The seasonal dynamics and host-parasite relationship of Opisocrostic bruneri (Baker), a flea on Franklin's ground squirrel, Spermophilus franklinii (Sabine) near Birds Hill Park, Manitoba
Reichardt, Todd Raymond
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The host-parasite relationship between the flea, Opisocrostis bruneri and its primary host, Franklin's ground squirrel, Spermophilus franklinii was evaluated during a 2 year study. Adult male ground squirrels were first captured each year on 5 May. The adult males were reproductively fit during the first two weeks of May. Adult female squirrels were first captured 5-8 days after the first male capture. Mating and subsequent parturition probably occurred in early May and mid-late June, respectively. The first observed signs of above ground juvenile squirrel activity were in mid-July. Adult squirrels immerged to hibernate in early August, followed by the juvenile females and males in early to mid-September. Thirty-six individual squirrels were involved in 95 total captures in 1982. In 1983, 40 individual squirrels were involved in 161 total captures. The recapture rate of S. franklinii was 2.6 and 4.0 in 1982 and 1983, respectively. Adult squirrels constituted approximately 75% of the total captures and this stage was most frequently recaptured in 1982 and 1983. Eight hundred and forty-nine and 1503 O. bruneri were removed from S. franklinii in 1982 and 1983, respectively. Adult male squirrels were most frequently infested and contributed 43% and 64% of fleas collected in 1982 and 1983, respectively. The observed sex ratio (m/f) of fleas removed from S. franklinii was 0.70 and 0.73 in 1982 and 1983, respectively. The biweekly sex ratio (m/f) favoured female fleas in each trapping period throughout the season except during a two week period starting at the beginning of May and the end of June. The observed prevalence of O. bruneri from all captured S. franklinii was greater than or equal to 0.75. The observed biweekly prevalence on adult male and female squirrel was always greater than or equal to 0.73 and 0.67, respectively. Juvenile male and female squirrels were always infested. Two discrete peaks of mean intensity of adult fleas were observed in early May and late August. Female fleas containing immature ovarioles (stage 0 and 1) with or without sperm in the spermatheca were predominant during the first three trapping periods. Parous females predominated during the remaining trapping periods. Oogenesis of O. bruneri was not stimulated by the oestrous cycle of female S. franklinii. Parous female fleas containing sperm within the spermatheca were found throughout the entire season...