Social and reproductive behavior ofChaetodontoplus mesoleucus (Pomacanthidae) at Bantayan island,Philippines, with notes on pomacanthid relationships

Chaetodontoplus mesoleucus occurs at Bantayan Island in a habitat of small patches of mixed scleractinian and alcyonacean corals of low diversity and simple structure. Male-female pairs were predominant, and the sex-ratio showed only a slight skew towards females. However, the presence of single male, two-female social groups demonstrates that the species is polygamous. Small size of social groups is attributed to a preference for a habitat lacking structural complexity. The species did not occur on complex coral reefs. Social and spawning behavior are nearly identical to that of most pomacanthids for which data are available, and although sex-change was not demonstrated, size-related dominance hierarchies and close phylogenetic relationships to sex-changing pomacanthids suggest protogynous hermaphroditism in this species. Behaviorally,C. mesoleucus appears quite similar to a large group of species proposed herein to represent a generalized pomacanthid behavioral type. Divergences from this generalized type by members ofGenicanthus, eastern PacificHolacanthus, and western AtlanticPomacanthus are discussed. Evidence is given to suggest the phylogenetic derivation of the subgenusCentropyge (genusCentropyge) from an ancestor of the subgenusXiphipops type. Color dimorphism and “rendezvous sites” are briefly discussed.     

Ribosomal RNA sequence conservation and gene number in the larval brine shrimp

The haploid genome size of Artemia is determined to be about 0.9·10¹², as evidenced both by Feulgen microspectrophotometry of individual diploid class nuclei, which are but one of five polyploid classes present within the larvae, and by analysis of the reassociation kinetics of the isolated single copy DNA component. Polysomes isolated from 24-h incubation stage larvae contain an average of 10 ribosomes per messenger RNA molecule. Their rRNAs are found to have sedimentation coefficients of 18 S and 26 S, corresponding to molecular weights of 0.70·10⁶ and 1.40·10⁶, respectively, as determined by polyacrylamide electrophoresis and also by sucrose density centrifugation. Denaturation in glyoxal followed by agarose gel electrophoresis shows that unlike deuterostome rRNAs, Artemia 26 S rRNA contains a cryptic nick about midway in the molecule, which is not found in the 18 S molecule. Isolated rRNAs were labelled in vitro with ¹²⁵I and hybridized with filter-immobilized DNA to saturation, which occurred at 0.051% for Xenopus, and at 0.074% for Artemia. From these results, it is calculated that in the haploid Artemia genome there are about 320 copies of the (18 S + 26 S) ribosomal RNA genes. Reciprocal heterologous hybridizations between these two species show that they share about 30% homology between their rDNA coding sequences.     

Relationship of chin spot size to dominance in the black-chinned mouthbrooding cichlid fish (Sarotherodon melanotheron)

Aggressive interactions of male Sarotherodon melanotheron were studied to determine the communicative value of chin spot size in relation to dominance. In addition, the effects of residency and size on the aggressiveness of this fish were determined. Two-factor analysis of variance was used for frequencies of each modal action pattern for residency and size. Results show that residency played a major role in the outcome of an aggressive interaction, whereas size had little effect. Dominance of each experimental fish was calculated using Barlow & Ballin's (1976) dominance index. A chin spot ratio was obtained by dividing the chin spot area by the total surface area of the individual fish. Simple linear regression was conducted to determine if dominance and chin spot size were correlated and a positive linear relationship was found to exist between the two variables.     

The influence of oxygen concentrations on denitrification in soil

Summary The influence of different O₂ concentrations on denitrification was studied in an agricultural soil. In both nitrate and nitrite amended soil, denitrification was not observed until the O₂ concentration decreased to 0.20 and 0.21 mol/ml, respectively. Denitrification was not observed in soil samples with O₂ concentrations above 0.28 mol/ml in the gas phase. These findings suggest that a completely anoxic environment is not required for denitrification to occur in soil.     

Temperature-pulse-induced "memory" in Bacillus subtilis macrofibers and a role for protein(s) in the left-handed-twist state

Macrofibers in steady-state growth at one temperature were subjected to pulses of various durations at a temperature at which the opposite helix hand would form and then returned to the initial temperature. In an upshift pulse (20 to 48 degrees C), at least 3 min of incubation was required to induce a transient inversion that occurred later after return to 20 degrees C. Longer pulses resulted in shorter delays in onset of the transient inversion. This "memory" of a brief high-temperature pulse suggests that even a small amount of material can influence the twist of the entire macrofiber. Similar results were found for temperature downshift pulses corresponding to the opposite inversion. Adding chloramphenicol during the temperature pulse blocked the establishment of memory associated with the right-to-left inversion but not that associated with left-to-right inversion. In contrast, inhibiting peptidoglycan synthesis with D-cycloserine during the temperature pulse did not prevent establishment of memory. Inhibiting protein synthesis in mutants fixed as left-handed structures over the entire temperature range induced conversion to right-handedness but did not affect mutants fixed as right-handed structures. Adding protease to either live or formaldehyde-killed macrofibers always induced rotations of right-handed orientation. Steady-state growth in the presence of protease was found to shift the initial macrofiber twist towards the right-hand end of the twist spectrum. The phenomenon was observed in several mutants with different initial twists.