Partheletterogenetic tetraploid (*); Parthenogenetic diploid (+); bisexual (o)
From for each population a random take to is actually drawn. Pet were anesthetized with some droplets from water over loaded which have chloroform and you can female, always over 20 (but LMT, and this underwent a leading mortality in the society) was basically split up on others. Next morphological details was basically quantified inside each female: full size; abdominal size; width regarding 3rd intestinal phase; depth of your ovisac; amount of furca; amount of setae entered on every part of your furca; thickness out of direct; maximal diameter and you may distance anywhere between substance sight; length of earliest antenna; and ratio intestinal size ? 100/complete size. Profile 2 depicts these types of aforementioned muscles methods. In most cases, an identical number of individuals each length interval is actually integrated manageable never to prejudice efficiency through the testing. Preadult citizens were thought to be better.
A couple of analyses was basically achieved: basic, all of the observations have been labeled from the particular population (bisexual diploid, parthenogenetic diploid and you may parthenogenetic tetraploid); on second investigation, brand new break up standard are the origin of one’s populace
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This multivariate procedure provides a series of variables (Z1, Z2,…), Which are linear functions of the morphological variables studied, with the form Zn = ?1X2+?2X2+… (Where ?s are the calculated discriminant coefficients and Xs the variables being considered). They maximize the ong different groups of observations defined a priori (Anderson, 1984). Thus, the first discriminant function is the equation of a line cutting across the intermixed cluster of points representing the different observations. This function is constructed in such a way that the different predefined groups will evaluate it as differently as possible. Obviously, this will not be accomplished if the number of groups is high, and subsequent discriminant functions will be needed. These analyses have been performed using a backward stepwise procedure that allows removing the different variables out of the model separately and ranking them for their relative importance in discriminating Artemia populations. Nevertheless, all described variables were kept in the model. These calculations have been performed with the help of the statistical package Statgraphics v. 3.0 (Statistical Graphics Corp., Rockville, MD) run on an IBM AT personal computer.
In Table II, the results obtained when the type of population was used as a separation factor are displayed. The two functions found give 100% separation, and both are statistically highly significant (P<0.001). Morphological characteristics allow a clear differentiation among the three groups considered (Table II, groups centroids). The morphological characteristics that most significantly contribute to the discrimination among the three groups are : lengh of first antenna, width of head and those related to the form and size of the head, the ratio abdominal length/total length in form of percentage and the width of ovisac and abdomen (Table II).
Results of the second analysis (factor of separation is population of origin) are shown in Table III and Figure 3. In this case, 12 discriminant functions are needed in order to separate thoroughly the 27 populations, but the first five of them give a cummulative separation percentage of (the four discriminant functions shown in Table III give a % cummulative separation). The first eight functions calculated are highly statistically significant (P,0.001), the ninth is also significant (P<0.05) and the last three are not significant. The morphological characteristics that most signifiantly contribute to separate the groups in this case are : distance between eyes, eye diameter, length of the first antenna and all variable related to the shape and size of the head and the length of the furca (Table III).
