Reproductive cycle and follicle cleaning process of Mytilus galloprovincialis (Mollusca: Bivalvia) from a polluted coastal site in Algeria

ABSTRACT

This work focused on the reproductive cycle and cleaning process of follicles in Mytilus galloprovincialis and aimed to extend knowledge of the reproductive cycles of Mytilidae. Biometric and histological measurements were taken monthly over 12 months from mussels at a polluted site, the port of Oran in Algeria. Environmental parameters were monitored concomitantly. Mytilus galloprovincialis reproduced throughout the year, with a main spawning period between November and February and a second between March and June. Several follicle cleaning processes were observed throughout the reproductive cycle. They occurred under two circumstances. First, in the absence of reserve tissues, mature gametes were degraded. This happened when spawning was about to end and corresponded to the last stage of reproduction. Second, atresia, gamete degeneration and a cessation of spawning occurred whatever the stage of the gonad development and whatever the environmental parameter values. These disturbances of reproduction may have resulted from pollution in the port of Oran and increased when temperature exceeded critical thresholds for gametogenesis. To conclude, gamete degeneration and spawning cessation because of coastal pollution and global warming could threaten M. galloprovincialis recruitment, and ultimately the shellfish economy, and could distort biomonitoring strategies using mussels.

KEYWORDS:

• Mytilidae
• gonad histology
• gamete degeneration
• environment
• pollution

Acknowledgments

This work is in tribute to Professor Zitouni Boutiba, peace to his soul. We thank the Society of Water and Sanitation of Oran (SEOR) for having given access to water physicochemical parameters analysis facilities and the pathological anatomy laboratory (ANA-PATH) of the pediatric hospital of Canastel (Oran) for the preparation of histological sections. We thank Dr Inke Sunila from Hermitcrab Underwater LLC Palmway, Lake Worth, Florida, US and Dr Antonio Villalba of the Centro de Investigaciones Mariñas, Spain for their precious help. We also thank the four anonymous reviewers whose comments greatly improved the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

Ethical Approval

The collection of wild Mytilus galloprovincialis in the port of Oran, Algeria, is not subject to any regulation. All applicable international, national and/or institutional guidelines for the care and use of animals were followed.

Additional information

Funding

This work was supported by the Complex Systems Research Institute (Complexys) of the University of Mons, Belgium [no grant number].