Obstructive Role of the Dimorphic Sperm in a Non-copulatory Marine Sculpin, Hemilepidotus gilberti, to Prevent Other Males' Eusperm from Fertilization |
| |
Authors: | Youichi Hayakawa Hiroyuki Munehara Akira Komaru |
| |
Institution: | (1) Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo, 153-8902, Japan;(2) Usujiri Fisheries Laboratory, Field Science Center for Northern Biosphere, Hokkaido University, 152, Usujiri, Minamikayabe-cho, Hokkaido, 041-1613, Japan;(3) Present address: Endocrine Disrupter Research Laboratory, National Institute for Environmental Studies, 16-2, Onogawa, Tsukuba, Ibaraki, 305-8506, Japan;(4) Faculty of Bioresources, Mie University, 1515, Uehama-cho, Tsu, Mie, 514-8507, Japan |
| |
Abstract: | In many species of animals, males normally produce parasperm (dimorphic sperm) along with eusperm (normal sperm) during spermatogenesis. In the present study, to clarify the role of parasperm of the non-copulatory sculpin Hemilepidotus gilberti, whose reproduction is characterized by polyandrous oviposition involving sneaking by neighboring territorial males, we observed the movements of parasperm. Parasperm could not move by themselves, but they were transported in solutions by passive movement due to collisions with actively swimming eusperm. In the viscous ovarian fluid (OF), which isolates eggs from seawater by covering them during spawning, parasperm did not exhibit any movement. However, they could be transported by eusperm movement in solutions with dissolved OF, partly because the viscosity of the fluid become lower. And then, in some solutions parasperm formed lumps. Lump formation of parasperm was also observed at the boundary surface of an egg mass where OF contacted seawater. Eusperm added experimentally to a solution in which parasperm were forming lumps were engulfed in the lumps and never escaped. Thus, lump formation of parasperm would be obstacles for the later arriving eusperm. Although lumps formed against both kin and non-kin eusperm, parasperm are thought to be available to overcome sperm competition which would occur during spawning that involves sneaking being almost concurrent with lump formation. The territorial male eusperm reach the eggs while his parasperm hinder other males' eusperm from reaching the eggs. Thus, we concluded that parasperm of H. gilberti play a role on protection of paternity by blocking rival eusperm physically from approaching eggs. |
| |
Keywords: | hyperpyrene sperm oviparous fish parasperm sperm competition sperm polymorphism paternity |
本文献已被 SpringerLink 等数据库收录! |
|