© 2020 Elsevier Inc. We propose a new analytical method for determining the response threshold in electroretinogram (ERG) in which the wave shows a biphasic slow dc-potential shift. This method uses the recorded wave to the highest intensity stimuli in each wavelength tested as a template wave f(t), and it was compared with other recorded waves obtained under lower intensities g(t). Our test recordings in medaka Oryzias latipes were analogous between the template and the compared waveforms, although there were differences in amplitude and time lag (τ, peak time difference) which occurred as a result of the difference in stimulus intensity. Cross-correlation analysis was applied. Based on the obtained cross-correlation function Cfg(τ) in each comparison, τ was determined as the time lag at which the cross-correlation coefficient Rfg(τ) showed the maximum value. Determined thresholds that were based on both the experimenter's visual inspection and this new method agreed well when the adoption condition was set to satisfy R(τ) ≥ 0.7 and τ ≤ 150 ms in scotopic or τ ≤ 120 ms in photopic conditions. We concluded that this “template wave matching method” is a quick and reliable objective assessment that can be used to determine the threshold. This study analyzed ERG recordings in response to 6 kinds of wavelength light stimuli (380 nm to 620 nm) at different photon flux densities. We report the threshold levels and relative spectral sensitivities in scotopic and photopic vision of medaka.

DOI： 10.1016/j.cbpa.2020.110808

Scopus

PubMed

Publisher：NATURE PUBLISHING GROUP  

© 2019, The Author(s). This study investigated whether irradiation of a specific light wavelength could affect the sex differentiation of fish. We first found that the photoreceptor genes responsible for receiving red, green, and ultraviolet light were expressed in the eyes of medaka during the sex differentiation period. Second, we revealed that testes developed in 15.9% of genotypic females reared under green light irradiation. These female-to-male sex-reversed fish (i.e. neo-males) showed male-specific secondary sexual characteristics and produced motile sperm. Finally, progeny tests using the sperm of neo-males (XX) and eggs of normal females (XX) revealed that all F1 offspring were female, indicating for the first time in animals that irradiation with light of a specific wavelength can trigger sex reversal.

DOI： 10.1038/s41598-019-38908-w

Web of Science

Scopus

PubMed

Publisher：SPRINGER JAPAN KK  

© 2018, Japanese Society of Fisheries Science. Efficient production of beneficial metabolites by microalgae using light-emitting diodes (LED) is attracting more interest. In batch cultures, metabolic changes that occur with nutrient deficiency over time must be monitored to estimate the metabolite content. Our previous study showed that nutrient deficiency in Nannochloropsis oculata can be briefly evaluated by measuring the absorption ratio at 490 and 680 nm (Abs 490 /Abs 680 ). However, little is known about the relation with this ratio and metabolic change, particularly in LED light-conditioned cultures. In this study, we investigate if Abs 490 /Abs 680 can be an indicator of the biochemical status of N. oculata cultured under various LED color regimes. Three LED treatments were used: Blue (B), Blue + Red (BR), and Red (R). In all LED treatments, the Abs 490 /Abs 680 decreased for several days and then increased when phosphate was limited or non-existent. The trends in the C16:0 and C20:5ɷ3 proportions and chlorophyll a content commonly changed at the turning points of the Abs 490 /Abs 680 . Furthermore, significant correlations were found among the metabolic state and absorption ratio, except in treatment R. We suggest that spectrophotometry can be used for monitoring metabolic changes in N. oculata cultures under various LED irradiance, unless there is excessive 630 nm-red light exposure.

DOI： 10.1007/s12562-018-1261-y

Web of Science

Scopus

Publisher：WILEY  

© 2018 Blackwell Verlag GmbH Knowledge on the visual spectral sensitivity of a given fish is important for determination of optimal light conditions for improvement of fish rearing in aquaculture. Sutchi catfish (Pangasianodon hypophthalmus Sauvage 1878) is an important freshwater fish species in Southeast Asia. The present study aimed to understand the visual spectral sensitivity of juvenile sutchi catfish through spectrophotometric measurement of the spectral absorbance of wholemounts of retinae. The spectral absorbance curves obtained from the spectrophotometric measurement indicated a parabolic shape. The curves for retinae photo-bleached with initial flash of blue, green and yellow lights, respectively had a peak at approximately 560 nm, which were the same as the curve for retinae photo-bleached with broad wavelength light. On the other hand, the curve for retinae photo-bleached with initial flash of red light had a peak shifted prominently toward shorter light wavelength at approximately 540 nm. This prominent shift of peak implied that the retinae of juvenile sutchi catfish absorb light wavelength of red. Therefore, the present results clearly suggested that juvenile sutchi catfish utilises longer light wavelengths.

DOI： 10.1111/jai.13792

Web of Science

Scopus

Publisher：ELSEVIER SCI LTD  

© 2018 Elsevier Ltd With New Washington-Batan estuary as study site, this study determined the impact of Typhoon Haiyan on capture fisheries through data that were collected before and after the typhoon event. To validate these results and to determine other related information (e.g., recovery of fishing after typhoon), key interviews and focus group discussions were conducted. The immediate impact of the typhoon event was disruption of fishing livelihood due to damage of fishing gears as about 94% of stationary fishing gears had considerable damage. Resumption of fishing operations varied largely among fishers depending on the degree of gear damage. Reconstruction of damaged stationary gears was hampered mainly by the financial capacity of fishers and the acute supply of bamboo which is the main component in the construction of these fishing gears. We also discuss typhoon impacts on other fishing gears such as line fishing, gillnets, and pots. These information are valuable in understanding impacts of extreme weather events on tropical small-scale fisheries so that managers may be able to devise measures to reduce vulnerabilities among coastal resource users.

DOI： 10.1016/j.ocecoaman.2018.03.032

Web of Science

Scopus

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