Evidence for adhesive activity of the ventrolateral flange in Giardia lamblia

Giardia lamblia is an intestinal protozoan that inhabits the intestinal tract of man and other mammals by attaching to the mucosal surface via the contractile activity of an attachment organelle called the ventral adhesive disk. We have investigated the presence of other attachment mechanisms in G. lamblia trophozoites by using microfabricated substrates that sterically interfere with formation of the hypothesized "negative pressure" under the ventral adhesive disk that would mediate attachment to a substratum. Pillars measuring 1 microm high and 2 microm in diam. were constructed in microarrays with spacings smaller than the diameter of the ventral adhesive disk. Using high resolution field emission scanning electron microscopy, the attachment of trophozoites to the tops of pillars in the microfabricated substrates was investigated. Firm adhesion of trophozoites was observed to be mediated by direct attachment of the ventrolateral flange membrane to the tops of microfabricated pillars. Attachment to microfabricated surfaces was 16% of that observed for attachment mediated by the ventral adhesive disk (4.4 +/- 1.5 cells/100 micro2 micropillar surface vs. 25.9 +/- 3.1 cells/100 micro2 flat substrate, p < 0.0001) This is the first report of trophozoite adhesion to a substratum by a mechanism other than the direct attachment of the ventral adhesive disk, and provides experimental evidence that the ventrolateral flange may play a role in trophozoite adhesion. A hypothesis is presented describing how the adhesive nature of the ventrolateral flange might be involved in normal attachment of G. lamblia trophozoites to a substratum.     

Structure of the organs of attachment of brachiolaria larvae of Stichaster australis (Verrill) and Coscinasterias calamaria (Gray) (Echinodermata: Asteroidea)

The structure of the brachiolar arms and adhesive disk of the brachiolaria larvae of Stichaster australis (Verrill) and Coscinasterias calamaria (Gray) was determined from light microscopy and from scanning and transmission electron microscopy. The structure of these organs was very similar in both species.The brachiolar arms are comprised of a stem region terminating in a crown of adhesive papillae which are made up of a variety of secretory cell types. Principal among these are elongated cells producing very electron-dense secretory particles, which are released at the free cell surface attached to cilia. Secretory particles appear to be important in temporary attachment of the brachiolar arms to the substratum. Ciliary sense cells, possibly used in the recognition of specific substrata are located at the tip of adhesive papillae.The adhesive disk is comprised of large cells packed with secretory droplets and elongated intracellular fibres. In the attached adhesive disk, secretory droplets are lost, having formed the cement that attaches the disk to the substratum. It appears that adhesive papillae lateral to the adhesive disk hold the disk in position close to the substratum during secretion and hardening of the cement. The intracellular fibres are the principal anchoring structures running from microvilli (locked into the attachment cement) on the surface of the disk to the underlying connective tissue of the attachment stalk.     

Permanent and Seasonal Expressions of Sexual Dimorphisms in a Weakly Electric Fish, Mormyrus rume proboscirostris Boulenger 1898 (Mormyridae, Teleostei)

Several sexually dimorphic characters of the anal-fin complex in the mormyrid fish, Mormyrus rume proboscirostris, assist during courtship when the male envelops the female's anal fin with its own to form a common spawning pouch (anal-fin reflex). We found that developmental growth and seasonally cycling gonadal activity selectively affect their expression. The structures defining the anal fin undergo a permanent sexually dimorphic transformation at a time when ripe spermatozoa first appear in the testis of young males. However, the expression of a dorsally directed indentation of the posterior ventral body wall, affecting the dorsal margin of the anal fin, appeared to be more plastic as it correlated with the gonadosomatic index, that is, testis size. We surmised that this indentation is influenced by cyclic anabolic action on muscle involved with the execution of the anal-fin reflex.     

Sex difference and response to testosterone in gabaergic cells of the medial preoptic nucleus and ventral bed nuclei of the stria terminalis in gerbils

The medial preoptic nucleus (MPN) and ventral bed nuclei of the stria terminalis (BST) are needed to maintain mating in sexually experienced male gerbils and rats. The gerbil ventral BST is also activated with mating, as assessed by Fos expression, as is the medial MPN (MPNm) of both species. In gerbils, many of those mating-activated cells contain glutamic acid decarboxylase (GAD), the enzyme that synthesizes γ-aminobutyric acid (GABA). Some of those cells are projection neurons, but others may release GABA locally. Through actions in the medial preoptic area, GABA inhibits and testosterone (T) promotes male sex behavior. Thus, T may promote mating, in part, by decreasing GAD in MPNm or ventral BST cells. In rats, T increases GAD mRNA in the central MPN (MPNc), where MPN GABAergic cells are densest, but mating behavior does not change in sexually experienced males when the MPNc is ablated. Therefore, this study focused on the MPNm and ventral BST to ask whether their GABAergic cells respond to T or are sexually dimorphic. This was done by visualizing cells immunoreactive (IR) for GAD₆₇, an isoform found primarily in cell bodies, in male and female gerbils and in castrated males with and without T. At both sites, males had more GAD₆₇-IR cells than females, and T decreased GAD₆₇-IR cell numbers in males. Thus, the MPNm and ventral BST have GABAergic cells that are sexually dimorphic and in which T decreases GAD, consistent with local effects of T and GABA on mating.     

The morphology of the adhesive organ of the sisorid fish,Glyptothorax pectinopterus

In the sisorid fish,Glyptothorax pectinopterus, the adhesive organ located on the ventral side of the thorax consists of a number of longitudinal ridges and grooves that alternate with each other around a triangular furrow lying in the centre. Adhesion of the fish to the rocky substratum in a hill stream habitat is brought about by the hooked and keratinized epidermal spines borne by the longitudinal ridges of the adhesive organ as well as those on the under surface of the pectoral and pelvic fins. The secretion of a surface coat of mucopolysaccharides by the mucous cells and the goblet cells is a device to protect the adhesive organ from mechanical abrasion.     

Microstructure of the adhesive pad in the millipede Orthomorphella pekuensis (Polydesmida: Paradoxosomatidae)

Secondary sexual structures in millipedes have evolved to improve the efficiency with which spermatophores are transferred from males to females. Here, we demonstrate the microstructural characteristics of the sexual dimorphism in the leg adhesive pads of the millipede Orthomorphella pekuensis, using field emission scanning electron microscopy. The adult male of this millipede has developed typical adhesive pads on the legs as a secondary sexual character: these help the male hold on to the female during mating. The adhesive pads are located on the ventral surface of the tarsus in the form of numerous filamentous bristles with horizontal striation. There are approximately 300 bristles, each with an average length of approximately 60 µm, on each tarsus. Each bristle has a round socket on the surface of the tarsus and an acuminate tip. The striation appears only on the distal half of each bristle, typically.     

Gross structure and dimensions of the gills in a hill-stream sisorid catfish,Glyptothorax pectinopterus

Gross structure and dimensions of the gills have been examined in a hill-stream sisorid catfish,Glyptothorax pectinopterus, which remains adhered to rocks by means of an adhesive organ developed on the ventral side of the thorax. The fish shows a greater weight-specific gill area and greater length of the gill filaments by comparison with other hill-stream fishes. Adaptation for life in a hill-stream habitat is shown by the presence of additional filaments on the gills and patches of specialised cells on the filament epithelium.     

鳜鳃部寄生河鲈锚首吸虫的扫描电镜观察

河鲈锚首吸虫头器表面分布着形状各异的孔状结构,每个中央头瓣上有两个随着器囊,而每个外侧头瓣上只有一个。口腔位于头器下方的腹面中线上,口腔表皮与周围的表皮无异。生殖孔在口腔正下方,阴道开口于虫体背侧面,周围有微纤毛的分布。交接器位于生殖孔左下方,交接管表面波纹状,辅助交配器表面布满疣状突起,后随着器的中央锚钩上具一凹槽,边缘小钩的钩尖弯向基部。虫体表面至少分布着两类可能的感受器末端,一类呈单纤毛状散布于体表,纤毛从体表凹坑中伸出,或在其基部围一环状领襟;另一类呈乳突状,位于外侧头瓣的顶部。在部分河鲈锚首吸虫体表可见车轮虫的超寄生。     

Shiny wing scales cause spec(tac)ular camouflage of the angled sunbeam butterfly,Curetis acuta

The angled sunbeam butterfly, Curetis acuta (Lycaenidae), is a distinctly sexually dimorphic lycaenid butterfly from Asia. The dorsal wings of female and male butterflies have a similar pattern, with a large white area in the female and an orange area in the male, framed within brown–black margins. The ventral wings of both sexes are silvery white, which is caused by stacks of overlapping, non‐pigmented, and specular‐reflecting scales. With oblique illumination, the reflected light of the ventral wings is strongly polarized. We show that the silvery reflection facilitates camouflage in a shaded, foliaceous environment. The ecological function of the silvery reflection is presumably two‐fold: for intraspecific signalling in flight, and for reducing predation risk at rest and during hibernation. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 279–289.     

Developmental and biochemical studies of adhesive specificity among embryonic retinal cells.

One pattern of cell-cell adhesion within the chick embryo neural retina follows a dorsoventral gradient in which cells at either end show maximal affinity for each other. Developmental and biochemical approaches have been applied to analyze the basis of this adhesive pattern. When retinal cells were prepared from eyes that had been inverted 180° in situ prior to retinal differentiation, an inverted pattern of adhesive preference resulted. These data suggest that adhesive preference is determined early in embryogenesis. Trypsinization of either dorsal or ventral retinal cells destroyed their adhesive preference. Treatment with neuraminidase resulted in a differential loss of adhesive preference by dorsal retinal cells. This effect could be mimicked by mild oxidation with NaIO₄. Since periodate inactivation of adhesive preference could be reversed by subsequent borohydride treatment, borotritiate was used to label those cell surface molecules crucial to the reactivation of adhesive preference. Fluorographs prepared after polyacrylamide gel electrophoresis revealed that periodate stimulated the appearance of a small number of radioactively labeled bands. These data suggest that adhesive preference is mediated by glycoconjugates, possibly sialoglycoproteins, on the dorsal cell surface.     

Exploration of embryonic origins of germline stem cells and neoblasts in Enchytraeus japonensis (Oligochaeta, Annelida)

An oligochaete annelid species, Enchytraeus japonensis, reproduces not only asexually but also sexually. It has been reported that putative mesodermal stem cells called neoblasts contribute to blastema formation and that Ej-piwi(+) germline stem cells participate in gonadal regeneration. To delineate the origin and formation of both of these stem cells, we isolated two vasa-related genes (Ej-vlg1 and Ej-vlg2) and analyzed the expression of each along with that of germline marker gene Ej-piwi. In adults, Ej-vlg1 and Ej-vlg2 were expressed in Ej-piwi(+) germline stem cells and germ cells in gonads, while only Ej-vlg2 mRNAs were detected in neoblasts. Expression analysis during embryogenesis indicated that clusters of Ej-vlg1(+)/Ej-vlg2(+) cells, located at the posterior ventral region in late embryos, became Ej-vlg1(+)/Ej-vlg2(+)/Ej-piwi(+) germline stem cells just after embryogenesis. On the other hand, Ej-vlg2 single positive cells with morphological characteristics of neoblasts became detectable much later after embryogenesis at the ventral position on each septum where adult neoblasts exist, although these early detected cells were much smaller in size than adult neoblasts. The present results suggest that (1) germline stem cells specified just after embryogenesis are derived from Ej-vlg1(+)/Ej-vlg2(+) cells which appear at the posterior ventral region in late embryos, and that (2) neoblasts appear much later in development.     

Factors shaping the evolution of colour patterns in Australian agamid lizards (Agamidae): a comparative study

Identifying general patterns of adaptive coloration in animals can help to elucidate the evolutionary processes that generate them. We examined the evolution of colour patterns in Australian agamid lizards, a morphologically and ecologically diverse group that relies primarily on visual communication. We tested whether certain types of colour (yellow–reds and black) were likely to be used as sexual signals, as indicated by their association with indices of sexual selection, namely, sexual dichromatism and sexual dimorphism in body size and head shape. We then tested whether sexually dichromatic colours are associated with specific patterns (uniform, mottled, striped, blotched, reticulated) or ecological variables such as habitat openness, arboreality, and substrate type. The presence of yellow–red on lateral and ventral body regions and black on ventral body regions was significantly more common in males than females. Lateral yellow–red in males was associated with the total extent of sexual dichromatism and size dimorphism, whereas ventral yellow–red was associated with sexual dichromatism. Both lateral and ventral yellow–red were associated with uniform patterning, suggesting that sexual signals in male agamid lizards may often comprise uniform patches or flushes of yellow–red. Although ventral black coloration was more prevalent on males (i.e. strongly sexually dichromatic), it was not associated with indices of sexual selection, suggesting that, in agamid lizards, yellow–red coloration is more likely to be sexually selected than black. Sexually dichromatic coloration was not strongly associated with any of the ecological variables measured. We found some associations, however, between female dorsal patterns and ecological variables, suggesting that female patterns are influenced by natural selection. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 101–112.     

Ultrastruktur der Haftapparate vonNematoplana coelogynoporoides (Turbellaria,Proseriata)

The adhesive systems ofNematoplana coelogynoporoides Meixner, which are almost indiscernible in live animals, were examined with scanning and transmission electron microscopes. There are conformities with the fine structure of the adhesive systems in other Proseriata. However, there are also some special characteristics: the position of the adhesive systems in the epidermis; the number of anchor cells pro adhesive system; and the coexistence of intra-epithelial and insunk anchor cells in each adhesive system.     

Tarsal attachment devices of the southern green stink bug Nezara viridula (Heteroptera: Pentatomidae)

Based on analyses with cryo‐scanning and transmission electron microscopy, the present study reports on the morphology and ultrastructure of the attachment structures of the green stinkbug Nezara viridula L. (Heteroptera: Pentatomidae), a cosmopolitan pest of different crops in most areas of the world. In addition, the presence and distribution of large proportions of the elastic protein resilin in these structures was revealed by confocal laser scanning microscopy. The attachment structures of each leg comprise two sclerotised claws, a pair of smooth flexible pulvilli and a hairy adhesive pad located at the ventral side of the basitarsus. No sexual dimorphism is evident. Contact areas of resting individuals on a smooth surface show that N. viridula creates contact to the substrate with the ventral surface of (a) the distal portions of the pulvilli, (b) the setae of the hairy adhesive pad, (c) the two paraempodia representing mechanosensory setae, and (d) the tips of the claws. Each pulvillus is a sac‐like structure formed by complex cuticular layers that vary in their structure and resilin content. The dorsal side consists of sclerotised chitinous material, while the ventral cuticle consists mainly of resilin and shows a very thin epicuticle and a thick exocuticle. The setae of the hairy adhesive pad are pointed and socketed. They exhibit a pronounced longitudinal gradient in the material composition, with large proportions of resilin being present in the setal tips. In most of these setae, especially in those of the distal‐most part of the pad, also a transverse gradient in the material composition is visible.     

The development of feeding behaviour in the lumpfish, Cyclopterus lumpus

This study concerned the development of feeding in larval lumpfish, Cyclopterus lumpus , and tested the hypothesis that these large, well-developed larvae would not use typical 'larval-like' modal action patterns (MAPs) in high frequency during early feeding. The early behavioural repertoire of larvae is unique, owing to a well-developed, ventral adhesive disk used to adhere ( Cling ) to available surfaces. Most early feeding MAPs were performed from the Cling position; larvae did not swim in the water column to chase and capture prey during the first three weeks post-hatch. Changes in feeding were not as predicted. The original hypothesis was refined to include a 'state of development' criterion as well as larval size.     

Is the adhesive material secreted by sea urchin tube feet species‐specific?

Sea urchin adoral tube feet are highly specialized organs that have evolved to provide efficient attachment to the substratum. They consist of a disk and a stem that together form a functional unit. Tube foot disk tenacity (adhesive force per unit area) and stem mechanical properties (e.g., stiffness) vary between species but are apparently not correlated with sea urchin taxa or habitats. Moreover, ultrastructural studies of sea urchin disk epidermis pointed out differences in the internal organization of the adhesive secretory granules among species. This prompted us to look for interspecific variability in the composition of echinoid adhesive secretions, which could explain the observed variability in adhesive granule ultrastructure and disk tenacity. Antisera raised against the footprint material of Sphaerechinus granularis (S. granularis) were first used to locate the origin of adhesive footprint constituents in tube feet by taking advantage of the polyclonal character of the generated antibodies. Immunohistochemical assays showed that the antibodies specifically labeled the adhesive secretory cells of the disk epidermis in the tube feet of S. granularis. The antibodies were then used on tube foot histological sections from seven other sea urchin species to shed some light on the variability of their adhesive substances by looking for antibody cross‐reactivity. Surprisingly, no labeling was observed in any of the species tested. These results indicate that unlike the adhesive secretions of asteroids, those of echinoids do not share common epitopes on their constituents and thus would be “species‐specific.” In sea urchins, variations in the composition of adhesive secretions could therefore explain interspecific differences in disk tenacity and in adhesive granule ultrastructure. J. Morphol., 2011. © 2011 Wiley Periodicals, Inc.     

Response biases in auditory forebrain regions of female songbirds following exposure to sexually relevant variation in male song

In many species of songbirds, individual variation between the songs of competing males is correlated with female behavioral preferences. The neural mechanisms of song based female preference in songbirds are not known. Working with female European starlings (Sturnus vulgaris), we used immunocytochemistry for ZENK protein to localize forebrain regions that respond to sexually relevant variation in conspecific male song. The number of ZENK-ir cells in ventral caudo-medial neostriatum [NCMv] was significantly higher in females exposed to longer songs than in those exposed to shorter songs, whereas variation in the total duration of song exposure yielded no significant differences in ZENK expression. ZENK expression in caudo-medial ventral hyperstriatum [cmHV] was uniformly high in all subjects, and did not vary significantly among the three groups. These results suggest that subregions of NCM in female starlings are tuned to variation in male song length, or to song features correlated therewith. Female starlings exhibit robust behavioral preferences for longer over shorter male songs (Gentner and Hulse; Anim Behav 59:443-458, 2000). Therefore, the results of this study strongly implicate NCM in at least a portion of the perceptual processes underlying the complex natural behavior of female choice.     

Prey from the eyes of predators: Color discriminability of aposematic and mimetic butterflies from an avian visual perspective

Predation exerts strong selection on mimetic butterfly wing color patterns, which also serve other functions such as sexual selection. Therefore, specific selection pressures may affect the sexes and signal components differentially. We tested three predictions about the evolution of mimetic resemblance by comparing wing coloration of aposematic butterflies and their Batesian mimics: (a) females gain greater mimetic advantage than males and therefore are better mimics, (b) due to intersexual genetic correlations, sexually monomorphic mimics are better mimics than female‐limited mimics, and (c) mimetic resemblance is better on the dorsal wing surface that is visible to predators in flight. Using a physiological model of avian color vision, we quantified mimetic resemblance from predators’ perspective, which showed that female butterflies were better mimics than males. Mimetic resemblance in female‐limited mimics was comparable to that in sexually monomorphic mimics, suggesting that intersexual genetic correlations did not constrain adaptive response to selection for female‐limited mimicry. Mimetic resemblance on the ventral wing surface was better than that on the dorsal wing surface, implying stronger natural and sexual selection on ventral and dorsal surfaces, respectively. These results suggest that mimetic resemblance in butterfly mimicry rings has evolved under various selective pressures acting in a sex‐ and wing surface‐specific manner.     

Structure of the tarsi in some Stenus species (Coleoptera,Staphylinidae): external morphology,ultrastructure, and tarsal secretion

SEM studies show that the differentiation among Stenus species with respect to the formation of the tarsi (wide bilobed vs. slender tarsomeres) takes place with a considerable augmentation of tarsal ventral setae in wide bilobed tarsomeres. The structural diversity of ventral tarsal setae among and within species is discussed with respect to 1) their different roles as mechanosensilla and tenent setae, respectively, and 2) the different selection pressures in terms of adhesive requirements along the longitudinal tarsus axis. The tarsi are provided with four groups of tarsal mechanosensilla, comprising hair and bristle sensilla, campaniform sensilla, and scolopidia. The tarsus wall is supported by an epidermis, which forms three different types of glands pouring their secretion via different exit paths onto the outer cuticle. The organization and ultrastructure of each of these glands is described. Only one (unicellular) gland is directly associated with the ventral tenent setae and is thus considered to form the main part of the adhesive secretion. The beetles appear to release the tarsal secretion through mediation of the tenent setae, which contains a lipid and a proteinaceous fraction. I propose that the secretion is discharged to the outside via a system of very fine pore canals in the wall of the setal shaft. Gas chromatography and infrared spectroscopy revealed that the lipid fraction of the secretion is a mixture of unsaturated fatty acid glycerides and aliphatic hydrocarbons whose spectra are similar to those of extractions of the superficial lipid coating of the body surface.     

Fine structural analysis of the fibrillar adhesion apparatus in ladybird beetle

The attachment system on the ladybird beetle Harmonia axyridis is composed of a pair of pretarsal claws and adhesive pads at the tarsal segments. The claws, which are connected to the pretarsal segment, are mainly used to hold the rough substrates by their apical diverged hooks. In contrast, the adhesive pads have an adhesive function when landing on smooth surfaces. They are interspersed at the ventral adhesive pad of each tarsomere, and are composed of two kinds of hairy setae. The discoid tip seta (DtS) is located at the central region of each adhesive pad. The DtS has a spoon‐shaped endplate with a long and narrow shaft. In contrast, the pointed tip seta (PtS) is interspersed along the marginal regions of each adhesive pad, and has a hook‐shaped spine near the tip. In the present study, we found numerous fine cuticular pores beneath the setae, which seem to be related to the secretion of some adhesive fluids. It may be deduced that ladybird beetles can attach to smooth surfaces more effectively by employing adhesive fluids filling in surface crevices to overcome problems cause by their larger size endplates.