Effects of light on reproduction of the Mediterranean medicinal leech, Hirudo verbana Carena, 1820: do circadian rhythm disruptions positively affect reproductive performance of leeches?

ABSTRACT

This study aimed to assess the impact of light on the reproductive performance of leeches for the first time using the Mediterranean medicinal leech Hirudo verbana Carena, 1820, which is important in medicinal leech aquaculture. Gravid leeches were subjected to three different light conditions: 24-h Light, 24-h Dark, and Daylight (14-h light and 10-h dark) for 11 weeks. Gravidity ended at the 8^th week for the Dark (5.33 ± 0.38 weeks) and Daylight (5.41 ± 0.29 weeks) groups, whereas it persisted for 11 weeks in the Light group (6.75 ± 0.51 weeks) (p = 0.031). In comparison to the Daylight group (cocoons: 40, offspring: 538), the Light (cocoons: 50, offspring: 723) and Dark (cocoons: 45, offspring: 576) groups achieved a greater yield of cocoons (p = 0.312) and offspring (p = 0.323). We invite discussion on the notion that the enhanced reproductive capacity of leeches in full light and full dark conditions, as opposed to daylight, may be attributed to the disturbance of their circadian rhythms.

Impact statement

• Effects of light on reproductive performance of leeches were investigated for the first time.

• Gravidity lasted 3 weeks longer in the 24-hour light group.

• Cocoon and offspring were more abundant in 24-h light and 24-h dark groups.

• Findings are thought to be due to the disruption of the circadian rhythms of the leeches.

KEYWORDS:

• Light regulation
• gravidity
• cocoon
• offspring

Acknowledgments

No specific grant was given to this research by any funding organization in the public, private, or non-profit sectors.

Disclosure statement

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

Data availability statement

The data in this study are available from the corresponding author upon reasonable request.

Contribution of the authors

MC: Conceptualization, Methodology, Formal analysis, Investigation, Writing – original draft, Supervision. HBEÖ: Formal analysis, Investigation, Writing – review & editing. MT: Investigation, Writing – review & editing.

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.