Integrative phylogenetic, phylogeographic and morphological characterisation of the Unio crassus species complex reveals cryptic diversity with important conservation implications.

The global decline of freshwater mussels and their crucial ecological services highlight the need to understand their phylogeny, phylogeography and patterns of genetic diversity to guide conservation efforts. Such knowledge is urgently needed for Unio crassus, a highly imperilled species originally widespread throughout Europe and southwest Asia. Recent studies have resurrected several species from synonymy based on mitochondrial data, revealing U. crassus to be a complex of cryptic species. To address long-standing taxonomic uncertainties hindering effective conservation, we integrate morphometric, phylogenetic, and phylogeographic analyses to examine species diversity within the U. crassus complex across its entire range. Phylogenetic analyses were performed using cytochrome c oxidase subunit I (815 specimens from 182 populations) and, for selected specimens, whole mitogenome sequences and Anchored Hybrid Enrichment (AHE) data on âˆ¼ 600 nuclear loci. Mito-nuclear discordance was detected, consistent with mitochondrial DNA gene flow between some species during the Pliocene and Pleistocene. Fossil-calibrated phylogenies based on AHE data support a Mediterranean origin for the U. crassus complex in the Early Miocene. The results of our integrative approach support 12 species in the group: the previously recognised Unio bruguierianus, Unio carneus, Unio crassus, Unio damascensis, Unio ionicus, Unio sesirmensis, and Unio tumidiformis, and the reinstatement of five nominal taxa: Unio desectusstat. rev., Unio gontieriistat. rev., Unio mardinensisstat. rev., Unio nanusstat. rev., and Unio vicariusstat. rev. Morphometric analyses of shell contours reveal important morphospace overlaps among these species, highlighting cryptic, but geographically structured, diversity. The distribution, taxonomy, phylogeography, and conservation of each species are succinctly described.

Retention of lead in growing rats with varying dietary lead supplements.

144 female rats with a beginning weight of 35 +/- 3 g were fed for 23 days a half-synthetic diet with a lead content that varied over 18 concentrations (0.025 to 600 mg/kg). Absolute lead retention was calculated as total body concentration of lead in animals at the end of the experiment minus the average lead concentration in carcasses of reference animals that had been sacrificed at the beginning of the experiment. The relative retention was calculated with regard to lead intake. Absolute lead retention increased in association with a lead supply of 0.225 mg per kg diet, but decreased thereafter. Not until a lead concentration of 5 mg per kg diet was reached did lead retention rise again. Relative lead retention decreased exponentially with an increasing lead supply and finally approached a constant value. Live mass development and feed intake were not affected by an increase in lead supply. Altogether, these results demonstrate that lead metabolism is homeostatically regulated.

Effect of dietary lead intake on lead retention in adult rats.

132 female rats with a live weight of 177 to 224 g were provided over a period of 17 days a half-synthetic diet with a lead concentration of 0.4 mg/kg. Then 120 of the animals were divided into 15 treatment groups fed with a diet different in Pb content (0.02, 0.04, 0.08, 0.12, 0.22, 0.42, 0.62, 0.82, 1, 5, 10, 50, 100, 400 and 800 mg Pb2+ per kg) over a period of 29 days. The feed was rationed so as to provide the minimum energy maintenance requirement. Pb retention dependent on different lead supplies was determined by subtracting the Pb contents of carcasses of 12 reference animals sacrificed at the beginning of the experiment from the Pb content of carcasses of rats at the end of the experiment. Up to a Pb concentration of 0.42 mg/kg in the diet Pb retention fluctuated around zero. Then the retention was slightly positive up to 5 mg/kg Pb in the diet. Up to 10 mg/kg Pb in the diet Pb retention increased sharply. Concentrations of iron, copper, zinc, and manganese in carcasses were affected only slightly by the varying concentration of lead in the diet.