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Kohei Ohta Mayumi Hirano Takayuki Mine Hiroshi Mizutani Akihiko Yamaguchi Michiya Matsuyama 《Marine Biology》2008,153(5):843-852
Gonadal sex steroid hormones are the principal factors that directly control the gonadal and morphological alterations during
sex change in hermaphrodite fish; however, the physiological mechanism of action by which these hormones govern body coloration
is poorly understood. The protogynous wrasse Pseudolabrus sieboldi is a good model for understanding the physiological mechanisms of gonadal and body color change during sex change in hermaphrodite
fish. To obtain information on the relationship between sex steroids and body color change during the process of gonadal sex
change, we analyzed body color, gonadal histology, and serum levels of sex steroids. Body color was analyzed using a quantitative
analytical method based on the hue value. Compared to other body parts of the fish, the anal fin changed color the most, becoming
increasingly redder in association with gonadal changes that converted ovaries to testes. Levels of serum 11-ketotestosterone
(11KT) increased as the gonadal sex change proceeded, whereas no significant change was observed in estradiol-17β (E2) levels.
Moreover, we found a significant correlation between the hue value of the anal fin and serum 11KT levels, but not E2 levels.
These results suggest that androgen, but not estrogen, plays a principle role in the changes in both gonadal morphology and
body color in the transformation from female to male in this species. To our knowledge, this is the first quantitative demonstration
of the relationship between body color and serum steroid levels during sex change in fish. 相似文献
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Akihiko Masui Satoshi Ikawa Nobuaki Fujiwara Hiroaki Hirai 《Journal of Polymers and the Environment》2011,19(3):622-627
The influence on soil environment by continuing use of the biodegradable plastic films (biodegradable mulching films) in farmland
was investigated. The difference was not seen in the amount of soil bacteria between mulching film plowing sections and non-plowing
sections. The total bacteria amount did not increase by the effect of plowing the biodegradable mulching film. Poly-(butylene
succinate and adipate) (PBSA) and poly-(ε-caprolactone) (PCL) decomposing bacteria did not increase in PBSA and PCL mulching
film plowing sections comparing polyethylene covering section (PE) and no-film section. Polylactic acid (PLA) decomposing
bacteria were not detected in all sections. Total denaturing gradient gel electrophoresis (DGGE) band patterns did not show
a clear transition of the bacterial community structure in both the cultivating and promoting sections. In usual usage condition
of the biodegradable plastic films, it was hardly influence to the soil environment such as bacterial community structure
in farmland. 相似文献
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Comparison of feeding habits of myctophid fishes and juvenile small epipelagic fishes in the western North Pacific 总被引:1,自引:0,他引:1
Kaori Takagi Akihiko Yatsu Hiroshi Itoh Masatoshi Moku Hiroshi Nishida 《Marine Biology》2009,156(4):641-659
To examine the potential trophic competition between myctophids and small epipelagic fishes in the nursery grounds in spring,
we compared the stomach contents of dominant myctophids (Symbolophorus californiensis, Ceratoscopelus warmingii and Myctophum asperum; n = 179) and juvenile epipelagic fishes (Japanese sardine, Sardinops melanostictus, Japanese anchovy, Engraulis japonicus, chub mackerel, Scomber japonicus, and spotted mackerel, S. australasicus; n = 78) that were simultaneously collected at nighttime with a midwater trawl net around the Kuroshio-Oyashio transition zone
in the western North Pacific. It was clear that the neritic copepod Paracalanus parvus s.l. was the most abundant species in NORPAC samples (0.335 mm mesh size) taken at the same stations. Diets of dominant myctophid
fishes differed from those of the juvenile epipelagic fishes; Japanese sardine and anchovy mostly preyed upon P. parvus s.l. (23.6% of stomach contents in volume) and Corycaeus affinis (16.1%), respectively. Both chub and spotted mackerels mainly preyed upon the seasonal vertical migrant copepod, Neocalanus cristatus (15.9 and 14.7%, respectively). On the contrary, myctophid fishes probably do not specifically select the abundant neritic
copepods. Namely, S. californiensis mostly preyed upon a diel vertical migrating copepod, Pleuromamma piseki (22.7 and 30.6% in stomach of juvenile and adult, respectively), while C. warmingii and M. asperum preyed on Doliolida (43.0% in stomach of juvenile C. warmingii), appendicularians (11.0% in stomach of juvenile M. asperum), and Ostracoda (6.3% in stomach of adult C. warmingii). Feeding habits of myctophid fishes seem adapted to their prey animals; low rate of digested material (less than 30% in
volume) in stomachs of S. californiensis may be linked to the movement of P. piseki, hence S. californiensis can easily consume this copepod at night since they are more concentrated at night than daytime. High rate of digested material
(over 40%) of M. asperum and adult C. warmingii suggest that they feed not only at night but also during the daytime in the midwater layer. Thus, myctophid fishes actually
fed in the surface layer but less actively than the small epipelagic fishes. These results suggest that the potential for
direct food competition between myctophids and small epipelagic fishes is low in the nursery ground, but there remains a possibility
of indirect effects through their prey items, since the above gelatinous animals feed on common prey items as juveniles of
Japanese sardine and anchovy. 相似文献
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Keiko Katayama-Hirayam Naoki To Akihiko Tauchi Atsushi Fujiok Tetsuya Akitsu Hidehiro Kaneko Kimiaki Hirayama 《环境科学学报(英文版)》2014,26(6):1284-1288
We examined the degradation of dibromophenols (DBPs), i.e. 2,4-DBP, 2,6-DBP and 3,5-DBP by ultraviolet (UV) irradiation and estimated the relationship between degradability and molecular orbital properties of each dibromopbenol. The removal of DBPs under a UV lamp system was successfully performed in an aqueous solution. After 5 min of irradiation, the initial DBPs concentration of 20 mg/L was decreased to below 1 mg/L, and about 60% of bromide ion was released. A decrease in the concentration of dissolved organic carbon (DOC) suggested the mineralization of DBPs, The mineralization may occur after release of bromide ions because the decrease of DOC was slower than the release of bromide ions. The degradability of 3,5-DBP was slightly lower than 2,6-DBP and 2,4-DBE Molecular orbital calculation suggested that the electrophilic frontier density and the highest occupied molecular orbital (HOMO) energy may be related to the degradability of DBPs. 相似文献