Courtship behaviour in the genus Nomada – antennal grabbing and possible transfer of male secretions

Due to low population densities, copulation in the cuckoo bee genus Nomada has not previously been observed, although a seminal paper by Tengö and Bergström (1977) on the chemomimesis between these parasitic bees and their Andrena or Melitta hosts postulated that secretions from male glands might be sprayed onto females during copulation. Our observations on the initiation and insertion phase of copulation in three species of Nomada now indicate antennal grabbing as a mechanism by which chemicals are transferred between the sexes. Histological studies of the antennae of N.fucata and N.lathburiana reveal antennal modifications associated with cell aggregations that represent glandular cells, and SEM studies revealed numerous excretory canals.

Novel exc Genes Involved in Formation of the Tubular Excretory Canals of C. elegans

ABSTRACTRegulation of luminal diameter is critical to the function of small single-celled tubes, of which the seamless tubular excretory canals of C. elegans provide a tractable genetic model. Mutations in several sets of genes exhibit the Exc phenotype, in which canal luminal growth is visibly altered. Here, a focused reverse genomic screen of genes highly expressed in the canals found 24 genes that significantly affect luminal outgrowth or diameter. These genes encode novel proteins as well as highly conserved proteins involved in processes including gene expression, cytoskeletal regulation, vesicular movement, and transmembrane transport. In addition, two genes act as suppressors on a pathway of conserved genes whose products mediate vesicle movement from early to recycling endosomes. The results provide new tools for understanding the integration of cytoplasmic structure and physiology in forming and maintaining the narrow diameter of single-cell tubules.

Intermediate filaments EXC-2 and IFA-4 Maintain Luminal Structure of the Tubular Excretory Canals in Caenorhabditis elegans

ABSTRACTThe excretory canals of Caenorhabditis elegans are a model for understanding the maintenance of apical morphology in narrow single-celled tubes. Light and electron microscopy shows that mutants in exc-2 start to form canals normally, but these swell to develop large fluid-filled cysts that lack a complete terminal web at the apical surface, and accumulate filamentous material in the canal lumen. Here, whole-genome sequencing and gene rescue show that exc-2 encodes intermediate filament protein IFC-2. EXC-2/IFC-2 protein, fluorescently tagged via CRISPR/Cas9, is located at the apical surface of the canals independently of other intermediate filament proteins. EXC-2 is also located in several other tissues, though the tagged isoforms are not seen in the larger intestinal tube. Tagged EXC-2 binds via pulldown to intermediate filament protein IFA-4, which is also shown to line the canal apical surface. Overexpression of either protein results in narrow but shortened canals. These results are consistent with a model whereby three intermediate filaments in the canals, EXC-2, IFA-4, and IFB-1, restrain swelling of narrow tubules in concert with actin filaments that guide the extension and direction of tubule outgrowth, while allowing the tube to bend as the animal moves.Article SummaryThe C. elegans excretory canals form a useful model for understanding formation of narrow tubes. exc-2 mutants start to form normal canals that then swell into fluid-filled cysts. We show that exc-2 encodes a large intermediate filament (IF) protein previously not thought to be located in the canals. EXC-2 is located at the apical (luminal) membrane, binds to another IF protein, and appears to be one of three IF proteins that form a flexible meshwork to maintain the thin canal diameter. This work provides a genetically useful model for understanding the interactions of IF proteins with other cytoskeletal elements to regulate tube size and growth.

Interactions between the intestinal cestode Polyonchobothrium clarias (Pseudophyllidea: Ptychobothriidae) from the African sharptooth catfish Clarias gariepinus and heavy metal pollutants in an aquatic environment in Egypt

In an aquatic environment, there is a profound and inverse relationship between environmental quality and disease status of fish. Parasites are one of the most serious limiting factors in aquaculture. Therefore, the present investigation was carried out during the period of February–December 2014 to determine the parasitic infections in the African sharptooth catfish Clarias gariepinus, relative to the capability of internal parasites to accumulate heavy metals. Up to 100 catfish were examined for gastrointestinal helminths and 38% of fish were found to be infected with the cestode Polyonchobothrium clarias. The morphology of this parasite species, based on light and scanning electron microscopy, revealed that the adult worm was characterized by a rectangular scolex measuring 0.43–0.58 (0.49 ± 0.1) mm long and 0.15–0.21 (0.19 ± 0.1) mm wide, with a flat to slightly raised rostellum armed with a crown with two semicircles each bearing 13–15 hooks, followed by immature, mature and gravid proglottids which were about 29–55 (45), 16–30 (24) and 15–39 (28) in number, respectively. The mature proglottid contained a single set of genitalia in which medullary testes measured 0.09–0.13 (0.11 ± 0.01) mm long and 0.05–0.08 (0.06 ± 0.01) mm wide; a bi-lobed ovary was situated near the posterior margin of the proglottid, extending laterally up to the longitudinal excretory canals; the tubular uterus arose from the ootype up to the anterior margin of the proglottid; and vitelline follicles were cortical. The greater portion of the gravid proglottid was occupied by a uterus filled with unoperculate and embryonated eggs. Chemical analysis confirmed that the concentrations of heavy metals (Zn, Cu, Mn, Cd, Ni and Pb) accumulated in P. clarias were higher than in fish tissues and values recommended by FAO/WHO, with the exception of Zn, which was found to be higher in fish kidneys than in the cestode. This supports the hypothesis that cestodes of fish can be regarded as useful bioindicators when evaluating the environmental pollution of aquatic ecosystems by heavy metals.

unc-53 controls longitudinal migration in C. elegans

Cell migration and outgrowth are thought to be based on analogous mechanisms that require repeated cycles of process extension, reading and integration of multiple directional signals, followed by stabilisation in a preferred direction, and renewed extension. We have characterised a C. elegans gene, unc-53, that appears to act cell autonomously in the migration and outgrowth of muscles, axons and excretory canals. Abrogation of unc-53 function disrupts anteroposterior outgrowth in those cells that normally express the gene. Conversely, overexpression of unc-53 in bodywall muscles leads to exaggerated outgrowth. UNC-53 is a novel protein conserved in vertebrates that contains putative SH3- and actin-binding sites. unc-53 interacts genetically with sem-5 and we demonstrated a direct interaction in vitro between UNC-53 and the SH2-SH3 adaptor protein SEM-5/GRB2. Thus, unc-53 is involved in longitudinal navigation and might act by linking extracellular guidance cues to the intracellular cytoskeleton.

Ultrastructural investigation of the secondary excretory system in different stages of the procercoid of Triaenophorus nodulosus (Cestoda, Pseudophyllidea, Triaenophoridae)

The formation of the definitive procercoid excretory system of the pseudophyllidean cestode Triaenophorus nodulosus has been investigated. This process can be divided into 3 main stages. In the first stage, active autophagic processes lead to the formation of intracellular excretory canals. In the second stage, the process of the autolysis is enhanced and the system of intercellular lacunae functioning as an excretory system is formed. A definitive excretory system of the procercoid forms at the next stage, by means of the migration and proliferation of undifferentiated cells replacing the lacunar system.

The Riddle of the Uvula

Since ancient times, the uvula has been a subject of interesting and contradictory observations. On the one hand, it was regarded as having a functional role in speech and in immunology, but on the other hand it was regarded as a potentially hazardous organ, possibly responsible for sudden infant death syndrome. None of these hypotheses, however, has been proved. In a previous study on patients undergoing uvulopalatopharyngoplasty, we suggested that the most important function of the uvula is connected with the muscularis uvulae. Its function could be related to drinking while bending over. This previous assumption was that the uvula is a philogenetic remnant from mammals that drink while bending their neck downward. In the present study, the soft palate of eight different mammals was macroscopically and microscopically studied and compared. Of all animals in the study, a small underdeveloped uvula was found only in two baboons. We found that the human uvula consists of an intermix of serous and seromucous glandular masses, muscular tissue, and large excretory canals. The serous and seromucous glands are absent in the other mammals. Thus, the uvula is a highly sophisticated structure, capable of producing a large quantity of fluid saliva that can be excreted in a short time. Both uvula and speech serve to differentiate human beings from animals. Our conclusion is that the uvula is possibly an accessory organ of speech, and may be another marker of human evolution that differentiates man from other mammals.