TY - JOUR
T1 - Functional nonequivalence of sperm in Drosophila pseudoobscura
AU - Snook, Rhonda R.
AU - Markow, Therese A.
AU - Karr, Timothy L.
PY - 1994/11/8
Y1 - 1994/11/8
N2 - We report on a form of sperm polymorphism, termed polymegaly, that occurs in species of the Drosophila obscura group. Individual males of species in this group characteristically produce more than one discrete length of nucleated, motile sperm. Hypotheses suggested to explain the evolutionary significance of sperm polymorphism have been either nonadaptive or adaptive, with the latter focusing on sperm competition or nutrient provisioning. These hypotheses assume all sperm types fertilize eggs; however, no data have been gathered to test this assumption. We found that two size classes of sperm are produced and transferred to females in approximately equal numbers by the male; only long sperm persist in significant numbers in female sperm storage organs. Furthermore, we used a DNA-specific dye (bisbenzimide) and sperm- specific antibodies to ask if both sperm types fertilize eggs in Drosophila pseudoobscura. Confocal microscopy and immunofluorescent analyses of fertilized eggs using anti-sperm polyclonal antisera demonstrated that only long sperm participate in fertilization. These data falsify those hypotheses in which all sperm types are assumed to be functionally equivalent (fertilize eggs). Any remaining or new hypotheses for the evolutionary significance of polymegaly must incorporate these findings. Several new areas of research are suggested.
AB - We report on a form of sperm polymorphism, termed polymegaly, that occurs in species of the Drosophila obscura group. Individual males of species in this group characteristically produce more than one discrete length of nucleated, motile sperm. Hypotheses suggested to explain the evolutionary significance of sperm polymorphism have been either nonadaptive or adaptive, with the latter focusing on sperm competition or nutrient provisioning. These hypotheses assume all sperm types fertilize eggs; however, no data have been gathered to test this assumption. We found that two size classes of sperm are produced and transferred to females in approximately equal numbers by the male; only long sperm persist in significant numbers in female sperm storage organs. Furthermore, we used a DNA-specific dye (bisbenzimide) and sperm- specific antibodies to ask if both sperm types fertilize eggs in Drosophila pseudoobscura. Confocal microscopy and immunofluorescent analyses of fertilized eggs using anti-sperm polyclonal antisera demonstrated that only long sperm participate in fertilization. These data falsify those hypotheses in which all sperm types are assumed to be functionally equivalent (fertilize eggs). Any remaining or new hypotheses for the evolutionary significance of polymegaly must incorporate these findings. Several new areas of research are suggested.
UR - http://www.scopus.com/inward/record.url?scp=0028130556&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028130556&partnerID=8YFLogxK
U2 - 10.1073/pnas.91.23.11222
DO - 10.1073/pnas.91.23.11222
M3 - Article
C2 - 7972038
AN - SCOPUS:0028130556
VL - 91
SP - 11222
EP - 11226
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 23
ER -