Eri Iwata

Prof. Eri Iwata

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Research Focus & Metrics

Academic Career Length

24Years (2003-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 January 2021 in Journal of Equine Science
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Journal Article
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TOTetsushi Ono
Tetsushi Ono
YIYoichi Inoue
Yoichi Inoue
KHKeiichi Hisaeda
Keiichi Hisaeda
YYYutaka Yamada
Yutaka Yamada
AHAkihisa Hata
Akihisa Hata
EIEri Iwata
Eri Iwata
This study aimed to evaluate the influence of seasons and sex on body size and hematological and biochemistry parameters of Noma horses, a native Japanese breed. Body size was larger in winter than in summer. Laboratory testing variables, including erythrocytic parameters and urea nitrogen, total cholesterol, and creatinine kinase levels, were higher in winter, while the eosinophil count was higher in summer. These seasonal differences may be related to increased energy consumption of horses due to heat stress. The higher eosinophil counts may have been related to the dermatitis observed in summer. Stallions tended to have smaller bodies compared with mares. Future studies are necessary to investigate the effect of stress in seasonal and sex-based groups.

1 January 2003 in Journal of Veterinary Medical Science
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Journal Article
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EIEri Iwata
Eri Iwata
TKTakefumi Kikusui
Takefumi Kikusui
YTYukari Takeuchi
Yukari Takeuchi
YMYuji Mori
Yuji Mori
A major constituent of the characteristic "goaty odor" 4-ethyl octanoic acid (4EOA) was previously shown to have no primer pheromone activity. This was also confirmed by our own bioassay system utilizing the recording technique of neural activity of the hypothalamic gonadotropin-releasing hormone pulse generator in goats. However, when the synthetic 4EOA solution was kept at room temperature for several months, primer pheromone activity appeared in the same solution. Headspace gas chromatography/mass spectrometry analysis revealed that there were several newly formed substances in addition to 4EOA samples with primer pheromone activity. These results suggest that 4EOA derived substance(s) but not 4EOA itself is(are) primer pheromone in goats.

10 May 2021 in BMC Zoology
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EIEri Iwata
Eri Iwata
KMKyouhei Masamoto
Kyouhei Masamoto
HKHiroyuki Kuga
Hiroyuki Kuga
MOMiho Ogino
Miho Ogino
Background: Teleost fish are known to respond to environmental manipulation, which makes them an ideal model animal for testing relationships between the environment and behavior. The Siamese fighting fish, Betta splendens, is a solitary, highly territorial fish that displays fierce stereotyped aggressive behavior toward conspecifics or members of other species. Adult fish, especially males, are generally housed in isolation in captivity. Here we report evidence that an enriched rearing environment can decrease the level of aggression in bettas and enable adults to be housed in groups. Results: B. splendens individuals were hatched in our laboratory and raised in groups in an enriched environment. At the juvenile or subadult stage, some individuals were relocated to a poor environment and kept in isolation. To evaluate aggression, a mirror-image test was conducted at the juvenile, subadult, and adult stages for each fish, and body parameters as well as plasma concentrations of 11-ketotestosterone, estradiol, and cortisol were evaluated. Male and female adult bettas raised in a group showed lower levels of aggression than other adult fish. The magnitude of threatening behavior was greater in adult bettas isolated as subadults, whereas the magnitude of fighting behavior was grater in adult bettas isolated as juveniles. The influence of rearing conditions on behavior was greater in females than in males. Plasma cortisol concentrations of adult bettas isolated as subadults after the mirror-image test were higher than those in other experimental groups. Adult males isolated as subadults had significantly higher plasma concentrations of 11-ketotestosterone than males raised in a group and isolated as juveniles. Females isolated as subadults had a higher gonadosomatic index than females raised in a group and females isolated as juveniles. Conclusions: These results indicate that bettas can be kept in a group under enriched environments and that the timing of isolation influences the aggression and sexual maturity of bettas. Female and male bettas responded differently to environmental manipulation. Judging from their level of sexual maturity, bettas isolated as subadults show proper development.

23 March 2020 in Fisheries Science
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Journal Article
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EIEri Iwata
Eri Iwata
NSNozomi Suzuki
Nozomi Suzuki

25 May 2020 in Journal of Fisheries
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Journal Article
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EIEri Iwata
Eri Iwata
TYTasuku Yoshida
Tasuku Yoshida
TATetsuya Abe
Tetsuya Abe
KTKou Takahara
Kou Takahara
KMKoji Masuda
Koji Masuda
Anemonefishes are some of the most popular marine ornamental fishes. Due to the adverse impacts of commercial fishing on the wild populations of anemonefishes, a more suitable and efficient captive breeding programme must be promoted. In the wild, anemonefishes are protandrous sex-changing fish, but when two immature individuals with ambisexual gonads are raised together in captivity, the two differentiate directly into a male and a female, to form a breeding pair. However, not all the formed pairs spawn, explaining the great care required in captive breeding. This behaviour appears to be counter-adaptative, as anemonefish social groups form randomly in the wild, and such phenomenon would disturb their breeding success. This study evaluated the behavioural and physiological differences between breeding and nonbreeding pairs of false clown anemonefish Amphiprion ocellaris under captive conditions. Behavioural observations revealed that nonbreeding females monopolized the shelter provided, whereas breeding females allowed breeding males to use the shelter and the pair frequently stayed together in the shelter. Both nonbreeding and breeding females possessed mature ovarian tissue and similar level of plasma estradiol concentrations, but nonbreeding males had a smaller amount of testicular tissue and lower plasma 11-ketotestosterone levels compared to breeding males.

25 August 2021 in Animals
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KSKaori Saeki
Kaori Saeki
KKKenji Kutara
Kenji Kutara
EIEri Iwata
Eri Iwata
MMMasahiro Miyabe
Masahiro Miyabe
YSYuki SHIMIZU
Yuki SHIMIZU
TATaketoshi Asanuma
Taketoshi Asanuma
In humans, radiation induces dilation of capillaries and inflammatory reactions to raise skin temperature. Thermography is used to detect abnormalities after radiation therapy (RT). However, in veterinary nursing, objective evaluation of the condition of dogs after RT using thermography has not been reported. We investigated the nasal irradiation temperature, behavioral changes, and post-irradiation pain scores in a dog receiving RT for intranasal tumors. The temperature of the nasal planum gradually increased after irradiation, reaching a significantly higher value at 120–240 min. The highest temperature was 42.3 °C and the average temperature increased by 4.4 °C. Behavioral analysis pre- and post-RT did not vary significantly. Post-RT pain levels evaluated by the pain scale ranged from 0 to 1 throughout. No veterinary treatment was provided. In humans, increased skin temperature after radiation causes psychological stress, i.e., pain and discomfort, but no such behavioral changes were observed in this case. Given individual differences in stress-related behaviors, such as pain and discomfort, assessing a dog’s painfulness using only subjective methods, such as appearance and behavioral evaluation, is limited. We used thermography to assess changes in conditions not detectable by routine monitoring alone. This method is non-invasive, objective, and indispensable for providing appropriate care.