Arrangement and structural conservation of the mitochondrial control region of two species of Plecoptera: utility of tandem repeat-containing regions in studies of population genetics and evolutionary history.

Low levels of primary sequence similarity across insect taxa have led to the suggestion of conserved structural elements in the insect mitochondrial control region. Our aim was to determine whether previously described motifs and secondary structures exist in stoneflies (Plecoptera). Several motifs and structural elements previously described in Orthoptera and Diptera were found, including a conserved 'hairpin' structure that may play a role in the initiation of mtDNA replication. The repeat region had the highest percentage similarity, lowest A-T content and highest transition to transversion ratio, suggesting a unique evolutionary pattern for the repeats. Finally, we discuss the usefulness of the control region in population genetic and evolutionary studies.

Gene flow, dispersal, and nested clade analysis among populations of the stonefly Peltoperla tarteri in the southern Appalachians.

We examined the genetic structure and phylogeography of populations of the stonefly Peltoperla tarteri in the Southern Appalachians to determine the extent and likely mechanism for dispersal of this stream insect. A 454-base-pair (bp) portion of the mitochondrial control region was sequenced from a minimum of 20 individuals from eight populations. Pairwise FST and exact tests showed high levels of differentiation among almost all populations except those on the same stream. amova analysis detected significant genetic differentiation between streams within drainages (phi(SD) = 0.14, P < 0.001), and there was a slight positive correlation between aquatic distance and genetic distance (r = 0.295, P = 0.03). According to nested clade analysis, the present day pattern of genetic variation in P. tarteri is the result of a historical range expansion coupled with restricted gene flow with isolation by distance. Together, these analyses suggest that adult dispersal is limited and that movement by larvae is the primary dispersal mechanism for P. tarteri.

The relationship of Chironomus riparius larval Se body burden and body concentration to larval dry mass and effects on sensitivity to selenium.

Selenium as selenite was added to laboratory cultures of Chironomus riparius. In two sets of cultures, substrate-bound Se concentrations were typically 10(3) times dissolved Se concentrations, while in the other set dissolved Se concentrations were about 10 to 50 times substrate-bound Se concentrations. Body burdens of individual second-, third-, and fourth-instar larvae and eviscerated fourth-instar larvae were measured. Regressions of Se body burden on larval dry mass found evidence for separate intercepts but common slopes for each instar, and Se body concentrations were diluted by growth. The derivation of body concentration from body burden as a function of larval dry mass was used to derive a model of body burden and body concentration as a function of instar. Toxicity tests were performed to check for a change in sensitivity to Se as a function of culture Se concentration. Larval Se concentrations were highly correlated with dissolved Se concentrations but not with substrate-bound Se concentrations. Increases in Se in substrate caused no sensitization, while increases in dissolved Se caused desensitization. We concluded that covariates such as larval dry mass should be incorporated when deriving water quality criteria.

Anaerobic degradation of cyanuric Acid, cysteine, and atrazine by a facultative anaerobic bacterium.

A facultative anaerobic bacterium that rapidly degrades cyanuric acid (CA) was isolated from the sediment of a stream that received industrial wastewater effluent. CA decomposition was measured throughout the growth cycle by using a high-performance liquid chromatography assay, and the concomitant production of ammonia was also measured. The bacterium used CA or cysteine as a major, if not the sole, carbon and energy source under anaerobic, but not aerobic, conditions in a defined medium. The cell yield was greatly enhanced by the simultaneous presence of cysteine and CA in the medium. Cysteine was preferentially used rather than CA early in the growth cycle, but all of the CA was used without an apparent lag after the cysteine was metabolized. Atrazine was also degraded by this bacterium under anaerobic conditions in a defined medium.