The paper is part of a larger scale study for some genes` (Cytb, ND4L and D-loop) nucleotidic structure identification by sequencing, to distinguish the structural differences and their exact length inase pairs. Research was carried out on individuals of Carassius gibelio (Bloch, 1782) (Actinopterygii,Cypriniformes) from two different populations, Iezăreni and Movileni (Iaşi, from which dorsal musculartissue was sampled. Mitochondrial DNA (mtDNA) isolation and purification was carried out automaticallyusing Promega’s Maxwell 16 (SEV module). Cytochrome b (cytb) was multiplied by a two stage>polymerase chain reaction (PCR), using two sets of complementary primers (1 set for each fragment).Direct sequencing of PCR products revealed that the cytochrome b has one sequence of 1140bp. Theobtained sequences were subsequently compared with sequences of the same gene from otherindividuals within this species, towards identifying possible differences in the nucleotidic structure.Key Words: Carassius, cytocrhome b, mtDNA.

Carassius --- cytocrhome b --- mtDNA

The researches made by our team have in view the bio-morphometric study of some brown trout populations. We aimed, on the one hand, to see the geographic and reproductive isolation impact and, on the other hand to highlight the environmental factors’ influence on morphological features in this species. The researches have in view three aquatic basins, known as sanctuaries of the brown trout,respectively Someş, Criş and Arieş. For the morphometric study were taken in calculus 14 bodydimensions, which allow to analyze on scientific basis the intra-specific variability degree, to which we add also the estimation of some meristic features (number of red or black spots). All data were statistically processed using modern methods thereby the interpretation errors to be more reduced. The results are presented in tables included in our paper.

brown trout --- geographic isolation --- morpho-physiological features

The authors analyze the modifications observed on a population of pumpkinseed (Lepomis gibbosus (Linnaeus, 1758)) after a 60 days period of exposure to starvation and attempt to correlate the obtained results to other body-related characteristics, either linearly-measured (such as length, volume and density) or weight-related, in order to achieve an estimation of a weight-loss allowance for the species of interest, that may be interpreted, if of a low daily value, as an advantage in the invasion process.

Lepomis gibbosus --- Pumpkinseed --- Weight-loss rate --- Starvation

In Poecilia reticulata, different phenotypes appear due to dominance, codominance, poligeny, or some demonstrated interallelic interactions. Recent(both molecular and classical) investigations suggest a mechanism of expression of several different loci in a single color pattern, resulting in high numbers of possible color pattern phenotypes. The color pattern seems to be determined by complex interactions of many genes (at the same locus or not, located on the same chromosome or not), under variable environmental conditions. For example, the Maculatus color pattern is due to the presence of  both Maculatus red and Maculatus black elements. On their turn, having in view the latest definitions of  the gene, both Maculatus red and Maculatus black could have a composite nature, too. Sexdetermination in the guppy is studied since the 1920s. The deepest mechanism of sex determination is not clear yet, but classical studies of Winge early in the past century and recent molecular studies revealed a possible composite nature of the so called master sex determining gene, located at SDL of the Y chromosome.

Color patterns --- Guppy --- Sex genes --- Complex interactions