Away from for each and every society a haphazard decide to try are pulled. Pet was in fact anesthetized with a few droplets out-of liquids over loaded having chloroform and you can girls, usually more than 20 (but LMT, hence underwent a top death during the culture) was indeed broke up in the others. Another morphological parameters had been quantified when you look at the for each girls: overall size; abdominal length; depth off 3rd intestinal part; depth of your own ovisac; amount of furca; number of setae registered on each part of one’s furca; thickness off lead; maximal diameter and you may point between compound attention; duration of basic antenna; plus the ratio abdominal size ? 100/complete duration. Contour 2 illustrates these types of aforementioned human body steps. Throughout times, a comparable amount of people for each and every duration interval was incorporated managed not to prejudice abilities through the testing. Preadult everyone was regarded as well.
Two analyses was basically accomplished: basic, all of the findings was in fact grouped by the kind of populace (bisexual diploid, parthenogenetic diploid and you may parthenogenetic tetraploid); on next investigation, the new breakup criterion was the foundation of one’s connexion profile society
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).
