Ž .
Aquaculture 186 2000 233–242 www.elsevier.nlrlocateraqua-online
Effects of ultraviolet irradiation on genetical inactivation and morphological structure of sperm
of the Japanese scallop, Patinopecten yessoensis
Qi Li
a
, Makoto Osada
a
, Masaru Kashihara
b
, Ken Hirohashi
b
, Akihiro Kijima
a,
a
Education and Research Center of Marine Bio-resources, Faculty of Agriculture, Tohoku UniÕersity, Onagawa, Miyagi 986-2242, Japan
b
Biomate, Higashikasai, Edogawa, Tokyo 134-0084, Japan Accepted 9 December 1999
Abstract
Ž .
Effects of ultraviolet UV irradiation on genetic inactivation and morphological structure of sperms were examined in the scallop, Patinopecten yessoensis. Haploid gynogenesis of the scallop
was successfully induced by 50–60 s UV irradiation of 720 mW cm
y2
s
y1
. The fertilization rate apparently decreased with increasing irradiation time, and the development of the eggs fertilized
with the genetically inactivated sperms terminated before reaching the D-shaped larvae stage. Ž
. Scanning electron microscopy
SEM showed clear destruction of the sperm acrosome and
flagellum in the UV-irradiated sperms. As the duration of UV irradiation increased, the acrosome of sperms tended to suffer greater damage, until the sperms eventually lost their flagella.
Abnormalities in these structures have appeared to account, at least in part, for the decline of the fertilization rate of eggs inseminated with UV-irradiated sperms. q 2000 Elsevier Science B.V.
All rights reserved.
Keywords: Japanese scallop; UV irradiation; Gynogenesis; Sperm morphology
1. Introduction
As a form of development in which eggs are activated by sperm that does not contribute genetically to the resulting embryo, artificial gynogenesis has been success-
Corresponding author. Tel.: q81-225-53-2436; fax: q81-225-53-2303. Ž
. E-mail address: a-kijimamail.cc.tohoku.ac.jp A. Kijima .
0044-8486r00r - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž
. PII: S 0 0 4 4 - 8 4 8 6 9 9 0 0 3 8 4 - 1
Ž fully induced in many fish species and used for examining sex-determination Avtalion
. Ž
. and Don, 1990 and gene–centromere recombination Arai et al., 1991 , as well as
Ž production of inbred line, mono-sexual broods or clones Naruse et al., 1985; Tabata and
Gorie, 1988; Taniguchi et al., 1988; Fujino, 1989; Fujioka, 1993; Kobayashi et al., .
1994 . In molluscs, however, studies on gynogenesis have been still preliminary. Although
Ž induction of gynogenetic diploids has been reported for Haliotis discus hannai Fujino
. Ž
. Ž
. et al., 1990 , Crassostrea gigas Guo et al., 1993 , Mytilus edulis Fairbrother, 1994
Ž .
and Mytilis galloproÕincialis Scarpa et al., 1994 , practical procedures for induction of gynogenetic diploid have not been established for molluscs as for fishes. One of the
plausible reasons for this is considered to be the decreasing fertilization rate with Ž
. increasing ultraviolet UV irradiation time of sperm that has been observed in all these
studies. Since the sperms of fish species do not lose their fertilizing ability at a dosage of Ž
UV irradiation for genetic inactivation Onozato and Yamaha, 1983; Tabata et al., 1986; .
Ž .
Taniguchi et al., 1986 , Kijima 1992 supposed that UV irradiation affects not only the Ž
. sperm genome, but also the acrosome structure which is absent in teleost fishes in the
Pacific abalone. However, the possibility has not been evidenced. The Japanese scallop, Patinopecten yessoensis, is one of the most commercially
important bivalves in Japan. Numerous studies have been performed on propagation of Ž
. the scallop Yamamoto, 1964; Kanno and Sato, 1980; Nagasaki, 1999 , but few studies
have been undertaken on gynogenesis or polyploidy. In the present study, the effect of UV irradiation on sperm morphology was examined
Ž .
by scanning electron microscopy SEM , and various durations of UV irradiation of sperm were also examined to determine the optimum conditions for induction of
gynogenesis in the Japanese scallop, P. yessoensis.
2. Materials and methods
