In the same year Konrad Lorenz, Niko Tinbergen and Carl Von Frisch jointly won the Nobel Prize in medicine for their pioneering work in animal behavior, the Israeli behaviorist, Amotz Zahavi, hypothesized that some birds aggregate in roosts to share information on locations of profitable food sources. Lorenz shared the Nobel prize, in part, for his work on imprinting: a phenomenon where hatchling birds immediately accept as parents the first object they see upon hatching (often Lorenz himself). In comparison, Zahavi’s ideas about the function of bird roosts, if correct, meant that some birds have much greater mental abilities.
0 Comments
Avian Cholera is the most important infectious disease affecting wild North American waterfowl. The Natural Sciences and Engineering Research Council of Canada has just awarded Carleton University Professor Mark Forbes and a team of researchers more than half a million dollars over the next three yearsto study this bacterial disease in Arctic Breeding waterfowl.
The picture above (taken by Heather Proctor) is a tandem pair of a small coenagrionid damselfly known as Nehalennia irene. The male is blue and green in colour and is above the female. His superior and inferior appendages are holding onto the hind margin of the female’s prothorax (right behind her head which is mostly just eyes). These individuals might have already mated or were about to do so before the photograph was taken. It is relatively clear in this picture even that the males and females of this species look different. However, males also pair with females that look very similar to them (known variously as andromorphs or androchromatypes). Those females can make up < 2% to >95% of the females in a population according to research done largely by Hans Van Gossum, with input from myself and Tom Sherratt. Why is this so? What maintains female morphs at relatively low or high frequencies in different regions or populations? Exciting stuff really.
The picture above shows four u-shaped burrows (the right arm of a short one overlaps the left arm of another broken one). I am not sure who took this picture but its quality makes me think it might be Jim Wolford. The leftmost and rightmost burrows are complete and easily transcribed. If we look at the left narrow u-shaped burrow, we see that the end of the u dips into some black muck: this is the anoxic layer. In this photograph the anoxic layer is probably 6 cm below the mud surface (the edge of which can be seen 4/5ths the way up the photo).
The left panel above is a photograph of a completely melanized stylostome or feeding tube (s) of a larval water mite (b). The feeding tube is collapsed but leads into the mouth region of the water mite, which is an oblong outline (jointed legs are visible just above b) orientated vertically. That mite is dead. The photograph is taken through the cleared damselfly cuticle. The right panel is a photograph of what a healthy stylostome looks like in this species (a long arm with a blind sac at its end). There is some melanization where the mite was attached to the host (marked by an arrow), but this mite engorged and dropped away from the host. Some of my students have been interested in this resistance expression. We know temperature and species associations are important in its expression. Recently, we have discovered marked year to year variation in numbers of Lestes disjunctus individuals showing resistance to a specialist mite, Arrenurus pollictus. We think that when mite loads get heavy enough, those individuals most likely to survive and leave offspring are the ones that respond to the parasite. We suspect it is all about recognition. A recent theoretical model we are working on will hopefully inform us about what patterns should exist between host condition (which is very difficult to define) and resistance expression.
The picture above is one I took and shows a Lestes forcipatus damselfly flipped upside down so the venter of its thorax is showing. You can definitely see the legs and the eyes (in fact, the pseudopupils are staring right at you).The deeply red-colored grape-like cluster are larval water mites (fully engorged mites are ~1mm in diameter). This species is Arrenurus planus. My students and collaborators Bruce Smith and Kit Muma have shown that this species of mite is found on several species of damselflies and principally on two species of dragonflies. We are interested in the fitness costs of mite parasitism in damselflies and dragonflies. Tonia Robb and I recently summarized all the available information on whether mites influence flight ability, mating success of males, fecundity of females, and/or survivorship of either sex. This information is summarized in a chapter in the newly released book entitled “Dragonflies and damselflies: model organisms for ecological and evolutionary research”. Ed. Alex Córdoba-Aguilar [for more information, see http://www.oup.com/uk/catalogue/?ci=9780199230693#authors].
Some years ago, I became very interested in a phenomenon known as fluctuating asymmetry (or FA). These were seen as small random deviations from perfect bilateral symmetry in an organism’s traits. One of my Ph.D. students at the time, Brian Leung, was very interested in whether such deviations could be used to measure environmental stress to organisms. His work showed that FA-stress and FA-fitness relations were often present, but they were weak and highly heterogeneous across species. FA theory and empiricism could be an exciting topic for science historians in a decade or two. I still think the concepts surrounding FA generation and its relation to fitness and stress are intriguing. But for know my thoughts on asymmetry are less definite. The painting above, by Paul Klee, is titled Senecio (1922).
|
AuthorProfessor & student Archives
April 2021
Categories |