担当区分：筆頭著者   記述言語：英語  

担当区分：筆頭著者  

記述言語：日本語   出版者・発行元：Frontiers in Marine Science  

The light characteristics of an ecosystem drive evolutionary adaptations in visual traits, enhancing the diversity and abundance of species living there. The visual systems of crustaceans are highly diverse and often correspond to the optical properties of their preferred environments. Although habitat depth is known to greatly influence visual specialization in marine crustaceans, it remains unclear whether depth drives visual adaptions in nocturnal species. Slipper lobsters (Scyllaridae) are nocturnal benthic marine crustaceans distributed throughout a wide range of depths. In order to understand the visual adaptive capabilities of slipper lobsters inhabiting different depths, we characterized the eye structures of a shallow-water species (Parribacus japonicas), an intermediate-depth species (Scyllarides squammosus) and a deep-water species (Ibacus novemdentatus). Moreover, we measured by electroretinogram (ERG) the spectral sensitivities and temporal resolutions for each species using the following light stimuli: UV (λmax 386 nm), blue (λmax 462 nm), green (λmax 518 nm), yellow (λmax 590 nm), and red (λmax 632 nm). Our histological experiments show that all three species possess a typical superposition compound eye with square facets, and their ERG measurements revealed a single sensitivity peak for each species. Notably, peak spectral sensitivity corresponded to habitat depth, with the estimated peak for I. novemdentatus (493.0 ± 9.8 nm) being similar to that of S. squammosus (517.4 ± 2.1 nm), but lower than that of P. japonicus (537.5 ± 9.9 nm). Additionally, the absolute sensitivities at respective peak wavelengths for I. novemdentatus and P. japonicus were higher than that of S. squammosus. No differences were observed among the three species for maximum critical flicker fusion frequency (CFFmax) across light stimuli. However, P. japonicus had lower CFFmax values than the other two species. These data suggest that all three nocturnal slipper lobsters are likely monochromatic and well adapted to dim light environments. Significantly, the deep-water slipper lobster displayed higher spectral sensitivities at shorter wavelengths than the shallow water species, but temporal resolution was not compromised.

DOI： 10.3389/fmars.2022.807347

Scopus

記述言語：日本語   出版者・発行元：Biochimie  

Neurogenesis is an important process for the formation of the central nervous system during ontogenesis. Mammalian sialidases are involved in neurogenesis through desialylation of sialo-glycoconjugates. However, the significance of fish sialidases, unlike that of mammals, in neurogenesis has not been investigated. The present study focuses on Nile tilapia (Oreochromis niloticus) because of its unique profiles of sialidases related to enzymatic properties, subcellular localization, and tissue-specific gene expression. First, the fish were cultured under aphotic condition, which is known to cause the delayed development of the retina and brain in various fish. Next, we investigate the effect of aphotic condition on the levels of tilapia sialidases. Our results revealed that the tilapia showed a decrease in the number of ganglion cell in the retina. The expression level of neu4 mRNA is up-regulated in the eyes from tilapia reared in Dark accompanied by the increase of retinal differentiation markers. These results indicated that tilapia Neu4 is involved in retinal development in Nile tilapia. Furthermore, we tried to clarify the function of tilapia Neu4 in the neuronal cells using two neuroblast cell lines (SH-SY5Y and Neuro2a cell lines). Tilapia Neu4 decreased sialic acid level of both nuclear glycoproteins as well as glycolipids. Moreover, tilapia Neu4 accelerated neurite formation in both two neural cell lines and, increased the acetylcholinesterase activity, but it did not affect cell proliferation. Collectively, these results suggest that Neu4 accelerates neurite differentiation during ontogenesis in tilapia.

DOI： 10.1016/j.biochi.2021.03.008

Scopus

PubMed

記述言語：日本語   出版者・発行元：Aquaculture  

Kawakawa tuna (Euthynnus affinis) is a novel target species for aquaculture in Japan and currently there is very limited knowledge on its early ontogenetic development in captivity. The ontogeny of E. affinis larvae from hatching to 20 days after hatching (DAH) was illustrated in the present study through an integrated approach of histology, biochemistry and molecular approaches. Larvae were fed enriched L-type rotifer Brachionus plicatilis species complex from 2 to 10 DAH, followed by enriched Artemia nauplii. Target digestive enzymes; trypsin, pepsin, lipase and amylase were assessed in order to evaluate nutritional condition. The larvae began exogenous feeding from 2 DAH, coinciding with the opening of the oral capacity and anus. The yolk sac was rapidly consumed and completely resorbed at 3 DAH, while the oil globule disappeared by 5 DAH. Enzymatic activity and expression of the target enzymes were detectable at hatching, except pepsin. With the development of the gastric glands, pepsin activity was then detected at 10 DAH, which was followed by rapid increase in pepsin activity at 15 DAH. The larvae showed rapid growth, however, high mortality also occurred at 6–10 DAH which has been highlighted as a critical stage in the larviculture of E. affinis. From 15 to 20 DAH, the histological structures of the digestive tract were completely segmented with the digestive tract resembling that of its juvenile stages. The activity of trypsin, pepsin, and lipase tended to increase sharply, while amylase dramatically dropped, possibly indicating a change in dietary preference. Findings from the present study provides a preliminary insight into the early development of the digestive system and associated digestive enzymes of E. affinis larvae and establishes an initial step towards the rearing and feeding protocol optimization of this novel target species.

DOI： 10.1016/j.aquaculture.2020.735935

Scopus

担当区分：筆頭著者