Maternal age and spine development in a rotifer: ecological implications and evolution.

Area of Science:

• Evolutionary Biology
• Ecology
• Developmental Biology

Background:

• Brachionus calyciflorus typically develops defensive spines in response to predator kairomones.
• Some clones exhibit an age-dependent increase in offspring spine length, even without predator cues.
• This maternal-age effect results in offspring with spines up to 50% of body length.

Purpose of the Study:

• To model the influence of maternal age on spine length distribution in Brachionus calyciflorus populations.
• To assess the effectiveness of this birth-order effect in providing defense against Asplanchna predation.
• To understand the adaptive significance of this novel bet-hedging strategy.

Main Methods:

• Life-table experiments were conducted to gather demographic data.
• Predator-prey experiments were used to simulate interactions with Asplanchna.
• Mathematical modeling was employed to analyze spine length distribution and predation dynamics.

Main Results:

• In the absence of Asplanchna, late-born individuals with long spines are rare, minimizing associated costs.
• When Asplanchna is present but below induction thresholds, predation on short-spined individuals drives an increase in long-spined individuals.
• A stable birth-order structure emerges, significantly reducing mortality from Asplanchna predation.

Conclusions:

• The maternal-age effect on spine length in Brachionus calyciflorus is a novel bet-hedging strategy.
• This strategy effectively mitigates predation by Asplanchna, particularly when kairomone induction is suboptimal.
• The birth-order effect enhances population resilience against predator-induced mortality.