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11.
Masato Kobayashi Tomohito Shimizu Koichi Okuzawa Kiyoshi Soyano Kenzo Yoseda 《Fisheries Science》2010,76(5):777-784
To determine the sexual maturity of fourteen male wild-caught hawksbill turtles [straight carapace length (SCL) range 63–79 cm]
held in captivity, we investigated their hormone levels in blood and morphological characteristics. Male turtles were divided
into two groups: five individuals showing mating behavior (group A) and nine individuals not showing mating behavior (group B).
Then, seasonal changes of plasma testosterone of both groups were studied. We also tried to determine male maturity based
on tail elongation (TE) index, i.e., the ratio of tail length (TL) to SCL. Plasma testosterone level of group A gradually
increased during premating and then sharply declined to low levels between mating and postmating seasons. In contrast, that
of group B remained low during the experimental periods. The distinct seasonal changes of plasma testosterone levels of groups A
and B correlated with their maturity. Furthermore, males were clearly divided into mature and immature based on TE values
>0.35 and <0.33, respectively, corresponding to results based on plasma testosterone levels. Our results indicate that TE
can be used more conveniently and accurately to determine maturity of male hawksbill turtles in captivity. 相似文献
12.
A temporal pattern of reproductive activities of biological resources is essential information for the implementation of specific
seasonal closures. First we investigated the relationship between the female pleonal expansion and female reproductive condition
(i.e., non-ovigerous, ovigerous, or with spermatophores) to clarify the morphological characteristics of female coconut crabs
that were able to mate. Second, we mated females with males in captivity to examine the relationship between the degree of
female pleonal expansion and mating success. The index of pleonal expansion (ratio of inter-tergite distances to thoracic
length) was significantly different among female reproductive conditions; females with spermatophores just before egg extrusion
had the most expanded pleon. In the mating trials, all females showing index values higher than 0.35 mated with males. These
results indicate that the female pleonal expansion has a strong relation to reproductive activities of females and can be
applied as a morphological criterion for selecting females being able to mate. Next, we investigated whether reproductive
activities of female coconut crabs are related to the lunar cycle. The reproductive activities were synchronized with the
lunar cycle, and most females mated and extruded eggs around the new moon phase. These results have considerable implications
for resource management and aquaculture for this species. 相似文献
13.
Tanaka Kenzo Ryo Furutani Daisuke Hattori Joseph Jawa Kendawang Sota Tanaka Katsutoshi Sakurai Ikuo Ninomiya 《Journal of Forest Research》2009,14(6):365-372
Although allometric equations can be used to accurately estimate biomass and/or carbon stock in forest ecosystems, few have
been developed for logged-over tropical rainforests in Southeast Asia. We developed allometric relationships between tree
size variables (stem diameter at breast height (dbh) and tree height) and leaf, branch, stem and total above-ground biomass
in two logged-over tropical rainforests with different soil conditions in Sarawak, Malaysia. The study sites were originally
classified as mainly lowland dipterocarp forest and have been selectively logged in the past 20 years. In total, 30 individuals
from 27 species were harvested to measure above-ground parts. The correlation coefficients for the allometric relationships
obtained for total above-ground biomass as a function of dbh had high values (0.99), although the relationships for leaf biomass
had a relatively low coefficient (0.83). We also found relatively high coefficients for allometric relationships between tree
height and plant-part biomass, ranging from 0.82 to 0.97. Moreover, there were no differences for allometric equations of
total above-ground biomass between study sites. A comparison of equations of above-ground biomass in various previously reported
tropical rainforests and pan-tropic general equations imply that our allometric equations differ largely from the equations
for tropical primary forests, early successional secondary forest, and even for the general models. Therefore, choosing the
biomass estimation models for above-ground biomass in the logged-over forests of Southeast Asia requires careful consideration
of their suitability. 相似文献
14.
Kazuki Yokouchi Yasuyuki Kaneko Kenzo Kaifu Jun Aoyama Kazuo Uchida Katsumi Tsukamoto 《Fisheries Science》2014,80(3):543-554
Catch statistics and biological data of the Japanese eel Anguilla japonica from 12 river systems in nine prefectures of Japan (36°N, 140°E–31°N, 130°E) during 1999–2004 were analyzed in order to evaluate the demography of A. japonica in Japan. Significant differences in biological characteristics of 6388 eels were found among the river systems. Fishery catches of eels in all locations have declined, but the magnitudes or patterns of decline seem to be different. Of sex-identified eels, mean total lengths ± SD (mm) of females (n = 3776) and males (n = 962) were 495.6 ± 104.3 and 412.9 ± 80.7, respectively, and overall sex ratio (% female) was 79.6 %. Mean age (years) and growth rate (mm year?1) were 5.0 ± 1.9 and 96.7 ± 38.6 for females (n = 3643) and 3.6 ± 1.7 and 120.5 ± 65.4 for males (n = 907), respectively. This study highlights the demographic heterogeneity of the A. japonica among the studied river systems, which suggests that it is important to conserve a variety of habitats in multiple river systems as an inclusive management target in addition to restoration of the diversity of habitats for eels in a single river system. 相似文献
15.
Yoshimasa SASAKI Taketoshi IWATA Masashi UEMA Kenzo YONEMITSU Shizunobu IGIMI Hiroshi ASAKURA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2022,84(6):743
Chicken is a major source of human campylobacteriosis. Chicken meat originates not only from broilers but also from spent layers; however, few reports have documented the prevalence and antimicrobial resistance of Campylobacter spp. in layers in Japan. Therefore, we investigated the prevalence and antimicrobial susceptibility of Campylobacter spp. in 47 layer farms in Japan. Fecal samples were collected from the youngest and oldest flocks on the farm, and Campylobacter spp. was isolated from 46/47 (97.9%) farms. Among the C. jejuni isolates, the resistance rates to ampicillin, tetracycline, and ciprofloxacin were 29.6%, 22.2%, and 19.8%, respectively. The ciprofloxacin resistance rate (7.3%) in C. jejuni isolated from old flocks was significantly (P<0.01) lower than that in young flocks (32.5%). 相似文献
16.
Milagros Virhuez MENDOZA Kenzo YONEMITSU Keita ISHIJIMA Yudai KURODA Kango TATEMOTO Yusuke INOUE Hiroshi SHIMODA Ryusei KUWATA Ai TAKANO Kazuo SUZUKI Ken MAEDA 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2022,84(7):992
In Japan, hepatitis E virus (HEV) causes hepatitis in humans through the consumption of raw or undercooked meat, including game meat. In the present study, nationwide surveillance of HEV infection among a total of 5,557 wild animals, including 15 species, was conducted in Japan. The prevalence of anti-HEV antibodies in wild boar was 12.4%, with higher positive rates in big boars (over 50 kg, 18.4%) than in small individuals (less than 30 kg, 5.3%). Furthermore, HEV RNA was more frequently detected in piglets than in older boars. Interestingly, the detection of HEV among wildlife by ELISA and RT-PCR suggested that HEV infection in Sika deer was a very rare event, and that there was no HEV infection among wild animals except for wild boar, Sika deer and Japanese monkeys. In conclusion, wild boar, especially piglets, are at high risk of HEV infection, while other wild animals showed less risk or no risk of HEV transmission. 相似文献
17.
Kenzo Ueda Loretta C. Gaughan John E. Casida 《Pesticide biochemistry and physiology》1975,5(3):280-294
Microsomal esterases of mouse and rat liver readily cleave the trans- but not the cis-isomers of resmethrin (5-benzyl-3-furylmethyl chrysanthemate). The ester linkage also appears to undergo oxidative cleavage when esterase attack is minimal, i.e., with (+)-cis- and particularly (?)-cis-resmethrin in microsome-NADPH systems and with any of the isomers when NADPH is added to microsomes pretreated with TEPP. Metabolites retaining the ester linkage are detected in significant amounts only with (+)-cis-resmethrin in which case they are formed by oxidation at either the trans(E)- or cis(Z)-methyl group of the isobutenyl moiety with or without oxidation of the benzylfurylmethyl group. Metabolites of each acid moiety include chrysanthemic acid and up to six derivatives of this acid formed by oxidation at the trans(E)- or cis(Z)-methyl group yielding the corresponding alcohol, aldehyde, or acid, with chrysanthemate isomer and enzyme source variations in the preferred site of oxidation. The major identified metabolite of the alcohol moiety is either benzylfurylmethanol or the corresponding carboxylic acid depending on the enzyme system used. In the course of microsomal oxidation, a fragment from the alcohol but not the acid moiety of (+)-trans- and (+)-cis-resmethrin is strongly bound to microsomal components. These findings confirm in vivo studies on the isomeric variations in metabolism of the resmethrin components. 相似文献
18.
By use of tree-tower and canopy-crane systems we studied variations in the water use, including transpiration, stomatal conductance, and leaf water potential, of the uppermost sun-exposed canopy leaves of four emergent dipterocarp species in an aseasonal tropical rain forest in Sarawak, Malaysia. Midday depression in stomatal conductance and leaf water potential was observed in all the species studied. Interspecific differences were clearly observed in the maxima of transpiration rates and stomatal conductance and the minima of leaf water potential among the four dipterocarp species. These interspecific variations were closely related to wood density and to factors affecting ecological patterns of distribution. Specifically, Shorea parvifolia and S. smithiana, both of which have a relatively low wood density for Dipterocarpaceae and are found on clay-rich soil, had a high transpiration rate in the daytime but had a large midday depression and a low leaf water potential. In contrast, Dryobalanops aromatica, which has a high wood density and is found in sandy soil areas, consumed less water even during the daytime. Dipterocarpus pachyphyllus, which has a high wood density and is found on clay-rich soil, stood intermediate between Shorea and D. aromatica in leaf water use. The two Shorea species had higher mortality than the others during the severe drought associated with El Ni?o in 1998, so daily pattern of leaf water use in each dipterocarp species might be correlated with its susceptibility to unusual drought events. 相似文献
19.
Iinuma YM Tanaka S Kawasaki K Kuwajima T Nomura H Suzuki M Ohtaishi N 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2004,66(6):665-669
Periodic growth incremental lines are found universally in dental hard tissues. This periodicity theoretically allows for estimation of age, even in days, which would be useful in studies of wild animals. In the present study, enamel and dentin increments of the sika deer (Cervus nippon) were observed in ground sections with a polarized light microscope, and their periodicity was examined by the use of a chronological labeling method with fluorochromes. Enamel increments occurred at a mean interval of 10.6 (SD=1.5) microm, and mean spacing of dentin increments was 17.3 (SD=1.8) microm. Fluorochromic marking revealed that incremental lines form each day in enamel and almost every second day in dentin. The fluorescence-labeled lines suggest that enamel formation of the first molar is complete by the age of 5 months. Due to its longer interval of incremental lines and longer term of formation, we conclude that dentin is more suitable than enamel for day-age estimation in sika deer. Experimental confirmation of incremental growth periodicity in various species can improve the reliability of use of tooth increments for age estimation and life history reconstruction. 相似文献
20.