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Browsing by Subject "Mysis relicta"

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  • Andersson, Oliver (2020)
    This study focused on the spectral sensitivity of two Norwegian lake populations of opossum shrimp (Mysis relicta), with a common implantation history and a temporal separation of about 50 years. Previous findings have indicated a difference in the absorption maximum (λmax) between sea and lake populations of Nordic mysids that have been separated about 9 000 years. Between the population groups, the spectral sensitivity correlates to the Wavelength of Maximal Transmission (WLMT) in the habitats. This may be considered a form of adaptive tuning. It is not known if the species-specific mechanism is based on chromophore shift or opsin modification or a combination of both, neither is the timescale of the adaption well understood. The intent was to determine λmax of both populations, what chromophore(s) they use and possible variations of the opsin gene. By comparison to spectrometric data of the habitats, the study aimed to broaden the insight into the mentioned unknowns. The light conditions of the lakes were determined by spectrometry down to depths of three and five meters. As predicted a positive, lake-bound correlation between the attenuation coefficient (k) and WMLT was found. Single-rhabdom microspectrophotometry (MSP) was used to determine λmax of the visual pigment in situ. Absorbance spectra were analysed by manual fitting to mathematical pigment templates and by script-based automation. Neither the chromophore nor differences in λmax could be determined, due to a small sample size that limited the statistical power of the results. The opsin genes from both populations were sequenced. No differences expected to have an effect on spectral sensitivity were found. Spectral tuning could not be demonstrated to have occurred in the populations due to the limited sample size. Nor did the results give support for any new findings on the mechanism or the time scale of spectral tuning among mysids. To answer the proposed questions of the study, additional sampling of both populations is needed.