Marginal Bristles Research Articles

Morpho-anatomical characterization of Eryngium yuccifolium ('Rattlesnake-master').

This paper provides detailed morpho-anatomical and histochemical characteristics of the leaves, peduncles, stems, and roots of Eryngium yuccifolium Michx. (Apiaceae) by bright-field light and scanning electron microscopy. Noteworthy morpho-anatomical features include the monocot-like leaves with parallel venation and distant marginal bristles, amphistomatic leaves with paracytic or anisocytic stomata and heterogenous isobilateral mesophyll, the presence of epicuticular wax crystalloids on both leaf surfaces, calcium oxalate druses and secretory canals in all the studied plant parts, presence of hypodermis, stem and peduncle with longitudinal ribs containing collenchyma, presence of aerenchyma in the peduncle and root, and absence of sclerenchyma in all the plant parts analyzed. These characteristics would aid in the taxonomy, species identification as well as quality control of the botanical.

Dionaea traps selectively allow small animals to escape

Dionaea muscipula selectively allows small animals to escape using a system of interlocking features that complement each other very efficiently. Ants of the species Lasius neglectus (length 3.5 mm) ran through open traps, pausing on the alluring glands along the rim of the trap moving their mouthparts over them. Analysis of videos revealed the ants primarily passed along the trap rim, over the alluring glands, but sometimes ran down to the leaf base through the trigger hairs occasionally brushing by a hair without triggering the trap, because they did not deliver the two stimuli needed to trigger trap closure. Traps observed for four weeks were estimated from sampled observations to have had a total of about 15,000 trap visits by ants during this time period. Six ants were captured during four weeks indicating a risk of capture of about 0.04%. During this same period ten prey other than ants were captured. Visits for prey other than ants was mostly nocturnal and so low that no visits were observed during the observation period. Compared with the large number of ant visits all other prey visits were orders of magnitude fewer. The selective system that allows small animals to escape includes: 1) Attraction of the ants away from the trigger hairs by alluring glands. 2) Clear visibility of the trigger hairs to a 3.5 mm ant. 3) The requirement of two stimuli for triggering trap closure. 4) The escape allowed for small animals by openings between the marginal bristles during the slower phase of trap closure that follows the rapid snap of the trap. Since ants are known to compose about one third of the captures by Dionaea in its native habitat, selection against the capture of small ants not worth the energy expenditure by the plant is an adaptive mechanism.

A Defensive Kicking Behavior in Response to Mechanical Stimuli Mediated by Drosophila Wing Margin Bristles.

We discovered a previously unknown function for recurved bristles on the Drosophila melanogaster wing. We found that when a mite (a parasitic pest for Drosophila) touches the wing margin, the fly initiates a swift and accurate kick to remove the mite. The fly head is dispensable for this behavior. Furthermore, we found that a TRPV channel, Nanchung, and a specific Nanchung-expressing neuron under each recurved bristle are essential for its mechanosensitivity and the kicking behavior. In addition, touching different regions of the wing margin elicits kicking directed precisely at the stimulated region. Our experiments suggest that recurved bristles allow the fly to sense the presence of objects by touch to initiate a defensive behavior (perhaps analogous to touch-evoked scratching; Akiyama et al., 2012).

Sol narae (Sona) is a Drosophila ADAMTS involved in Wg signaling.

ADAMTS (a disintegrin and metalloproteases with thrombospondin motif) family consists of secreted proteases, and is shown to cleave extracellular matrix proteins. Their malfunctions result in cancers and disorders in connective tissues. We report here that a Drosophila ADAMTS named Sol narae (Sona) promotes Wnt/Wingless (Wg) signaling. sona loss-of-function mutants are lethal and rare escapers had malformed appendages, indicating that sona is essential for fly development and survival. sona exhibited positive genetic interaction with wntless (wls) that encodes a cargo protein for Wg. Loss of sona decreased the level of extracellular Wg, and also reduced the expression level of Wg effector proteins such as Senseless (Sens), Distalless (Dll) and Vestigial (Vg). Sona and Wg colocalized in Golgi and endosomal vesicles, and were in the same protein complex. Furthermore, co-expression of Wg and Sona generated ectopic wing margin bristles. This study suggests that Sona is involved in Wg signaling by regulating the level of extracellular Wg.

Characterisation of Drosophila Ubx CPTI000601 and hth CPTI000378 protein trap lines.

In Drosophila, protein trap strategies provide powerful approaches for the generation of tagged proteins expressed under endogenous control. Here, we describe expression and functional analysis to evaluate new Ubx and hth protein trap lines generated by the Cambridge Protein Trap project. Both protein traps exhibit spatial and temporal expression patterns consistent with the reported endogenous pattern in the embryo. In imaginal discs, Ubx-YFP is expressed throughout the haltere and 3rd leg imaginal discs, while Hth-YFP is expressed in the proximal regions of haltere and wing discs but not in the pouch region. The Ubx CPTI000601 line is semilethal as a homozygote. No T3/A1 to T2 transformations were observed in the embryonic cuticle or the developing midgut. The homozygous survivors, however, exhibit a weak haltere phenotype with a few wing-like marginal bristles on the haltere capitellum. Although hth CPTI000378 is completely lethal as a homozygote, the hth CPTI000378/hth C1 genotype is viable. Using a hth deletion (Df(3R)BSC479) we show that hth CPTI000378/Df(3R)BSC479 adults are phenotypically normal. No transformations were observed in hth CPTI000378, hth CPTI000378/hth C1, or hth CPTI000378/Df(3R)BSC479 embryonic cuticles. We have successfully characterised the Ubx-YFP and Hth-YFP protein trap lines demonstrating that the tagged proteins show appropriate expression patterns and produce at least partially functional proteins.

Description deNosopsyllus (N.) Atsbin. sp. (Siphonaptera : Ceratophyllidae) d’Éthiopie et révision de l’espèce affineN. (N.) Incisus(Jordan & Rothschild, 1913) ; discussion biogéographique

Nous décrivons un Nosopsyllus s. sto. nouveau du nord de l’Éthiopie, N. atsbi, montrant des ressemblances phylétiques avec N. incisus (Jordan & Rothschild, 1913), espèce cantonnée à la partie orientale de la région afrotropicale. Ceci nous conduit à revoir les populations classées comme incisus sur l’unique critère de la sétation du télomère (trois fortes soies marginales, au lieu des deux classiquement observées dans ces genre et sous-genre). Il apparaît que N. incisus s. sto. est connu au nord-est de la République Démocratique du Congo, au Kenya, au Burundi et en Tanzanie. Au nord et au sud de cette région (centre de l’Éthiopie, d’une part, Zambie et Malawi, d’autre part), deux taxa sont morphologiquement à part et nous les érigeons au rang de sous-espèces : Nosopsyllus (N.) incisus traubi n. ssp. et N. (N.) incisus lewisi n. ssp. À l’heure actuelle, le “complexe incisus” est riche de quatre taxa, à savoir, du nord au sud, N. atsbi n. sp., N. incisus traubi n. ssp., N. incisus incisus (Jordan & Rothschild, 1913) et N. incisus lewisi n. ssp.

Interpretation of the Wingless Gradient Requires Signaling-Induced Self-Inhibition

In a classical view of development, a cell can acquire positional information by reading the local concentration of a morphogen independently of its neighbors. Accordingly, in Drosophila, the morphogen Wingless produced in the wing's prospective distal region activates target genes in a dose-dependent fashion to organize the proximodistal pattern. Here, we show that, in parallel, Wingless triggers two nonautonomous inhibitory programs that play an important role in the establishment of positional information. Cells flanking the source of Wingless produce a negative signal (encoded by notum) that inhibits Wingless signaling in nearby cells. Additionally, in response to Wingless, all prospective wing cells produce an unidentified signal that dampens target gene expression in surrounding cells. Thus, cells influence each other's response to Wingless through at least two modes of lateral inhibition. Without lateral inhibition, some cells acquire ectopic fates. Lateral inhibition may be a general mechanism behind the interpretation of morphogen gradients.

Morphogenesis of Drosophila pupal wings in vitro

We have developed an in vitro culture system which supports the differentiation of Drosophila pupal wings. Cultured wings develop marginal bristles and wing veins, and wing cells form a single prehair at their distal vertex at the appropriate developmental stages. We have tested two molecules with well defined activities to determine the usefulness of this system for applying pharmacological approaches to wing differentiation. Cycloheximide (CY) is a small molecule which inhibits protein synthesis. We found that 50 nM CY rapidly blocks all stages of wing differentiation without lowering cell viability. Chitinase is an enzyme which cleaves chitin polymers and is involved in normal cuticle apolysis. Chitinase applied prior to 28 h apf caused a contraction of the wing without affecting the general wing pattern. We have detected connections between the epithelium and pupal cuticle that are presumably targets of chitinase and are necessary for maintaining normal tissue shape during morphogenesis. Later in development exposure to chitinase caused a loss of normal prehair and bristle polarity, and high doses resulted in a severe disruption of the actin cytoskeleton.

Shaggy (zeste-white 3) and the formation of supernumerary bristle precursors in the developing wing blade of Drosophila

The development of supernumerary bristle precursors induced by the mutation shaggy (sgg; also known as zeste-white 3) was examined in the developing wing blade of imaginal and pupal Drosophila. sgg clones were induced by mitotic recombination; clones were marked using enhancer-trap flies which express β-galactosidase ubiquitously in imaginal tissues, while bristle precursors were identified using sensillum and bristle-specific enhancer-trap lines. It was shown that the precursors of supernumerary sgg bristles in the wing blade mimicked the development of morphologically similar margin bristles, developing in a manner similar to that of anterior sensory bristles in anterior clones and posterior noninnervated bristles in posterior clones. Interestingly, supernumerary anterior sensory bristles appeared outside the normal regions of “proneural” gene activity as identified using anti- achaete. Moreover, sgg could induce the ectopic expression of achaete in anterior clones. Thus, in the anterior wing blade the sgg mutation leads to the formation of ectopic proneural regions.

The sensory projections of Drosophila mutants which show abnormal wing formation or flying behavior

The central projection pattern of sensory neurones from the wing of Drosophila melanogaster arise from a small number of differencentiated entiated cell types which are localized in a pricise and reproducible spatial pattern. We report here the distribution of the nerve pathways revealed by filling with peroxidase and the structure and number of the wing sensory receptors, in files which have wings but which nevetheless are flightless, including one which presents abnormal wing formation. Our results indicate that in dumpy and taxi mutants, there are no detectable modifications in the neural projections or in the number and morphology of sensory receptors. Vestigial mutants however, present several alterations including the absence of the ovoid projection, a fact consistent with the existence of very few marginal bristles. The projection of the large campaniform sensilla branch profusely along the ventromedial tract and more sensory fibers cross the midline in the mesothorax. Wings of vestigial mutants show a decrease in the number of large campaniform sensilla, and more importantly some receptors present abnormally oriented trichomes in the neighboring cells.

Restoration of wing margins in Lyra mutants of Drosophila melanogaster

Lyra is a dominant, homozygous lethal mutation of Drosophila melanogaster; in heterozygotes the wings lack portions of the anterior and posterior margins including the characteristic bristles. We have found that, in addition to the loss of bristle forming cells, there is a decrease in the number of wing surface cells that varies between 10 and 20%. However, we observed no histological evidence of excessive cell death in either the larval discs or the pupal wing precursors in Lyra flies. Restoration of all or part of the normal wing margins occurs in some, but not all, cases of morphogenetic mosaics, in which there were patches of wild-type cells in Lyra wing margins due to irradiation-induced mitotic recombination. Analysis of these restorations, using margin bristles as indicators, shows that the Lyra wild-type gene is not involved in bristle formation per se and further that its expression is not cell autonomous. Instead the effect of the Lyra mutation appears to be associated with development of a margin forming subpopulation of cells and to influence the characteristic pattern of cells and bristles in the wing margin via an inductive interaction. The dorsal-ventral boundary can be demonstrated in the de facto wing margins of Lyra mutants suggesting that its origin is independent of any function Lyra might have in normal wing margin morphogenesis. In wing margin restorations the dorsal-ventral boundary is clearly delimited by trichomes and somewhat less rigorously shown by the margin bristles. Further, in these restorations ventral clones induce dorsal bristles, as well as ventral ones, and vice versa, indicating that the influence of Lyra is not restricted by the dorsal-ventral boundary.

Observations on the Chætotaxy of Calliphorinae.*

Moreover, he says, “The chætotaxy is invariable for each species except for an occasional evident deformity, and it differs in the different species only in the number of achrostical bristles.” Observations were made on this subfamily during the past season and especial attention was given to the matter of chætotaxy in Lucilia. Thus some estimate may be obtained of the extent of deformity as it occurs in nature. Female flies of this genus, moreover, were obtained alive and set in cages containing fish, in order that their offspring might be obtained for the purpose of studying the range of variation in the progeny of the separate females. Each family probably represents the offspring of several males as copulation is frequent. The bristles studied comprise only the achrosticals and the dorsocentrals posterior to the transverse suture of the thorax, with the exception that in L. sylvarum the marginal bristles on the second abdominal segment were recorded as they showed considerable divergence from the normal condition recorded by Hough and are regarded as a specific character.