Eupyrene sperm migrates to spermatheca after apyrene sperm in the swallowtail butterfly, Papilio xuthus L. (Lepidoptera: Papilionidae) |
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Authors: | M Watanabe M Bon'no A Hachisuka |
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Institution: | (1) Department of Biology, Faculty of Education, Mie University, 1515 Kamihama-cho, Tsu 514-8507, Japan Tel. +81-59-231-9259; Fax +81-59-231-9352 e-mail: watanabe@edu.mie-u.ac.jp, JP |
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Abstract: | When swallowtail butterflies, Papilio xuthus, are mated by the hand-pairing method, both types of sperm, eupyrene and apyrene sperm, are transferred from the male to
the spermatheca via the spermatophore in the bursa copulatrix. This mechanism is demonstrated by two different kinds of experiments.
The first set of experiments employed interrupted copulation, and the second set was examination of the sperm in the spermatophore
and spermatheca after the termination of copulation. The sperm was transferred 30 min after the start of copulation. The eupyrene
sperm was still in the bundle; the number of the bundles ranged from 9 to 108 (mean, 42.7; n = 27). The bundles were gradually released after the completion of copulation, and the free eupyrene spermatozoa then remained
in the spermatophore at least 2 h before migrating to the spermatheca. On the other hand, about 160 000 apyrene spermatozoa
were transferred to the spermatophore and remained there for more than 1 h. We observed 11 000 apyrene spermatozoa in the
spermatheca 12 h after the completion of copulation, but most of this type of sperm disappeared shortly thereafter. In contrast,
the eupyrene sperm arrived in the spermatheca more than 1 day after the completion of copulation and remained there at least
1 week. Therefore, these findings suggest that apyrene sperm migrate from the spermatophore to the spermatheca earlier than
eupyrene sperm. Accordingly, if females mated multiply, the time difference might avoid the mixing of sperm. In addition,
the predominance of sperm from the last mating session may occur not in the bursa copulatrix but in the spermatheca.
Received: January 7, 2000 / Accepted: May 24, 2000 |
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Keywords: | Apyrene sperm Bursa copulatrix Eupyrene sperm Spermatheca Spermatophore Sperm competition |
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