Antennal Tactile Learning And Memory In Bombus Terrestris

Bumblebees are important insect pollinators.They are also model animals used to the study of o life science.In-depth study of bumblebee cognition is of great significance in the the protection and utilization of insect pollinators and the understanding of lower invertebrates.At present,the study of learning and memory of bees including bumblebees is mainly focused on olfactory and visual modalities,while there is a lack of studies on tactile learning and memory.So far,the antennal tactile learning and memory ability of bumblebees remains unclear.Here,using traditional behavioral paradigm and a new behavior paradigm that can detect the specificity of antennal tactile learning and memory developed by us,we explored the antennal tactile learning ability of Bombus terrestris,and respectively examined the relationship between antennal tactile learning and memory and antennal tip structure,and between antennal tactile learning and memory and nicotinic acetylcholine receptor.The results were as follows:1.We developed a new experimental paradigm which can test the specific antennal tactile learning of bumblebees.We successfully matched unconditional reward stimuli and punitive stimuli with different conditioned tactile stimuli.Under this strict reward/punishment pairing condition,only the bumblebees whose proboscis extension reflex responds to the tactile stimulus paired with the reward and does not respond to the tactile stimulus paired with the punishment is considered to have the specificity of learning and memory.2.Under the traditional reward pairing paradigm,bumblebees quickly learned to associate tactile cues with sucrose solution.The 80.45% of bumblebees were capable of associating tactile cues with sucrose solution after 4 trainings.63.31% of bumblebees formed tactile long-term memory(24 hours),and 53.20% of bumblebees could maintained long-term memory after 48 hours.This result showed that bumblebees had the ability of antennal tactile learning and memory.However,under the traditional paradigm,about 60% of bumblebees also extended their proboscis to unpaired tactile cues,indicating that bumblebees seem to have no specific tactile learning and memory abilities.Under the condition of our newly developed reward/punishment pairing paradigm with great learning difficulty,the number of bumblebees who successfully "learned" after 10 trainings was 58.76%,and the memory declined rapidly within 4 hours,and only 20.41% of bumblebees retained memory after 4hours.However,based on the newly developed paradigm,it is found that more than85% of bumblebees did not extension their proboscis to unpaired tactile cues,indicating that bumblebees have a "stimulus-response" specific learning ability.On the other hand,under the traditional pure reward pairing paradigm,the learning performance of single antennae was significantly lower than that of double antennae(p < 0.01),and the ability of memory retention was also significantly lower than that of double antennae(p < 0.01).However,there was no significant difference in learning and memory ability between left and right antennae(p > 0.05),showed there was no lateralization.Under the reward / punishment pairing paradigm,the learning and memory ability of single antennae was significantly lower than that of double antennae(p < 0.01),but the learning and memory ability of right antennae was significantly stronger than that of single left antennae(p < 0.05).There was tactile lateralization of left and right antennae.3.There are mainly 7 kinds of sensilla in bumblebee antennae,among which Sensilla trichodea B is a mechanical tactile sensor.The number of Sensilla trichodea B in the 10 th section of the antennal flagellum(antennal apical segment)of bumblebee worker bees was significantly higher than that in section 8(318 ±22 vs.128 ±27,p < 0.01),and the Sensilla trichodea B in section 10 was concentrated in the tip area of the dorsal anterior part.When the sensilla covered by high vacuum silicone grease was used to cover the tip of antennae,bumblebees still could not respond correctly to paired stimuli after 10 times of training,and almost lost the ability of antennal tactile learning.The results show that antennal tactile learning and memory mainly depends on the specialized area where the antennal tip sensilla is concentrated.4.Methyllycaconitine(0.9μl,0.1m M),a nicotinic acetylcholine receptor antagonist sensitive to α-bungarotoxin,was injected into the middle ocellus.There was no significant difference in learning stage between the treatment group and the control group,and there was no significant difference in memory retrieval between the treatment group and the control group at 10 min,1h and 4h.However,after ocellus injection of Mecamylamine(0.9μl,10 m M),a nicotinic acetylcholine receptor antagonist insensitive to α-bungarotoxin,the learning performance of the treatment group was significantly lower than that of the control group,and the performance of memory retrieval of 10 min,1h and 4h were significantly different from that of the control group(p < 0.01).The results showed that the antennal tactile learning and memory of bumblebees depended on nicotinic acetylcholine receptor which was insensitive to α-bungarotoxin.In conclusion,this study for the first time revealed the ability of antennal tactile learning and memory in Bombus terrestris,and that the antennal tip segment of bumblebees and nicotinic acetylcholine receptors which are not sensitive toα-bungarotoxin were involved in antennal tactile learning and memory.These results will deepen people’s understanding of bumblebees cognition.In addition,an experimental paradigm developed by us to test the specific antennal learning and memory of bumblebee will also provide a new technical tool for related researches.