Aspectos da biologia de Amblyomma cajennense (Fabricius, 1787) e Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae), em condições experimentais. / Aspects of the biology of Amblyomma cajennense (Fabricius, 1787) and Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae), em condições experimentais.

Armando de Lemos Ribeiro

The first experiment was set up to measure the drop-off rhythm of larvae and nymphs of Amblyomma cajennense feeding on the rabbits as experimental hosts. Infestations were carried out with unfed larvae and nymphs aging 15 and 45 days post eclosion and host larval moulting, respectively. Three rabbits were infested with approximately 825 larvae (50 mg of eggs) and 100 nymphs for each age totaling 12 rabbits. Each host were examined at 8, 12, 16 and 24 hours and the dropped larvae and nymphs collected. Regardless of age and instar higher drop-off rhythm were observed from 8 to 16 hours: 73,6 and 72,8% larvae with 15 and 45 days post eclosion and 69,6 and 57,5 nymphs with 15 and 45 days post larval moulting, respectively. The second experiment was set up to evaluate the effect of age on the attachment of larvae and nymphs of Amblyomma cajennense using the rabbit as experimental host. Infestations were carried out with unfed larvae aging from 0-4 to 150 days post-eclosion and unfed nymphs aging from 0-2 to 165 days post-larval moulting. A total of 11 and 12 infestations respectively for larvae and nymphs with 15 days interval were monitored. Three rabbits were infested with 825 larvae and 100 nymphs per rabbit at each interval. Larvae and nymphs with 0-2 day post-eclosion and post larval moulting were able to attach and feed at rates of 45 and 77%. Higher attachment rates for larva (>70%) were observed from days 15 to 60 post eclosion. Then, start to decrease until 25% at 150 days post-eclosion. Higher attachment rates for nymphs were observed from days 15 to 90 post moulting (>80%). Then, start to decrease until 36% at 165 days. The periods of attachment and ecdisis, and the percentage of ecdisis were similar for both stages regardless the age prior attachment. When the period of pre-ecdisis is analyzed one might note a shortening as the nymphs because older whereas it was similar for larvae in ali evaluated ages. This third experiment was conduct as an attempt to correlate the weight pre-ecdisis period and timing of drop-off of nymphs with the forecast of the sexes in adults of Rhipicephalus sanguineus. The mean weight of nymphs that moulted to males (n = 96) was 1,97 0,97 and 2,52 0,90 to females (n = 103) (P >0,05) between the weight of nymphs can not be used to forecast the sexes due to overlapping of to weight ranges. The pre-ecdisis periods were 15,13 0,94 and 14,60 0,77 days for nymphs that moulted to males (n = 96) and females (n = 103) (P >0,05) respectively. Nymphs (n = 50) that dropped-off on both third and fourth day (mode) post-infestation moulted to 29 females and 21 males whereas those (n = 50) that dropped-off on the fifth day post-infestation moulted to 30 females and 20 males (x2 >0,05). Although there are numerical differences in ali evaluated parameters none can be used to forecast the sexes in R. sanguineus due to an extensive overlapping.

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