Spatial distribution analysis of the North Pacific spiny dogfish,Squalus suckleyi,in the North Pacific using generalized additive models

The North Pacific spiny dogfish (SPD), Squalus suckleyi, is a commercially exploited shark species that plays an important role in the ecosystem. To elucidate the distribution of the SPD in the North Pacific and to evaluate the effects of sea surface temperature (SST) and prey availability on its distribution, we estimated the probability of SPD presence using a generalized additive model with a binomial error distribution from SPD presence/absence data on 14,824 operations in fishery‐independent gillnet surveys between 1972 and 2011. The habitat model was structured in the east and west to reflect differences in the North Pacific oceanic environments. In the east, a higher probability of SPD presence was identified along the coast from the eastern Gulf of Alaska to Queen Charlotte Sound. In the west, it was identified around northern Japan. The estimated distribution was continuous between the two areas, whereas the probability of SPD presence was relatively low. Although the probability of SPD presence was higher at SSTs between 6°C and 12°C, the SST at the peak probability of SPD presence differed between the west and east. The prey species, Japanese sardine, Sardinops melanostictus, and walleye pollock, Gadus chalcogrammus, in the west and boreal clubhook squid, Onychoteuthis borealijaponica, in the east significantly affected the probability of SPD presence, which was higher if the prey species co‐existed with SPD. Therefore, SPD might adapt their distribution to that of available prey species. SPD stock assessment and management in these two important areas are required for its sustainable utilization.     

Evaluation of environmental impact of the raised-bed-dike (Rong Chin) system along the Tha Chin river in Suphan Buri-Nakhon Pathom Provinces,Thailand

Vegetable cultivation on an embankment surrounded by water (raised-bed-dike system, Thai name rong chin) along the Tha Chin (Suphan Buri) river in the Suphan Buri and Nakhon Pathom Provinces was surveyed. The system was introduced by Chinese immigrants to produce vegetables in the river delta. The rong chin system in this area produced mainly Chinese kale, chili, bitter gourd, yard-long bean, taro, and sweet potato, while fruit trees and flowers were seldom cultivated, because of the flooding of the river in the rainy season. The amounts of nitrogen and phosphorus applied into field soils as fertilizers were far higher than those recovered in the harvested vegetables, indicating that only a limited portion of the nutrients was taken up by the crops and that part of the nutrients remained in the soils and in the dike water. Periodical flooding promoted leaching of the accumulated nutrients in the fields. Analyses of the soils and river waters revealed that phosphorus had started to accumulate in the environment, whereas only a small amount of nitrogen was detected in the river, canal, and dike waters, presumably because of the active uptake of nitrogen by biomass and denitrification.     

Effects of spawning temperature on the reproductive characteristics of walleye pollock Gadus chalcogrammus

Fisheries Science - Reproductive characteristics under different water temperature regimes were examined in hatchery-reared walleye pollock Gadus chalcogrammus. The fish had been cultured for...     

Trophic sources and linkages to support mesozooplankton community in the Kuroshio of the East China Sea

Many migratory fishes reproduce and recruit around the Kuroshio, and their survival of early life stages is supported by mesozooplankton. Mesozooplankton standing stocks and productivity equivalent to those on the continental shelf have been found in the Kuroshio; however, there is limited information on trophic sources and linkages to support the mesozooplankton community. Here, we evaluate mesozooplankton feeding on protists and their trophodynamics importance by removal bottle experiments in the Kuroshio of the East China (ECS‐Kuroshio). Pico‐ and nano‐autotrophs dominated chlorophyll a concentrations throughout the study sites across the continental shelf, within the Kuroshio path and in adjacent waters. Calanoid and poecilostomatoid copepods comprised more than 85% of mesozooplankton biomass. Significant mesozooplankton ingestion rates were found for nano‐autotrophs based on size‐fractionated chlorophyll; for haptophytes, chrysophytes, chlorophytes, and diatoms from pigment‐based phytoplankton analysis; and for naked ciliates in the microzooplankton. Based on the estimates of individual carbon budgets, nano‐autotrophs and naked ciliates ingested by mesozooplankton composed 39% of their food requirements, suggesting other available prey like nano‐heterotrophs. These results imply that mesozooplankton ingestion in the ECS‐Kuroshio has great impacts on protozoan and phytoplankton communities and their major trophic pathways are from nano‐sized auto‐ and heterotrophs and ciliates to copepods.     

Time-course changes in 5-fluorouracil-induced neural progenitor cell damages in the developing rat brain

5-Fluorouracil (5-Fu) is a DNA-damaging agent and teratogenic in rodents. This study aimed to investigate its influence on neural progenitor cells (NPCs) in the developing fetal rat brain. Dams were intraperitoneally injected with 5-Fu (50 mg/kg b.w.) on gestation day 13 and its effects on fetal NPCs were observed from 3 to 72 hours after treatment (HAT), via periodic examination at six intervals. In NPCs of the fetal brain, the p53-labeling index (LI%) was markedly elevated at 3 HAT. Pyknosis and cleaved caspase-3-LI% also increased at 3 HAT, reaching peak values at 9 and 12 HAT. These parallel changes suggested the induction of apoptosis through a p53-mediated pathway. Pyknotic NPCs were distributed across the ventricular zone (VZ) of the telencephalic wall until 12 HAT, and became localized in the medial and dorsal layers at 12 and 48 HAT. Significant decreases in the numbers of mitotic NPCs and BrdU-LI% were noted from 3 HAT and 24 HAT, respectively. BrdU-positive NPCs were located in the ventral and middle layer at 24 and 48 HAT. p21-positive cells were detected at 12 and 24 HAT. The present results demonstrated that p53-mediated apoptosis was induced in all phases of the cell cycle of the NPCs in the early stage after 5-FU treatment. Furthermore, apoptosis of NPCs and suppression of cell proliferative activity are the events that take place in parallel leading to prominent reduction in the width of the telencephalic wall.     

Effects of bisphenol A (BPA) on placentation and survival of the neonates in mice

The effects of bisphenol A (BPA) on placentation have not been fully determined. The aim of this study was to clarify the structural changes of the placenta, abortion rate, and survival of neonates after BPA administration in mice. BPA (10 mg/kg/day) was administered to pregnant mice (BPA mice) subcutaneously from the first day of pregnancy (Day 0) to Day 7 (8 days total). The number of embryos and weights of whole uteri were measured on Days 10 and 12. Morphological changes in the placentae were examined by light microscopy on the corresponding days of pregnancy. The number of neonates was also counted. Survival rates were periodically calculated for neonates from the first day after parturition (P-Day 0) to P-Day 56. The number of embryos and weight of the uterus on Days 10 and 12 were significantly decreased by BPA injection. No notable differences were recognized between the left and right uteri. The proportion of the labyrinthine zone per whole placenta in the BPA mice became lower than that in the controls, and that of the metrial gland was higher in the BPA mice. The intervillous spaces of the placenta were narrower in the BPA mice. Degenerative changes were found in the trophoblastic giant cells and spongiotrophoblast layers of the BPA mice. The number of BPA mouse neonates was drastically decreased within 3 days after birth, and no mice survived after P-Day 56. The results suggest that BPA not only disrupts placental functions and leads to abortion through chronic stimulation of gene expression by binding to DNA but that it also affects the mortality of neonates through indirect exposure of embryos.     

Embryo and fetal position during pregnancy by ultrasonographic examinations in bottlenose dolphin (Tursiops truncatus)

From 2012 to 2017, serial ultrasonographic evaluation of 5 healthy bottlenose dolphins, Tursiops truncatus, were performed over the course of 6 pregnancies in Enoshima Aquarium. A total of 98 ultrasonographic examinations were included in the study. In three out of six cases, two embryos were observed between umbilicus and genital slit, and side of umbilicus in the dam’s body. All embryos were located in right below the peritoneum and observed from 308 to 325 days pre-partum. These days were corresponding to from 58 to 61 days after copulation respectively. The diameter of the embryo sac was approximately 4 cm. In three cases, the fetal head was located in the dam’s left lateral between umbilicus and genital slit from approximately 90 days pre-partum to the parturition. A snout of fetus is at the top of the uterine horn, and the tail lies close to the cervix. All six calves were fluke-first births (breech presentation). It was conjectured that the contraction of the dam’s uterus during parturition forced the fetus to invert, and the fetal tail fluke was expelled from the dam’s body. In three cases, judging from orientation of fetal tail fluke faced towards left side of the dam, a fetal position might be RSL (Right Sacrum-Lateral) within the birth canal. In the other three cases, the left and right positions of the fetus and the dam’s body are reversed during pregnancy and parturition.     

Phosphorus limitation in microorganisms leads to high phosphomonoesterase activity in acid forest soils

We addressed the mechanistic basis for a negative correlation between soil pH and phosphomonoesterase activity, often found in various soils. Also in the present study, a significant negative correlation was observed between soil pH and phosphomonoesterase activity measured at pH 6.5 in Japanese acidic forest soils (3 Inceptisols, 3 non-allophanic Andisols, and 2 allophanic Andisols). A hypothesis that higher activity of phosphomonoesterase in acid forest soils results from increased synthesis of phosphomonoesterase by microorganisms in response to P limitation was tested. Soils with lower pH showed a lower optimum pH for phosphomonoesterase activity and greater activity at the optimum pH than other soils. To assess nutrient limitations of the soil microbial community, the effects of addition of C, N, or P on phosphomonoesterase and dehydrogenase activities, which is an intracellular enzyme and the activity of which reflects overall microbial activity, were examined in the soil samples. Addition of P increased dehydrogenase activity in some forest soils. Also, microorganisms in some soils were co-limited by C, N, and P. Response ratios (RR) of phosphomonoesterase and dehydrogenase activities in P-amended soil to their activity in non-amended soil were used to evaluate the response of soil microorganisms to P limitation. The ratio of RR-dehydrogenase to RR-phosphomonoesterase was strongly correlated with phosphomonoesterase activity at the optimum pH (P < 0.01). The results indicate that P limitation accounts for higher phosphomonoesterase activity in the more acid forest soils.     

Nippon Dojohiryogaku Zasshi (Journal of the Science of Soil and Manure,Japan)

Some allophanic soils in Japan, developed from deposits of volcanic ashes have aggregates, the sizes of which are mostly those of silt and sand, and which are very stable against the ordinary soil dispersion treatment such as decomposition of organic matter with hydrogen peroxide and addition of deflocculants to the suspension, but can be broken to smaller particles by mechanical forces. Oba and Kono (1, 2) reported that there were aggregates stable even against deferration treatment in the soils, especially plenty in ones developed from basic volcanic ashes, and these aggregates could be broken up into clay of allophane mainly by a sonic-wave vibration technique. Miyazawa (3) recognized that the aggregates were only found in Andosols developed under warm-temperate climates, being concentrated in B horizon, but not so much in A horizon and few in gleyey subhorizon, and assumed that they were formed under a specific weathering like seasonal wetting and drying. Yasuo et al. recognized a high correlation between the degree of aggregation and free iron oxide content of the soils in Kanto Plain and suggested that sesquioxide and structure of allophane might associate with the aggregate fonnation. On the other hand, airdrying of volcanic ash soils sometimes reduces their dispersibilities through irreversible formation of aggregates. Kishita (5) found that this effect of drying was remarkable at subsoiLs, and similar results were obtained by TAPA et al. (6). The poor dispersibility and the irreversible change by drying are known also about volcanic ash soils of New Zealand (7, 8), and Latin America (10, 11), Hawaii (9).