Bite traces on dicynodont bones and the early evolution of large terrestrial predators

Nied?wiedzki, G., Gorzelak, P. & Sulej, T. 2010: Bite traces on dicynodont bones and the early evolution of large terrestrial predators. Lethaia, Vol. 44, pp. 87–92. Dicynodont (Synapsida: Anomodontia) bones from the Late Triassic (late Norian/early Rhaetian) of Poland yield characteristic tooth marks that can be attributed to three ichnotaxa (Linichnus serratus, Knethichnus parallelum and Nihilichnus nihilicus). The general shape and dimension of these traces perfectly match the dental morphology of a co‐occurring carnivorous dinosaur. It is therefore concluded that early carnivorous dinosaurs were feeding on dicynodonts. This discovery constitutes one of the oldest evidence of dinosaur predator–prey interaction. It is suggested that an evolutionary increase in the size of dicynodonts across the Late Triassic may have been driven by selection pressure to reach a size refuge from early dinosaur predators. □Bite traces, dicynodonts, dinosaurs, predation, Triassic.     

Early Cretaceous record of microboring organisms in skeletons of growing corals

Ko?odziej, B., Golubic, S., Bucur, I.I., Radtke, G. & Tribollet, A. 2011: Early Cretaceous record of microboring organisms in skeletons of growing corals. Lethaia, Vol. 45, pp. 34–45. A spectacularly preserved assemblage of microbial euendoliths, penetrating into skeletons of growing scleractinian corals, has been recognized in Early Aptian (Early Cretaceous) reef limestone of the Rar?u Mountains (East Carpathians, NE Romania). Microboring euendolithic filaments were found in five coral colonies of the suborder Microsolenina. They remained in part well‐preserved, often impregnated with iron oxides, which made them visible even in strongly recrystallized parts of coral skeletons. Filaments of a wide range of sizes (2–40 μm in diameter) were concentrated within medium parts of coral septa, oriented along the septa in the direction of the coral growth. The larger filaments were tubular, occurring in bundles and branched into finer, often tapering branches. Their behaviour and organization were quite similar to the modern euendolithic siphonalean chlorophyte Ostreobium. Filament diameters exceeded those reported for the modern species, but covered a similarly wide size range. Narrower frequently branching filaments, 4–8 μm in diameter, resemble distal branching patterns of modern Ostreobium quekettii. Some very thin filaments (ca. 1–2 μm) observed within skeleton or inside the large tubular filaments, sometimes associated with globular swellings, may represent euendolithic fungi. The recrystallization of coral skeleton had limited effect on preservation of euendoliths due to their impregnation with iron oxides; microbial euendoliths were subjected to different taphonomic changes. □Chlorophytes, Early Cretaceous, fungi, microbial euendoliths, Romania, scleractinian corals.     

Extended lifespan traded for diapause in Daphnia

1. Most freshwater crustaceans of the genus Daphnia are cyclically parthenogenetic organisms that are well adapted to unstable habitats due to their short life cycle, wide phenotypic plasticity, and the ability to produce protective diapausing eggs in anticipation of environmental deterioration. Short lifespan and heterogonic reproduction are typical features of Daphnia in a broad spectrum of freshwater habitats, from small temporary pools to large permanent lakes. However, in some locations, departures may be observed from this typical life history pattern to obligate asexuality or extended lifespan. 2. A 3‐year field study in a deep ultraoligotrophic fish‐free alpine‐type lake (Czarny Staw in the Tatra mountains in southern Poland) revealed the coexistence of two closely related asexual lineages of Daphnia of the pulex complex, which differ in body colour (transparent versus orange) and in their strategies for surviving long winters. 3. The ‘transparent’ clone of European origin exhibits an ephemeral lifestyle. It completes its life cycle within a single season, forming two generations of active specimens during the short summer and producing diapausing eggs late in the season. Transparent individuals live no longer than 5–6 months in this cold lake and survive winter exclusively in the form of diapausing eggs. 4. Individuals of the ‘orange’ lineage, which are closely related to eastern Nearctic Daphnia pulicaria, exhibit a biennial lifestyle unique to this genus. They do not form diapausing eggs or produce them only occasionally. Instead, they are active throughout the year and live for up to 13–14 months. Reproduction is postponed until the second year of life when food conditions have improved. Rich lipid reserves accumulated in the first season fuel them during the long winter and permit early reproduction the following spring. 5. Possible reasons for the evolution of obligatory parthenogenesis and long lifespan in Daphnia are discussed.     

Identification of Rhodococcus equi using the polymerase chain reaction

K.S. BELL, J.C. PHILP, N. CHRISTOFI AND D.W.J. AW. 1996. Two regions in the gene coding for 16S rRNA in Rhodococcus equi were selected as species-specific primer sequences for the polymerase chain reaction (PCR). PCR using these primers was tested against 10 strains of R. equi (including the type strain) and gave positive results for all but was negative for all other tested species of Rhodococcus ; representatives of the most closely related genera and a number of other bacterial species. This method could therefore be used to identify this species which can infect the lungs or other organs of horses, pigs, humans and other animals.     

The oligomerization of a family of four genetically clustered human gastrointestinal mucins

Mucins are synthesized and secreted by many epithelia. They are complex glycoproteins that offer cytoprotection. In their functional configuration, mucins form oligomers by a biosynthetic process that is poorly understood. A family of four human gastrointestinal mucin genes (MUC2, MUC5AC, MUC5B, and MUC6) is clustered to chromosome 11p15.5. To study oligomerization of these related mucins, we performed metabolic labeling experiments with [35S]amino acids in LS174T cells, and isolated mucin precursors by specific immunoprecipitations that were analyzed on SDS-PAGE. Each of the precursors of MUC2, MUC5AC, MUC5B, and MUC6 formed a single species of disulfide-linked homo-oligomer within 1 h after pulse labeling. Based on apparent molecular masses, these oligomeric precursors were most likely dimers. Inhibition of vesicular RER-to-Golgi transport, with brefeldin A and CCCP, did not affect the dimerization of MUC2 precursors, localizing dimerization to the RER. O-Glycosylation of MUC2 followed dimerization. Inhibition of N- glycosylation by tunicamycin retarded, but did not inhibit, dimerization, indicating that N-glycans play a role in efficient dimerization of MUC2 precursors. Based on sequence homology, the ability of MUC2, MUC5AC, MUC5B and MUC6 to dimerize most likely resides in their C-terminal domains. Thus, the RER-localized dimerization of secretory mucins likely proceeds by similar mechanisms, which is an essential step in the formation of the human gastrointestinal mucus- gels.      

Daily changes in the sensitivity of wax-moth larvae, Galleria mellonella, to cooling stress

ABSTRACT. Sensitivity to cooling stress in the last instar larvae of Galleria mellonella was measured as (a) the number of extra larval moults, (b) the number of larvae retaining the ability to secrete silk, and (c) the number showing arrested development. With respect to (a) and (b) there were considerable differences in sensitivity across the day. A relationship was observed between the number of additional larval moults induced by chilling and the ability of prepupal larvae to spin silk: the periods during the 24 h when the most larvae passed through additional larval moults were periods characterized by the smallest number of larvae capable of spinning, and vice versa. These daily changes were apparently partly independent of developmental age. Daily variations in sensitivity also occurred when larvae of the same age were cooled at different times of day. It is suggested that these rhythms in cold-sensitivity are related to a cold-sensitive rhythm in juvenile hormone secretion, or hormone sensitivity in the tissues.     

Genotyping of bovine k-casein (k-CNA, k-CNB, k-CNC, k-CNE) following DNA sequence amplification and direct sequencing of k-CNE PCR product

Genomic DNA isolated from blood and semen of dairy cattle with known kappa-casein (kappa-CN) genotypes was subjected to Southern blot hybridization and polymerase chain reaction (PCR) using up to 14 restriction endonucleases. kappa-casein genotypes AA, AB and BB were identified using Hin dIII and Hin fI while genotypes with kappa-CNC and kappa-CNE were misidentified. Direct sequencing of the PCR product (kappa-CN EE) showed a substitution of guanine (kappa-CNA,B) by adenine (kappa-CNE) which creates a HaeIII restriction site. Therefore using PCR followed by Hin dIII or HinfI and Hae III digest allows discrimination between kappa-casein A, B and E directly at the DNA level.     

Detection of a new K-casein variant in cow''s milk

In German Simmental cattle a new kappa-casein variant was detected by isoelectric focusing, which cannot be distinguished from kappa-casein A by polyacrylamide and starch gel electrophoresis. It was named kappa-casein D. The frequencies of kappa-casein alleles were kappa-Cn A 0.75, kappa-Cn B 0.24, kappa-Cn D 0.01.