Masanao Michinomae

On the three visual pigments in the retina of the firefly squid, Watasenia scintillans

SummaryThe deep-sea bioluminescent squid, Watasenia scintillans, has three visual pigments: The major one (A1 pigment) is based on retinal and has λmax = 484 nm, the second one (A2 pigment) is based on 3-dehydroretinal and has λmax = 500 nm, and the third one (A4 pigment) is based on 4-hydroxyretinal and has λmax = 470 nm. The distribution of these 3 visual pigments in the retina was studied by HPLC analysis of the retinals in retina slices obtained by microdissection. It was found that A1 pigment was not located in the specific region of the ventral retina receiving the down-welling light which contains very long photoreceptor cells, forming two strata. A2 and A4 pigment were found exclusively in the proximal pinkish stratum and in the distal yellowish stratum. The role of these pigments in the retina is hypothesized to involve spectral discrimination. The extraction and analysis of retinoids to determine the origin of 3-dehydroretinal and 4-hydroxyretinal in the mature squid showed only a trace amount of 4-hydroxyretinol in the eggs. Similar analysis of other cephalopods collected near Japan showed the absence of A2 or A4 pigment in their eyes.

Visual pigments in the pineal complex of the Japanese quail, Japanese grass lizard and bullfrog: Immunocytochemistry and HPLC analysis

We investigated localization of visual pigments in the pineal complex of Japanese quail, Japanese grass lizards and bullfrogs immunocytochemically by use of the antiserum against bovine rhodopsin (Rh-As) and monoclonal antibodies against chicken iodopsin (Io-mAb). We also analyzed retinoids, chromophores of visual pigments, by a high performance liquid chromatography (HPLC). The outer segments and cell membranes of some photoreceptor cells in the pineal organ of the Japanese quail exhibited immunoreactivity to Rh-As, but there are also many immunonegative cells. The number of immunoreactive cells among individuals varied. Immunoreactivity to Io-mAb was weak or did not exist. The HPLC analysis revealed peaks of 11-cis and all-trans isomers of retinal in the oxime extracts of the pineal organ of Japanese quail and chickens. In the pineal of Japanese grass lizards, the outer segments of some cells were immunopositive to Io-mAb, but there were no cells immunoreactive to Rh-As. The parietal eye exhibited a well-developed lens and photoreceptor cells, but the outer segments of photoreceptor cells were immunonegative to both Rh-As and Io-mAb. In bullfrogs, three types of cells were identified in both the pineal and frontal organ; (1) immunopositive to Rh-As, (2) immunopositive to Io-mAb and (3) immunonegative to either of the antibodies. In the pineal organ of bullfrogs, 11-cis and all-trans retinal and 11-cis 3-dehydroretinal were detected, and 11-cis and all-trans retinal were also detected in the frontal organ. We detected 11-cis and all-trans retinal in the ventral part of diencephalon including the hypothalamus. Thus, the chromophore is the same between the retinal and pineal visual pigments, but the expression of opsins is different between the retina and pineal complex, which probably reflects the different function of each organ.

Luciferase activity of the intracellular microcrystal of the firefly squid, Watasenia scintillans

The arm light organ of the firefly squid, Watasenia scintillans, emits extremely bright flashes of light, which are caused by a luciferin–luciferase reaction involving ATP, Mg2+ and molecular oxygen. The molecular mechanism underlying the bioluminescence reaction has remained unresolved, because the luciferase could not be identified or isolated. The arm light organ contains numerous rod‐like bodies that are 2–6 μm long and 1–2 μm thick. This paper addresses the characterization of the extracted rod‐like body. We found that the rod‐like bodies emit the light in vitro by the luciferin–luciferase reaction. Furthermore, by using the X‐ray powder diffraction method, we confirmed that the rod‐like bodies are well‐ordered microcrystals.

Apis Cerana Japonica Discriminates between Floral Color Phases of the Oriental Orchid, Cymbidium floribundum

Foragers of the Japanese honeybee (Apis cerana japonica) were attracted by flowers of an oriental orchid (Cymbidium floribundum) and were observed to carry the pollinia on their scutella. After the removal of pollinia from the flowers, their labial color changed from white to reddish brown. Both artificial removal of pollinia and ethrel treatment of the flowers also induced this labial color change. Labia in color-changed flowers showed a decreased reflectance of wavelengths less than 670 nm compared to control intact flower. Both reflectance irradiance spectra and ultraviolet photographs showed that only the nectar guide in white (unchanged) flowers reflected ultraviolet light, and that this reflectance decreased with labial color change. Dual choice experiments showed that the honeybee foragers preferentially visited flowers having white labia rather than reddish brown. We suggest that Japanese honeybees discriminate between the floral phases of C. floribundum using color vision.