Comparative trichome morphology in feather-legged assassin bugs (Insecta: Heteroptera: Reduviidae: Holoptilinae)

The trichome in ant-feeding Holoptilinae (Insecta: Heteroptera: Reduviidae) comprises remarkable modifications of abdominal sternites 2 and 3. It has been hypothesized that this structure plays a role in attracting and drugging ants. In the present study the trichome of 14 species of Holoptilini, comprising 11 species of Ptilocnemus Westwood and representatives of three additional genera of Holoptilini, is examined using scanning electron and light microscopy. The astoundingly diverse species-level modifications of sternites and vestiture are described and primary homology hypotheses are proposed. The trichome provides species-specific diagnostic characters within Ptilocnemus and evidence for species-groups within the genus, but also for the sistergroup relationship of Ptilocnemus and Smiliopus Bergroth. The comparative morphology establishes a framework for investigations into systematics, functional morphology, and behavioral ecology of these myrmecophagous assassin bugs.     

Sternal gland structures in males of bean flower thrips,Megalurothrips sjostedti,and Poinsettia thrips,Echinothrips americanus,in comparison with those of western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae)

Sternal pores are important features for identification of male thrips, especially within the subfamily Thripinae. They vary in shape, size and distribution even between species of one genus. Their functional role is speculated to be that of sex- and/or aggregation pheromone production. Yet, sexual aggregations are not reported in Echinothrips americanus, known to have sternal pores, while we observed aggregations in Megalurothrips sjostedti, previously reported to lack them.We examined the sternal glands and pores of the thripine species E. americanus and M. sjostedti males, in comparison with those of Frankliniella occidentalis using light microscopy, as well as scanning and transmission electron microscopy. Pore plates of F. occidentalis were ellipsoid and medial on sternites III–VII, while in E. americanus they were distributed as multiple micro pore plates on sternites III–VIII. In M. sjostedti they appeared as an extremely small pore in front of the posterior margin of each of sternites IV–VII. Pore plate and pore plate area were distributed similarly on sternites III–VII in F. occidentalis. However, in E. americanus the total pore plate area increased significantly from sternites III to VIII. Ultrastructure of cells associated with sternal glands showed typical characteristics of gland cells that differ in size, shape and number. The function of sternal glands is further discussed on the basis of morphological comparisons with other thrips species.     

Morphological variability of Arthrospira (Spirulina) fusiformis (Cyanophyta) in relation to environmental variables in the tropical soda lake Chitu,Ethiopia

Although variability of Arthrospira morphology, widely used in taxonomy and other valuable aspects, as a response to changes in environmental variables has been studied in laboratory cultures, little is known about such responses in the natural habitats. In this study, Arthrospira fusiformis was characterized morphologically in relation to selected environmental variables in the natural ecosystem. Three distinct morphotypes, tightly coiled (H-type), spiral or loosely coiled (S-type), and intermediately coiled (C-type) were observed and described. They varied largely in the degree of coiling, trichome and helix dimensions, coils, shape of trichome end and trichome abundance. The H-type was the most dominant (50%) followed by the S-type (40%). The dominance of H-type and tightening of helix pitch were strongly associated with NO₃ ^? and HCO₃ ^? deficiencies, and high levels of photosynthetically active radiation (PAR) and temperature of the lake. The abundance of S-type was more strongly but negatively related to the high salinity of the lake, probably indicating that decreasing salinity may favor the S-type. In conclusion, the variability in abundance and morphology seem to suggest that A. fusiformis could show morphological modifications in response to environmental stresses in their natural soda lakes, resulting in occurrence of various morphotypes of the same species.     

Comparative morphology of abdominal glands in Paederinae (Coleoptera : Staphylinidae)

Glandular structures at the sternites of 31 species of Paederinae (Coleoptera : Staphylinidae) are described in detail for the first time. A median gland of unknown biological significance is situated at the front margin of the 4th sternite in Paederus and Paederidus (Paederus s.l.). A gland tissue at the posterior border of the antecosta opens into a reservoir situated between the antecosta and the intersegmental membrane. Each of the numerous glandular units obviously consist of 2 secretory cells that are drained by a tubule. They are thus related to dermal glands. Two types of pores, single pores and pore plates, are dispersed over the body, but are aggregated in the vicinity of the aperture of the reservoir. In Rugilus, 2 hitherto unknown glands of the same shape are located at the front margins of sternites 4 and 5. In contrast to the glands of Paederus s.l., there are big pores under the gland tissue and the opening area lies in a pit. One further species, Stilicosoma rufipes, was recently classified in the genus Rugilus, but does not have any glands, and therefore the genus Stilicosoma Casey, which was once named for S. rufipes, is re-established. Ochthephilum fracticorne does not have a reservoir, but otherwise combines features of both the glands of Paederus s. l. and those of Rugilus. This link points out the possible derivation of these glands from a common origin. All species of Lathrobiina have accumulations of tubules at the front margins of at least the 4th sternites, and thus represent a rather primitive stage in the development of the glands, while the lack of glandular peculiarities at the 4th sternites in Medonina is plesiomorphic. With respect to a special type of dermal tubules, the genera Medon, Pseudomedon, and Sunius are distinguished from Lithocharis, hence denoting a clear dividing line between the subtribes Medonina and Lithocharina. These features as well as the glands themselves, provide the basis for clarifying the largely unknown phylogeny of Paederinae.     

Evolution of trichome types and its systematic significance in the genus Phlomoides (Lamioideae–Lamiaceae)

Despite a number of recent molecular phylogenetic studies on Phlomoides, in terms of trichome morphology the genus is still among the most poorly studied taxa in the family Lamiaceae. In order to test the utility of trichome characters for delimitation of sections, subsection and species of Phlomoides, we examined trichomes of 64 species representing all recognized sections and subsections using stereomicroscopy and scaning electron microscopy. Two basic types of trichomes could be identified: non‐glandular and glandular. Both trichome types can be simple or branched. The glandular trichomes were sessile, short stalked or long stalked. Different kinds of branched trichomes were observed in most species of P. sect. Phlomoides, i.e. symmetrically stellate, stellate with a central long branch, bi‐ or trifurcate. The species of P. sect. Filipendula were mostly covered by simple trichomes. Moreover, variation in trichome characters appears to have particular value, not only for the classification at sectional or subsectional rank, but also for delimitation of species within each section. For example, all studied species of P. subsect. Fulgentes are characterized by various kinds of stellate trichomes, while the trichome variability in P. subsect. Tetragonae was sufficiently high for species discrimination. An ancestral character state reconstruction was performed in order to investigate the evolution of trichome types and it revealed the following evolutionary trends in trichome characters of Phlomoides: 1) branched trichomes are primitive in Phlomoides as compared to simple ones, 2) long simple non‐glandular trichomes are derived as compared to short simple ones and 3) the presence of stalked glandular trichomes is advanced as compared to subsessile or sessile ones.     

Seed and trichome morphology of the Egyptian Fagonia (Zygophyllaceae) with emphasis on their systematic implications

Seed and trichome morphology of 13 taxa representing the genus Fagonia in Egypt have been studied using light (LM) and scanning electron microscopy (SEM). Macro‐ and micro‐morphological characters, including seed shape, seed size, seed coat sculpture, trichome density and structure were studied to evaluate their systematic significance. Seed shape and trichome density were found to have only minor taxonomic value, but seed coat sculpturing and trichome structure proved to be valuable characters. These characters offer evidence to combine certain species, e.g. Fagonia kassasii and F. schimperi in F. bruguieri, Fagonia microphylla in F. scabra and Fagonia thebaica in F. arabica. However, F. sinaica, F. tristis, F. boveana and F. isotricha should be maintained as separate species. Generally, the different patterns of seed and trichome morphology are useful in delimitation of species within the genus Fagonia, but they could not be used to characterize groups of related species.     

Comparison of polyphenol oxidase expression in glandular trichomes of solanum and lycopersicon species

Tetralobulate glandular trichomes are present on the foliage of many solanaceous species. Resistance of many of these species to insects is conditioned by the ability of trichomes to rupture upon contact and to rapidly polymerize their contents, resulting in entrapment of insects in hardened trichome exudate. In the wild potato, Solanum berthaultii, polymerization of trichome exudate is initiated by a soluble M_r 59,000 polyphenol oxidase (PPO), which is a dominant protein constituent of the organ. PPOs, although ubiquitous in angiosperms, typically display great heterogeneity in molecular weight and are found at low levels in plant cells. Because of the unusually high accumulation and tissue-specific expression of the M_r 59,000 PPO in S. berthaultii glandular trichomes, we analyzed trichome proteins of a number of Lycopersicon and Solanum species to assess the extent to which possession of the M_r 59,000 PPO is conserved. Trichomes were collected manually and examined for PPO activity, immuno-cross-reactivity with S. berthaultiiM_r 59,000 PPO, and protein content. In addition, N-terminal amino acid sequences were obtained for five trichome PPOs. All species analyzed possessed trichome PPOs similar in structure and level of expression to that of S. berthaultii. The relationship between sequences and structures of these conserved PPOs and the variable PPOs of leaf is discussed.     

Trichome micromorphology of Iranian Stachys (Lamiaceae) with emphasis on its systematic implication

Trichomes of 37 taxa of the genus Stachys and one species of Sideritis (S. montana) were examined using light and scanning electron microscopy. The indumentum shows considerable variability among different species, but is constant among different populations of one species, and therefore, affords valuable characters in delimitation of sections and species. The characters of taxonomic interest were presence of glandular and non-glandular trichomes, thickness of the cell walls, number of cells (unicellular or multi-cellular), presence of branched (dendroid) trichomes, presence of vermiform trichomes, orientation of trichomes in relation to the epidermal surface, curviness of trichomes, and presence of papillae on trichome surface. Two basic types of trichomes can be distinguished: glandular and non-glandular trichomes. The glandular trichomes can in turn be subdivided into subtypes: stalked, subsessile, or sessile. The stalks of the glandular trichomes can be uni- or multi-cellular. Simple unbranched and branched trichomes constitute two subtypes of non-glandular trichomes. Our data do not provide any support for separation of Sideritis from Stachys. The following evolutionary trends are suggested here for Stachys: vermiform trichomes with stellate base are primitive against vermiform trichomes with tuberculate base, long vermiform trichomes are primitive against the short simple trichomes, appressed trichomes are advanced against spreading ones, and loss of glandular trichomes is advanced against their presence. Overall, trichome micromorphology is more useful in separation of species within sections rather than characterizing large natural groups known as sections, except for few cases.     

Boomeranging in structural defense: Phytophagous insect uses cycad trichomes to defend against entomophagy

Plant defensive behaviors that resist arthropod herbivory include trichome-mediated defenses, and variation in plant trichome morphology and abundance provides examples of the mechanistic complexities of insect-plant interactions. Trichomes were removed from Cycas revoluta cataphylls on the island of Guam to reveal Aulacaspis yasumatsui scale infestation, and predation of the newly exposed insects by pre-existing Rhyzobius lophanthae beetles commenced within one day. The quotient of predated/total scale insects was 0.5 by day 4 and stabilized at that found on adjacent glabrous leaves in about one week. The trichome phenotype covering the C. revoluta cataphyll complex offers the invasive A. yasumatsui armored scale effectual enemy-free space in this system. This pest and predator share no known evolutionary history with C. revoluta, therefore, the adaptive significance of this plant behavior in natural habitat is not yet known.     

Raphidiopsis mediterranea Skuja represents non-heterocytous life-cycle stages of Cylindrospermopsis raciborskii (Woloszynska) Seenayya et Subba Raju in Lake Kastoria (Greece), its type locality: Evidence by morphological and phylogenetic analysis

The taxonomical relationship of Cylindrospermopsis raciborskii and Raphidiopsis mediterranea was studied by morphological and 16S rRNA gene diversity analyses of natural populations from Lake Kastoria, Greece. Samples were obtained during a bloom (23,830 trichomes mL⁻¹) in August 2003. A high diversity of apical cell, trichome, heterocyte and akinete morphology, trichome fragmentation and reproduction was observed. Trichomes were grouped into three dominant morphotypes: the typical and the non-heterocytous morphotype of C. raciborskii and the typical morphotype of R. mediterranea. A morphometric comparison of the dominant morphotypes showed significant differences in mean values of cell and trichome sizes despite the high overlap in the range of the respective size values. Additionally, two new morphotypes representing developmental stages of the species are described while a new mode of reproduction involving a structurally distinct reproductive cell is described for the first time in planktic Nostocales. A putative life-cycle, common for C. raciborskii and R. mediterranea is proposed revealing that trichome reproduction of R. mediterranea gives rise both to R. mediterranea and C. raciborskii non-heterocytous morphotypes. The phylogenetic analysis of partial 16S rRNA gene (ca. 920 bp) of the co-existing Cylindrospermopsis and Raphidiopsis morphotypes revealed only one phylotype which showed 99.54% similarity to R. mediterranea HB2 (China) and 99.19% similarity to C. raciborskii form 1 (Australia). We propose that all morphotypes comprised stages of the life cycle of C. raciborkii whereas R. mediterranea from Lake Kastoria (its type locality) represents non-heterocytous stages of Cylindrospermopsis complex life cycle.     

Host plant effects on the behaviour and performance of Amblyseius swirskii (Acari: Phytoseiidae)

Biological control in ornamental crops is challenging due to the wide diversity of crops and cultivars. In this study, we tested the hypothesis that trichome density on different host plants influences the behavior and performance of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Behavioural observations of this predator in the presence or absence of prey (western flower thrips, Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) were done on leaf squares of ornamental plant species differing in trichome density (rose, chrysanthemum and gerbera) and compared to a smooth surface (plastic). Tomato leaves were used to observe the influence of glandular trichomes. The performance of A. swirskii was assessed by measuring predation and oviposition rate. Behaviour of A. swirskii was influenced by plant species. Up to a certain density of trichomes, trichome number had a negative effect on walking speed. It was highest on plastic, followed by rose. No differences were found among chrysanthemum, gerbera and tomato. Walking speed was slightly higher on disks without prey. Proportion of time spent walking was the same on leaf disks of all plant species, with and without prey. No effect of glandular trichomes on tomato leaves was seen. Most thrips were killed and consumed on gerbera, and least on rose. Predation rates on chrysanthemum and plastic were intermediate. In contrast, no differences in oviposition rate were found among plant species. The results of this study indicate that trichome density can explain some of the variability in efficacy of A. swirskii on different crops. Release rates of A. swirskii may need to be adjusted depending on the crop in which it is used.     

MORPHOLOGICAL ADAPTATION TO HOST PLANTS IN UROLEUCON (HOMOPTERA: APHIDIDAE)

The morphology of host-specific Old World Uroleucon (Homoptera: Aphididae) species is related to features of their host plant species (Asteraceae and Campanulaceae) by canonical correlation analysis. Aphid species on pubescent host species have longer rostra and shorter hind tarsi, adaptations for feeding and walking on hirsute surfaces. Also, aphid species on taller hosts are larger. The positive relationship between rostrum length and host trichome density is further supported by simple regression analyses on two species complexes. Regression parameters differ between groups, suggesting different responses to different trichome types. This morphological adaptation involves characters used extensively by taxonomists and could result in convergence obscuring phylogenetic relationships of herbivore taxa and, particularly, the relation of herbivore phylogeny to host phylogeny.     

Trichome micromorphology of the Chinese-Himalayan genus <Emphasis Type="Italic">Colquhounia</Emphasis> (Lamiaceae), with emphasis on taxonomic implications

Trichome micromorphology of leaves and young stems of nine taxa (including four varieties) of Colquhounia were examined using light and scanning microscopy. Two basic types of trichomes were recognized: eglandular and glandular. Eglandular trichomes are subdivided into simple and branched trichomes. Based on the number of cells and trichome configuration, simple eglandular trichomes are further divided into four forms: unicellular, two-celled, three-celled and more than three-celled trichomes. Based on branching configuration, the branched eglandular trichomes can be separated into three forms: biramous, stellate and dendroid. Glandular trichomes can be divided into two subtypes: capitate and peltate glandular trichomes. Results from this study of morphological diversity of trichomes within Colquhounia lend insight into infrageneric classification and species relationships. Based on the presence of branched trichomes in C. elegans, this species should be transferred from Colquhounia sect. Simplicipili to sect. Colquhounia. We provide a taxonomic key to species of Chinese Colquhounia based on trichome morphology and other important morphological traits.     

Reproductive morphology,copulation, and inter-populational variation in the diamondback moth,Plutella xylostella (L.) (Lepidoptera: Plutellidae)

Copulatory mechanisms and internal reproductive systems of male and female Plutella xylostella (L.) were investigated. Both male and female specimens exhibited characteristics typical of ditrysian Lepidoptera, with some peculiarities. Female structures appear to be relatively simple: the bursa copulatrix lacks cuticular signa within, the spermatheca lacks lagenar arms exhibited in some Lepidoptera, and colleterial glands have secretory system and reservoir combined. Male accessory gland ducts are joined distally, a condition that has not been described in other Lepidoptera. Genitalia of both sexes appear simple; females possess a posterior cuticular extension of abdominal sternites that houses the bursal duct and accomodates the needle-like aedeagus of a male during copulation. Despite the apparent simplicity, configuration of genitalia is highly specific in shape, angle, and size, which is likely to be important in maintaining reproductive isolation within the species. However, a population of P. xylostella from Australia showed some modification to both aedeagal and bursal structures. These variations suggest some important implications for considering species with worldwide distributions.     

Comparative morphology of leaf epidermis in the genus Lithocarpus and its implication in leaf epidermal feature evolution in Fagaceae

Leaf epidermal features are considered to be taxonomically important in Fagaceae. In this study, we examined and compared leaf epidermal features of 112 specimens, representing 105 species and one variety of Lithocarpus from China and adjacent areas and Notholithocarpus densiflorus. As a result of the different interpretations of terms in previous studies, trichome terminology in Lithocarpus and its relatives was re-assessed aiming to reveal the trichome evolutionary patterns in Fagaceae. Twelve types of trichomes and five types of trichome bases were detected in Lithocarpus, among which the broad-based trichome (BBT) is newly reported. Stomata in Lithocarpus are restricted to the cyclocytic type and their size range is 28.6 ± 8.2 μm × 26.5 ± 9.3 μm. The distribution of epidermal features in Lithocarpus revealed three distinct morphological groups: glabrous, BBT, and appressed parallel tufts (APT). The importance of epidermal features across Fagaceae for taxon delimitation is evaluated. Species of Lithocarpus can be accurately identified by the presence of APT or flat epidermal cells combined with non-dark stained subsidiary cells and non-cutinized trichome bases only, or in addition, fasciculate trichome bases. The phylogenetic distribution of epidermal features and their evolutionary trends in Fagaceae is also discussed.     

<Emphasis Type="Italic">Pectapalochrus</Emphasis> gen. n., a new genus of soft-winged flower beetles of the tribe apalochrini (Coleoptera,Malachiidae)

Analysis of species of Dromanthomorphus Pic from South-East Asia has shown that the genus is distinguished by the following special male characters: flabellate, serrate, or filiform antennae; one-colored white pubescence of the surface; a swollen metathorax with a gladiate appendage; stout and excavate fore and middle tibiae; elongate and modified fore and middle coxae; apical tergites with a specific slanting and tile-like sculpture at the apex; apical abdominal sternites bilaciniate, with specifically sculptured apices. These characters are completely lacking in the Palaearctic species attributed to Dromanthomorphus, which are characterized by flabellate or serrate antennae, by a simple, not swollen metathorax lacking appendages, double white and black pubescence of the surface, simple, evenly rounded apical abdominal tergites, and evenly narrowed apical abdominal sternites emarginate in the middle and having simple, not sculptured apices. Based on these differences, a new genus, Pectapalochrus gen. n., is described for the Palaearctic species. Keys to Pectapalochrus species and to genera of Apalochrini of Eurasia and also illustrations of the habitus and male structures of the new genus are given.     

A new species of Themus (Themus) Motschulsky from Yunnan,China and a redescription of T. (T.) testaceicollis Wittmer, 1983 (Coleoptera,Cantharidae)

A new species is described, Themus (Themus) dimorphus sp. n. from Yunnan, China. Themus (Themus) testaceicollis Wittmer, 1983 is redescribed and compared with the new species. The two species are illustrated with habitus and genitalia of both sexes and abdominal sternites VIII of female.