Rapid Gamete Maturation and Social Modulation Shape Reproductive Dynamics in a Brood Parasitic Catfish

Area of Science:

• Behavioral Ecology
• Reproductive Biology
• Ichthyology

Background:

• Obligatory brood parasitism necessitates precise reproductive synchronization between parasite and host.
• Cuckoo catfish (Synodontis multipunctatus) exploit cichlid mouthbrooding by intruding during host spawning.
• The unpredictable nature of host reproduction requires rapid responses from brood parasites.

Purpose of the Study:

• Investigate the reproductive physiology of cuckoo catfish, focusing on gamete maturation.
• Examine the social modulation of gamete maturation in both male and female catfish.
• Analyze reproductive skew and factors influencing parasitism success during spawning events.

Main Methods:

• Conducted linked laboratory experiments to assess reproductive physiology.
• Monitored gamete maturation rates in relation to social housing and interactions.
• Quantified parasitism success and reproductive skew during simulated host spawning events.

Main Results:

• Male catfish showed consistent sperm production, indicating continuous reproductive readiness.
• Female catfish ovulated approximately weekly, with significant increases in maturation rates due to social interactions.
• Parasitism success was not correlated with female gamete production frequency; smaller males had higher success.
• Reproductive skew was low overall, but individual spawning events were often monopolized by a single pair.

Conclusions:

• Cuckoo catfish possess adaptations for rapid reproduction, including frequent gamete maturation and social facilitation.
• Male morphology (size, slimness) appears crucial for competitive success during parasitic spawning.
• Reproductive strategies involve a balance of physiological readiness, social cues, and scramble competition for mating opportunities.