Textures and traction: how tube‐dwelling polychaetes get a leg up

By controlling the traction between its body and the tube wall, a tube‐dwelling polychaete can move efficiently from one end of its tube to the other, brace its body during normal functions (e.g., ventilation and feeding), and anchor within its tube avoiding removal by predators. To examine the potential physical interaction between worms and the tubes they live in, scanning electron microscopy was used to reveal and quantify the morphology of worm bodies and the tubes they produce for species representing 13 families of tube‐dwelling polychaetes. In the tubes of most species there were macroscopic or nearly macroscopic (~10 μm–1 mm) bumps or ridges that protruded slightly into the lumen of the tube; these could provide purchase as a worm moves or anchors. At this scale (~10 μm‐1 mm), the surfaces of the chaetal heads that interact with the tube wall were typically small enough to fit within spaces between these bumps (created by the inward projection of exogenous materials incorporated into the tube wall) or ridges (made by secretions on the interior surface of the tube). At a finer scale (0.01–10 μm), there was a second overlap in size, usually between the dentition on the surfaces of chaetae that interact with the tube walls and the texture provided by the secreted strands or microscopic inclusions of the inner linings. These linings had a surprising diversity of micro‐textures. The most common micro‐texture was a “fabric” of secreted threads, but there were also orderly micro‐ridges, wrinkles, and rugose surfaces provided by microorganisms incorporated into the inner tube lining. Understanding the fine structures of tubes in conjunction with the morphologies of the worms that build them gives insight into how tubes are constructed and how worms live within them.     

Generation of Functional Organs Using a Cell-Competitive Niche in Intra- and Inter-species Rodent Chimeras

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Attachment sites of the tick Amblyomma marmoreum on its tortoise host,Geochelone pardalis

Leopard tortoises (n=162) were collected over a period of 19 months at the National Zoological gardens, Pretoria, South Africa and the attachment sites of larvae, nymphs and adults of A. marmoreum monitored. Most of the larvae (80%) and nymphs (87%) were found on the anterior parts of the tortoise while adults (90%) were found mainly on the posterior regions of the host body. The immature stages were predominant in soft skinned areas protected by the carapace especially the neck and upper leg areas. Male and female ticks were most commonly found on the posterior armpit. posterior legs and the areas surrounding the base of the tail. Interstadial competition as a major factor influencing attachment site segregation is doubtful. Anterior attachment site selection of the immature stages is believed to result largely from ticks lying passively in wait and then climbing onto the host as it moves through the vegetation and the requirement for soft skinned and protected areas to allow for blood feeding. Adult females usually attach posteriorly in areas that allow them to fully engorge without being dislodged by mechanical disturbance, while males prefer to attach at sites where they are protected but still remain in close proximity to female pheromone signals.     

Oxytocin receptor is not required for social attachment in prairie voles

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Effect of temperature on the pathogenicity of entomopathogenic nematodes (Steinernema and Heterorhabditis spp.) to Delia radicum

Susceptibility of last instarlarvae of Delia radicum to Steinernema feltiae, S. carpocapsae,S. arenarium, Heterorhabditismegidis and H. bacteriophora wasevaluated in the laboratory at 10 °C,15 °C and 20 °C. S. feltiaewas the only species that killed the larvae at10 °C; S. carpocapsae, S.arenarium and H. megidis were effectiveat 15–20 °C whereas H.bacteriophora killed the maggot only at20 °C. The temperature significantlyaffected the host searching ability of alltested species. Mobility was reduced at lowtemperatures. Significant effects of the hostpresence on nematode mobility were found forS. feltiae, S. arenarium and H. megidis but not for S. carpocapsaeand H. bacteriophora. The dynamics of theattachment to and penetration into the hostwere monitored for S. feltiae at10 °C, 15 °C or 20 °C and forS. carpocapsae at 20 °C. In theperiod of 6–30 hours after inoculation, S.carpocapsae attached in higher number at20 °C than did S. feltiae at alltemperatures. At 20 °C, S.carpocapsae penetrated the host only after 30hours while S. feltiae penetrated alreadyafter 15, 9, 6 hours at 10 °C,15 °C and 20 °C, respectively.     

Cytoskeletal control of the apical surface transformation of rat uterine epithelium

Summary— During early pregnancy, in the lead up to blastocyst implantation, the apical cell surface of luminal epithelial cells of the rat uterus undergo a dramatic shape transformation. This study aims to investigate the role of the cytoskeleton in this apical transformation by considering the effects of the drugs cytochalasin D and colchicine on the uterine luminal cell surface. The results are determined using transmission and scanning electron microscopy. In vivo exposure to cytochalasin D during oestrus, as well as on day 1 of pregnancy, did not affect the long, regular surface microvilli. This drug, however, did disrupt the terminal web within the apical cytoplasm of these cells. Disruption of microfilament (MF) polymerization by cytochalasin D on day 4 of pregnancy induced a cell surface transformation, resulting in the appearance of numerous irregular projections normally present during blastocyst implantation on day 6 of pregnancy. Colchicine did not alter the uterine microvilli of oestrus or day 1 pregnant tissue. Unlike the effect of cytochalasin D, colchicine-induced microtubule (MT) disruption on day 4 of pregnancy did not increase irregular projections and hence this treatment did not result in the cell surface appearance associated with blastocyst implantation. These results indicate that the disruption of MF, rather than MT, contributes to the transformation of the uterine luminal cell surface during the lead up to blastocyst attachment.     

Epidermal cell-patterning genes of the stem parasitic plant Cuscuta campestris are involved in the development of holdfasts

Cuscuta campestris, a stem parasitic plant, commences its parasitic behavior by forming a specialized disk-like adhesive structure called a holdfast, which facilitates tight adhesion to the stem surface of the host plant. The morphology of epidermal cells in the holdfast is similar to that of the leaf trichome and root hairs of dicotyledonous plants. However, the regulatory network underlying the development of the holdfast has not been elucidated to date. In this study, we assessed the roles of epidermal cell-patterning genes in the development of a holdfast. Epidermal cell-patterning genes of C. campestris, including CcWER, CcGL3, CcTTG1, CcGL2, and CcJKD, were expressed slightly before the initiation of the outgrowth of stem epidermal cells. CcJKD-silencing repressed CcJKD, CcWER, CcGL3, CcTTG1, CcGL2; therefore, CcJKD is an upstream regulator of other epidermal cell-patterning genes. Unlike other genes, CcCPC was not upregulated after attachment to the host, and was not repressed by CcJKD-silencing. Protein interaction assays demonstrated that CcJKD interacted with CcTTG1 and CcCPC. Furthermore, CcJKD-silencing repressed the outgrowth of holdfast epidermal cells. Therefore, C. campestris invokes epidermal cell-patterning genes for the outgrowth of holdfast epidermal cells, and their regulatory mechanism is different from those for leaf trichome or root hairs.     

Differential alterations in the distribution of three phosphatase enzymes during the plasma membrane transformation of uterine epithelial cells in the rat.

Ultrastructural and light microscopic cytochemical methods were used to study the distribution and changes in distribution of three phosphatase enzymes: 5'-nucleotidase (5N); thiamine pyrophosphatase (TPP); and adenosine triphosphatase (ATP) in the rat endometrium during early pregnancy up to the time of blastocyst attachment. The authors were particularly interested in changes in the apical plasma membrane and reaction product for all three enzymes was clearly localized along this membrane especially on day 1 of pregnancy. However, the three enzymes showed markedly different patterns of organization of reaction product at later times during early pregnancy. 5N, while showing a continuous lining along the microvilli on day 1 was virtually undetectable by day 6. TPP was also strongly present apically on day 1, but reaction product was not always found as a continuous lining. Again, by day 6, there was no presence of this enzyme along the apical surface. ATP differed from the other two in that it produced a strong, and relatively unchanged reaction product along the apical plasma membrane from day 1 through to day 6 of pregnancy. The changes in distribution of these enzymes was particularly obvious at the electron microscopic level and we consider their contribution to the process of 'plasma membrane transformation' of early pregnancy.