Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 16

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych:  peled
help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The aim of the experiment was to examine prey size selection of peled (Coregonus peled Gmel.) larvae using Strauss linear index for food selection. For this purpose larval peled were held in illuminated cages at two stocking densities (10 000 and 40 000 individuals per cage) in three water bodies of diverse trophic characteristics. In the first days of rearing peled larvae fed on zooplankton up to 0.5 mm in length. Then most peled larvae significantly more often selected organisms up to 1 mm, which were most abundant in the environment. Under good feeding conditions, reared fish selected medium-sized zooplankters (from 0.6-1.0 mm length class, less often those 1.0-1.5 mm in length). Stronger food pressure for small prey appeared at a time of poor feeding conditions. Fish fed rather randomly on larger planktonic organisms (>1.5 mm), which were not abundant in the environment. Statistically significant differences were observed in food selection between the cages with different stocking densities, even when the feeding preferences were similar. Large variability in the feeding behaviour of peled larvae was observed during the whole rearing period.
The objective of this study was to examine the influence of water temperature (10,17 and 21ºC) on the sex differentiation process in peled. A high temperature, even a sub-lethal one, was not observed to have an influence on the sex ratio in this species; from day 81 after hatching until the end of the experiment the sex ratio in all three experimental groups was 1:1. It was noted, however, that thermal conditions determine the rate of sex differentiation and, in particular, of cytological differentiation. The first female-line cells, oogonia, were observed on day 102 after hatching in the peled kept in water at a temperature of 10ºC. Cytological differentiation was observed in the fish that were reared in higher temperatures as soon as day 81 after hatching. The first symptoms of anatomical differentiation were noted at this time in fish from all experimental groups. Two types of gonads were observed in histological cross-sections; one had a thicker anterior part with the generative and somatic parts located separately (ovaries), and the other had small, spindle-like gonads (future testes). No cytological differentiation of the male sex cells was observed during the experiment.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.