Transcript Bats
‘Ope’ape’a: The Hawaiian Hoary Bat • Overview of the subspecies • Upcoming Research • Echolocation and moth auditory sensory evolution • Ebola update Morphological Studies Suggest Relative of Mainland Hoary bat Lasiurus cenerius cenerius (North American) L. c. vittosissimus (South American) L. c. semotus (Hawaiian) Hawaiian Hoary Forest Species • Mainland species also forest species -utilizes tree roost in native forest -commonality still remains overtime -Hawaiian hoary could be good indicator species • Strange findings in lava tube on Mauna Loa • Variable habitat range -found in wet and dry areas of the island -from sea level to 13,000 ft • Mean home range (consisting of several disjunct activity centers and the day roost) -males 121 ha -females 5.6ha Inaccurate population counts Most current population counts based on sightings Difficulties with Anabat II Future intraspecific echolocation analysis The importance of microphone location Mainland hoary’s rather lengthy migration Only terrestrial mammals to reach Hawaii Hawaii—A great place to study evolutionary trends Morphological Comparisons between L. c. cinerius and L. c. semotus • Character divergence: -flight -feeding -45% decrease in body size Microchiropteran utilize echolocation during hunting Potential drawback— May alert prey of impending attack Researchers find it difficult to quantify information The Hawaiian archipelago is an ideal place to examine moth hearing as a bat predation defense • Only one bat species known to exist on the islands • L. c. semotus exerted entire predatory selection pressure on the ears of sympatric moths. L. c. semotus prey preferences Endemic vs. adventive moths Why is H. euclidias preferred over similar sized endemic moths? Effects of artificial lighting Insect nervous system auditory processing center evolution • Ears have appeared 19 times in the class Insecta • Fundamentally similar structures • Common selection pressure (bat predation) Moth ears—neurologically simple • Consist of up to four auditory receptors • It has been proposed that the closeness of the bat as perceived by the moth determines the bimodal defense flight behavior 5 acoustic stages in foraging echolocation: 1. 2. 3. 4. 5. Search Approach Tracking Terminal Buzz (I) Terminal Buzz (II) The moth also has certain neurological stages that somewhat correlate to the approaching bat behavior Stage #1: The most sensitive receptor, A1 The moth directionally detects with its most sensitive receptor, A1, a foraging bat that is echolocating in a searching mode-----responses of A1 evoke controlled directional flight away from the bat so that the bat does not have a chance to detect the moth. Second defense mode Bat echolocating in tracking or terminal buzz mode -As bat approaches target, alters the duration, intensity, frequency, and structure of calls - Acoustical reason for this (avoidance of pulseecho overlap) A1 and less sensitive A2 receptor activated Triggers erratic flight pattern A1 receptors encodes bat calls as a near bat until 100-200 ms before the attack disactivation of interneurons and a premature cessation of near-bat responses. -little selection pressure to maintain vigorous A1 response for the final ms of a moth’s life? -may be an adaptive tactic used by the bat to facilitate captured of eared moths A2 receptor may be vestigial and not used in flight response May play a role in a different bat defense—sound emission (echo jamming effect Function of the B cell • may in fact be vestige of a homologous proprioceptor in thoracical earless moths • persistence in eared noctuid moths is reflection of low evolutionary cost of simple nervous systems So if moths evolved ability to avoid bat predation, shouldn’t they eventually lose this ability when relieved from bat predation pressures? Four suggested conditions that must be met before phenoypic effects of bat release will occur: 1. Complete isolation from bats 2. Absense of alternative uses for ears 3. Genetic isolation from bat-exposed conspecifics 4. Sufficient evolutionary time in batreleased condition Bats in the news: Ebola resevoirs? • Scientists have long wondered where the ebola virus hides between outbreaks. -fast killer, so often covers tracks quickly -primates die from infection • Maybe it’s the bats Researchers have injected bats with the virus and they have survived, but only recently have 3 fruit bats been found in nature with genetic sequences from the virus or evidence of an immune response to it. Traces of the virus were found in the animals' liver and spleen Maybe it’s the birds… the outer protein shell of filoviruses, such as Ebola, have a biochemical structure similar to retroviruses carried by birds, making a common evolutionary origin more likely. Until more is known public education is important in preventing the spread of the disease