Outcrossing hermaphroditic polychaete worms adjust their sex allocation to social conditions

Sex allocation theory predicts that simultaneous hermaphrodites shift sex allocation facultatively in response to variation in local group size. This study was performed to evaluate the relative investment in each sex function by the simultaneously hermaphroditic polychaete worm Ophryotrocha diadema and to test whether allocation to each sex depends on the number of reproductive competitors. Four experimental groups were set up (in a 2 x 2 factorial design) with small or large group size and with small or large enclosures to control for potential confounding effects of density. We measured the proportion of female and male investment in focal individuals. Results revealed that individuals regulated their reproductive output so that when reproductive competitors were present, the number of female gametes was strongly reduced and the male function increased. In contrast, under monogamy, individuals in small groups produced lower numbers of sperm but had a higher egg output than worms in large groups. Density did not affect sex allocation in our experiment. Our findings provide qualitative support for Local Mate Competition theory, but also show that the pattern of sex allocation specific to this species is more complex than expected by current theory.     

Effects of Nais elinguis on the performance of an activated sludge plant

The oligochaete worm Nais elinguis was counted during a year and a half in a full-scale, completely mixed, municipal activated sludge plant consisting of four aeration tanks connected in parallel. Simultaneously the operating variables, i.e. effluent quality, energy costs in kWh for oxygen supply in the aeration tanks, and sludge-disposal were measured. The number of worms varied both seasonally and among the aeration tanks. A major worm bloom resulted in a low sludge volume-index, lower energy consumption for oxygen supply expressed in kWh and, depending on the temperature, less sludge-disposal. The worms had no influence on the effluent quality.     

The kinetic disposition of pyrantel citrate and pamoate and their efficacy against pyrantel-resistant Oesophagostomum dentatum in pigs

The pharmacokinetic disposition of pyrantel after intravenous (i.v.) and oral (p.o.) administration as the citrate and p.o. administration as the pamoate salt was determined in pigs. Following i.v. administration pyrantel was quickly cleared from the bloodstream, exhibiting a terminal halflife of 1.75 ± 0.19h and a residence time (MRT) of 2.54 ± 0.27h. After p.o. administration as the citrate salt, the absorption time (MAT) of pyrantel was 2.38 ± 0.25h and although significant quantities of pyrantel were absorbed (mean bioavailability of 41%) the rapid clearance resulted in a MRT of only 4.92 ± 0.36h. By comparison, the significantly extended MAT of the less soluble pamoate salt resulted in reduced circulating concentrations and a significantly lower mean bioavailability of 16%. The poor efficacy of pyrantel citrate against nematodes inhabiting the large intestine of pigs is therefore suggested to result from insufficient quantities of drug passaging to the site of infection. When tested against pyrantel-resistant adult Oesophagostomum dentatum the efficacy of pyrantel citrate was only 23%, whereas the efficacy of the lesser absorbed pyrantel pamoate was 75%. These results indicate that for maximum activity pyrantel should be administered to pigs as the pamoate salt.     

Studies on the bacterial flora of tubificid worms

Study of the bacterial flora of the gut of the turbificid worms has shown that u. v. starilization, serial culturing, and standard bacterial identification procedures can be employed successfully. Eighteen species of bacteria were isolated and identified from the gut of tubificid worms. Eleven of the species were Gram negative which may be reflected in their possible association with chlorogonal cell metabolism in tubificid worms. Of the eighteen species identified our genera and two species are on a similar list produced by Brinkhurst & Chua in an earlier study (1969) of worms from the Great Lakes. None of the organisms identified were other than common to fresh water, organic decay processes or animal digestive systems. Their role in tubificid nutrition is now under study.Supported by a grant from the Council on Faculty Research, Eastern Illinois University.     

Schistosoma mansoni: A comparison of mouse and rat worms with respect to host antigens detected by the technique of transfer into hamsters

A significant proportion of schistosomes transferred from the mouse into the mesenteric veins of hamsters pre-immunized with mouse erythrocytes were rejected. The rejection was specific, could be passively transferred with immune serum and was demonstrable with mouse worms which had been ‘washed’ in normal hamsters for up to 24 h. On the contrary, schistosomes transferred from the rat into the mesenteric veins of hamsters pre-immunized with rat erythrocytes were generally not rejected to any significant extent. Rejection was not brought about by variations in the immunization procedure, or by passive transfer of immunity, or by the use of ‘older’ rat worms. Rat antigens could be detected on rat schistosomes with the use of mixed agglutination techniques, but they appeared to be present in relatively low amounts. The significance of these findings is discussed in relation to a possible protective function of host antigens.