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Horatio Morgan

Jan. 25 Bats and Moths BATS Neuroanatomical basis of bat echolocation Donald Griffen: bats produce ultrasound and detect echoes from these emitted ultrasonic pulses Bats can produce frequency-modulated calls, much like FM radio Frugivorous bat producing frequency modulated calls for food Insectivorous bat producing frequency modulated calls increase in frequency and end with a terminal pulse – characteristic of tracking moving targets - The terminal pulse may be a way of honing in on their target over a large field of view Insectivorous bat producing constant frequency calls Bat species size correlated to frequency of ultrasound pulses produced Types of bats compared - Big brown bat, Eptesicus fuscus - Whiskered bat, Myotis mystacinus - Leaf nosed bat Big brown bat vs whiskered: high frequency sounds produced by small bats to capture smaller insects? Bats also produced sound through their leaf nose Sonar beam width decreases as emitter (bat) size increases relative to wavelength - To achieve the optimal directionality, larger bats will need a lower frequency and smaller bats will need higher frequency Bat emits sound  sound echoes off  perceived by bat’s auditory machinery Perception and memory for particular sounds triggers motor response to fly towards potential food and water site - “Refresh” these images by producing sound If a bat’s call is used to find a target, then some characteristic of the call should encode for distance, direction and target The waves that echolocate back to the bat would be characteristic of the specific surface - E.g. water source should be located by the waves that echo back from the smooth water surface o Water important for drinking and water insects Quantitative analysis of bats’ responses Greif and Simmers (2010): bat echolocation of water sources Bats flew into flight room under red light Covered room surfaces with smooth plates vs textured plates - Smooth plates reflect sound like water does - Texture plates would be like a “sandy floor” Nature video: Bat Sense - Researchers aimed to study sensory cues that help animals recognize features in their environment, i.e. bats’ senses in foraging - Bats showed drinking behaviour when echolocating over a smooth plate, even when it was on a table (unnatural place for a pond) - Even newborn bats that had never seen a water source did the same - First evidence of innate habitat recognition cue, such as a pond, in mammals - Behaviour related to the echolocation signatures of different surfaces o Very similar signatures of water and smooth plates To measure drinking-like behaviour, they would first have to 1. Describe the drinking behaviour in natural environment 2. Deprive bats of water to ensure motivation Control: water thirst - To show similar levels of motivation Species difference in persistence of drinking water - But none of them tried drinking from the textured plates Do conflicting sensory stimuli, i.e. vision, affect the bats’ use of echolocation? - Bats were allowed to fly under red light or complete darkness - M. schreibersii bats made more drinking attempts from smooth plate under complete darkness o Suggests they use vision to discrinate between a metal plate and water surface Is the ability to use the reflective sounds from a water surface innate or learned? - Adult wild caught bats were compared to juvenile bats, who had never encountered a water body before - Like the adults, the juveniles attempted to drink from the smooth metal plate in darkness – but not in light condition MOTHS Moths can use olfactory cues (pheromones) OR sounds for courtship - Noctuid moths produce sounds to attract females and detect bats - Saturniid family of moths lack ears Hearing If moths can detect sound, we would expect an anatomical region that would have a membrane and mechanoreceptors that can detect vibrations - = Ears In moths that have ears, they use tympanal organs - Tympanic membrane: “drum” with the centre part as the opaque zone where the neurons are attached - In the Arctiid moths, tympanal organs are on the metathorax - In crickets, the tympanaal organs are on their forelegs Sound production Tymbals: sound-producing membranes; also on metathorax of Arctiid moths APs recorded from moths By recording action potentials from the nerves that detect vibrations, it was found that there is A1 cell activity in response to sounds produced from the bat - Moths are able to detect the presence and approach of the bat, also depending on whether its own wings are pointed up or down As moths respond to the frequencies that the bats produce, the c
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