Studies on the tardigrades. I. Fine structure of the anterior foregut of Milnesium tardigradum Doyère

The fine structure of the anterior foregut of the tardigrade Milnesium tardigradum is presented. The oral region consists of a terminal mouth opening surrounded by six plate-like lips lying within a circlet of six prominent papillae. The buccal cavity is enclosed within a thick cuticular tube which possesses appendage structures, the stylet sheaths, stylet supports and paired protrusible stylets. Two large salivary glands envelop the buccal structures and contain voluminous amounts of secretory product. The arrangement, possible functions and phyletic significance of these structures are discussed.     

Graphical Presentation of the African Tardigrade FaunaUsing GIS with the Description of Isohypsibius malawiensis sp. n. (Eutardigrada: Hypsibiidae) from Lake Malawi

The tardigrade fauna of the African continent is reviewed and presented graphically using Worldmap, a Geographical Information System (GIS) developed for exploring geographical diversity patterns in large biological datasets. References to the African tardigrade fauna have been gathered from published literature and supplemented with unpublished species information from the collection of Prof. Reinhardt M. Kristensen (RMK), Zoological Museum, University of Copenhagen. 156 species belonging to 36 genera of tardigrades are present. They consist of 105 eutardigrade species and 51 heterotardigrade species, of which 42 species are semiterrestrial and 9 species are marine. The presence of tardigrades are reported from 20 countries, but of these 9 are represented by a single reference. Marine tardigrades in particular have been neglected, with only a single report from the shores of the African continent. Data from the RMK collection of samples from Egypt is included in the analysis.

The scattered and sparse knowledge of the African tardigrade distribution makes general conclusions difficult, but emphasises the large regions which require further investigation. The current distribution patterns corresponds with easy accessible or ‘tourist’ locations. Regions where GIS could be used to illustrate ecological preferences are also pointed out by the analysis.

Isohypsibius malawiensis sp. n. is described from Lake Malawi. It has a smooth body surface and lacks eyes. The heteronych claws are without lunulae, but below the claws a double arched cuticular bar is present. The dorsal and ventral apophyses of the buccal tube have a large drop-shaped swelling. The first macroplacoid is the largest followed by the second, which is only slightly larger than the third; microplacoid is absent. Males are smaller than females. Females lay only one to two very large eggs in the exuvium. The Malpighian tubules are clover-shaped. The new species is interstitial in coarse sediment and no other tardigrade species were present.     

Turbellarien der GattungPromesostoma von der nordamerikanischen Pazifikküste

Two new species of the genusPromesostoma, P. infundibulum nov. spec. andP. hymanae nov. spec., are described from the mesopsammal of the San Juan Archipel (Washington, USA). They are closely related toP. dipterostylum Karling from the Californian coast. These three species have a differentiated seminal receptacle with special cuticular structures, which represents a remarkable synapomorphy. The cuticular connection between the stylet and the seminal receptacle was unknown until now in the organization of turbellarians.     

Myoanatomy of the marine tardigrade Halobiotus crispae (Eutardigrada: Hypsibiidae)

The muscular architecture of Halobiotus crispae (Eutardigrada: Hypsibiidae) was examined by means of fluorescent‐coupled phalloidin in combination with confocal laser scanning microscopy and computer‐aided three‐dimensional reconstruction, in addition to light microscopy (Nomarski), scanning electron microscopy, and transmission electron microscopy (TEM). The somatic musculature of H. crispae is composed of structurally independent muscle fibers, which can be divided into a dorsal, ventral, dorsoventral, and a lateral musculature. Moreover, a distinct leg musculature is found. The number and arrangement of muscles differ in each leg. Noticeably, the fourth leg contains much fewer muscles when compared with the other legs. Buccopharyngeal musculature (myoepithelial muscles), intestinal musculature, and cloacal musculature comprise the animal's visceral musculature. TEM of stylet and leg musculature revealed ultrastructural similarities between these two muscle groups. Furthermore, microtubules are found in the epidermal cells of both leg and stylet muscle attachments. This would indicate that the stylet and stylet glands are homologues to the claw and claw glands, respectively. When comparing with previously published data on both heterotardigrade and eutardigrade species, it becomes obvious that eutardigrades possess very similar numbers and arrangement of muscles, yet differ in a number of significant details of their myoanatomy. This study establishes a morphological framework for the use of muscular architecture in elucidating tardigrade phylogeny. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.     

Soil tardigrade biodiversity with the description of a new eutardigrade genus and its phylogenetic position

Sixteen tardigrade species have been identified from a total of 943 specimens isolated from 69 positive soil samples collected in southern Spain (Andalusia, Huelva). Three genera (Hexapodibius, Xerobiotus and the new genus Sarascon) and eight species are new records for the Iberian Peninsula, increasing Iberian tardigrade biodiversity by 6%, and 10 species are new records for soil habitats, increasing soil tardigrade biodiversity by 9% (from 96 to 108 species). A newly discovered species and genus are described, followed by an analysis and discussion of the species' phylogenetic position and synapomorphies, based on morphological and total evidence (morphology and molecular – 18S and 28S rRNA – data combined) phylogenetic analyses. The new genus is distinguished from other Itaquasconinae genera, to which it is phylogenetically related, by having a Parascon buccopharyngeal apparatus and Ramajendas claws. In contrast to general eutardigrade evolution, which is primarily determined by claw morphology, itaquasconid evolution is more related to buccopharyngeal apparatus morphology, which shows homoplastic evolution at superfamily, family and subfamily levels, and also defines functional trophic groups in soil-related environments.

http://zoobank.org/urn:lsid:zoobank.org:pub:068B9D87-27E2-4B26-8920-FF03CEF9869A     

Analysis of mouthpart movements during feeding of Frankliniella occidentalis (pergande) and F. schultzei trybom (Thysanoptera : Thripidae)

Scanning electron microscopy was used to elucidate the morphology and sequential movement of thrips feeding structures in the 2 species, Frankliniella occidentalis and F. schultzei, (Thysanoptera : Thripidae). The mouthcone consists of paired paraglossae, and fringed labral pad, a single, apically fused mandible and a pair of interlocking maxillae. The maxillae are open apically and form a feeding tube. Ten pairs of sensory pegs of 3 distinct morphological types (sensilla basiconica with a cuticular collar, sensilla basiconica without a cuticular collar, and sensilla trichoidea) were found on the paraglossae. The possible function of these sensory structures in host finding and choice are discussed. No structure for rasping the leaf's surface was found on the mouthcone or the ventral surface of the insect. Live specimens were observed feeding through Parafilm on artificial media (sucrose solution) and lettuce leaf tissue. These observations support earlier findings that thrips feed by piercing leaf cells with the mandible and ingesting cell contents through the feeding tube formed by the maxillary stylets. Based on these findings, we suggest that thrips be classified as piercing-sucking rather than rasping-sucking insects.     

Tardigrades from Ecuador,with the Description of Two New Species: Mixibius ornatus n. sp. and Diphascon (Adropion) onorei n. sp. (Eutardigrada,Hypsibiidae)

Seven species are reported from Ecuador, South America, two of which, Mixibius ornatus and Diphascon (Adropion) onorei, are new to science. Mixibius ornatus n. sp. differs from Mixibius saracenus (Pilato 1973) and from M. fueginus Pilato & Binda 1997 by having a sculptured cuticle, broader claws, lunulae present, stylet supports inserted on the buccal tube in a more caudal position, and shorter placoids. Diphascon (A.) onorei n. sp. has an elongate pharyngeal bulb with small apophyses, three rod-shaped macroplacoids, a granular microplacoid, and septulum; claw bases enlarged, smooth (first three pairs of legs) or crenate (outer claws on the hind legs); a cuticular bar is present near the inner claws on the first three pairs of legs. Other species reported are Echiniscus aliquantillus Grigarick, Schuster & Nelson 1983; Minibiotus intermedius (Plate 1888); Macrobiotus coronatus De Barros 1942; Macrobiotus danielae Pilato, Binda, Napolitano & Moncada 2001, and Astatumen bartosi Weglarska 1959.     

Examination of the interior of sand fly (Diptera: Psychodidae) abdomen reveals novel cuticular structures involved in pheromone release: Discovering the manifold

The males of many species of New World Phlebotomines produce volatile terpenoid chemicals, shown in Lutzomyia longipalpis s.l. to be sex/aggregation pheromones. Pheromone is produced by secretory cells which surround a cuticular reservoir which collects the pheromone and passes it through a cuticular duct to the surface of the insect. The pheromone then passes through specialised cuticular structures on the abdominal surface prior to evaporation. The shape and distribution of the specialised structures are highly diverse and differ according to species. In this study we used SEM to examine the interior cuticular pheromone collection and transport structures of 3 members of the Lu. longipalpis s.l. species complex and Migonemyia migonei. We found a new structure which we have called the manifold which appears to be a substantial extension of the interior tergal cuticle connected in-line with the cuticular duct and reservoir. The manifold of the Campo Grande member of the complex is longer and wider than the Jacobina member whereas the manifold of the Sobral member was shorter than both other members of the complex. Overall, the secretory apparatus of the Sobral member was smaller than the other two. The manifold of M. migonei was very different to those found in Lu. longipalpis s.l. and was positioned in a pit-like structure within the tergal cuticle. The secretory reservoir was connected by a short duct to the manifold. Differences in the size and shape of the manifold may be related to the chemical structure of the pheromone and may have taxonomic value. Examination of the interior cuticle by SEM may help to locate the secretory apparatus of vector species where pheromonal activity has been inferred from behavioural studies but the external secretory structures or pheromones have not yet been found.     

Itaquascon unguiculum and Itaquascon cambewarrense. two new species of eutardigrades from Australia

Abstract

Two new species of eutardigrade, Itaquascon unguiculum and Itaquascon cambe‐warrense, are described from Australia. Itaquascon unguiculum differs from the other species of the genus by having small claws with respect to the body size, and in other quantitative characters. Itaquascon cambewarrense is characterised by stylet furcae which are triangular in shape, with apices thickened but not prolonged to form postero‐lateral processes.     

Ultrastructure of feeding tubes formed in giant-cells induced in plants by the root-knot nematodeMeloidogyne incognita

Summary The plant pathogenic nematodeMeloidogyne incognita forms conspicuous tubular structures referred to as feeding tubes in special food cells, called giant-cells, induced and maintained in susceptible host roots by feeding nematodes. Feeding tubes are formed by nematode secretions injected into giant-cells via a stylet and apparently function to facilitate withdrawal of soluble assimilates by the parasite. In giant-cells in roots of the four host species examined in this study, feeding tube morphology was identical. Tubes were straight to slightly curved structures just less than 1 μm wide and up to slightly more than 70 μm long. At the ultrastructural level, each tube consisted of a 190–290 nm thick, electron-dense, crystalline wall surrounding an electron-transparent lumen with a diameter of 340–510 nm. The distal end of the tube was sealed with wall material. Older tubes were found free in the host cytoplasm while the proximal ends of young tubes were attached to the host cell wall via short wall ingrowths through which the nematode's stylet was inserted. An elaborate membrane system was associated with the feeding tubes and was most extensive around newly formed tubes. Contiguous to the feeding tube wall, this membrane system consisted of strands of smooth endoplasmic reticulum while rough endoplasmic reticulum predominated toward the outer margin of the membrane system. Vacuoles and mitochondria were excluded from a zone of cytoplasm surrounding feeding tubes. This zone of exclusion, as well as the membrane system noted above, tended to be less pronounced or absent around older tubes no longer being used by the nematode.     

Fossil leaves of Buxus (Buxaceae) from the Upper Pliocene of Yunnan,SW China

A new species, Buxus pliosinica H.S. Huang, T. Su et Z.K. Zhou n. sp. (Buxaceae) is designated based on leaf architecture and cuticular features of five compressed fossil leaves from the Upper Pliocene Sanying Formation of Yunnan, SW China. Leaves of B. pliosinica are elliptic and small, with entire margin, retuse tip, intramarginal vein, and exmedially ramified tertiary veins. The leaves are hypostomatic with anomocytic stomatal apparatuses and giant stomata. Based on comparisons of leaf morphological and cuticular features, B. sempervirens Linnaeus is considered as the nearest living relative of B. pliosinica. Morphologically, these species share similar elliptic shape and size, cuneate base, retuse tip, similar ranges of petiole length, angles of 2° vein to midvein, and distance from the intramarginal vein to the margin. In terms of cuticular features, they are similar in type of stomatal apparatus, maximum length of giant stomata and range of stomatal length, but differ in the presence of indumentum. This discovery represents the first fossil record of Buxus from the SE margin of the Tibetan Plateau, and confirms the existence of Buxus in this region by the late Pliocene. Meanwhile, the newly described fossil species contributes to our understanding of the evolution of extant Buxus.     

Geonemy,ecology, reproductive biology and morphology of the tardigrade <Emphasis Type="Italic">Hypsibius zetlandicus</Emphasis> (Eutardigrada: Hypsibiidae) with erection of <Emphasis Type="Italic">Borealibius</Emphasis> gen. n.

The morphology, biology and geographic distribution of Hypsibius zetlandicus (Murray 1907) are considered. Scanning electron microscopy (SEM) and/or light microscopy (LM) analyses have been carried out on H. zetlandicus and the type species of Hypsibius: Hypsibius dujardini (Doyère 1840), with particular emphasis on the buccal–pharyngeal apparatuses. Some unusual characteristics of this apparatus in H. zetlandicus lead us to the erection of the new genus Borealibius, to which H. zetlandicus (Borealibius zetlandicus comb. n.) is transferred. In the light of new discoveries of this species from polar, sub-polar and alpine regions, and based on the available bibliographic references, we hypothesize a boreo–alpine distribution for this species. The presence of traits that are unusual and rare (in other tardigrade species) have been observed whilst analyzing the reproductive biology and ecology of B. zetlandicus (i.e., the presence of hermaphroditism, parental care and the colonization of very different substrates).     

A new species of the genus Hypsibius (Tardigrada: Parachela: Hypsibiidae) from Sakhalin island, far East Russia

A new species of semiterrestrial eutardigrade, Hypsibius stiliferus, is described from Sakhalin Island, Far East Russia. The new species is distinguished from its congeners by having an irregular, polygonal or subtriangular dorsal sculpture, which increases in size posteriorly, two granular macroplacoids, and a cuticular bar near the base of posterior claw 4, and by lacking a microplacoid and septulum. It is currently known from its type locality and several other localities in northern and southern Sakhalin Island. This is the first report concerning tardigrades from Sakhalin Island.     

The location of raspberry ringspot and tomato black ring viruses in the nematode vector, Longidorus elongatus (de Man)

Electron microscopy of thin sections of Longidorus elongatus (de Man) fed on plants infected with raspberry ringspot and tomato black ring viruses showed virus-like particles in the lumen of the buccal capsule and in the space between the stylet and the guiding sheath. In sections of L. elongatus fed on plants infected with arabis mosaic virus, which it does not normally transmit, a few virus particles were seen in the buccal capsule but none was associated with the stylet guiding sheath. It is suggested that the association of virus particles with the cuticular guiding sheath is an explanation of the specificity of virus transmission evident in L. elongatus.     

Asian citrus psyllid stylet morphology and applicability to the model for inter-instar stylet replacement in the potato psyllid

In Hemiptera, presumptive stylets for each consecutive postembryonic instar are manufactured prior to ecdysis to replace the ecdysial stylets discarded with the exuviae. With the discovery that the bacterium “Candidatus” Liberibacter solanacearum accesses the tissues involved in the stylet replacement process of the potato psyllid, a hypothesis was formed that the bacterium could adhere to the stylets of freshly emerged instars and hence gain access to the host plant when feeding is resumed. Although unproven, it was imperative that a model for stylet replacement be built. Stylet morphology and the stylet replacement process of the Asian citrus psyllid (ACP), vector of “C.” L. asiaticus, causal pathogen of citrus greening disease, are comparable to the potato psyllid model system. Morphology consists of a basal terminus with its tab-shaped auricle, a base, shaft, and an apical terminus. Each of the four auricles act as a platform for the replacement apparatus, which is compacted into a tight aggregate of cells, the ‘end-cap’. As modeled, on apolysis of larval instar hypodermis, the aggregate ‘deconstructs’ and expands into a snail shell-shaped tube, the ‘atrium’, that houses the presumptive stylet as it is synthesized. Completed stylets then despool from the atrium and are fitted into their functional positions as the next instar emerges from its exuviae.     

湖南安息香属植物的叶片比较解剖学研究

利用光学显微镜和扫描电镜对湖南产安息香属10种植物叶表皮微形态和解剖结构进行了观察和测量。结果表明:(1)表皮均由单层细胞构成,细胞形状为多边形和无规则形,垂周壁式样为平直、弓形、波状;(2)气孔器大小及密度在种间的差异明显;(3)气孔外拱盖内缘主要为波状和浅波状,气孔器外围角质纹饰以越南安息香的鸟巢状和栓叶安息香的碗状为显著区别特征;(4)老鸹铃、垂珠花和白花龙的气孔器保卫细胞两极有"T"形加厚;(5)栓叶安息香和大果安息香叶上表皮由大型细胞组成;(6)叶肉分化为栅栏组织和海绵组织,二者的厚度及比值在种间有明显的差异,其中越南安息香栅栏组织分化为2层;(7)大果安息香和芬芳安息香的主脉维管组织构成一圈封闭的环状结构,而其他种则为开放的半圆形结构;(8)叶片及主脉的厚度在种间差异明显。安息香属植物的表皮微形态及解剖结构特征比较稳定,可作为种间鉴定和分类的重要依据。