Associations between enzyme genotypes and dark respiration in perennial ryegrass,Lolium perenne L.

Summary In this study, we determined whether relationships existed between dark respiration and genotype at five enzyme polymorphisms in perennial ryegrass, Lolium perenne L. Positive correlations were found between Q ₁₀ of dark respiration and genotype at the phosphoglucomutase (PGM) and 6-phosphogluconate dehydrogenase (6PGD) loci. Plants doubly homozygous for the common allele at these loci were found to have Q ₁₀ values 20% higher than those for double heterozygotes. In plants that were heat stressed for five consecutive days, Q ₁₀ was found to be negatively correlated with apparent vigor after stressing. Individuals homozygous for PGM and 6PGD (with higher Q ₁₀ values) exhibited more apparent damage following the stress than heterozygous individuals. Both PGM and 6PGD occupy positions in metabolism with regulatory potential. Although caution must be used in assigning causal relationships, the results suggest that specific forms of these enzymes are directly related to, or are correlated with, the determinants of respiratory efficiency in L. perenne.     

Scanning Electron Microscopic Studies on Four Species of the Genus Syphacia (Nematoda, Oxyuridae)

The ultrastructure of the head end and surface structure of the cuticle of Syphacia petrusewiczi, S. nigeriana, S. frederici and S. stroma was studied. These species may be easily separated on the basis of the differences in their morphology: S. frederici possesses longitudinal septa on the body surface, a row of denticles on each of the three main teeth, and cervical alae; S. nigeriana has longitudinal septa and denticles but lack cervical alae; S. petrusewiczi has longitudinal septa and cervical alae but lacks denticles; S. stroma lacks these three characters.     

Multiple bradykinin-related peptides from the capture web of the spider Nephila clavipes (Araneae, Tetragnatidae)

Three bradykinin-related peptides (nephilakinins-I to -III) and bradykinin itself were isolated from the aqueous washing extract of the capture web of the spider Nephila clavipes by gel permeation chromatography on a Sephacryl S-100 column, followed by chromatography in a Hi-Trap Sephadex-G25 Superfine column. The novel peptides occurred in low concentrations and were sequenced through ESI-MS/MS analysis: nephilakinin-I (G-P-N-P-G-F-S-P-F-R-NH2), nephilakinin-II (E-A-P-P-G-F-S-P-F-R-NH2) and nephilakinin-III (P-S-P-P-G-F-S-P-F-R-NH2). Synthetic peptides replicated the novel bradykinin-related peptides, which were submitted to biological characterizations. Nephilakinins were shown to cause constriction on isolated rat ileum preparations and relaxation on rat duodenum muscle preparations at amounts higher than bradykinin; apparently these peptides constitute B2-type agonists of ileal and duodenal smooth muscles. All peptides including the bradykinin were moderately lethal to honeybees. These bradykinin peptides may be related to the predation of insects by the webs of N. clavipes.     

Structure and function of defensive glands in soldiers of Glossotermes oculatus (Isoptera: Serritermitidae)

The soldier caste represents the most conspicuous realization of termite eusociality, characterized by an extreme anatomical, behavioural, and physiological specialization. Numerous strategies have evolved in soldiers, including extreme adaptations such as self‐sacrifice by autothysis. In the present study, we investigated the structure and function of defensive glands in Glossotermes oculatus soldiers aiming to understand their use in combat. Three glands are involved in defence: labral, frontal, and labial glands. Mandibles are used to bite the enemy, whereas the secretions of labral and labial glands are discharged into the wound. A striking characteristic of G. oculatus is the lack of the frontal pore; the secretion of the frontal gland is discharged by a rupture of the body wall. We hypothesized that this self‐sacrifice is an efficient way of blocking a gallery under attack. A similar development of the frontal gland occurs in Serritermes serrifer, which supports the close relationship between the two genera inferred from morphological and genetic analyses. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 99 , 839–848.     

Differential controls by climate and substrate over the heterotrophic and rhizospheric components of soil respiration

The partitioning of soil respiration rates into the component processes of rhizospheric respiration (because of live roots and those microorganisms that subsist on root exudations) and heterotrophic respiration (because of decomposer microorganisms that subsist on the oxidation of soil organic matter) is difficult to accomplish through experimental observation. In order to minimize disturbance to the soil and maximize preservation of the natural relationships among roots, rhizospheric microorganisms, and decomposers, we conducted a girdling experiment in a subalpine forest dominated by lodgepole pine trees. In two separate years, we girdled trees in small forest plots (5–7 m in diameter) and trenched around the plots to sever invading roots in order to experimentally stop the transport of photosynthate from needles to roots, and eliminate rhizospheric respiration. Soil respiration rates in plots with trees girdled over 1 year prior to measurement were higher than those in plots with trees girdled 2–3 months prior to measurement. These results suggest that any stimulation of respiration because of the experimental artifact of fine root death and addition of labile carbon to the pool of decomposer substrates is slow, and occurs beyond the first growing season after girdling. Compared with control plots with nongirdled trees, soil respiration rates in plots with girdled trees were reduced by 31–44% at the mid‐summer respiratory maximum. An extreme drought during one of the 2 years used for observations caused greater reductions in the heterotrophic component of soil respiration compared with the rhizospheric component. In control plots, we observed a pulse in K₂SO₄‐extractable carbon during the spring snowmelt period, which was absent in plots with girdled trees. In control plots, soil microbial biomass increased from spring to summer, coincident with a seasonal increase in the rhizospheric component of soil respiration. In plots with girdled trees, the seasonal increase in microbial biomass was lower than in control plots. These results suggest that the observed seasonal increase in rhizospheric respiration rate in control plots was because of an increase in rhizospheric microbial biomass following ‘soil priming’ by a spring‐time pulse in dissolved organic carbon. Winter‐time, beneath‐snow microbial biomass was relatively high in control plots. Soil sucrose concentrations were approximately eight times higher during winter than during spring or summer, possibly being derived from the mechanical damage of shallow roots that use sucrose as protection against low‐temperature extremes. The winter‐time sucrose pulse was not observed in plots with girdled trees. The results of this study demonstrate that (1) the rhizospheric component of soil respiration rate at this site is significant in magnitude, (2) the heterotrophic component of soil respiration rate is more susceptible to seasonal drought than the rhizospheric component, and (3) the trees in this ecosystem exert a major control over soil carbon dynamics by ‘priming’ the soil with sugar exudates during the late‐spring snowmelt period and releasing high concentrations of sucrose to the soil during winter.     

The Evolution of Dental Eruption Sequence in Artiodactyls

The sequence of eruption of the second generation of teeth varies across taxa, is highly functional, and is strongly influenced by genetic effects. We assessed postcanine dental eruption sequence across artiodactyls in order to test two hypotheses: 1) dental eruption sequence is a good phylogenetic character for artiodactyls; and, 2) eruption sequence is adaptive and associated with life history variables like postnatal growth and longevity in artiodactyls (Schultz’s Rule). We examined postcanine eruption sequence in 81 genera (100 species) spanning ten families of Artiodactyla. Our ancestral state reconstruction supports the interpretation that the third molar erupted last in the ancestor of Artiodactyla, and that the fourth premolar erupted after the third molar in the ancestor of Ruminantia. Our results indicate that eruption of the third molar last evolved secondarily in the caprines, likely sometime in the Miocene. Overall, our results support the hypothesis that dental eruption sequence is phylogenetically conserved in artiodactyls. Caprines occupy high elevation habitats, and we hypothesize that evolution of their unique dental eruption sequence may be associated with limited resource availability in high elevation mountain systems and the necessity to process a wide range of vegetation types.     

Patterns of growth and body condition in sea otters from the Aleutian archipelago before and after the recent population decline

1. Growth models for body mass and length were fitted to data collected from 1842 sea otters Enhydra lutris shot or live-captured throughout south-west Alaska between 1967 and 2004. Growth curves were constructed for each of two main year groups: 1967-71 when the population was at or near carrying capacity and 1992-97 when the population was in steep decline. Analyses of data collected from animals caught during 2004, when the population density was very low, were precluded by a small sample size and consequently only examined incidentally to the main growth curves. 2. Growth curves demonstrated a significant increase in body mass and body length at age in the 1990s. Asymptotic values of body mass were 12-18% higher in the 1990s than in the 1960s/70s, and asymptotic values for body length were 10-11% higher between the same periods. Data collected in 2004 suggest a continued increase in body size, with nearly all data points for mass and length falling significantly above the 1990s growth curves. 3. In addition to larger asymptotic values for mass and length, the rate of growth towards asymptotic values was more rapid in the 1990s than in the 1960s/70s: sea otters reached 95% of asymptotic body mass and body length 1-2 years earlier in the 1990s. 4. Body condition (as measured by the log mass/log length ratio) was significantly greater in males than in females. There was also an increasing trend from the 1960s/70s through 2004 despite much year-to-year variation. 5. Population age structures differed significantly between the 1960s/70s and the 1990s with the latter distribution skewed toward younger age classes (indicating an altered lx function) suggesting almost complete relaxation of age-dependent mortality patterns (i.e. those typical of food-limited populations). 6. This study spanned a period of time over which the population status of sea otters in the Aleutian archipelago declined precipitously from levels at or near equilibrium densities at some islands in the 1960s/70s to < 5% of estimated carrying capacity by the late 1990s. The results of this study indicate an improved overall health of sea otters over the period of decline and suggest that limited nutritional resources were not the cause of the observed reduced population abundance. Our findings are consistent with the hypothesis that the decline was caused by increased killer whale predation.     

Comparison of the NH2-Terminal sequences of chick Type I preprocollagen chains synthesized in an nRNA-dependent reticulocyte lysate

The histone variants and high-mobility-group (HMG) proteins of a transcribing fraction of chromatin, described in the preceding paper of this journal, have been analysed qualitatively and quantitatively by a combination of one-dimensional and two-dimensional gel electrophoresis. The stoichiometry of the four core histones (all variants included) in this fraction is equimolar and is not detectably different from that in the nontranscribing fraction or in total chromatin. The molar ratio of histone H1 to the core histones is markedly lower, by approximately 72%, than that in the nontranscribing fraction. A minor histone variant identified as M1 (an H2A variant) is detected only in the transcribing fraction, while variant H3.1 is found only in the non-transcribing fraction. Proteins A24, HMG1 and HMG2 are essentially absent from the transcribing fraction; HMG14 is found uniquely in this fraction, while HMG17 occurs at a relatively lower level.