Giant,accordioned sperm acrosomes of the greater bulldog bat,Noctilio leporinus

Sperm of the greater bulldog bat Noctilio leporinus display an architecture that is totally unique among mammalian spermatozoa. The sperm head of Noctilio is extraordinarily large and flat and lies eccentrically with respect to the sperm tail. The major portion of the atypically large acrosome lies anterior to the nucleus and is shaped into a dozen accordionlike folds that run parallel to the long axis of the sperm. The ridge of each fold is shaped into ∼60 minute, evenly spaced rises that extend along the entire length of the fold. We speculate that acrosome ridges may serve to strengthen the sperm head during transport. Mol. Reprod. Dev. 48:90–94, 1997 © 1997 Wiley-Liss, Inc.     

Fecundity and size in the housefly: investigations of some environmental sources and genetic correlates of variation

Environmental sources and genetic correlates of variation in fecundity and size were studied in field and laboratory housefly populations in central Iowa, U.S.A. Electrophoresis of enzymatic proteins was used to monitor genotypes and heterozygosity. In the field, mean fecundity declined as adult densities increased. Fecundity varied greatly within breeding seasons. Fly body size varied spatially and temporally during summer and winter. Fecundity and size were positively correlated. Size was independent of genotypes at the six loci studied. No relationship was observed between heterozygosity and the magnitude or variability of body size.     

Dipeptidase-C inDrosophila melanogaster: Genetic,ontogenetic, and tissue-specific variation

Dip-A, Dip-B, and Dip-C constitute structural genes for three peptidic enzymes in Drosophila melanogaster distinct from the leucine aminopeptidases. Their ontogenetic and tissue distributions of activities suggest the involvement of these enzymes in a general metabolic role, such as the regulation of amino acid and oligopeptide pools to make amino acids available for protein synthesis. Screening of chromosome substitution isogenic lines for DIP-C activity indicated that, like DIP-A and DIP-B, unlinked activity modifiers exist for Dip-C. The developmental profiles of dipeptidase activities are very similar, except in the pupal stage, during which DIP-C activity is markedly low compared to the other two enzymes. Intercorrelations of dipeptidase activities vary ontogenetically, which is consistent with the need for coordinate expression of these enzymes during certain developmental stages. Tissue-specific expression of dipeptidases in larvae and adults are also similar, although the relative levels of DIP-A activity differ from those of DIP-B and DIP-C in certain organs and body parts. Some of the differences among chromosome substitution lines for dipeptidase activities appear to be systemic, while others are developmental stage-specific and tissue-specific. Second- and third-chromosome variants for DIP-C activity differed in their tissue distribution. This is consistent with the presence of temporal and spatial variants in natural populations for other Drosophila enzymes.     

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.