Macroborings in Otodus megalodon and Otodus chubutensis shark teeth from the submerged shelf of Onslow Bay,North Carolina,USA: implications for processes of lag deposit formation

Abstract

The shallow continental shelf in the Cape Fear Region of southwestern Onslow Bay, North Carolina, contains lag deposits with an abundance of megatoothed shark teeth belonging to Otodus megalodon (Agassiz 1835) and Otodus chubutensis (Ameghino 1906) that derive from the Pliocene Yorktown and Miocene Pungo River formations, respectively. These teeth exhibit different frequencies and orientations of macroborings identified as Gastrochaenolites torpedo Kelly and Bromley (1984 Kelly, S., and R. Bromley. 1984. “Ichnological Nomenclature of Clavate Borings.” Palaeontology 27: 793–807.[Web of Science ®] , [Google Scholar]), Gastrochaenolites lapidicus Kelly and Bromley (1984 Kelly, S., and R. Bromley. 1984. “Ichnological Nomenclature of Clavate Borings.” Palaeontology 27: 793–807.[Web of Science ®] , [Google Scholar]), Maeandropolydora sulcans Voigt (1965 Voigt, E. 1965. “Über parasitische Polychaeten in Kreide-Austern sowie einige andere in Muschelschalen bohrende Würmer.” Paläontologische Zeitschrift 39 (3–4): 193–211.[Crossref] , [Google Scholar]) and ?Entobia isp. attributed to endolithic bivalves, serpulid worms and clionaid sponges. Different frequencies and orientations of macroborings seen in lag deposits containing O. megalodon and O. chubutensis teeth are the result of repeated exhumation and reworking in response to bathymetrically controlled wave-based erosion during storm events and glacioeustatically driven sea-level cyclicity across Onslow Bay. Chronological ranges of O. megalodon and O. chubutensis teeth that contain macroborings indicate that these lag deposits may have been forming since the late early Miocene.     

Contrasting patterns of change in the distribution and abundance of farmland birds in relation to farming system in lowland Britain

Patterns of change in distribution (presence/absence) and abundance since the late 1960s were examined in 20 species of farmland bird in southern Britain in predominantly arable (eastern), predominantly mixed (central) and predominantly grassland (western) regions. Comparisons were made between changes in distribution and in abundance to determine whether these measures show similar relationships to environmental change. Local extinctions of selected species and reductions in species richness were significantly greater in the predominantly grassland region. Decreases in abundance were greatest in seven species in the predominantly arable region, two in the mixed region and nine in the grassland region. Changes in distribution and abundance showed consistent patterns in three species, turtle dove Streptopelia turtur L., yellow wagtail Motacilla flava L. and reed bunting Emberiza schoeniclus L. In another four species, grey partridge Perdix perdix L., lapwing Vanellus vanellus L., tree sparrow Passer montanus L. and corn bunting Miliaria calandra L., decreases in abundance were greatest in the arable region, yet declines in distribution were lowest. For other individual species, changes in distribution were too small to draw any conclusions in relation to farm type. We suggest that modern grassland systems are suboptimal habitats compared to arable or mixed agricultural land for many farmland species that occur at relatively low density in the more western, grass‐dominated region. Declines in abundance are therefore more likely to lead to local extinction in these areas than in eastern areas where abundance is higher. However, the role of changes in grassland management on bird populations requires further research. It is suggested that conclusions drawn from changes in distribution alone, in the absence of supporting data on changes in abundance, may be misleading where the aim is to assess how large‐scale spatial dynamics of populations relate to environmental change.     

Phenols as nutrients for a phytophagous insect Anacridium melanorhodon

Gallic acid and certain 3,4-dihydroxyphenols increased the growth rate of Anacridium melanorhodon (Acrididae) when added to a diet deficient in them. The evidence suggests that these phenolics replace or spare phenylalanine in the production of cuticular tanning agents. The natural food plants were found to be rich in such phenolics and low in protein and it is concluded that the insect has become physiologically adapted, so that the utilisation of phenolics preserves a maximum amount of protein for other growth processes.     

Barley embryo globulin 1 gene,Beg1: Characterization of cDNA,chromosome mapping and regulation of expression

We report identification of a 2189 by cDNA clone from barley corresponding to a single-copy gene, Beg1 (Barley embryo globulin), on chromosome 4, which encodes a storage globulin. In barley, the major protein reserve in the aleurone layer belongs to the 7S globulin class of proteins found in many seeds. Electrophoretically and antigenically similar proteins are present in the barley embryo. Accumulation of Beg1 mRNA was noted beginning 15–20 days post-anthesis in both the aleurone layer and embryo of the developing barley grain but not in the starchy endosperm. A high level of Beg1 mRNA is also present in the mature imbibed aleurones, which can be repressed by treatment with gibberellic acid. This repressive effect of gibberellin on the levels of Beg1 mRNA is confirmed in the gibberellin response-constitutive mutant, slender, whose aleurone layers do not accumulate Beg1 mRNA even in the absence of applied gibberellic acid. The deduced primary translation product of the Beg1 mRNA is a 637 amino acid (72 kDa) protein with homology to maize embryo globulin 1 (GLB1) and a partial sequence of a wheat 7S globulin. The internal amino acid sequence of BEG1 closely matches the N-terminal sequence of isolated barley aleurone globulin. Seven imperfect tandem repeats of 16 amino acids each are present near the N-terminus of BEG1, which conform to the consensus HGEGEREEEXGRGRGR, and contribute to the observed unusual amino acid composition of this protein. A second, distinct barley globulin gene, Beg2, which is homologous to maize Glb2, was detected by Northern and Southern analysis. Beg-2 and Beg1 are regulated differently which may indicate variation in storage or utilization properties among the barley globulins.