Ref ID : 669
Richard S. Stemberger and John J. Gilbert; Multiple-species induction of morphological defenses in the rotifer Keratella testuda. Ecology 68(2):370-378, 1987
Reprint
In File
Notes
Filtrates of cultures of 10 of 12 common freshwater zooplankton species induced posterior spines in the rotifer Keratella testuda. Filtrates of cultures of Asplanchna spp. and those of crustacean zooplankton, including cladocerans and cyclopoid and calanoid copepods, generally produced the strongest induction responses. The filtrates of Daphnia pulex cultures, at densities as low as 0.4 individuals/L, promoted significant posterior spine development. This is the first known case of a competitor-controlled development polymorphism in zooplankton. Filtrates of cultures of the herbivorous rotifer Synchaeta pectinata and the fourth instar larvae of the dipteran Chaoborus punctipennis were ineffective as spine-promoting agents. In some, but not all, interactions with inducing species, the posterior-spined Keratella phenotype had higher survivorships than the unspined one. Spined individuals were significantly more protected than unspined ones against injury by mechanical interference by Daphnia. Direct observations showed that the spined phenotype was more rapidly rejected after entering the branchial chambers of Daphnia. This decreased the retention time in the branchial chambers and, consequently, reduced the likely hood of injury by the filtering limbs and mouthparts of Daphnia. The ability of this rotifer to respond to many zooplankton species seems advantageous, because the spined phenotype is less vulnerable to predation and interference competition from a variety of larger, co-occurring zooplankton than is the unspined phenotype.