The mytilid bivalve Mytilus trossulus exhibits area-specific proportions of heteromorphic spermatozoa in the Sea of Japan

ABSTRACT

The present study is devoted to a comparison of the structure and quantitative ratio of heterogeneous spermatozoa of native wild mussels Mytilus trossulus Gould, 1850, collected in four areas of the Peter the Great Bay of the Sea of Japan (the northwestern part of the Pacific Ocean). The mussels were identified as M. trossulus by shell appearance, and the species was confirmed by sequencing the mitochondrial cytochrome c oxidase subunit I gene (COI). Heteromorphic spermatozoa were found; namely, a total of eight morphs (SPERM1–SPERM8) in M. trossulus. Surprisingly, some of the detected sperm morphs overlap morphologically with the sperms of other mytilids such as M. edulis, Crenomytilus (M.) grayanus and M. coruscus. Possible reasons for this phenomenon are discussed. In each geographic area, the ‘quantitative proportions of heterogeneous spermatozoa’ (QPHS) were unique. It has been suggested that the QPHS score can be considered in the context of its applicability as a biological marker for finding optimal mussel rearing sites.

KEYWORDS:

• Sea of Japan
• Mytilus trossulus
• COI DNA barcoding
• shells
• sperm heteromorphism

Acknowledgments

The authors are grateful to colleagues from the A. V. Zhirmunsky National Scientific Centre of Marine Biology FEB RAS (Vladivostok, Russia), who helped to carry on this project such as the Director of the scuba diving service A.G. Goloseev and Director of the Collective Use Microscopy Unit D.V. Fomin. Part of the study was conducted at the Microscopy Facility Unit at St. Francis Xavier University (Antigonish, Nova Scotia, Canada).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

All authors contributed to the study. EV conceived, designed the study, analysed the data, performed the routine work with scanning electron microscopy, wrote the paper. KK obtained the COI sequences, wrote the genetic protocol description, analysed the genetic data. YA and AA performed routine work using transmission electron microscopy. YR participated in work using scanning electron microscopy and performed statistical analyses. AR analysed the data, submitted important topics for discussion, and edited the article. All authors read and approved the final version of the manuscript.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.