Parthenogenetic tetraploid (*); Parthenogenetic diploid (+); bisexual (o)
The fresh twelve morphological details, counted in every people (Table step one), were used to ascertain dating of these populations courtesy discriminant study

From for each and every inhabitants a haphazard decide to try are pulled. Animals was basically anesthetized which includes droplets off liquids over loaded which have chloroform and you may lady, usually over 20 (except LMT, which undergone a leading death for the culture) was basically broke up from the rest. The following morphological variables was in fact quantified in the each ladies: total length; abdominal duration; depth away from third intestinal segment; depth of the ovisac; period of furca; level of setae registered on each part of furca; width of head; maximal diameter and distance anywhere between substance vision; duration of basic antenna; and ratio abdominal size ? 100/complete length. Profile 2 illustrates this type of previously mentioned human anatomy steps. In every times, a comparable amount of people for every size interval try provided manageable not to prejudice overall performance from sampling. Preadult citizens were regarded as well.

Two analyses have been accomplished: basic, every observations was basically classified by the style of inhabitants (bisexual diploid, parthenogenetic diploid and you can parthenogenetic tetraploid); about next analysis, the fresh new break up traditional try the origin of inhabitants

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).