Bruno Streit

The toxicity of lindane, hexachlorobenzene, and copper sulfate toTubifex tubifexandLimnodrilus hoffmeisteriwas determined using an easily applicable and standardizable 72-h short-term test system. It was designed for the quick assessment of sublethal and lethal effects of sediment-associated chemicals on the worms. An artificial sediment based on the Artificial Soil according to OECD Guideline No. 207 was used as test medium. The

Male reproductive biology can by characterized through competition over mates as well as mate choice. Multiple mating and male mate choice copying, especially in internally fertilizing species, set the stage for increased sperm competition, i.e., sperm of two or more males can compete for fertilization of the female's ova. In the internally fertilizing fish Poecilia mexicana, males respond to the presence of rivals with reduced expression of mating preferences (audience effect), thereby lowering the risk of by-standing rivals copying their mate choice. Also, males interact initially more with a non-preferred female when observed by a rival, which has been interpreted in previous studies as a strategy to mislead rivals, again reducing sperm competition risk (SCR). Nevertheless, species might differ consistently in their expression of aggressive and reproductive behaviors, possibly due to varying levels of SCR. In the current study, we present a unique data set comprising ten poeciliid species (in two cases including multiple populations) and ask whether species can be characterized through consistent differences in the expression of aggression, sexual activity and changes in mate choice under increased SCR. We found consistent species-specific differences in aggressive behavior, sexual activity as well as in the level of misleading behavior, while decreased preference expression under increased SCR was a general feature of all but one species examined. Furthermore, mean sexual activity correlated positively with the occurrence of potentially misleading behavior. An alternative explanation for audience effects would be that males attempt to avoid aggressive encounters, which would predict stronger audience effects in more aggressive species. We demonstrate a positive correlation between mean aggressiveness and sexual activity (suggesting a hormonal link as a mechanistic explanation), but did not detect a correlation between aggressiveness and audience effects. Suites of correlated behavioral tendencies are termed behavioral syndromes, and our present study provides correlational evidence for the evolutionary significance of SCR in shaping a behavioral syndrome at the species level across poeciliid taxa.

Patterns and processes of molecular evolution critically influence inferences in phylogeny and phylogeography. Within primates, a shift in evolutionary rates has been identified as the rationale for contrasting findings from mitochondrial and nuclear DNA studies as to the position of Tarsius. While the latter now seems settled, we sequenced complete mitochondrial genomes of three Sulawesi tarsiers (Tarsius dentatus, T. lariang, and T. wallacei) and analyzed substitution rates among tarsiers and other primates to infer driving processes of molecular evolution. We found substantial length polymorphism of the D-loop within tarsier individuals, but little variation of predominant lengths among them, regardless of species. Length variation was due to repetitive elements in the CSB domain-minisatellite motifs of 35 bp length and microsatellite motifs of 6 bp length. Amino acid evolutionary rates were second highest among major primate taxa relative to nucleotide substitution rates. We observed many radical possibly function-altering amino acid changes that were rarely driven by positive selection and thus potentially slightly deleterious or neutral. We hypothesize that the observed pattern of an increased amino acid evolutionary rate in tarsier mitochondrial genomes may be caused by hitchhiking of slightly deleterious mutations with favored D-loop length variants selected for maximizing replication success within the cell or the mitochondrion.

Male homosexual behaviour-although found in most extant clades across the Animal Kingdom-remains a conundrum, as same-sex mating should decrease male reproductive fitness. In most species, however, males that engage in same-sex sexual behaviour also mate with females, and in theory, same-sex mating could even increase male reproductive fitness if males improve their chances of future heterosexual mating. Females regularly use social information to choose a mate; e.g. male attractiveness increases after a male has interacted sexually with a female (mate choice copying). Here, we demonstrate that males of the tropical freshwater fish Poecilia mexicana increase their attractiveness to females not only by opposite-sex, but likewise, through same-sex interactions. Hence, direct benefits for males of exhibiting homosexual behaviour may help explain its occurrence and persistence in species in which females rely on mate choice copying as one component of mate quality assessment.

... Lisa Padur1), Juliane Wedekind1), Öznur Öztürk2), Bruno Streit3), Ralph Tiedemann2) & Martin Plath3,4) (1 University of Potsdam, Institute of Biochemistry and ... 2008), since poeciliid males may copy other males' mate choice (P. latip-inna: Schlupp & Ryan, 1997; Witte & Ryan ...