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We examined the larval population densities and biomass of a caddisfl y grazer, Micrasema quadriloba, and the abundance and community structures of periphyton at a segment scale (7.4 km with four study sites), along a second- to fourth-order Japanese mountain stream through- out the grazer's life cycle. In the uppermost riffl e of the study segment (site 1), periphyton abundance was kept at low levels when the larvae occurred. The larval distribution spread downstream as larvae developed from fi rst instars in May to fi fth instars in January. We performed multiple regression analyses to test the effects of environmental variables and larval biomass on periphyton abundance in both the riffl e of site 1 and the study segment; the results revealed that the larval biomass was signifi cantly negatively correlated with periphyton abundance similarly in both the riffl e and the study segment. In addition, both the correla- tion and community analyses showed that the larval biomass was signifi cantly negatively correlated to the rela- tive abundance of large and/or fi lamentous microalgae, which appeared in the uppermost layer of the periphyton mat, and that larval biomass was signifi cantly positively correlated to the relative abundance of small diatoms, which strongly adhered to the substrate. Thus, the present study implied that the grazing of M. quadriloba larvae would regulate the abundance of periphyton in a riffl e and also regulate the abundance and community structure of periphyton at the segment scale with the expansion of their longitudinal distribution.

Egg period was compared among several temperature conditions (11°C, 16°C, 20°C, 23°C) in Sweltsa sp., Stavsolus japonicus, and Isoperla aizuana (Plecoptera). The shortest mean egg incubation period was 27.8 days at 20°C in Sweltsa sp., 118.1 days at 16°C in Stavsolus japonicus, and 162.0 days at 20°C in Isoperla aizuana on average. Egg hatching rate was also the highest at the water temperature that provided the shortest egg incubation period. Based on laboratory data, eggs of Sweltsa sp. were considered to be deposited in May and hatched in June in the field. Thus, they must have spent the summer as nymphs in the field. Eggs of Stavsolus japonicus and Isoperla aizuana were considered to be deposited in April to May and hatched in September to October in the field. Visible eyes of Stavsolus japonicus and Isoperla aizuana appeared in August. It is likely that the long egg period of Stavsolus japonicus and Isoperla aizuana reflects that these two species spend the summer as dormant eggs in the field.

Locomotor activity rhythms of the Japanese newt, Cynops pyrrhogaster, were recorded under a semi-natural condition using phototransistor systems. The daily activity rhythm showed a seasonal change: the locomotor activity was mainly diurnal (active during the daytime) from spring to early summer; mainly nocturnal (active during the night-time) from summer to autumn; and showed either a diurnal or nocturnal pattern, depending on the ambient temperature, in winter. To analyze the daily activity in detail, we observed the behavior of a group of newts (three males, three females) throughout 24 h. Four types of behavior (respiration, feeding, mating, and resting on the land) were observed. Each behavior had daily rhythms and showed a seasonal change. The behavior on land showed mainly a nocturnal or bimodal pattern (activity rhythms with two peaks) throughout the year and was more frequently observed in summer. Mating behavior also showed a seasonal change: high activity in spring, with peaks in the early morning and evening, but no activity in summer. Except in winter, feeding and respiratory behavior showed no seasonal changes in either activity period or frequency. Coupling between behavior and the clock seems to be weak in the Japanese newt because of indistinct daily rhythms and frequent phase changes of locomotor activity in water. Physical factors such as humidity and temperature seem to affect strongly the daily activity of the newts.

This study deals with the daily activity rhythm and its change in a loath,Misgurnus anguillicaudatus, by season and age. We set traps in an irrigation creek and ditches around the paddy fields near Nara city every month for 2 years. The fish appeared in spring, declined in early summer, and increased in mid-summer again, and disappeared in late autumn. The number of fish captured at night was greater than that during the daytime in summer. There were some differences in the daily rhythms by sex and age. Nocturnal activities of males and immatures were more prominent than those of females. Younger generation were more nocturnally active than elders in summer. Changes in the daily activity rhythms of the loath are possibly adaptive to unstable environments around paddy fields.

Morningness-eveningness (M-E) preference and whether it was related to varying mental and physical conditions during the menstrual cycle of female students attending a Japanese junior high school, located in the suburban region in Nangoku city (33.3 N), Kochi prefecture, was studied. Those students who were beyond their first year after menarche were more evening-typed than those who were in their first year of menarche or those who had not yet begun their menstrual function. The M-E preference has no significant correlation with mood, periodical stability of the menstrual cycle or menstrual pain. The bedtime of those students who had an irregular menstrual cycle was significantly later than that of the students who had a stable cycle.

The aim of this study has been to examine whether iodopsin immunoreaction exists in the photoreceptor cells of the retina of the river lamprey, Lampetra japonica, and whether this immunoreaction also appears in the photoreceptors of the pineal complex. The lamprey retina possesses long and short photoreceptor cells that display iodopsin immunoreactivity and rod-opsin immunoreactivity, respectively. In the pineal organ, iodopsin immunoreaction has been observed in the peripheral region and the dorsal wall of the end-vesicle. Immunoreactivity is also found in the atrium and the pineal stalk. The iodopsin-immunoreactive outer segments are smaller than those displaying rod-opsin immunoreactivity. In the parapineal organ, iodopsin immunoreactivity is distributed in both dorsal and ventral portions. Double immunostaining has been employed to investigate whether iodopsin and serotonin immunoreactivities are colocalized in one and the same cell. This approach has revealed that the iodopsin-immunoreactive outer segments belong to serotonin-immunopositive and to serotonin-immunonegative photoreceptor cells. These results demonstrate that rod-type or cone-type visual pigments are contained in both typical and modified pineal photoreceptors.

We investigated circadian ocular rhythms in the Japanese quail, Coturnix coturnix japonica. The birds were placed under light-dark cycles (LD 12∶12), constant light (LL) and constant darkness (DD), and the retinas were dissected out at four-hour intervals throughout 24 h. Following measurements were performed. (1) Melatonin content in the retina was measured by radioimmunoassay. It was low in light and several folds higher in darkness under LD 12∶12. The rhythm continued in DD, but disappeared in LL. (2) Mitotic figures in the corneal epithelium were counted. Similar rhythms to the melatonin content were observed in the corneal mitotic rate with a slight phase delay. (3) The retinas were fixed at 4-h intervals and immunostained with anti-bovine rhodopsin serum and anti-chicken iodopsin monoclonal antibodies. The outer segments of photoreceptor cells were stained intensively throughout 24 h in LD 12∶12, LL and DD. In contrast, the stainability of the locus close to the outer limiting membrane where the Golgi apparatus exists changed diurnally. Scores showing the ratio of cells with positive staining indicated high values from 4 h after the onset of light to the beginning of dark phase under LD 12∶12. The values were high throughout 24 h in LL and intermediate or low in DD. (4) To investigate the effect of melatonin on the corneal mitotic rate and visual pigments at the Golgi region, melatonin was injected into one eye and saline into the contralateral eye. Melatonin induced a phase advance in the corneal mitotic rate under LD 12∶12, but did not induce a rhythm under LL. The ratio of photoreceptor cells with positive staining to anti-visual pigment antibodies at the Golgi region was not affected by melatonin injection.