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Volume 61, Issue 3
Displaying 1-5 of 5 articles from this issue
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Maiko HORI, Kazuko MORIKAWA2000 Volume 61 Issue 3 Pages 223-231
Published: October 30, 2000
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSSeasonal fluctuations in the abundance and composition of epilithic protozoa were studied at Nishiaokidaira in the Akigawa River from October 1997 to December 1998. The fluctuation in the abundance of protozoa showed a similar pattern to that of the biomass, chlorophyll contents and AODC of epilithon at the point, as well as showing a significant correlation coefficient. The number of protozoa examined on May, however, exhibited 1/2 the value of that on February in 1998. Along the epilithon formation, at first Mastigophora appeared among the stone surface community and were then joined by Sarcodina and Ciliphora. Mastigophora dominated in almost all samples and Bodo spp.was the dominant species.View full abstractDownload PDF (693K) -
Makoto TAIRA2000 Volume 61 Issue 3 Pages 233-239
Published: October 30, 2000
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe biomass and species composition of crustacean plankton in the pools of the Ozegahara high moor were studied in 1996 and 1997. In all pools, the dominant species were Acanthodiaptomus pacificus, Diaphanosoma brachyurum and Daphnia rosea; A. pacificus was the most dominant species. The biomass of crustacean plankton and seston concentration in the pools were negatively correlated. As the biomass of crustacean plankton, particulary A. pacificus, gets larger, the seston concentration tends to get smaller in the pools. This result suggests that the seston concentration in a pool was influenced by crustacean plankton. The fact that the egg numbers in a clutch of A. pacificus tend to increase in pools with a higher seston concentration suggests that such pools provide rather favorable feeding conditions for A. pacificus.View full abstractDownload PDF (423K) -
Yoshinori TAKEUCHI, Takuzo YAMADA2000 Volume 61 Issue 3 Pages 241-250
Published: October 30, 2000
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSWe investigated the life-history patterns of Protohermes grandis (Thunberg, 1781) (Megaloptera: Corydalidae) in 4 small mountain streams in Hyogo Prefecture, Honshu, western Japan. We estimated the larval periods from the composition of head widths. In the Kizu River, P. grandis usually had a 2-year life cycle, while in the other streams, 2- or 3-year life cycles were found. The adult flight period was shorter in the Kizu River than in the other streams. We also compared the adult or mature larval body sizes with prey density among 4 streams. The body size of P. grandis was smaller in the Kizu River where the density of larger prey was lower than the other streams. Therefore, prey density may be an important factor in determining body size at maturation of the larvae of this species.View full abstractDownload PDF (647K) -
Hiromune MITSUHASHI2000 Volume 61 Issue 3 Pages 251-258
Published: October 30, 2000
Released on J-STAGE: June 12, 2009
JOURNAL FREE ACCESSThe longitudinal distribution, life history patterns and microhabitat of two lotic caddisflies, Neophylax japonicus Schmid and N. koizumii (Iwata), were studied in the Akikawa River and its tributaries in central Japan. Between these two species, there was a distinct difference in longitudinal sequence with some overlap: N. japonicus in the upstream section and N. koizumii in the downstream. The life history patterns of these species were examined in a sympatric site. Both species had a univoltine life cycle. Larvae grew from December to April in N. japonicus and from March to June in N. koizumii, and adults emerged in October (N. japonicus) and November (N. koizumii). Both species had summer pre-pupal diapauses. This study indicated that two species of Neophylax differ in their longitudinal distribution and seasonality of larval development, and that both species form aggregations of pre-pupae and pupae. The larvae of both species co-occurred in the same stream reach. However, the microhabitats of these two species differed clearly in physical environmental factors such as near-bed current velocity and depth in this period. Some implications of species coexistence and summer prepupal diapause are considered.View full abstractDownload PDF (610K) -
Harumi KUSANO2000 Volume 61 Issue 3 Pages 259-266
Published: October 30, 2000
Released on J-STAGE: December 11, 2009
JOURNAL FREE ACCESSLife history and reproductive traits of Jesogammarus jesoensis were compared among populations of 3 sites in southern Hokkaido: a brook in Eniwa City, a small brooklet in Sapporo City, and the lake shore close to the effluent site of Lake Chitose. In the brook of Eniwa, juveniles of different sizes and reproductive adults appeared throughout the year, whereas reproduction occurred only from late autumn to spring in the small brooklet of Sapporo and at Lake Chitose. The adult size significantly differed among the 3 sites (Eniwa<Sapporo<Chitose); significant differences were also detected in egg size (Eniwa>Sapporo≅Chitose), clutch size (Eniwa<Sappro<Chitose), and clutch volume (Eniwa≅Sapporo<Chitose). The results indicated that the seasonal variation in water temperature induced an amphipod life cycle in which breeding occurred during the cold season, and that the adult size and clutch size were larger as nutritional conditions in the habitats improved. In addition, the amphipods in Sapporo and Chitose had a larger clutch of smaller eggs than in Eniwa, although the egg sizes at these 3 sites were between the lake-type and the stream-type species in the genus Jesogammarus.View full abstractDownload PDF (453K)
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