Pharyngeal Pumping Assay v1

The pharynx is a is a neuromuscular pump found at the anterior end of the alimentary tract, consisting of 20 muscles and 20 neurons. A proper feeding rate in worms is coordinated by the precise timing of pharyngeal movements, with one complete cycle of synchronous contraction and relaxation of the corpus and terminal bulb termed a “pump”. A simple way to measure C. elegans feeding is to count how many times worms pump in a minute (pumps per minute). Movement of the grinder (in the terminal bulb) can easily be observed using a stereomicroscope, and because cycles of contraction/relaxation are synchronised along the pharynx, pumps per minute can be measured simply by counting grinder movements.

Litylenchus coprosma gen. n., sp. n. (Tylenchida: Anguinata), from leaves of Coprosma repens (Rubiaceae) in New Zealand

A new genus and species of anguinid nematode, Litylenchus coprosma gen. n., sp. n., was recovered from leaves of Coprosma repens A. Rich. from an amenity planting in Wellington, New Zealand. The genus is characterised by having slender males and slender or semi-obese females, pharynx with a weak non-muscular median bulb, a terminal bulb containing the pharyngeal glands, female with a single gonad having a quadricolumella and post-uterine sac; male with arcuate spicules and the bursa arising 1-2 anal body diam. anterior to the cloacal aperture and extending nearly to the tail tip, and does not induce galls, only foliar chlorosis. The species is characterised by having a short, robust stylet with conus forming ca 40% of stylet length and three well developed rounded knobs, secretory/excretory pore opening posterior to the nerve ring, terminal bulb abutting the intestine, and tail tip of variable form. Molecular phylogeny of near full length small subunit, D2/D3 expansion segments of the large subunit and internal transcribed spacer rRNA genes support the description of L. coprosma gen. n., sp. n. as a new genus and species.

Muscle-specific functions of ryanodine receptor channels in Caenorhabditis elegans

Ryanodine receptor channels regulate contraction of striated muscle by gating the release of calcium ions from the sarcoplasmic reticulum. Ryanodine receptors are expressed in excitable and non-excitable cells of numerous species, including the nematode C. elegans. Unlike vertebrates, which have at least three ryanodine receptor genes, C. elegans has a single gene encoded by the unc-68 locus. We show that unc-68 is expressed in most muscle cells, and that the phenotypic defects exhibited by unc-68 null mutants result from the loss of unc-68 function in pharyngeal and body-wall muscle cells. The loss of unc-68 function in the isthmus and terminal bulb muscles of the pharynx causes a reduction in growth rate and brood size. unc-68 null mutants exhibit defective pharyngeal pumping (feeding) and have abnormal vacuoles in the terminal bulb of the pharynx. unc-68 is required in body-wall muscle cells for normal motility. We show that UNC-68 is localized in body-wall muscle cells to flattened vesicular sacs positioned between the apical plasma membrane and the myofilament lattice. In unc-68 mutants, the vesicles are enlarged and densely stained. The flattened vesicles in body-wall muscle cells thus represent the C. elegans sarcoplasmic reticulum. Morphological and behavioral phenotypes of unc-68 mutants suggest that intracellular calcium release is not essential for excitation-contraction coupling in C. elegans.