جستجوی مقالات مرتبط با کلیدواژه "larva" در نشریات گروه "زیست شناسی"

The present study was to investigate the effect of various dietary levels of unsaturated fatty acids (HUFA and PUFA) on some morphometric features of duodenum in newly weaned rainbow trout larvae. Therefore, eight different experimental diets consisted of various dietary levels of HUFA (0, 0.5, 1 and 2 percent) at a fixed dietary PUFA of 20 percent (the first experiment) and various dietary PUFA levels (10, 20, 30 and 40 percent) at a fixed dietary HUFA of 8 percent (the second experiment) were formulated. Stocking density of larvae was 100 larvae per each container and the experiments lasted for six weeks. At the end of the experiments, six fish were randomly taken and the proximal intestine was dissected out and fixed for classical histological studies. In the first experiment concomitant with any increase in dietary HUFA content, epithelial thickness and villous height significantly decreased (P<0.05) and according to the results the appropriate HUFA level could be 0.5 percent of the dietary lipid moiety. However, in the second experiment only villous height of duodenum was affected by experimental diets (P<0.05) and villous height was the highest (207.2±10.3μm) at PUFA level of 20 percent of the total dietary lipid. In conclusion, it is recommended that in the case of using vegetable oils in feed formulation (to replace marine lipid sources) led to higher PUFA levels, dietary HUFA levels could be increased to eight percent for keeping normal intestine morphometry.

Persian salamander Paradactylodon gorganensis is endemic, unique and valuable genetic pool of Iranian Amphibians that exists in forests of Golestsn province. In this research, for the investigation of biological aspects of this species, for the first time natural habitats include Odaneh, Req and Gorgloo springs have been recognized in forested area of Ziarat village in south of Gorgan in 1250-1600m elevation above the sea level. We studied these localities 12 times from August 2009 to September 2010. Also, geographical position, climate, substrate, fauna, flora were investigated. In every time characters of larvae were studied. Results, shows that larvae are active at all time of the year, even when the habitat covered with snow and air temperature is -3°C. The larvae were seen with different sizes and ages in a same time, Therefore, it seems that they don’t transform during the first year. There was cannibalism relationship in larvae. Also some of larvae may be eaten by crabs (Potamon sp). Although larvae have 4 fingers and toes in the limbs but some specimens were seen without, 3 and 5 fingers and toes. It seems that the air and water temperature do not have serious effect on growth and metamorphosis in larvae. Habitat destruction by farmers and animals, pH changes, water shortage are the most important and threating factors for population of this endemic species that live in specific habitats with limited distribution.