Sperm Length Variation as a Predictor of Extrapair Paternity in Passerine Birds

The rate of extrapair paternity is a commonly used index for the risk of sperm competition in birds, but paternity data exist for only a few percent of the approximately 10400 extant species. As paternity analyses require extensive field sampling and costly lab work, species coverage in this field will probably not improve much in the foreseeable future. Recent findings from passerine birds, which constitute the largest avian order (∼5,900 species), suggest that sperm phenotypes carry a signature of sperm competition. Here we examine how well standardized measures of sperm length variation can predict the rate of extrapair paternity in passerine birds.We collected sperm samples from 55 passerine species in Canada and Europe for which extrapair paternity rates were already available from either the same (n = 24) or a different (n = 31) study population. We measured the total length of individual spermatozoa and found that both the coefficient of between-male variation (CV(bm)) and within-male variation (CV(wm)) in sperm length were strong predictors of the rate of extrapair paternity, explaining as much as 65% and 58%, respectively, of the variation in extrapair paternity among species. However, only the CV(bm) predictor was independent of phylogeny, which implies that it can readily be converted into a currency of extrapair paternity without the need for phylogenetic correction.We propose the CV(bm) index as an alternative measure to extrapair paternity for passerine birds. Given the ease of sperm extraction from male birds in breeding condition, and a modest number of sampled males required for a robust estimate, this new index holds a great potential for mapping the risk of sperm competition across a wide range of passerine birds

Variation of Basal EROD Activities in Ten Passerine Bird Species – Relationships with Diet and Migration Status

Inter-specific differences in animal defence mechanisms against toxic substances are currently poorly understood. The ethoxyresorufin-O-deethylase (EROD) enzyme plays an important role in defence against toxic chemicals in a wide variety of animals, and it is an important biomarker for environmental contamination. We compared basal hepatic EROD activity levels among ten passerine species to see if there is inter-specific variation in enzyme activity, especially in relation to their diet and migration status. Migratory insectivores showed higher EROD activity compared to granivores. We hypothesize that the variable invertebrate diet of migratory insectivores contains a wider range of natural toxins than the narrower diet of granivores. This may have affected the evolution of mixed function oxidases (MFO) system and enzyme activities. We further tested whether metabolic rates or relative liver size were associated with the variation in detoxification capacity. We found no association between EROD activity and relative (per mass unit) basal metabolic rate (BMR). Instead, EROD activity and relative liver mass (% of body mass) correlated positively, suggesting that a proportionally large liver also functions efficiently. Our results suggest that granivores and non-migratory birds may be more vulnerable to environmental contaminants than insectivores and migratory birds. The diet and migration status, however, are phylogenetically strongly connected to each other, and their roles cannot be fully separated in our analysis with only ten passerine species

Chemical changes in detrital matter upon digestive processes in a sesarmid crab feeding on mangrove leaf litter

Pathways and rates of decomposition of detrital matter partly depend on its chemical composition. Digestive processes of detritivores drive changes in the chemical composition of detritus, and these changes translate into the chemical composition of the organic matter sequestered into soils and sediments. The latter, in turn, determines how stable organic matter stocks are towards further decay and release of climate-active gases thereupon. We used metabolic fingerprinting to monitor changes in the chemical composition of mangrove detritus upon digestion by a mangrove crab. According to analyses through pyrolysis-GC/MS, the decaying leaf litter of three mangrove species of the Indo-West Pacific, Bruguiera gymnorhiza (L.) Savigny ex Lam. and Poiret 1798, Ceriops tagal (Perr.) C.B. Robinson 1908, and Rhizophora mucronata Lam. 1804, clearly differed from each other in their chemical signature. The feces of detritivorous crabs (Sesarma bidens de Haan 1835) feeding on these detrital sources differed from the source litter in their chemical composition, obviously owing to digestive processes. However, the chemical signatures of feces were more similar to those of their source litter than to those of feces from different litter sources, indicating that the origin of organic matter can be tracked in fecal material. Moreover, male and female crabs appear to exhibit sex-specific digestive processes, as they produced feces that clearly differed from each other in their chemical signature. The 15 chemical compounds most relevant for distinguishing litter sources and fecal material provide first hints on which compounds discriminate the different tree species and characterize digestion by S. bidens. For instance, coumaran (dihydro-benzofuran), indicative of certain carbohydrates, was abundant as a pyrolysis product of the litter of R. mucronata and, to a much lesser degree, C. tagal. Hence, the carbohydrates that were pyrolysed into coumaran seem to discriminate the former two litter sources. Similarly, a pyrolysis-derivate of plant phenolics or proteins, discriminated C. tagal from the other litter sources. From this, we conclude that even subtle differences in litter chemistry and digestive processes of detritivores can be characterized and followed with high resolution through (py-)GC/MS. Further, we propose that the origin of fecal material can be identified with the aid of this technique, and we are currently studying whether the origin of organic matter in the sediment can also be inferred from (py-)GC/MS-data.info:eu-repo/semantics/publishedVersio