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The aim of the present study was to evaluate the effects of three formulated diets: wheat gluten proteinbased diets supplemented with Lys^Gly dipeptide (PP) or free lisine and glycine (AA), and a control diet without lysine supplementation (CON), two commercial starters: Aller Futura (AF), Aglo Norse (AN) and frozen Chironomidae larvae (CH) for on the growth and digestive system development of rainbow trout. The experiment lasted 28 days and survival at the end of the experiment was the highest in the group fed AF (87.9 AE 4.2%) and the lowest in the group fed the CON diet (74.0 AE 4.3%). Fish fed the CON diet showed a signi¢cantly lower crude protein content, and the AA group had a signi¢cantly higher lipid level (P 0.05) in body carcass compared with the other groups. The highest density of intestinal goblet cells (P 0.05) was observed in ¢sh fed the CON diet, while the lowest density was seen in the distal intestine in the AF group. The hepatocyte cytoplasm of all ¢sh stored more glycogen than lipids. These results indicate that wheat gluten protein-based diets supplemented with dipeptide Lys^Gly (PP) or free lysine and glycine (AA) supported growth, protein e⁄ciency rate and intestine epithelium homeostasis. On the other hand, ¢sh fed CON (lysine-de¢cient diet) showed lower survival and growth rate, and disturbances of intestine epithelium homeostasis, probably as a result of lysine de¢ciency.

Background Conservation of noble crayfish (Astacus astacus) populations is becoming particularly important since the number of individuals is rapidly declining across the distribution range of the species in Europe. Five crayfish populations in northwestern Poland have been constantly monitored for two decades. However, the genetic structure of these populations has not been analysed, although this information is important to devise effective conservation strategies. Methods Noble crayfish were collected in the autumn of 2014 by scuba diving in Lakes Graniczne, Babinki, Biwakowe, Sęki and Kwisno, all of which are situated in the Bytów Lakeland of northwestern Poland. Genetic diversity of the five populations was assessed based on allele variability in nine SSR regions and six AFLP primer combinations. Results Microsatellite results analysed with AMOVA showed that the diversity between populations corresponds to 18% of total variability, which was confirmed by similar results obtained using AFLP. Additionally, significant genetic diversity was revealed by high average FST values. All of the studied crayfish populations significantly deviated from the expected Hardy–Weinberg genetic equilibrium and were characterised by negative values of inbreeding coefficient (FIS). Discussion The invariably negative inbreeding coefficients (FIS) suggest a low number of mating individuals, a possible consequence of the phenomenon known as genetic bottleneck. However, additional comprehensive analyses are needed to assess the genetic structure, origin and vulnerability of the remaining populations of noble crayfish in the Bytów Lakeland of northwestern Poland, which have high conservation value and are particularly important as a live genetic bank for breeding and restitution purposes.

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