Gabriela Dumitru


THE STUDY OF SOME MORPHOLOGICAL CHARACTERS AT THE ARISTICHTHYS NOBILIS SPECIES IN DIFFERENT STAGES OF DEVELOPMENT

Gabriela Dumitru, Elena Ciornea, Silvia Vasile

Abstract
The work aimed to the study of some bodily variables at the three summer-old, respectively, four summer-old Aristichthys nobilis (bighead carp) representatives, derived from a systematic arrangement. For that, were used a number of a 100 individuals for each age in part, determining a series of morphological characters, such as: the body’s total and standard length, the head’s length, the height, the body’s circumference and weight. Thus, for each pair of analyzed variable (the body’s standard length in regard with the head’s length, the body’s total length and weight, respectively, the height in regard with the body’s circumference), was calculated the Pearson index of parametric correlation, being then tested the signification of this one. The values of t calculated were compared with those of t critic (a=0.05, n-2) = 1.985, establishing the null hypothesis (that doesn’t exist correlation) and alternatives (that exists correlation), and on the basis of the comparing of t calculated value with critical t was accepted one of the two hypothesis. Hereinafter was traced the straight line of regression and the regression equation of the straight line, then was determined the coefficient of regression, that is in what measure a variable determines the increasing of the other variable as well as the determination coefficient (R2) which denotes how percent from the values took of the dependent variable are determined of the independent one and reciprocal. The statistical analysis denotes the existence of some positive correlations between all the pairs of morphological characters studied, with the mention that at the three summer-old bighead carp the correlation between the body’s standard and total length resulted to be the most significantly statistic (r=0.966), while at the four summer-old representatives on the first place is the correlation between the body’s circumference and height (r=0.996).

Key words: morphological characters, bighead, correlation, regression


STUDIUL UNOR CARACTERE MORFOLOGICE LA SPECIA ARISTICHTHYS NOBILIS ÎN DIFERITE STADII DE DEZVOLTARE

Gabriela Dumitru, Elena Ciornea, Silvia Vasile

Rezumat
Lucrarea a vizat studiul unor variabile corporale la exemplare de Aristichthys nobilis (novac), în vârsta de trei, respectiv, patru veri provenite dintr-o amenajare sistematica. Pentru aceasta, s-au utilizat un numar de 100 de indivizi pentru fiecare vârsta în parte, determinându-se o serie de caractere morfologice, precum: lungimea totala si standard a corpului, lungimea capului, înaltimea, circumferinta si greutatea corpului. Astfel, pentru fiecare pereche de variabile analizata (lungimea standard a corpului în raport cu lungimea capului, lungimea totala si greutatea corpului, respectiv, înaltimea în raport cu circumferinta corporala) s-a calculat indicele de corelatie parametrica Pearson, fiind apoi testata semnificatia acestuia. Valorile lui t calculate au fost comparate cu cele ale lui t critic (a = 0,05, n-2) = 1,985, stabilindu-se ipotezele nule (ca nu exista corelatie) si alternative (ca exista corelatie), iar pe baza compararii valorii lui t calculat cu t critic s-a acceptat una din cele doua ipoteze. În continuare s-a trasat dreapta de regresie si ecuatia de regresie a dreptei, apoi s-a determinat coeficientul de regresie, adica în ce masura o variabila determina cresterea celeilalte variabile precum si coeficientul de determinare (R2) care indica cât la suta dintre valorile luate de variabila dependenta sunt determinate de variabila independenta si reciproc. Analiza statistica demonstreaza existenta unor corelatii pozitive între toate perechile de caractere morfologice studiate, cu mentiunea ca la novacul în vârsta de trei veri corelatia dintre lungimea standard si lungimea totala a corpului s-a dovedit a fi cea mai semnificativa din punct de vedere statistic (r = 0,966), în timp ce la exemplarele de patru veri pe primul loc se situeaza corelatia dintre înaltimea si circumferinta corpului (r = 0,996).

Cuvinte cheie: caractere morfologice, novac, corelatie, regresie