ABSTRACT
The genetic background of inducible morphological defences in Daphnia is still largely unknown. Dissolved infochemicals from the aquatic larvae of the phantom midge Chaoborus induce so-called ‘neck-teeth’ in the first three post-embryonic stages of Daphnia pulex. This defence has become a textbook example of inducible defences. In a target gene approach, by using three Daphnia genotypes which show a gradient of neck-teeth induction in response to equal amounts of kairomone, we report a high correlation of neck-teeth induction in Daphnia pulex and relative gene expression of two chitin deacetylases. Further, previous studies suggested genes from both the juvenoid and the insulin hormone signalling pathways as well as several morphogenetic genes downstream to be responsible for neck-teeth induction in D. pulex. However, these data were not supported by our study. None of the three D. pulex clones showed an upregulation of these previously proposed candidate genes as a response to predator kairomone, which is interpreted as the result of refined methods used for both RNA sampling and kairomone enrichment yielding unambiguous results compared with earlier studies. The assessment of a clonal gradient of Daphnia in the presence and absence of infochemicals provides a promising approach to identify further genes involved in the induction of morphological defences by correlating gene expression and morphology.
FOOTNOTES
Competing interests
The authors declare no competing or financial interests.
Author contributions
M.C., P.F. and E.v.E. made a substantial contribution to conception and design. M.C. and P.F. made a significant contribution to data acquisition. M.C. and E.v.E. were involved in data analysis and interpretation, and in drafting the manuscript and revising it critically for important intellectual content. All authors gave their final approval of the version to be published.
Funding
This research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.
- Received October 19, 2015.
- Accepted March 11, 2016.
- © 2016. Published by The Company of Biologists Ltd
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