques may help to clarify the detailed function of the pitcher plant peristome and to explore its potential for biomimetic applications.Key words: carnivorous plants, insect aquaplaning, superhydrophilic leaves, Nepenthes, peristome     

Monograph of the moss genus Macrodictyum (Broth.) E.H.Hegew. (Dicranaceae)

Abstract

Macrodictyum is a small acrocarpous moss genus of three species (M. latifolium (E.B.Bartram) M.J.Price, M. proliferum (Mitt.) E.H.Hegew., M. wrightii (Sull.) E.H.Hegew.). It grows in tufts and mats on trees or rocks at 450–1500 m in the Neotropics. The genus has a restricted distribution within the Neotropics and is currently known from only a few localities in Cuba, the Dominican Republic, and southeastern Brazil. Macrodictyum is characterized by four main features: 1) appressed, non-crispate, ovate–oblong, lingulate to ligulate or linear leaves; 2) large, rhomboidal, thin-walled cells in the upper leaf; 3) large, irregular, multicellular apical teeth; and 4) guide cells that are ventral at and above mid-leaf. These features are atypical of the Dicranaceae. However, Macrodictyum shares pseudautoicous sexuality, sheathing perichaetial leaves, and peristome structure with the large pantropical Dicranaceous genus Holomitrium Brid. In these two genera the peristome consists of 16 single, triangular, entire or weakly divided, fenestrate, striate teeth that are papillose throughout on both the inner and outer surfaces. Macrodictyum is retained in the Dicranoideae (Dicranaceae), close to Holomitrium, based on its pseudautoicous sexuality, sheathing perichaetial leaves, and peristome structure.     

帕米尔木灵藓和细齿木灵藓（木灵藓科）的形态特征及其在中国的新分布

该文报道了采自新疆的木灵藓属中国2个新记录种——帕米尔木灵藓(Orthotrichum pamiricum)和细齿木灵藓(O.scanicum)。帕米尔木灵藓的识别特征为:叶尖钝,气孔隐型,多着生于孢蒴下部,外齿层齿片8对,干燥时蒴齿背曲,内齿层蒴条16,上部内曲;细齿木灵藓的识别特征为:叶尖部具细齿,气孔半隐型,蒴帽具分散的透明毛,内齿层和外齿层均16片,具8条黄色细沟,干燥时中部以上具沟。对这2种藓类的形态特征、生境和地理分布及与其相似种的形态学进行了比较分析,并绘制了每种的形态结构墨线图。木灵藓属植物在中国的新分布记录进一步表明,新疆地区富含生物多样性,并与中亚植物区系存在密切关系。     

Studies on growth indices of the fresh water prosobranch,Melania scabra

Growth indices of Melania scabra have been studied. The length of shell, length of spire, length of base, width of shell, length of peristome (aperture) and width of peristome were measured. Similarly weights of the snails were also determined. In all the above cases, relationships were established taking length as the basic index.     

Structure of Adnate Colony Portions in Crisiidae (Bryozoa Cyclostomata)

The “rhizoidsrdquo; surrounding the base of the erect “colony” emanating from the ancestrula in the Crisiidae, especially the simple species Crisidia cornuta (L.), are a regular adnate system of autozooids. Each autozooid is composed of a proximal adnate part and a distal peristome (in some species kenozooids are possibly intercalated). The autozooid peristomes support erect branches identical in budding and structure with the branch emanating from the erect peristome of the ancestrula. Thus, the complete crisiid colony consists of an adnate system of ancestrula and autozooids, which form erect branches from their peristomes. The adnate zooid system is comparable in autozooid morphology and budding pattern with simple uniserial stomatoporids. The tentative hypothesis is proposed that the crisiid group has developed from primitive stomatoporids; the adnate zooid system of the stomatoporids apparently evolved peristomial budding to produce the erect colony branches characteristic of crisiids.     

Tayloria rudimenta (Musci,Splachnaceae), a new species from Ningxia Huizu Autonomous Region of China

Tayloria rudimenta X.-L. Bai & B. C. Tan is described and illustrated as a new species based on a recent collection made from Helan Shan (Mt.), Ningxia Huizu Autonomous Region, China. The new species is characterized by the absence or with only rudimentary peristome, among the Chinese congeners.     

The Cytology of Sheep Rumen Ciliates. I. Ultrastructure of Epidinium caudatum Crawley1

Epidinium caudatum has an anterior vestibulum containing the adoral zone syncilia (AZS) on an extrusible peristome. The cytopharyngeal structures include a funnel-shaped arrangement of nematodesmata, longitudinal and transversely oriented microtubular ribbons all of which are located in the peristome, a structure which also contains filamentous phagoplasm. The origins of the microtubular ribbons indicate affinities to the rhabdos type of cytopharynx. The peristomal base is continuous with the tubular esophagus, the region connecting the two being ensheathed by a fibrous layer and low density cytoplasm. The esophagus has a microtubular/microfilamentous wall. A distinct cytoproct with associated myonemal structures occurs posteriorly. The skeletal plates consist of a large number of interconnected, variably shaped platelets and may have dual skeletal and storage functions. The endoplasm is more vesicular than the ectoplasm, the two separated by a fibrous boundary layer. The five-layered cortex has an external glycocalyx, a plasma membrane with two subtending membranes, homogeneous, microtubular, and microfilamentous layers. The syncilia of the AZS are mounted in a U-shaped band on the peristome with transversely oriented kinetics consisting of kinetosomes linked by a sub-kinetosomal rod. There is a bifurcated kinetodesma, dense support material forming a lateral spur with associated transverse microtubules, and postciliary, interkinetal, and occasional basal microtubules, nematodesmata, and a subciliary reticulum. A barren, possibly vestigial, somatic infraciliature consists of non-ciliated kinetosomes and a basal striated fiber with associated basal and perpendicular (cortical) microtubules.     

Evidence for alternative trapping strategies in two forms of the pitcher plant, Nepenthes rafflesiana

Nepenthes pitchers are specialized leaves that function as insect traps. Several pitcher components may contribute to trapping, including the pitcher fluid, slippery wax crystals and downward-pointing epidermal cells on the inner pitcher wall, and the wetness-dependent pitcher rim (peristome), but the relative importance of these traits is unclear. Mechanisms of prey capture and retention in the field were investigated by quantifying the effect of 'knock-out' manipulations of individual pitcher structures, and by testing the ability of pitcher fluids and water to retain insects. Two forms of Nepenthes rafflesiana Jack ('elongate' and 'typical') with contrasting combinations of pitcher traits were compared. Wax crystals on the inner pitcher wall were found to be the most important trapping structure in the elongate form, whereas the typical form relied primarily on the peristome. The pitcher fluids of both forms, differing markedly in the degree of viscoelasticity, retained significantly more ants than water. The present results show that pitcher plants utilize several mechanisms for prey capture and retention, varying in efficiency and relative importance between forms. It is proposed that these differences represent alternative prey capture strategies that may provide a mechanism to reduce competition and facilitate species co-existence in nutrient-limited habitats.