Overlapping niches between two co-occurring invasive fish: the topmouth gudgeon Pseudorasbora parva and the common bleak Alburnus alburnus

Invasive fish species impact aquatic ecosystems and modify native communities, often leading to a decline in local species. These ecological impacts include the transmission of pathogens, predation, competition as well as hybridization. Two invasive fish species, the common bleak Alburnus alburnus and the topmouth gudgeon Pseudorabora parva, have both been recently found co-occurring in several regions of southern Europe, such as the Italian Arno River. Nonetheless, the trophic relationships among invasive fish species, especially cyprinids, remain poorly understood, and no studies have reported the trophic interaction between these two species. This study compared length–weight relationship and used stomach content and stable isotope analysis of two co-occurring populations in the Arno River to characterize the growth and overlap of potential trophic niches. It also found similar allometric growth in both species, a wider generalist trophic niche for P. parva and a more specialized niche for A. alburnus. A considerable niche overlap was found, suggesting that feeding competition can occur if resources were to be limited. Moreover, the niche of P. parva was more likely to overlap with that of A. alburnus than vice versa, suggesting that P. parva can be considered as a potential over competitor. Nonetheless, the authors found in the overlapping populations no evidence of realized competition, probably avoided through a combination of fine-scale mechanisms. They also highlighted that these two invasive species can co-exist and share resources, at least in an open ecosystem like a river, thus potentially doubling up their trophic impact on local communities.     

Isolation and Characterization of Spawning Inhibitors in Ovary of the Starfish,Asterias amurensis

Biologically active substances which inhibit spawning of mature starfish, Asterias amurensis, have been isolated from ovaries of the same organisms and identified as asterosaponins A and B.     

Preventive Effect of Germinated Barley Foodstuff on Diarrhea Induced by Water-soluble Dietary Fiber in Rats

We investigated the preventive effect of germinated barley foodstuff (GBF) added to the diet on diarrhea induced by the dietary water-soluble dietary fibers, polydextrose, hemicellulose, and poly-acrylic acid sodium salt, in Sprague-Dawley rats. The minimum content of GBF necessary for blocking diarrhea was 3% (by weight) of the diet.

Since GBF is mainly derived from the aleurone and scutellum of malted barley, we assessed the physiological effects of the aleurone and scutellum fractions derived from barley grains before and after germination. The addition of fractions containing only germinated barley, and not barley collected before germination, increased the fecal output and jejunal mucosal protein content. The effects of malted barley were very similar to those of GBF.

It was concluded that germination was necessary to bring about the physiological effects of GBF. Since non-lignified hemicellulose and Gin-rich protein were newly synthesized during germination, these might have contributed to the increased fecal output and jejunal mucosal protein content.