Molecular and morphological evidence of Alvinellidae relationships (Terebelliformia, Polychaeta, Annelida)

In this study we assessed the phylogenetic relationships of the hydrothermal vent polychaete group Alvinellidae, based on parsimony analyses of combined morphological and molecular data. Morphological data were obtained from newly examined specimens and literature information of 16 terminal taxa belonging to Alvinellidae, Ampharetidae, Pectinariidae, Terebellidae, Trichobranchidae, and the outgroups Oweniidae and Sabellidae. Molecular data were based on 28S rRNA from 13 of the 16 morphological terminals (10 previously published sequences plus three new ones). The combined analysis indicated the clades ((Alvinellidae, Trichobranchidae) Pectinariidae) and (Ampharetidae, Terebellidae). Alvinellidae, Ampharetidae and Terebellidae, as currently delineated, are monophyletic. The positions of Trichobranchidae and Pectinariidae contradicted traditional views, and they also had low Bremer support and merit further studies. Well-supported clades included Alvinellidae and Terebellinae. Previous statements that Alvinellidae are either nested within Ampharetidae or the sister to this taxon were not supported. The traditional but here contradicted view that Terebellidae and Trichobranchidae are closely related may be based on plesiomorphic similarities between these two taxa.     

Phylogenetic information from three mitochondrial genomes of Terebelliformia (Annelida) worms and duplication of the methionine tRNA

Mitochondrial genomes have been useful for inferring animal phylogeny across a wide range of clades, however they are still poorly sampled in some animal taxa, limiting our knowledge of mtDNA evolution. For example, despite being one of the most diverse animal phyla, only 5 complete annelid mitochrondial genomes have been published. To address this paucity of information, we obtained complete mitochondrial genomic sequences from Pista cristata (Terebellidae) and Terebellides stroemi (Trichobranchidae) as well as one nearly complete mitochondrial genome from Eclysippe vanelli (Ampharetidae). These taxa are within Terebelliformia (Annelida), which include spaghetti worms, icecream cone worms and their relatives. In contrast to the 37 genes found in most bilaterian metazoans, we recover 38 genes in the mitochondrial genomes of T. stroemi and P. cristata due to the presence of a second methionine tRNA (trnM). Interestingly, the two trnMs are located next to each other and are possibly a synapomorphy of these two taxa. The E. vanelli partial mitochondrial genome lacks this additional trnM at the same position, but it may be present in the region not sampled. Compared to other annelids, gene orders of these three mitochondrial genomes are generally conserved except for the atp6-mSSU region. Phylogenetic analyses reveal that mtDNA data strongly supports a Trichobranchidae/Terebellidae clade.     

The phylogenetic position of Siboglinidae (Annelida) inferred from 18S rRNA, 28S rRNA and morphological data

We assess the phylogenetic position of Siboglinidae (previously known as the phyla Pogonophora and Vestimentifera, but now referred to Annelida) in parsimony analyses of 1100 bp from 18S rRNA, 320 bp from the D1 region of 28S rRNA, and 107 morphological characters, totaling 667 parsimony informative characters. The 34 terminal taxa, apart from six siboglinids, include polychaete members of Sabellida, Terbelliformia, Cirratuliformia and Spionida, plus two Aciculata polychaetes as outgroups. Our results contradict most recent hypotheses in showing a sistergroup relationship between Siboglinidae and Oweniidae, and in that the latter taxon is not a member of Sabellida. Furthermore, our results indicate that Sabellariidae is not closely related to Sabellida, that Serpulidae may be nested within Sabellidae, and that Alvinellidae is nested within Ampharetidae. © The Willi Hennig Society 2004.     

Phylogenetic analysis of the Amphitritinae (Polycnaeta: Terebellidae)

The phylogenetic relationships of the Amphitritinae (Polychaeta: Terebellidae) were studied using parsimony analysis of 22 external morphological characters. To choose outgroups to polarize the characters, I carried out a preliminary analysis of the relationships of the four terebellid subfamilies and the Trichobranchidae. The single most parsimonious tree from the analysis supports monophyly of the Terebellidae by the presence of ventral glandular shields. However, this character is homoplasious within the Terebellomorpha, and further evaluation of the Terebellidae is recommended. Artacama and Thelepus were chosen as outgroups for the analysis of amphitritine genera. The generic level analysis yielded seven equally parsimonious trees, which are consistent in their topologies except for the relationships among seven genera in one large clade. In all trees, Artacama is the sister taxon to a large clade within the Amphitritinae; the Artacaminae is therefore synonymized with the Amphitritinae, which is diagnosed by the presence of double rows of uncini. Within the Amphitritinae, the status of several monotypic genera is questioned; plesiomorphic character states indicated by the analysis are discussed. The results presented are offered as working hypotheses of the relationships among amphitritine genera. The large number of homoplasies indicated by the analysis emphasizes the need to further evaluate these hypotheses using additional characters. With a robust phylogenetic hypothesis of amphitritine relationships, a re-classification of the group based on apomorphic character states can be undertaken, and questions regarding the evolution of morphological characters, reproductive modes, or biogeographical patterns can be properly addressed.     

Lateral organs in sedentary polychaetes (Annelida) – Ultrastructure and phylogenetic significance of an insufficiently known sense organ

Lateral organs are sense organs visible as densely ciliated pits or papillae between the noto‐ and the neuropodia in certain taxa of sedentary polychaetes. Ultrastructural studies in about 10 species of the following taxa Maldanidae, Opheliidae, Orbiniidae, Paraonidae, Magelonidae, Spionidae, Poecilochaetidae and Terebellidae have been designed to evaluate whether these organs are homologous among polychaetes. In spite of great external diversity, the investigations revealed an overall ultrastructural similarity. Differences between species investigated mainly concern the size of the organs as well as the number and arrangement of cells. The organs comprise supportive cells and uniciliated penetrative sensory cells. Their dendrites are closely arranged and thus their cilia may resemble multiciliated cells. There are two types of sensory cells: one type possesses no or mainly thin microvilli of which usually only a few reach the cuticular surface, and in the other type the cilium is consistently surrounded by 10 strong microvilli, which form a pore‐like opening in the cuticle. Further differences occur in the structure of the rootlet system. Basally, a retractor muscle attaches to the organ. The systematic significance of these organs within Annelida is discussed with respect to the conflicting phylogenetic hypotheses explaining the relationships of annelid taxa.     

Ultrastructural study of the jaw structures in two species of Ampharetidae (Annelida: Polychaeta)

Two species of jaw bearing Ampharetidae (Adercodon pleijeli (Mackie 1994) and Ampharete sp. B) were investigated in order to describe the microanatomy of the mouth parts and especially jaws of these enigmatic polychaetes. The animals of both studied species have 14–18 mouth tentacles that are about 30 µm in diameter each. In both species, the ventral pharyngeal organ is well developed and situated on the ventral side of the buccal cavity. It is composed of a ventral muscle bulb and investing muscles. The bulb consists of posterior and anterior parts separated by a deep median transversal groove. In both species, the triangular teeth or denticles are arranged in a single transversal row on the surface of the posterior part of the ventral bulb just in front of its posterior edge. There are 36 denticles in Adercodon pleijeli and 50 in Ampharete sp. B. The height of the denticles (6–12 µm) is similar in both species. Each tooth is composed of two main layers. The outer one (dental) is the electron‐dense sclerotized layer that covers the tooth. The inner one consists of long microvilli with a collagen matrix between them. The thickness of the dental layer ranges from 0.95 to 0.6 µm. The jaws of the studied worms may play a certain role in scraping off microfouling. The fine structure of the jaws in Ampharetidae is very similar to that of the mandibles of Dorvilleidae, the mandibles and the maxillae of Lumbrineridae, Eunicidae and Onuphidae, and the jaws of other Aciculata. This type of jaw is characterized by unlimited growth and the absence of replacement. The occurrence of jaws in a few smaller Ampharetidae is considered as an apomorphic state.     

CLSM analysis of the phalloidin-stained muscle system in Nerilla antennata, Nerillidium sp. and Trochonerilla mobilis (Polychaeta; Nerillidae)

The entire muscle system of Nerilla antennata, Nerillidium sp. and Trochonerilla mobilis was three-dimensionally reconstructed from whole mounts. In juvenile and adult specimens the F-actin musculature subset was stained with FITC-conjugated phalloidin and visualized with a confocal laser scanning microscope (cLSM). The muscle system shows the following major organization: 1) circular muscles are totally absent in the body wall; 2) the longitudinal muscles are confined in two ventral and two dorsal thick bundles; 3) additional longitudinal muscles are located in the ventro- and dorsomedian axis; 4) three segmental pairs of ventral oblique muscles elongate into the periphery: the main dorsoventral muscles that run along the body side posterior and dorsally and the anterior and posterior oblique parapodial muscles, which contribute to the ventral chaetal sacs; 5) one segmental pair of dorsal oblique parapodial muscles, contributing to the dorsal chaetal sacs; 6) five to seven small dorsoventral muscles per segment; and 7) complex head and pharyngeal musculature. These results support the belief that absence of circular muscles in the polychaete body wall is much more widely distributed than is currently presumed.     

Accessory hemolymph pump in the mesothoracic legs of locusts, (Schistocerca gregaria forskal) (Orthoptera,Acrididae)

An accessory pulsatile organ located in the mesothoracic legs pumps hemolymph towards the tip of the leg ventrally and towards the body near the dorsal side. It consists of a muscle attached to the ventral side of the trochanter and to the central region of a transverse connective tissue diaphragm located at the trochanter-femur border. The diaphragm has a ventral outlet that permits efferent hemolymph flow through a narrow femoral sinus. A second dorsal outlet allows the afferent countercurrent back to the thorax through a separate hemolymph channel. During abdominal ventilation, the pumping rhythm of the legfn2heart is neurally synchronized with abdominal ventilation. Expiratory pressure expands tracheal air sacs in the ventral trochanter and helps driving hemolymph out of this space. In idle periods of resting ventilation, an autonomous myogenic rhythm of the leg–heart can maintain hemolymph circulation in the mesothoracic leg without neural control.     

白枕鹤的呼吸系统及其生态适应

白枕鹤的呼吸系统由喉头、气管、鸣管、肺及气囊组成。喉头有淋巴小结分布。气管在龙骨突起内盘旋,并随年龄而增长,软骨环逐渐骨化。鸣管由左右两个支气管特化而成,呈膜状扁管入肺。肺的长度约占躯干的1/2。气囊几遍布全身,高度发达。整个呼吸系统的结构,与其高空飞翔生活相适应。     

Comparative pollen morphology of Glechoma and Marmoritis(Nepetinae,Lamiaceae)

The pollen morphology of 13 taxa(34 specimens)of the genera Glechoma L.,and Marmoritis Benth.was investigated in detail using light,scanning electron,and transmission electron microscopy.Pollen grains of all studied taxa are small to large in size(P = 32.5-60.4μm,E = 20.2-50.5μm),prolate-spheroidal to prolate in shape and mostly hexacolpate(the amb more or less circular or rarely ellipsoid)with granular membranes.The sexine ornamentation of Glechoma is bireticulate; the muri of the primary reticulum are irregularly circled,and lumen size is short.In contrast,the sexine surfaces of the Marmoritis pollen tend to more elongate or wider at the muri of the primary reticulum than those of the Glechoma.The pollen wall stratification of selected taxa(three from Glechoma and one from Marmoritis)is characterized by unbranched columellae,and continuous or distinctly discontinuous endexine based on transmission electron microscopy observation.The results of Glechoma and Marmoritis reveal rather similar pollen morphological features,however,fine details of sexine ornamentation are characteristic to differentiate the pollen taxa.Although these differences may be useful in establishing the taxonomic boundary between two genera,they are too weak to segregate diagnostic characters.     

豆蔻属(姜科)植物叶的比较解剖学研究

采用石蜡切片法对豆蔻属12个种的叶片横切面结构进行比较解剖学研究。结果显示:豆蔻属植物叶片表皮层由1层表皮细胞组成,在无下皮层的种中,近轴面的表皮细胞通常体积较大,而在有下皮层的种中,表皮层通常较薄,细胞壁增厚;下皮层的结构具有多样性;叶肉中栅栏组织通常1~2层,海绵组织2~6层细胞,常含丹宁,所观察的大部分种含有方晶或砂晶;中脉韧皮部极端维管束形态多样,维管束系统II通常缺失,未发现同时具有4个系统的种。此外,对叶缘的形态特点进行了概括性描述,并结合前人的研究资料讨论了叶解剖结构的系统学意义。     

荒漠早春开花植物囊果草大小孢子发生与雌雄配子体发育

囊果草(Leontice incerta Pall.)为生长于天山北坡荒漠和低山山坡的小檗科(Berberidaceae)多年生早春开花植物，具有较高的观赏价值、饲用价值和生态价值，为探究该物种的有性生殖特征，并为后续进行栽培育种等工作提供理论依据，作者利用光学显微镜和石蜡制片技术，对该物种大/小孢子发生和雌/雄配子体发育进行了观察。结果表明，(1)花药具4室，药壁由5层细胞组成，发育为基本型。药室内壁在发育后期具纤维状加厚现象；腺质型绒毡层具2核或多核现象。(2)小孢子母细胞减数分裂时胞质分裂为同时型；小孢子四分体为四面体型，被胼胝质壁所包围，游离小孢子形成后胼胝质壁逐渐消失。成熟花粉多为2细胞型，偶见3细胞型。(3)雌蕊由1心皮组成，子房1室，倒生胚珠，具双珠被，厚珠心。大孢子四分体呈线形排列，最终发育为7细胞8核的蓼型胚囊，助细胞具发达的漏斗形丝状器。这些特点说明，囊果草大/小孢子发生和雌/雄配子体发育正常，未见败育现象，表现出较原始的发育特征。研究结果丰富了小檗科植物的胚胎学资料，为该物种及其近缘物种的生殖生物学研究积累了理论基础。     

A multigene framework for polychaete phylogenetic studies

Producing a robust phylogenetic reconstruction for Polychaeta using either morphological or molecular data sets has proven very difficult. There remain many conflicts between morphological analyses and hypotheses based on DNA data, the latter principally derived from 18S rRNA sequences. For the present study a data set covering a broad range of polychaete diversity was assembled, including 38 new sequences from 21 species. Besides available 18S rRNA data, five additional gene segments were examined: the D1 and D9-10 expansion regions of 28S rRNA, histone H3, snU2 RNA and cytochrome c oxidase subunit I. Maximum parsimony, maximum likelihood and Bayesian analyses were conducted.Annelida and Mollusca were reciprocally monophyletic in maximum likelihood analyses, but Polychaeta included a cephalopod in maximum parsimony analyses, and a patellogastropod in Bayesian analyses. When rooted on the Mollusca, optimal topologies from maximum likelihood analyses showed a recognisable basal group of taxa, including Oweniidae, Chaetopteridae and Amphinomidae. The six studied phyllodocidan families plus Orbiniidae (as the sister group of the scale-worms) formed the next most basal group. All analyses support the inclusion of Echiura, Clitellata and Siboglinidae within polychaetes. Bayesian analyses show Echiura as the sister group of Capitellidae, in agreement with previous 18S rRNA results, In contrast, Echiura formed the sister group to Trichobranchidae in maximum likelihood and maximum parsimony analyses.Supra-familial groupings consistently recovered within Polychaeta in the analyses are: (i) Terebellida without Ampharetidae; (ii) Scolecida (excepting Orbiniidae); (iii) Eunicidae, Lumbrineridae and Clitellata; and (iv) “Cirratuliformia” (including Sternaspidae) plus Sabellidae, Serpulidae and Spionidae.     

Determinants of transdiaphragmatic pressure in dogs

We measured the transdiaphragmatic pressure (Pdi) during bilateral phrenic nerve stimulation and evaluated the determinants of its change with lung volume, chest wall geometry, and respiratory system impedance in supine dogs. Four rows of radiopaque markers were sewn onto muscle bundles of the costal and crural diaphragm between their origin on the central tendon and their insertion on the rib cage and spine. The length of the diaphragm (L) was determined from the projection images of marker rows using biplane fluoroscopy. Measurements were made at lung volumes between total lung capacity and functional residual capacity before and after the infusion of Ringer lactate solution into the abdominal cavity. In contrast to relaxation, during tetanic stimulation the active lengths of the muscle bundles were similar at all volumes, but the diaphragm assumed different shapes. Although the small differences in active muscle length with volume and liquid loads are consistent with only small changes in muscle force output, Pdi varied by a factor of greater than or equal to 5. There was no single L/Pdi curve that fitted all data during 50-Hz stimulations. We conclude that under these experimental conditions Pdi is not a unique measure of the force produced by the diaphragm and that lung volume, chest wall geometry, and respiratory system impedance are important determinants of the mechanical efficiency of the diaphragm as a pressure generator.     

GYNOECIUM AND DEVELOPMENT OF EMBRYO SAC,ENDOSPERM, AND SEED IN PHOLISTOMA (HYDROPHYLLACEAE) RELATIVE TO TAXONOMY

The objective of this research was to provide data for a taxonomic evaluation of Pholistoma and for a later survey of evolutionary morphology within the tribe Hydrophylleae. The unilocular ovary bears specialized unicellular prickles. Ovary and capsule wall consist of five or seven cell layers, of which three develop thickened walls for protection and dehiscence. Two parietal placentae enlarge to fill the entire locule. The four to eight ovules per ovary, some of which degenerate, are irregularly ventral and half-epitropous to half-hypotropous. Each ovule is tenuinucellate, unitegmic, and anatropous with a feeble vascular strand. A large amount of ovular parenchyma is produced from two meristems, one of which is the integumentary tapetum. Cells of the ovular epidermis grow into giant cells, each with a tubular portion penetrating deep into the seed interior, thereby producing a most unusual seed coat. The embryo sac is of the Polygonum type, the embryo of the Onagrad type. The endosperm is cellular with a micropylar and a chalazal endosperm haustorium. Both haustoria produce lateral branches. The mature endosperm is porously pitted, due to the giant cells of the testa. Great similarity between the three Pholistoma species, and in particular the presence in all species of two lateral haustorium branches, of gigantic, funnel-shaped epidermal cells, and of a porously pitted endosperm, strongly supports the notion that these three species constitute a natural entity.     

Mitochondrial framework (reticulum mitochondriale) in rat diaphragm muscle

Reconstitution of rat diaphragm mitochondria has been carried out with the use of the serial section technique. It is shown that mitochondrial material is organized as networks transpiercing the I band regions of the muscle near the Z-discs. Each network forms tubules, oriented perpendicular to its plane, and branches, connecting the network with mitochondrial clusters in the fiber periphery. Such a system, defined as mitochondrial reticulum, is found to be characteristic of the diaphragm of adult animals. It is absent in the diaphragm of rat embryos and newborn rats. The junctions of the branches of mitochondrial reticulum are described. In the junction site, the outer membranes of two mitochondrial branches are in contact, and spaces between outer and inner membranes are filled with an osmiophilic substance. No junctions were found in the embryos and in newborn animals whose diaphragm contains single, elliptical or worm-like mitochondria. The hypothesis is put forward that the mitochondrial reticulum serves as a system for transport of energy, oxygen and fatty acid residues along mitochondrial membranes over distances commensurable with the muscle fiber diameter.     

The influence of caudofemoral musculature on the titanosaurian (Saurischia: Sauropoda) tail skeleton: morphological and phylogenetic implications

Due to their abundance, taxonomic and morphological diversity, wide range of body sizes and broad geographical distribution, titanosaurian sauropods were one of the most important Cretaceous herbivorous dinosaur groups. Consequently, titanosaurs constitute one of the best samples in which to evaluate the relationship between bony structures and unpreserved soft-tissues within Sauropoda. We reconstruct the morphology and interpret the implications of selected soft-tissues associated with the titanosaurian caudal skeleton. These tissues, especially the M. caudofemoralis longus (CFL), exerted a considerable influence on the anatomy of the caudal vertebrae and haemal arches. In all studied titanosaurian taxa, the reconstructed caudofemoral musculature corresponds to one of three principal morphotypes that accord with previously recognised phylogenetic patterns within the clade. Basal titanosaurians had an elongate M. CFL that extended for much of the proximal half of the tail; in saltasaurines, this muscle was much shorter. Non-saltasaurine lithostrotians exhibited an intermediate condition. Furthermore, the differing position of the fourth trochanter, and therefore, the insertion of the caudofemoral muscles, among various titanosaurian taxa suggests distinctions in the locomotor function of these animals.     

Megasporogenesis,Microsporogenesis and Development of Gametophytes in Eleutherococcus senticosus (Araliaceae)

This paper describes megasporogenesis, microsporogenesis, and development of female and male gametophytes in Eleutherococcus senticosus. The main results are as follows: Flowers of E. senticosus are epigynous, pentamerous. Anthers are 4 -microsporangiate. An ovary has 5 loculi. Each ovary loculus has 2 ovules: the upper ovule and the lower ovule. The upper one is orthotropous and degenerates after the formation of archesporial cell, while the lower one is anatropous, unitegmic and crassinucellar, and able to continue developing. In male plants, microsporogenesis and development of male gametophytes took place in regular way, but a series of abnormal phenomena were found in megasporogenesis and development of female gametophytes. The microspore mother cells gave rise to tetrahedral tetrads by meiosis. Cytokinesis was of the simultaneous type. The mature pollen was 3-celled and shed singly. The anther wall formation belonged to the dicotyledonous type. At the stage of microspore mother cell, the anther wall consisted of four layers, i.e. epidermis, endothecium, middle layer, and tapetum. The tapetum was of glandular type and its most cells were binucleate. When microspores were at the uninucleate stage, the tapetum began to degenerate in situ. When microspores developed into 3-celled pollen grains, the tapetum had fully degenerates. In the lower ovule of male flower, the megaspore mother cell gave rise to a linear or “T” -shaped tetrad. In some cases, a new archesporial cell over the tetrad or two tetrads parallel or in a series were observed. Furthermore, the position of functional megaspore was variable; any one or two megaspores might be functional, or one megaspore gave rise to a uninucleate embryo sac, but two other megaspores also had a potentiality of developing into the embryo sac. In generally, on the day when flowers opened, female gametophytes contained only 4 cells: a central cell, two irregular synergids and one unusual egg cell. In female plants, microspore mother cells and secondary sporogenous cells were observed. But at the stage of secondary sporogenous cell, the newly differentiated tapetum took the appearance of degeneration. Later, during the whole stage of meiosis, the trace of degenerative tapetum could be seen. At last, the microsporangium degenerated and no tetrad formed. On the blossom day, all anthers shriveled without pollen grains. In female flowers, megasporogenesis and development of female gametophytes were normal: the tetrad of megaspores was linear or “T”-shaped; the chalazal megaspore was usually functional; the development of embryo sac was of the Polygonum type. On the blossom day, most embryo sacs consisted of 7 cells with 8 nuclei or 7 cells with 7 nuclei; but the egg apparatus was not fully developed. In hermaphroditic plants, microsporogenesis was normal but the development of male gametophytes was partially abnormal. When the hermaphroditic flowers blossomed, there were more or less empty pollen grains in the microsporangium and these pollen grains were quite different in size. The development of most gynoecia was normal but numerous abnormal embryo sacs could be seen. On the blossom day, female gametophytes were mainly 7-celled with 8-nuclei or with 7-nuclei or 4-celled with antipodal cells degenerated; the egg apparatus wasnot fully developed either.