Song is a reliable signal of bill morphology in Darwin's small tree finch Camarhynchus parvulus, and vocal performance predicts male pairing success

The shape and movement of the vocal tract are known to influence bird song. Current theory predicts that large bill and body size are correlated with low frequency song and slow trill rate. It is also widely accepted that song characteristics are important for mate choice by females. We investigated the relationship between bill morphology, song characteristics, and pairing success in Darwin's small tree finch Camarhynchus parvulus , on the Galapagos Islands. Contrary to predictions from a previous cross-species study on Darwin's finches, we found that individuals with larger bill size produced songs with slow trill rate, high dominant frequency, and broad frequency bandwidth, indicating that song is a reliable signal of bill morphology. Vocal performance as indicated by the deviation from an upper performance limit was higher in paired than unpaired males. Pairing was not skewed in favour of a particular bill size, and both small and large billed males that sang high performance song had high pairing success. The reliable signalling function of song has implications for female choice and territorial defence, given that both females and conspecific competitors can assess the relative size of males' bills through song, while females may use vocal performance as a signal of male quality.     

LIPID COMPOSITION OF CHLORARACHNIOPHYTES (CHLORARACHNIOPHYCEAE) FROM THE GENERA BIGELOWIELLA,GYMNOCHLORA, AND LOTHARELLA1

The Chlorarachniophyceae are unicellular eukaryotic algae characterized by an amoeboid morphology that may be the result of secondary endosymbiosis of a green alga by a nonphotosynthetic amoeba or amoeboflagellate. Whereas much is known about the phylogeny of chlorarachniophytes, little is known about their physiology, particularly that of their lipids. In an initial effort to characterize the lipids of this algal class, four organisms from three genera were examined for their fatty acid and sterol composition. Fatty acids from lipid fractions containing chloroplast‐associated glycolipids, storage triglycerides, and cytoplasmic membrane‐associated polar lipids were characterized. Glycolipid‐associated fatty acids were of limited composition, principally eicosapentaenoic acid [20:5(n‐3)] and hexadecanoic acid (16:0). Triglyceride‐associated fatty acids, although minor, were found to be similar in composition. The polar lipid fraction was dominated by lipids that did not contain phosphorus and had a more variable fatty acid composition with 16:0 and docosapentaenoic acid [22:5(n‐3)] dominant along with a number of minor C₁₈ and C₂₀ fatty acids. Crinosterol and one of the epimeric pair poriferasterol/stigmasterol were the sole sterols. Several genes required for synthesis of these sterols were computationally identified in Bigelowiella natans Moestrup. One sterol biosynthesis gene showed the greatest similarity to SMT1 of the green alga, Chlamydomonas reinhardtii. However, homologues to other species, mostly green plant species, were also found. Further, the method used for identification suggested that the sequences were transferred to a genetic compartment other than the likely original location, the nucleomorph nucleus.     

CELL DIVISION AND MORPHOGENESIS OF THE CENTRIC DIATOM CHAETOCEROS DECIPIENS (BACILLARIOPHYCEAE) II. ELECTRON MICROSCOPY AND A NEW PARADIGM FOR TIP GROWTH

Valve morphogenesis starts when the silica deposition vesicle (SDV) expands across a cleavage furrow covered by an unidentified layer, which may aid in its shaping. A labiate process (LP) is present only in the outer valve of terminal cells in the filament. Before these particular cells form setae, a layered "labiate process apparatus" (LPA) appears on the SDV in the exact center of the forming valve, near the microtubule center arising after cleavage. The LPA thereafter surmounts the lips of the LP as it forms. After the girdle bands separate slightly, two lateral protrusions develop in the corners of the cell. These nascent setae are lined internally by a cylindrical, fibrous band (sleeve), which assembles immediately ahead of the expanding edge of the SDV, very close to the plasmalemma. Then these protrusions, lined by the fibrous band, the SDV, and the forming silica wall, grow through two gaps in the girdle bands. The cytoplasm at the tip of the growing seta is naked. Immediately behind the tip, this fibrous band is adpressed to the plasmalemma and thereby apparently defines the diameter of the seta; it extends to internally ensheath the tipmost edge of the SDV for a short distance, like a tight-fitting inner sleeve. This structure is considered the major organelle involved in seta morphogenesis. Microtubules (MTs), while present, are variable in extent and disposition within the seta. Turgor pressure is considered irrelevant in driving seta growth. Instead, a new paradigm proposed for tip-growing cells generally, may apply to seta morphogenesis, as follows. If, as is suspected, the fibrous band contains actin, cycling of this actin (as in animal cells undergoing ruffling or filopodial extension) could drive seta extension via attachment of the band to the just-formed silica wall. The band is visualized as a molecular treadmill whose support base, the new wall, is being continually extended; extension is controlled and generated strictly at the tip.     

Nucleotide sequences at the sites of action of the deoxyribonucleic acid modification enzyme of bacteriophage P1

Labelled oligonucleotides have been fractionated from DNAase digests of phage λ DNA that had been methylated with the phage P1 modification enzyme and S-[methyl-¹⁴C]adenosyl-l-methionine. The longest sequences established are the tetranucleotides pG-ǎ?-T-C4 and p?-T-C-T, which, together with the other sequences determined, particularly pA-G-?, show that the modification enzyme, M.EcoP1, methylates adenine residues within defined sequences and suggest that the oligonucleotide sequence recognized by this enzyme is the hexanucleotide pA-G-A-T-C-T. The duplex formed by base-pairing this hexanucleotide with its complementary sequence resembles the recognition sequence for several restriction enzymes in being bisected by an axis of 2-fold rotational symmetry.     

Synthesis of deoxyribonucleic acid in BHK-21/C13 cells

Newly synthesized (3)H-labelled DNA was extracted from baby hamster kidney cells (BHK-21/C13 cells) and was shown to possess single-stranded properties when examined by column chromatography on benzoylated naphthoylated DEAE-cellulose, hydroxyapatite and methylated albumin on kieselguhr, and by its affinity for nitrocellulose filters. Some of the newly synthesized DNA was shown to be of lower molecular weight than the bulk of the DNA when examined by alkaline sucrose-density-gradient centrifugation. The properties observed were not affected by treatment of the DNA with ribonuclease, Pronase or amylase. The effect of the size of the DNA on its observed properties was examined and is discussed. It is concluded that DNA synthesis in BHK-21/C13 cells proceeds according to the discontinuous-mechanism model in at least one of the strands.     

Comparative Studies of Wild-Type and “Cold-Mutant” (Temperature-Sensitive) Influenza Viruses: Polypeptide Synthesis by an Asian (H2N2) Strain and Its Cold-Adapted Variant

The structure and replication of a cold-adapted, temperature-sensitive (TS) mutant of an Asian (H2N2) influenza virus was compared with that of its wild-type (WT) parent. Viruses were grown in a chicken kidney cell system, and at the nonpermissive temperature of 40 C, production of infectious TS virus was about 100,000-fold less than at 35 C, in contrast to WT virus. Major structural polypeptides of each virus grown at 35 C were similar, except that the hemagglutinin glycopolypeptide (HA) of the TS virions was slightly more heterogenous than that of WT virions. Synthesis of viral polypeptides was examined by sodium dodecyl sulfate acrylamide gel electrophoresis of pulse-labeled infected cells. This revealed a defect in the synthesis of TS viral hemagglutinin that was most pronounced at the nonpermissive temperature. Other TS viral polypeptides appeared to be synthesized normally at 40 C. A defect in the TS virus hemagglutinin was also indicated by serological studies that demonstrated that TS virus hemagglutinin had lost antigenic sites present on the WT virus. Thus, it is concluded that the virus mutant examined contains lesions in the hemagglutinin gene, although the possibility of additional unrecognized lesions is not excluded.