Eight species were recorded for the first time in the Shimoyama River system. The survey was conducted between September and October 2016 in the lower reaches of the Shimoyama River and in one of its ...tributaries, the Yokote stream. Five tropical/subtropical species (Lutjanus argentimaculatus, Eleotris melanosoma, E. fusca, Redigobius bikolanus, and Scatophagus argus) were collected in its lower reaches of the Shimoyama River. Rhinogobius mizunoi and E. oxycephala, listed as near threatened (NT) and endangered (EN) species in The Red Data Species in Kanagawa Prefecture 2006, respectively, were also obtained in the Shimoyama River system. In addition, the photographic record of E.acanthopoma from the lower reaches of the Shimoyama River in September 2013 was also described.
Disarticulated fossil lateral arm plates of brittle stars from the Middle Pleistocene Miyata Formation, Miura, Kanagawa Prefecture, eastern Japan, are described. They are assigned to Stegophiura ...sladeni on the basis of their microstructural morphology. This is the first description based on disarticulated fossil lateral arm plates of brittle stars from Japan and should encourage further exploration of the Japanese ophiuroid microfossil record.
Disarticulated fossil euryalid ophiuroid vertebrae from the Middle Pleistocene Miyata Formation, Miura, Kanagawa Prefecture, eastern Japan, are described. The vertebrae are assigned to the family ...Gorgonocephalidae on the basis of arm branching and the presence of an open oral groove along the entire arm. This is the first record of fossil euryalids from the Indo-Pacific region.
Display omitted
•We investigated the driving mechanism of polymer nanofiber actuators.•A multilateral study revealed the mechanism as thermal expansion by joule heating.•We compared the driving of ...nanofibers made of different polymers.•The effects of temperature change and diameter on driving were investigated.•Compositing a nanofiber with carbon nanotubes improved the driving displacement.
An actuator generally requires low-voltage actuation, high displacement, and high responsiveness. However, no polymer actuator meets all these requirements. Because nanofibers have a diameter of 1 μm or less and a large specific surface area, physicochemical energy change is expected to affect the driving process. We expected polymer nanofibers to meet these requirements owing to the shape effect of nanofibers. Previously, we successfully drove a polyurethane/FeCl3 composite nanofiber as an actuator by applying voltage. FeCl3 was used as a conductive filler. However, the mechanism of driving was not revealed. In this paper, we report the driving behavior of a nanofiber actuator. We considered thermal expansion by the joule heating of nanofibers as the mechanism of actuation in polymer nanofiber. For investigating the effect of joule heating on a nanofiber, we employed a multilateral approach. First, we compared the driving of nanofibers made of two types of polymers with different coefficients of thermal expansion. Next, we investigated the effect of temperature change and the nanofiber diameter on driving. The results suggest that the nanofiber actuator was driven by thermal expansion with a temperature change of 33 °C at an applied voltage of 50 V. Finally, we improved the nanofiber heat transfer by fabricating a poly (ethylene co vinyl acetate)/carbon nanotube composite nanofiber. We successfully improved driving displacement by introducing carbon nanotubes into the nanofibers.
Otoliths are calcified structures that are located in the inner ears of fish, as in most vertebrates, that are responsible primarily for the perception of gravity, balance, and movement and ...secondarily of sound detection. Microstructural and chemical analyses of the inner otolith growth layers, called increments, constitute powerful tools for estimating fish age and elucidate many life history and demographic traits of fish populations. Otolith analyses often require the production of a thin cross section that includes the otolith core and all increments formed from birth (core) until the moment of collection (otolith edge) in the same plane of view. Here we report on the suitability of single‐component UV‐cured resins to obtain otolith cross sections for both microstructural examination and chemical analysis by electron probe microanalysis. Embedding blocks that were produced with UV‐cured resins had transparency that was comparable to that of the commonly used two‐component epoxy resins and provided similar adhesion and mechanical support for the otoliths during grinding or cutting with a precision cutter and analysis. In addition, UV‐cured resins offer on‐demand, extremely rapid (minute‐order) hardening that makes them useful in classroom situations in which time for otolith embedding becomes a constraint.
The amount of interspecific and ontogenetic variation in otolith shape among clupeid fishes from Japan was investigated to create a key to identify otoliths of these species found in the stomach ...contents of piscivorous predators, fossiliferous beds, and archaeological sites. The interspecific comparison with 12 species (
Clupea pallasii
,
Etrumeus micropus
,
Herklotsichthys quadrimaculatus
,
Ilisha elongata
,
Konosirus punctatus
,
Nematalosa come
,
Nematalosa japonica
,
Sardinella aurita
,
Sardinella melanura
,
Sardinella zunasi
,
Sardinops melanostictus
, and
Spratelloides gracilis
) revealed morphological variation in otolith shape, OL:OH and AL:RL ratios, rostrum, marginal structures, and features of the crista superior. Intraspecific changes were analyzed in two species (
E. micropus
and
S. melanostictus
), revealing ontogenetic changes in OL:OH ratio and consequently otolith shape as well as changes in marginal features. Overall, this study shows that the key morphological features can be used as diagnostic features for identification of clupeid otoliths.
The Silond catfish
Silonia silondia
, locally known as Nga Myin Yinn, is a commercially important fish in Myanmar; however, fundamental knowledge of its population structure is insufficient. ...Specimens caught in different regions of the Ayeyarwady River, the basin of which is the country’s largest, from 2017 to 2019 were used to sequence two mitochondrial (mt)DNA genes, cytochrome
b
and ATP
ase
6/8, for investigating population differentiation. Phylogenetic trees and pairwise fixation index values revealed that the populations of
S. silondia
differed between Myanmar and Bangladesh/India, whereas the populations and mtDNA haplotypes were not significantly different among four regions of the Ayeyarwady River (Ayeyarwady, Yangon, Magway, and Mandalay). In addition, no unique haplotype was observed, given the lack of nucleotide diversity. Thus,
S. silondia
in the Ayeyarwady River can be considered a single population, which is different from those of Bangladesh/India. Our study provides the first content for understanding the genetic diversity of
S. silondia
in the Ayeyarwady River in Myanmar according to molecular analyses. These genetic data will be useful for understanding the genetic diversity of this species in South and Southeast Asia.
