Influence of temperature on population growth in Macrocheles subbadius (Acarina: Mesostigmata)
1977 - Volume: 19 Issue: 4 pages: 563-578
Macrocheles subbadius, found in central Italy on dairy cattle and horse manure and in phoresy on nuscid flies, is a coprophilous, arrhenotokous mite that feeds on house fly eggs and living rhabditid nematodes. The morphological characteristics previously described for females (BERLES1E9,0 4) and males (FILIPPONI and PEGAZZAN19O6,3 ) of this species were found to apply completely to the present material and to AXTELL Sm aterial (1963)while EVANSa nd BROWNIN(G19 56) and BREGETOVaAn d KOROLEV1A9 60) reported different characteristics in their material (Macrocheles scutatus sensu Berlese). The procedures described by FILIPPONanId co-workers in similar studies were used in the present experiments, in order to compare their results to those obtained with macrochelid mites that feed on Madsca domestica eggs. The innate capacity for increase of M . subbadizbs was evaluated by calculating r, or its antilog Rm (finite rate of increase), which indicates how many times the population will multiply in one day. Not all the temperatures at which the species can multiply were considered, but only those within the optimal range. This was determined by preliminary stuhes in which two population attributes were considered; the rate of oviposition (Table I) and the duration of preimaginal development (Table 11), both within the 10-400C range. The results indicated a provisional optimal range of 25-33°C, and the tests were conducted at 25, 27, 29, 31, and 330C. Cohorts of 16 females, each composed of two subsamples of 8 each (corresponding to two laboratory cultures of the same field strain) were tested for net fecundity (adult progeny per female), adult female longevity, and fertility rate (adult progeny per female per day) at each of these temperatures. Analysis of variance of the data (Table IV) showed that each of the three population attributes reacted differently to temperature (first value of F), while the two subsamples and the interaction among females (second and third values of F) were not modified. As there were no differences due to subsampling, the data were cumulated, and a comparison of the means (Table V) showed that the maximum net fecundity occurred at 27OC, that the adult female longevity was influenced by temperature (only at 27 and 2gOC was there no apparent influence on longevity, in that the comparison revealed no statistically significant differences), and that the optimal range for the fertilitv rate was 27,- za,oC . In the 25-33OC range the minimum duration of preimaginal development occurred at 31OC for both females and males (Table VI), and analysis of variance (Table VII) showed that males complete their preimaginal development more rapidly than females. To compile the life and fertility tables, and therefore to estimate Rm, the sex ratio had to be determined, nsince this is an arrhenotokous species. By cumulating all the progeny data (Table VIII), the mean sex ratio, expressed as female probability, was found to be 0.449 at 270C. On the basis of these data, the life and fertility table (Table IX) were compiled, and the parameters regarding the capacity for increase (r,; Rm; R, = rate of multiplication per generation; T = mean length of a generation) were defined. In terms of R,, a population of M. subbadius can multiply 1.97 times per day at 2s0C; 2.24 at 270C; 2.37 at 290C; 2.41 at 31OC; and 2.04 at 33%. The values of R, of other macrochelid mites studied bv the same ex~erimenta~l roceduresa nd of U. Musca domestica, the natural food source of these mites, are: for Macrocheles robustulus, 1.96 at 250C; 2.05 at 270C; and 2.03 at 290C: for M. ~eniculatus1, .65 at 240C; 1.76 a t 260C; and 1.70 at 280C: for M. penicilliger, 1-34 at 220C; 1.38 at 240C; and 1.32 at 260C; for M. muscaedomesticae, 2.17 at 280C; 2.47 at 30°C; 2.31 at 32°C; and 2.08 at 34°C: for M. matrius, 1.71 at 24°C; 1.92 at 26°C; 2.10 at 280C; 2.15 at 300C; 2.20 at 320C; 2.25 at 340~; and 1.50 at 360C: for~~usdcoam estica, 1.17 at 240C; 1.45 a t 280C; 1.41 at 32OC; and 1.37 at 360C.
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