Diehl, Peter-Allan

1995, Dotson, Ellen Marie, Connat, Jean-Louis, Diehl, Peter-Allan

Three embryonic cuticles are formed before larval cuticle deposition during embryonic development of Amblyomma hebraeum. The quantity of radioimmunoassay-positive material varied between 50 and 200 pg ecdysone equivalents per mg, but no significant peaks were detected. Maternally incorporated [³H]-20-hydroxyecdysone and [³H]-ecdysone contained in freshly laid eggs appear to be conjugated to C-22 fatty acid esters and 3 α epimers of those esters and, thus, appear doubly inactivated. In addition, ecdysone is converted to an unknown product called 2′. The role of these maternally derived ecdysteroids is unknown.

1995, Kuhnert, Frank, Diehl, Peter-Allan, Guerin, Patrick

The life-cycle of the hard tick Amblyomma hebraeum was completed in vitro by feeding all life-stages of the tick through silicone membranes on bovine blood from an abattoir. Ticks were placed in a simple feeder consisting of a honey jar containing the blood with a glass tube insert (o.d. 42 mm) across the end of which the membrane was stretched. This feeding unit was held in a water bath (38°C). Larvae and nymphs fed on a membrane (<90 μm thick) made of silicone reinforced with Kodak® lens cleaning paper, and adults on a silicone membrane (0.5 mm thick) reinforced with Terylene® netting. To control microbial growth, gentamicin (5 μg/ml) and nystatin (100 i.u./ml) were added to the weekly open-collected blood, which was manually defibrinated. The blood was changed twice daily for nymphs and three times for adults and larvae. Attachment of ticks was induced with combinations of host hair, tick faeces, a bovine pelage extract and a synthetic aggregation-attachment pheromone mixture. The in vitro life-cycle started with unengorged “natural” adults, which had moulted from nymphs fed on steer. The life-cycle closed with unengorged, first in vitro generation adults which had moulted from nymphs fed in vitro. Although the feeding and development of larvae and nymphs were similar to in vivo controls, females fed and developed poorly in vitro. The toxicity of the systemic acaricide Ivermectin® for nymphs of A. hebraeum was confirmed using the in vitro feeding method.

1991, Diehl, Peter-Allan, Guerin, Patrick, Vlimant, Michèle, Steullet, Pascal

The aggregation-attachment pheromone componentso-nitrophenol (ONP) and methyl salicylate (MS) in male Amblyomma variegatum ticks appeared after three days of feeding on the host and reached high values after about six days. Variable quantities of 1.3–7.3 μg ONP and about 0.6 μg MS were present within ticks. ONP and MS were released at the high rates of 300–1800 ng/hr and 20–600 ng/hr per male tick, respectively. After a temporary decrease, males continued to emit at high rates after nearby attachment of females. In A. hebraeum, ONP showed a similar pattern, but with a delay of about a day. A male, which had fed during 14 days, contained about 2 μg and released 225–280 ng/hr. Emission in forcibly detached males of both species dropped rapidly to low levels of less than 10 ng/hr per tick. Host skin and tick feces in the vicinity of feeding males were pheromoneimpregnated. The very high emission rates are consistent with the observations that the pheromone is an important component of the host-location mechanism of conspecifics. ONP and MS are produced in the dermal glands type 2 associated with the ventrolateral cuticle.