Diet composition of an invasive population of Lithobates catesbeianus (American Bullfrog) from Argentina

The American bullfrog Lithobates catesbeianus has been introduced around the world, with invasive populations reported from almost all South American countries. A population of this species was introduced in the Calingasta department of San Juan province, which is an arid environment in western Argentina. This work provides information on the dietary composition of an invasive population of L. catesbeianus, and compares the degree of dietary overlap between adults and juveniles. Stomach contents of 169 bullfrogs (82 adults and 87 juveniles) were analysed. Adults consumed 40 prey taxa and Hymenoptera (Insecta) was the most numerous prey item (41.8%), followed by Araneae (13.6%) and Aeglidae (13.4%). Juveniles consumed 29 prey taxa and Hymenoptera constituted the highest percentage in prey number (77.2%). The trophic overlap niche index at the same level shows a value of 0.64 overlap in dietary community between adults and juveniles of this bullfrog. Aeglidae was volumetrically the most important trophic item (25.4%), followed by Anura (25.02%). Our results showed that cannibalism in bullfrogs is more common than the consumption of native anurans, coinciding with that reported in other populations of introduced bullfrogs. The high similarity in the diets of both size classes and the association between the size of the predator and prey suggest that the impact caused by bullfrogs throughout their ontogeny is high and probably has an impact on their prey. Freshwater crabs are the main items in the diet of Lithobates catesbeianus in other introduced populations and are usually the most conspicuous at our study site. The crabs in freshwater ecosystems are part of the lowest trophic level in the food chain. The major threats to the southern region’s freshwater crabs include deforestation, farming and exotic species. Lithobates catesbeianus has a generalist diet and high overlap between adults and juveniles.     

DMP1 mutations in autosomal recessive hypophosphatemia implicate a bone matrix protein in the regulation of phosphate homeostasis

Hypophosphatemia is a genetically heterogeneous disease. Here, we mapped an autosomal recessive form (designated ARHP) to chromosome 4q21 and identified homozygous mutations in DMP1 (dentin matrix protein 1), which encodes a non-collagenous bone matrix protein expressed in osteoblasts and osteocytes. Intact plasma levels of the phosphaturic protein FGF23 were clearly elevated in two of four affected individuals, providing a possible explanation for the phosphaturia and inappropriately normal 1,25(OH)2D levels and suggesting that DMP1 may regulate FGF23 expression.     

The tumor necrosis factor α of the bony fish seabream exhibits the in vivo proinflammatory and proliferative activities of its mammalian counterparts,yet it functions in a species-specific manner

Information on the bioactivities of non-mammalian cytokines is scant due to the lack of the recombinant molecules and specific antibodies. We produced the mature predicted peptide of tumor necrosis factor (TNF) from the bony fish gilthead seabream (Sparus aurata L.) (sbTNF), and its biological role was determined in vitro and in vivo. We first demonstrated by analytical size-exclusion chromatography that sbTNF is an oligomeric protein but the dimer appears to predominate over the trimeric form, in contrast to mammalian TNF. Intraperitoneal injection of native sbTNF resulted in (i) priming of the respiratory burst of the peritoneal exudate and head-kidney (HK) leukocytes, the latter being the bone marrow equivalent in fish; (ii) rapid recruitment of phagocytic granulocytes to the injection site, and (iii) induction of granulopoiesis in the HK. Interestingly, sbTNF was able to induce a strong proliferation of HK cells in vitro, whereas human TNF did not. Conversely, sbTNF was not cytotoxic for murine L929 fibroblasts.Received 12 February 2004; received after revision 15 March 2004; accepted 29 March 2004     

How to Finance Pensions: Optimal Strategies for Pay‐as‐You‐Go Pension Systems

The aim of this paper was to design optimal strategies using nonlinear dynamic programming to guarantee the required level of liquidity in pay‐as‐you‐go pension systems through changes in the key variables of the system, such as the contribution rate, retirement age and/or indexation of pensions. These strategies, also known as automatic balancing mechanisms (ABMs), calculate the optimal path of these variables over time, managing fluctuations in longevity, fertility rates, salary growth or any other kind of uncertainty faced by the pension scheme without repeated legislative intervention. A numerical application of our model, which uses the projection of the population structure of two representative countries, illustrates the main findings of the paper. Copyright © 2015 John Wiley & Sons, Ltd.