Ammonia increases buffer capacity of methanogenic medium in mesophilic anaerobic reactor thus increasing the stability of anaerobic digestion process. Optimal ammonia concentration ensures sufficient buffer capacity while not inhibiting the process. It was found out in this paper that this optimum depends on the quality of anaerobic sludge under investigation. The optimal concentrations for methanogens were 2.1, 2.6 and 3.1 g/L of ammonia nitrogen in dependence on inoculum origin. High ammonia nitrogen concentration (4.0 g/L) inhibited methane production, while low ammonia nitrogen concentration (0.5 g/L) caused low methane yield, loss of biomass (as VSS) and loss of the aceticlastic methanogenic activity. It was found out that negative effect of low ammonia nitrogen concentration on biomass is caused not only by low buffer capacity but also by insufficiency of nitrogen as nutrient. It was also found out that anaerobic sludge with higher ammonia nitrogen concentration (4.2 g/L) tolerates even concentration of volatile fatty acids (160 mmol/L) which causes inhibition of the process with low ammonia nitrogen concentration (0.2 g/L).

Abstract. The aim of this study was to characterize karyotypes of central European spiders of the genera Arctosa, Tricca, and Xerolycosa (Lycosidae) with respect to the diploid chromosome number, chromosome morphology, and sex chromosomes. Karyotype data are reported for eleven species, six of them for the first time. For selected species the pattern in the distributions of the constitutive heterochromatin and the nucleolar organizer regions (NORs) was determined. The silver staining technique for detecting NORs of lycosid spiders was standardized. The male karyotype consisted of 2n = 28 (Arctosa and Tricca) or 2n = 22 (Xerolycosa) acrocentric chromosomes. The sex chromosome system was X1X20 in all species. The sex chromosomes of T. lutetiana and X. nemoralis showed unusual behaviour during late diplotene, namely temporary extension due to decondensation. C-banding technique revealed a small amount of constitutive heterochromatin at the centromeric region of the chromosomes. Two pairs of autosomes bore terminal NORs. Differences in karyotypes among Arctosa species indicate that the evolution of the karyotype in this genus involved autosome translocations and size changes in the sex chromosomes. Based on published results and those recorded in this study it is suggested that the ancestral male karyotype of the superfamily Lycosoidea consisted of 28 acrocentric chromosomes.

Spiders are characterized by their spinning activity. Much of the current knowledge of the spinning apparatus comes from studies on orb web spiders and their relatives, whereas wolf spiders have been more or less neglected in this respect. Therefore, we studied developmental changes in the spinning apparatus of four wolf spiders (Tricca lutetiana, Arctosa alpigena lamperti, Pardosa amentata, and Xerolycosa nemoralis) throughout their life cycles. Each of these lycosids has a stenochronous life cycle, but of varied length (from 1 to 3 years) and number of instars (from seven to ten). Use of the spinning apparatus begins in the first instar, after leaving the egg sac. Secondary ampullate, all piriform, and all but four aciniform glands are tartipore-accommodated. The tartipores, collared openings through which silk gland ducts pass during proecdysis, appear on the spinning field starting with the second instar. Tartipore-accommodated glands can function during proecdysis and their evolution corresponds with the way spiders secure themselves when molting. We suggest that the function of aciniform silk in juvenile wolf spiders is to serve as an ancillary "scaffold" supporting the spider's body during ecdysis. Invertebrate Biology 133(3): 281-297.

Abstract:For the first time in the Czech Republic, the PAX-18 coagulant has been used to restore a eutrophic fishpond. The polyaluminium hydrochloride coagulant was applied repeatedly to a shallow eutrophic fishpond in spring 2005. Two cylindrical plastic enclosures were used to isolate parts of the pond as untreated controls. Selected environmental variables were measured in situ. Water samples were analyzed regularly for nutrients, chlorophyll a concentration and phytoplankton abundance and structure with special focus on Planktothrix agardhii. The PAX-18 treatment led to a marked increase in the N/P ratio and changes in the structure and abundance of phytoplankton in the fishpond and P. agardhii blooms were eliminated in the fishpond. By contrast, P. agardhii dominated the phytoplankton in the control enclosures, as it had in the fishpond in 2004, prior to the PAX-18 treatment.