Biological rhythms: Hormones under moon control.

Area of Science:

• Reproductive biology
• Marine ichthyology
• Endocrinology

Background:

• Grass puffers (Takifugu spp.) are known for mass spawning events synchronized with lunar phases.
• The precise molecular mechanisms coordinating these reproductive cycles remain incompletely understood.

Purpose of the Study:

• To investigate the role of prostaglandins in fine-tuning lunar-controlled spawning in grass puffers.
• To identify molecular regulators involved in the long-term synchronization of gonadal maturation with lunar cycles.

Main Methods:

• Analysis of prostaglandin signaling pathways in grass puffer reproduction.
• Investigation of gene expression patterns, including GnRH1 and associated transcription factors.
• Correlation of molecular events with lunar phases and spawning activity.

Main Results:

• Prostaglandins released by both male and female grass puffers were found to modulate spawning timing.
• A specific transcription factor exhibiting a semilunar rhythm was identified, regulating the expression of the gonadotropin-releasing hormone 1 (GnRH1) gene.
• This regulation suggests a molecular clock mechanism for coordinating reproductive maturation.

Conclusions:

• Prostaglandins play a crucial role in the immediate fine-tuning of grass puffer mass spawning events.
• The semilunar regulation of GnRH1 provides a potential molecular basis for the long-term synchronization of gonadal maturation with lunar cycles in fish.