Research Article

Asplanchna-kairomone induces life history shifts in Brachionus angularis (Rotifera)

Provincial Key Laboratory for Conservation and Utilization of Important Biological Resource in Anhui, College of Life Sciences, Anhui Normal University, Wuhu 241000, Anhui Province, PR China

^* Corresponding author: ylxi1965@126.com

Received: 28 October 2017
Accepted: 29 January 2018

Abstract

Predator-derived kairomones play an important role in ecological and evolutionary processes that enable the prey to survive predation pressure. In the presence of predatory Asplanchna, some Brachionus and Keratella species develop morphological and behavioral defenses, but whether rapid population growth and diapause are inducible defenses largely remains unknown. In the present study, parental B. angularis females cultured at 1.0 × 10⁶ and 2.0 × 10⁶ cells · mL⁻¹ of Scenedesmus obliquus were indirectly exposed to 0, 40, 80 and 160 ind. L⁻¹ of A. brightwelli using mesh enclosure, and their life-table demographic parameters, population growth rates and morphological characters were calculated and measured. The results showed that Asplanchna-released kairomone decreased significantly average lifespan, life expectancy at hatching, generation time and net reproduction rate, but increased the proportion of sexual offspring of parental B. angularis females. The threshold Asplanchna density required for significant effects varied with food level. Kairomone released by Asplanchna at 80 ind. L⁻¹ increased significantly the intrinsic rate of population increase of B. angularis cultured at 2.0 × 10⁶ cells · mL⁻¹ of S. obliquus, which would offset the mortality of exposed females from predation. The accumulation of kairomone in aquatic environments enhanced the indirect effect of Asplanchna on the population growth of B. angularis. The present results indicated that rapid population growth of B. angularis induced by Asplanchna kairomone might facilitate the coexistence of preys with predators, and higher proportion of sexual offspring and then resting egg production might help the preys avoid the predator in time instead of facing the enemy through defenses.