Behavioral response to predators reverses the outcome of competition between prey species

Summary In a laboratory experiment it was shown that piscivorous predators reversed the outcome of competitive interactions between two fish prey species, juveniles of roach (Rutilus rutilus) and perch (Perca fluviatilis), by behaviorally affecting their use of two available habitats, an open water habitat and a structurally complex refuge. The shift in the competitive relationship was the result of predators forcing the juvenile fishes into a prey refuge with high structural complexity. While roach was competitively superior in the unstructured habitat, perch was superior in the structurally complex prey refuge. The reversal in competitive relationship was demonstrated both with respect to foraging rate and growth rate and resulted from the high structural complexity in the prey refuge interfering with the roach's swimming performance. Because survival and growth patterns through the juvenile stages have profound effects on the population/community dynamics of size-structured populations such as those of fish, behaviorally induced changes in competitive ability should have significant implications also at the population and community levels.     

Incest avoidance and bonding between siblings in gerbils

Summary Social and sexual preferences for siblings versus non-siblings have been investigated in Mongolian gerbils (Meriones unguiculatus) in a series of laboratory and outdoor enclosure (100 m²) studies. When first social contact took place at pairing in adulthood full siblings and nonsiblings did not differ with respect to onset of reproduction. Correspondingly, both siblings and non-siblings paired at weaning age had a delayed onset of reproduction. Thus, no effect could be established in either case, related to the individuals' relatedness, but the importance of social exposure was clear. Non-siblings paired when 2 months old had a delayed onset of reproduction, which did not differ statistically from the onset in siblings, raised together, and housed pairwise since the same age. When sexually mature animals were paired at 3 months of age, siblings were found to start reproducing later than non-siblings (Ågren 1981). Following an initial delay in both siblings and nonsiblings paired when 5 months old, all non-sibling pairs reproduced before any sibling pair. At pair formation, at least the females in both groups were known to be sexually immature. These results indicate that for sibling-bonding to occur social exposure may be delayed until the animals are old enough, or somatically developed, to mature sexually. Thus, social exposure before weaning age during the period for primary socialization seem not to be crucial, nor the actual maturational state, sexually, in older females. To study the stability of the social bonds between siblings and non-siblings, animals kept pairwise in the laboratory were released in large outdoor enclosures. Pairs brought together before the age of sexual maturity did not remain stable, whether or not the former cagemates were siblings. Non-sibling pairs formed after this age, which had also reproduced successfully in the laboratory, did remain stable. Social and sexual interactions were studied within and between two mixed-sex sibling groups of four. The sibling groups had the possibility to establish group territories before being exposed to each other. Although the sibling groups remained stable, the females still preferred non-sibling males as sexual partners. However, socially dominant brothers copulated more frequently than subordinant brothers. This rank difference was not evident in non-siblings.     

Urban Geochemistry: A Multimedia and Multielement Survey of a Small Town in Northern Europe

The concentrations and distributions of chemical elements (Ag, Al, As, Au, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Se, Sr, Te, Th, Ti, Tl, U, V, W and Zn) were studied in till, humus and urban soil in Jakobstad, a small town (20,000 inhabitants) in W. Finland. The analyses were performed with ICP-MS after aqua regia leaching of till (n = 37), urban topsoil (n = 32) and subsoil (n = 32), and HNO3 leaching of humus (n = 37). The till and humus samples, collected at the same sites, were divided into urban and rural samples. The urban till was not significantly enriched in metals. In contrast, a majority of the elements occurred in higher concentrations in the urban than the rural humus samples. Statistical and spatial interpretations of the humus data revealed that traffic (Pb, V and Ni), metal industry (Pb, Zn, Bi, Sb and Cr), an abandoned shooting range (Pb and Sb) and other sources contribute to higher metal levels in the urban humus. The urban soil samples were collected at parks, yards, abandoned industrial sites, roadsides, etc. The topsoil samples were enriched in most elements, also by elements not enriched in the urban humus (e.g. Cd). At several sites, the concentrations far exceeded the limit concentrations for contaminated soils in Finland. A large variety of sources were identified or indicated.     

Spermatozoan ultrastructure and spermatogenesis in aplousobranch ascidians,with some phylogenetic considerations

Spermatozoa and some stages of spermatogenesis were studied for four species of aplousobranch ascidians. Spermatozoa of Clavelina lepadiformis (Müller) (family Clavelinidae) are plesiomorphous in that they have apical acrosomal vesicles and a moderately elongated, cylindrical nucleus. The elongated mitochondrion is twisted ea. 11/2 times around the nucleus. In their ultrastructural morphology, C. lepadiformis sperm conform in some respects to the least-derived ascidian sperm, those of the phlebobranch ascidian Ciona intestinalis L.; however, the sperm of Clavelina lepadiformis have two apomorphies not shared with those of Ciona sp.: (1) the mitochondrion of Clavelina lepadiformis is long and spiralled along the entire nucleus rather than being comparatively compact and not at all helical; (2) the mitochondrial cristae are elongated parallel to the long axis of the nucleus, whereas in Ciona sp. sperm the cristae are unmodified. In Distaplia sp., Aplidium sp. and Synoicum pulmonaria (Ellis and Solander) the spermatozoa are more derived and consist of a proximal cylindrical and a distal corkscrew-like part. The mitochondrion in Distaplia sp. and Aplidium sp. contains electron-dense material and extends in a long thread around the nucleus. In S. pulmonaria the mitochondrion surrounds the anterior part of the nucleus in mature spermatozoa, and an elongated, dense structure displaying fine striation is enclosed in the mitochondrion in late spermatids. The sperm ultrastructural morphology observed in this study is consistent with the majority view that clavelinids are closest to the ancestral ascidian but is also consistent with other conclusions, particularly that the Cionidae are closest to the stem ascidian.     

Biliary secretion,retention and excretion of five 14C-labelled polychlorinated biphenyls in the rat

Five ¹⁴C-labelled polychlorinated biphenyls: 2,4′,5-trichlorobiphenyl, 2,2′,4,5′-tetrachlorobiphenyl, 2,2′,4,5,5′-pentachlorobiphenyl, 2,2′,3,4,4′-pentachlorobiphenyl and 2,2′,4,4′,5,5′-hexachlorobiphenyl were administered orally to bile-cannulated rats. The activity secreted in the bile, excreted in the feces and the urine was determined. Residues of radioactivity in certain tissues and the carcass were also measured.The trichlorobiphenyl showed the highest absorption (93.8%±5.4) from the gastrointestinal tract and biliary secretion of radioactivity (87.6%±6.1 of the dose). The hexachlorobiphenyl showed the lowest absorption and biliary secretion, 28.2%±1.4 and 18.6%±1.3, respectively. The urinary excretion was low and the radioactive residues in the eviscerated carcasses increased with the chlorine content of the biphenyls.     

Keeping the blood flowing—plasminogen activator genes and feeding behavior in vampire bats

The blood feeding vampire bats emerged from New World leaf-nosed bats that fed on fruit and insects. Plasminogen activator, a serine protease that regulates blood coagulation, is known to be expressed in the saliva of Desmodus rotundus (common vampire bat) and is thought to be a key enzyme for the emergence of blood feeding in vampire bats. To better understand the evolution of this biological function, we studied the plasminogen activator (PA) genes from all vampire bat species in light of their feeding transition to bird and subsequently mammalian blood. We include the rare species Diphylla ecaudata and Diaemus youngi, where plasminogen activator had not previously been studied and demonstrate that PA gene duplication observed in Desmodus is not essential to the vampire phenotype, but relates to the emergence of predominant mammalian blood feeding in this species. Plasminogen activator has evolved through gene duplication, domain loss, and sequence evolution leading to change in fibrin-specificity and susceptibility to plasminogen activator inhibitor-1. Before undertaking this study, only the four plasminogen activator isoforms from Desmodus were known. The evolution of vampire bat plasminogen activators can now be linked phylogenetically to the transition in feeding behavior among vampire bat species from bird to mammalian blood. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The kinetics of reductive dehalogenation of a set of halogenated aliphatic hydrocarbons in anaerobic sediment slurries

Disappearance rate constants are reported for the reductive transformation of 17 halogenated aliphatic hydrocarbons in anaerobic sediment-water samples. Statistical experimental design in combination with multivariate chemical characterization of their chemical properties was used to select the compounds. Degradation followed pseudo first-order kinetics through at least two half-lives for 15 of the 17 compounds. Of all the compounds investigated, 1,2,3-trichloropropane and dichloromethane were unique in that they were dehalogenated according to zero-order kinetics. Reductive dehalogenation was the sole transformation reaction taking place.