This research explores the capacity for functional photoreception in larvae of the
mountain pine beetle (Dendroctonus ponderosae), an extremely important forest pest
insect that is well adapted for development beneath the bark of pine trees. Phototaxis
tests, gene expression analysis and development experiments were integrated to assess
mountain pine beetle larvae for light sensitivity. When presented with a phototaxis
choice test, larvae preferred dark over light microhabitats, revealing that larvae sense and
respond behaviourally to light. Long wavelength opsin transcription was identified in all
life stages, including eggs and larvae, suggesting that D. ponderosae possesses
extraretinal photosensitive capabilities across its life cycle. The long wavelength opsin
could function in phototaxis or the development phenology of immature beetles, while
the ultraviolet opsin, only found to be expressed in pupae and adults, is likely to function
in dispersal via the compound eyes. Results from two development experiments reveal
an effect of photoperiod treatment on beetle development rate when reared from the egg
stage, but not when reared from mature larvae, indicating that a critical photosensitive
life stage(s) must occur in D. ponderosae prior to the third larval instar. An effect of
photoperiod on adult emergence rates, however, appears to be independent of larval
rearing conditions. The discovery of opsin expression and negative phototaxis in eyeless
mountain pine beetle larvae, in addition to an effect of photoperiod on immature
development and adult emergence rates, suggest that light and photoperiodism likely
function in survival and life cycle coordination in this species. / Graduate / 2018-10-17
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/8853 |
| Date | 11 December 2017 |
| Creators | Wertman, Debra |
| Contributors | Perlman, Steven John |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
| Rights | Available to the World Wide Web |
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