On the persuasiveness of visual arguments in mathematics

Two experiments are reported which investigate the factors that influence how persuaded mathematicians are by visual arguments. We demonstrate that if a visual argument is accompanied by a passage of text which describes the image, both research-active mathematicians and successful undergraduate mathematics students perceive it to be significantly more persuasive than if no text is given. We suggest that mathematicians' epistemological concerns about supporting a claim using visual images are less prominent when the image is described in words. Finally we suggest that empirical studies can make a useful contribution to our understanding of mathematical practice

Skrjabinodon heliocostai sp.n. (Nematoda, Pharyngodonidae) parasitizing Mabuya frenata (Cope) (Lacertilia, Scincidae) in Brazil and the reallocation of Skrjabinodon capacyupanquii (Freitas, Vicente & Ibanez) in the genus Thelandros Wedl

The present report is related to an oxyurid nematode recovered from a reptilian host, Mabuya frenata (Cope, 1862) and the proposal of Skrjabinodon helicostai sp.n., based mainly on findings referring to the lateral alae, position of excretory pore and vulvar apertures, cuticular spines of the tail and aspect of the eggs. The examination of types of Skrjabinodon capacyupanquii (Freitas, Vicente & Ibanez, 1968) from a Peruvian lizard, indicated the reallocation of this species in the genus Thelandros Wedl., 1862, as T. capacyupanquii comb.n., based on the diameter of the caudal appendage of males and position of the vulvar aperture. The new species described herein represents the first report of a species of the genus Skrjabinodon Inglis, 1968 in South America

Tackling the Sulfide Gradient: A Novel Strategy Involving Marine Nematodes and Chemoautotrophic Ectosymbionts

The Stilbonemutinue (marine free-living nematodes) arc remarkable for cctosymbiotic bacteria, which cover the greatest part of their body in a highly ordered and species specific pattern. Using SEM we describe the main types of symbiotic cover and give evidence for the role of the bacteria in the nutrition of their host on the basis of stable carbon isotope ratios. In experimental systems the worms migrated repeatedly across a sulfide gradient during 12 h when sulfide concentrations were low, but stayed above the sulfide maximum at high concentrations. The migration across the chemocline exposes the symbionts alternately to reduced sulfur compounds and oxygen; this constitutes an alternative strategy to the ventilation/circulation systems in symbiotic macrofauna from sulfidic habitat