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Vyhodnocení plodnosti raka signálního včetně post-ovulačního stavu vaječníků
FOJT, Martin
The theoretical part of diploma thesis is aimed at breeding, growth and molting events in crayfish. Thesis is also aimed at life cycle and reproduction of three indigenous crayfish species (Astacus astacus, Austropotamobius torrentium, Pontastacus leptodactylus) and two introduced crayfish species (Faxonius limosus, Pacifastacus leniusculus). The results show apparent linear dependence between female size (POCL), abdomen surface (1M: y = -1061,2 + 65,4*x; r2 = 0,9829; p10-5; 2M: y = -1160,4 + 68,7*x; r2 = 0,8732; p < 10-5) and fertility (1M: y = -194,4 + 12,8*x; r2 = 0,4104 p = 0,0042; y = -330.9 + 15,9*x; r2 = 0.4372; p < 10-4) in once (1M) and twice (2M) molted females. As the length of carapax increase, the area of the abdomen increase and fertility increase in both groups of females. Furthermore, the differences in fertility, carapax length, abdomen surface, and weights in once and twice molted females of signal crayfish. In group of once molted females fertility (t-test, t = -3.12, p = 0.003), carapax length (t-test, t = -3.17, p = 0.003) = -3.24; p = 0.002) and the weight (t-test, t = -3.35; p = 0.002) was higher than in twice molted group of female. Consequentially evaluation of egg size of females. The size of the eggs did not differ between groups of females (1M and 2M) (t-test, t = -0.975, p = 0.335). The mean egg size for both groups of females was 2.71 ? 0.18 mm. Evaluation of post-ovulation conditions of the ovary, including visible signs of females that resorbed unovulated oocytes. Evaluating how much unovulated oocytes were found in the ovaries. Only in 46.4% of the total number of females were ovaries completely empty. In once and twice molted females were found in average 2.2 ? 3.8 and 1.9 ? 2.6. unovulated oocytes, respectively. In once molted, three females didn't lay eggs, two females lost the clutch of eggs. In twice molted females, six females did not lay the eggs and four females lost the clutch.
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Tolerance raka mramorovaného vůči zvýšené salinitě vody
HRBEK, Vladimír
Eastern Europe comprises a significant part of the native ranges for indigenous crayfish species (ICS) belonging to the genus Astacus. This region has been largely overlooked by astacologists and considered relatively immune to the impacts of non-indigenous crayfish species (NICS). The recent discovery of two marbled crayfish Procambarus fallax f. virginalis populations in Ukraine has changed this view. The potential increased propagule pressure (mainly due to pet trade), has raised concerns of NICS which may negatively impair the ecosystems of Azov, Black and Caspian Seas and their tributaries inhabited by ICS. In this study, we provide the first insight into salinity tolerance of marbled crayfish. We performed a 155-day experiment using 5 different salinities (6, 9, 12, 15, and 18 ppt) and a freshwater control. Evaluation of survival, growth and reproduction suggests that marbled crayfish have a lower salinity tolerance than other crayfish species, which may limit their invasive potential in brackish environments. However, its ability to survive for more than 90 days at 18 ppt opens up the possibility of gradual dispersion and adaptation to brackish conditions. Our study highlights the need for further studies elucidating the potential for marbled crayfish to negatively impair these ecosystems.
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Demonstration of the basic characteristics of population dynamics in the school aquarium synchronization of ecdysis and food availability in a model organism.
HROUDOVÁ, Eva
This bachelor thesis is focused on the synchronization of ecdysis and food availability in semiaquatic bugs Microvelia reticulata (Heteroptera: Gerromorpha). Ecdysis, or molting, is a process when an individual sheds the old cuticle and gradually replaces it by a new one. The main task was to determine whether the ecdysis is influenced by the presence of food. It was also necessary to assess whether such an experiment would be feasible within the school environment. There were 18 cohorts with initial number ca 20 individuals each monitored during this experiment. The cohorts were fed every second day and every day the number of molts and deaths was recorded. Three methods of analysis - 2 test, t-test analysis and nested ANOVA were used for determination whether ecdysis depends on food availability. The results show that the food availability may influence the molting, when higher molting rate was usually in the days without food. It is thus possible M. reticulata nymphs are limited by competition and prefer molting during the food shortage. This long-term experiment is not appropriate in a normal school environment, it is very time and space consuming, and failed to show convincing results.
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