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Lecture

NROC34 Lec 1.docx

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Department
Neuroscience
Course
NROC34H3
Professor
Karen Williams
Semester
Winter

Description
NROC34 - Want to observe behaviour - Video assignment: o at 10:15 on the 2 Fridays – look at animal behaving and observe, describe and write what they are doing o will only be shown ONCE - Poster: o Summarize experiment and put it on a poster o Assigned a reading from the textbook and analyze - Critical review of article o Everyone has the same article o After observing and doing experiments, write paper about it To Bee or Not to be Lec 1 - To be a NURSE or to be a FORAGER - 4 questions: o How does behaviour promote survival? o How do they use motor and sensory o How does it change during growth o How do bees behaviour relate to closely related bee species - Know which are PROXIMATE and which are ULTIMATE questions o Are linked – not mutually exclusive - Bees are more social than we are o Have a division of labour where only one of them reproduces: the QUEEN o The rest are nurses or foragers - Workers are employed as nurses then as foragers and the jobs vary by age How is their job chosen? Division of Labour - Job as non-reproducing workers is chosen for them Bee basics: Haplodiploidy - Have haploid males and diploid females - System of reproduction - Because of haplodiploidy, workers are more closely related to their sisters than their offsprings - ¾ related to their sisters o Humans are 50% related to their sisters - Unfertilized eggs become haploid sons Sources of variation Division of labour among bees - As they emerge, they have egg/larvae pupil adult - After emerging, they stick around at home and stay as nurses o Can move after this - After a while, become foragers and forage for pollen and nectar - Foragers: o Bees you see outside the nest and come and go - Bees never seen are NURSE bees - When observing division of labour, can watch bees as to what they are doing - Feed by trophallaxis (regurgitating or feeding) - When watching brewed cell, bee with head stuck in it is the NURSE - Middle-aged bees mostly have heads in the honey cells and are NOT going out of the hive - Those that go outside of the hive are foragers - Most nurses do head in cell behaviour o Other 2 behaviours of nurse cells:  Feed brewed  Groom - When plotting ages of bees, see nurse bees are really young and forager bees are really old (21 days old) o Confound: are nurses doing job because they are young or are they doing it WHILE they are young Nurse or Forager - Temporal polyethism o Nurses (5-9 days) o Forager (21-28 days)  Pollen load is usually on the leg - For sensing a target in space: foraging - What region of bee brain is important? o HOW would we do this? Finding out which part of brain is part of nurse behaviour and which is forager behaviour  Can do lesions on the brain  BUT bees are very small; hard to lesion. They might not be the same after they recover  Cut the bees, killed them, sliced the brain and looked at VOLUME  differences; shapes, size, etc - Know neuroanatomy of animal so you know what you are looking for in terms of changes - CONFOUND: age o Employment as a nurse or forager depends on age - By using microarrays of bees, took whole brain of the bee, grounded it, put on microarray o Found 39% of genes differed depending on nurse or forager  Might be related to AGE or BEHAVIOUR - To determine if behaviour was related to age or behaviour, took bees and introduced different numbers of them and can change their behaviours o Take bees immediately after emergence o Take away the old bees o In absence of inhibitory pheromones, some young bees initiate foraging o One of the reasons they forage is because the HIVE is HUNGRY o Have a young nurse and young forager  OR could have older bees that turn back into nurse cells if there are not many in the hive  Become old nurses  Sane age as normal foragers - Microarray is looked at In typical colony: o Different genes are expressed in bee brain depending on if they are a nurse or forager - In single-cohort colonies: o Have old nurses with same genes as young nurses  depends more on role o Genes highly expressed depending on behaviour o Therefore, can conclude it is NOT due to age Young nurse Young Forager Old Nurse Old Forager 5-9 days old 7-9 days old 28-32 days 28-32 days Juvenile hormone (JH) – governs changing of growth and metamorphosis. Influences the onset of FORAGING. Adding it stimulates precocious foraging. - One of 2 main hormones in Insects - If you feed this to young bees, bring on foraging faster and younger - Younger bees have lower JH titres than older bees - Precocious foragers have more JH in their brains than similar aged nurses Physiological basis - Hormones: mainly JH - Use single colonies and do same thing, feed baby bees JH vs a control o Can compare young vs old and precocious vs foraging - Feed bees methoprene in sucrose – grind bees brains, put in microarray and look at age of onset of foraging o When this is done, can see what genes are highly expressed in nurses vs foragers (markers) - A bee would be a nurse or forager and would have nurse-like predictor genes that are up- regulated in nurses and same genes are down-regulated in foragers o Can describe foraging in the reverse way - Find with methoprene up-regulated genes: o Nurse markers - 6 o Foragers – 23 - Methoprene down-regulated: more nurse markers o Methoprene UP-regulated = more forager markers - Can use genetic expression profiles to say something about physiological mechanism of what is happening; can look at genes being identified specifically and see what pathways they are involved in To bee or not to be: Foraging and Decisions (pg 327-333; 354-365) - Somewhere along evolution, queen’s pheromonal control of worker behaviour left more progeny for that queen bearing that profile - Pheromones from the queen bee that changed development physiology : o Queen mandibular pheromone (most known) o Inhibitory pheromones from old bees, if removed, the young bees begin to initiate foraging - In a colony, have young resident bees and experimentally add bees, the number of foragers is high - If experimentally adding bees, the number of foragers among the young residents is low - In absence of pheromones from old bees, young bees initiate foraging - Homovanill alcohol (HVA)  similar structure as dopamine o Can ask about DA levels in bees and queen mandibular pheromone Can measure DA in bees; control vs HVA, QMP, etc - Find most DA in control bees – those NOT exposed to QMP - In presence of virgin vs mated queen, higher DA is found in bees in presence of virgin queen - Higher DA found away from QMP or around virgin queen - HVA in bees is like being in presence of mated queen - Exposure to QMP in DA in brain: - HOB – another component of QMP… o Not a big difference with control - When HVA+ HOB vs control, there is a bigger difference between the amounts of DA in the brain o Therefore, HVA is more likely to be the active component  HVA gives the same lower level of DA in the brain like if in the presence of queen bee QMP-induced chang
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