Coming Events


2010 4th CIMST Interdisciplinary Summer School on Bio-medical Imaging September 6–17, 2010, ETH Zurich, Switzerland www.cimst.ethz.ch/education/summer _ school/10


37th Annual SCUR Meeting September 7–8, 2010, Helsinki, Finland www.scur.org


The Fourth Brazil School for Single Particle Cryo-EM September 8–19, 2010, Rio de Janeiro, Brazil www.single-particles.org/school_2010/index.html


Bio-Trac 35 “Immunofl uorescence and Confocal Microscopy” September 14–16, 2010, Bethesda, MD www.biotrac.com


XXI International Symposium of Morphological Sciences (ISMS) September 18–22, 2010, Messina-Taormina, Sicily, Italy www.ismstaormina2010.com/index.asp


International Microscopy Congress September 19–24, 2010, Rio de Janeiro, Brazil www.imc-17.com


ALM2010—Advanced Light Microscopy Symposium 2010 September 23–24, 2010, Ghent University, Belgium www.alm2010.ugent.be/


Histotechnology Symposium September 24–29, 2010, Seattle, WA www.nsh.org/content/registration


American Society for Clinical Pathology Annual Meeting October 27–31, 2010, San Francisco, CA www.ascp.org/2010AnnualMeeting/


Optical Microscopy & Imaging in the Biomedical Sciences—MBL October 5–14, 2010, Woods Hole, MA www.mbl.edu/education/courses/special_topics/ om.html


2011 Microscopy & Microanalysis 2011 August 7–11, 2011, Nashville, TN


2012 Microscopy & Microanalysis 2012 July 29–August 2, Phoenix, AZ


2013 Microscopy & Microanalysis 2013 August 4–8, Indianapolis, IN


More Meetings and Courses Check the complete calendar near the back of this magazine and in the MSA journal Microscopy and Microanalysis.


6


Carmichael’s Concise Review Sperm Seen Competing


Stephen W. Carmichael Mayo Clinic, Rochester, MN 55905


carmichael.stephen@mayo.edu It is well known that females of some insects mate with more than one male before the


ova are fertilized. T e post-copulatory behavior of the sperm has been studied for decades, but until now there has not been a method to defi nitively determine the “ownership” of sperm within the female genital tract. In a very clever study, Mollie Manier, John Belote, Kirstin Berben, David Novikov, Will Stuart, and Scott Pitnick off er an answer to this dilemma [1]. T e solution was to genetically engineer two groups of Drosophila melanogaster (fruit fl ies)


males. Each group would express a protein labeled with either green fl uorescent protein (GFP) or red fl uorescent protein (RFP) in sperm heads that can be easily observed and unambigu- ously diff erentiated within the reproductive tracts of females (see Figure 1). Multiple tests of male fi tness relevant to sperm and/or ejaculate function were assayed, with transgenic males compared to each other and to a wild-type strain. Although there were some diff erences, all three strains fell within the known typical range of values. Moreover, subsequent experi- ments were unbiased because adequate controls were consistently performed, such as varying the mating order of GFP and RFP males. Manier et al. quantifi ed 1) spatiotemporal


patterns of sperm storage and use by the female aſt er re-mating, 2) the extent and timing of sperm ejection by females, and 3) the infl uence of re-mating on resident sperm motility. T ey also revealed two diff erent mechanisms by which resident sperm are displaced from the sperm-storage organs aſt er re-mating and which contribute to last-male sperm precedence. First, there was an early release of some resident sperm from storage organs, a process that does not involve second-male sperm. T is release of resident sperm was presumptively mediated by the female and triggered by male accessory gland proteins and/or mechanical stimulation of copulation. Second, resident sperm appear to have been physically displaced over time from sperm-storage organs by incoming second- male sperm. T ey also addressed the question of why males ejaculate many more sperm than can be


Figure 1: Rival sperm with green or red heads (protamine-tagged GFP or RFP) within the sperm-storage organs (i.e., paired sperma- thecae and seminal receptacle) of a female D. melanogaster.


stored in the female genital tract. T is is important because the sperm of these fruit fl ies are many times longer (1800 µm) than any distance they travel within the female and that storage appears to be a rapid and effi cient process. T eir evidence suggests that excess sperm, and perhaps their mobility, are adaptations to sperm competition, specifi cally to physical displacement of resident sperm. T eir results also suggest that ejaculate size is evolving via sexual selection mediated by sperm competition. It was also established that females can eject sperm. Finally, experiments suggested that sperm motility did not change upon re-mating and


that sperm were used in direct proportion to their prevalence. T is suggests that the sperm of either male is equally competitive in regards to fertilization, which correlates directly with their prevalence. T e observations of Manier et al. corroborate some previously conjectured mechanisms


related to fertilization success. T ese include sperm displacement and sperm ejection by females. Most importantly, a complex and dynamic array of processes underlying fertilization success can now be dissected in targeted, detailed genetic analyses to reveal specifi c behavioral, physiological, and biochemical mechanisms relevant to post-copulatory sexual selection. T is is certainly an important contribution to the fi eld [2].


References [1] MK Manier, JM Belote, KS Berben, D Novikov, WT Stuart, and S Pitnick, Science 328 (2010) 354–57.


[2] T e author gratefully acknowledges Dr. Scott Pitnick for reviewing this article. doi:10.1017/S155192951000074X www.microscopy-today.com • 2010 September


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76