Histological evidence of lunar-synchronized ovarian development and spawning in the spiny rabbitfish Siganus spinus (Linnaeus) around the Ryukyus

ABSTRACT: This study clarifies the annual reproductive cycle and the lunar-synchronized spawning of the spiny rabbitfish ( Siganus spinus ) that inhabit the Okinawan waters. Annual and weekly changes in the gonadosomatic index (GSI) and the histological features of the ovaries were checked. Gonadosomatic index was high during the months of May to July, and yolk-laden oocytes were observed in the ovaries from March to July. Some of the ovaries collected during June and July contained oocytes at maturation stage or ovulatory follicles. These results suggest that the spiny rabbitfish undergo active vitellogenesis and spawning from May to July. During the reproductive season (May to July), collection of fish according to the lunar phase revealed that a high GSI occurred around the time of the new moon. Cyclic oocyte development with peaks around the time of the same moon phase was also observed, suggesting that, in Okinawan waters, this species is a lunar-synchronized spawner and spawns three times.     

Microhabitat use of wood mice ranging from a reserved belt with evergreen broad-leaved trees to a coniferous plantation

Wood mice Apodemus speciosus and Apodemus argenteus are potentially important seed dispersers and predators of Quercus and Castanopsis in Japan. We investigated the existence of two species of wood mice in warm-temperate forests ranging from a reserved belt of evergreen broad-leaved trees to a coniferous plantation, and analyzed the relationship between wood mouse occurrence and environmental factors to confirm their microhabitat use. We used two-way analysis of variance to analyze differences in the captured number of each wood mouse species in two trapping seasons as well as two stand types to confirm the interaction between the stand type and trapping season. Apodemus speciosus were often captured in the reserved belt, while captures of A. argenteus were independent of season and stand types. It is reasonable to conclude from the results of the trends in occurrence that the two species of wood mice showed different uses of the microhabitat. The result of linear discriminant analysis made it clear that the distance from the reserved belt had much to do with the difference in microhabitat use between the two species in the fruiting season of Quercus and Castanopsis. On average, A. speciosus moved 19.9 m during nonfruiting and 61.3 m during fruiting, while A. argenteus moved 8.1 m during nonfruiting, and 29.0 m during fruiting from analysis of the recapture position. The results indicate that both species of mice move around during the fruiting season more than in the nonfruiting season.     

In-crisis delivery rate: a novel measure of success in communal water management

Of the plethora of studies that discuss requirements for successful irrigation management, few pay close attention to what actually happens when the supply of water becomes extremely low. Such an oversight in the literature is unfortunate, because this is precisely when management matters. To understand what separates success from failure in irrigation management at times of critical water shortages, the authors conducted emergency fieldwork in February 2010 along four major irrigation channels in a drought-stricken rice-growing area within the Chinese province of Yunnan. Separately, satellite images of the four villages dated February 2009 and February 2010 were jointly analysed to produce a novel indicator for a village’s success in water management. Called the in-crisis delivery rate, this indicator compares water delivery between normal and drought years and directly evaluates performance in water management during crisis periods. The results led to an unexpected discovery that, contrary to common expectations, the only village of the present study that deployed a traditional earthen water channel secured substantially more water throughout the drought period than those with concrete-lined channels. It is hypothesised that the labour intensive, rather than capital intensive, nature of repair work of the earthen channel enabled flexible operations, and hence had the comparative advantage under a skilled management team. This result confirms the importance of daily maintenance work, which tends to occur less often after modernisation of water paths.     

Soil seed banks in a mature Hinoki (<Emphasis Type="Italic">Chamaecyparis obtusa</Emphasis> Endl.) plantation and initial process of secondary succession after clearcutting in southwestern Japan

To profile secondary succession after clearcutting a conifer plantation, we examined the composition of the soil seed bank and the process of vegetation recovery after clearcutting a mature Hinoki (Chamaecyparis obtusa) plantation in southwest Japan. We set up two study plots and collected 25 and 26 soil samples (each 20 cm × 30 cm × 5 cm depth), respectively, in April 1999, before clearcutting. Using the seedling emergence method, we detected 500–839 buried viable seeds m⁻² in 42–44 species. Soil seed banks in both plots contained typical pioneer species but few late-successional species. After clearfelling the plantation in June 1999, we censused seedling establishment for 4 years and the composition of the vegetation for 6 years. More than half of the seedlings emerged in the second year, suggesting that the timing of clearcutting is possibly critical to seedling establishment. Nineteen plant species disappeared after clearcutting, 40 species were retained and 43 species newly emerged after clearcutting. Most of the newly emerged species were pioneer species which originated in the soil seed bank. Seven of the pioneer species, as typified by Rubus crataegifolius, showed clonal growth from the third year after clearcutting. Japanese serow browsed the seedlings of major pioneer species, possibly affecting the process of secondary succession. Late-successional species such as Abies firma declined in coverage or disappeared after clearcutting. Our results suggest that the soil seed bank makes a major contribution to vegetation recovery after clearcutting, but possibly not to restoration of the late-successional species.     

Lignosulfonate/APP IFR and its flame retardancy in lignosulfonate-based rigid polyurethane foams

Lignin containing substantial aromatic rings and high content of carbon has been employed as carbonizing agent to investigate the flame retardancy in the lignin/ammonium polyphosphate (APP) intumescent flame retardant (IFR) system. In addition, owing to the abundant phenolic and aliphatic hydroxyl groups, lignosulfonate, which is considered as a renewable aromatic macropolyols, substituted part of diethylene glycol (DEG) and copolymerized with isocyanate to produce lignosulfonate-based rigid polyurethane (LRPU) foams. Thermal stability was characterized by thermogravimetric analysis (TGA), and flame retardancy was investigated by limiting oxygen index (LOI) and cone calorimetry testing (CCT). Lignosulfonate increases thermal stability of LRPU foams and LRPU containing 15 wt% of lignosulfonate based on DEG (L₁₅RPU) give rise to the best thermal stability. When 15% of lignosulfonate incorporated in the LRPU, reduced the heat release rate (HRR) and total heat release (THR) value 21 kW/m² and 13 MJ/m², respectively, and postponed 96 s time-to-peak carbon monoxide production than that of pure DEG rigid polyurethane (RPU) foam, the LOI values increased progressively with lignosulfonate content increasing. These results showed that lignosulfonate polyol may substitute polyol to produce lignosulfonate-based RPU foam and the presence of lignosulfonate could improve the flame retardancy. The mass loss gradually decreases with increasing APP addition, and the highest char yield was obtained from LRPU5 foam which at the lignosulfonate-to-APP ratio is 1:5. At the lignosulfonate-to-APP ratio of 1:5, the LOI value increased over 30%, and the HRR value reduced and the time-to-peak HRR postponed significantly. In addition, LRPU5 foams give rise to the lowest effect heat combustion (EHC) value, less smoke, and carbon monoxide (CO) production. Lignosulfonate acts as carbonizing agent in the lignosulfonate/APP IFR system, and the best fire retardancy is obtained at 1:5 of lignosulfonate-to–APP ratio.     

Origin of plasma insulin-like growth factor-I (IGF-I) during estrus in goats

The objective of this study was to clarify the origin of the increase in plasma insulin-like growth factor-I (IGF-I) during estrus in goats. Focusing on the uterus, the effect of estradiol-17 beta (E2) on the secretion of IGF-I was examined using ovariectomized and hysterectomized animals. A single 5 microg/kg BW of E2 was injected intramuscularly into ovariectomized and hysterectomized goats for 3 consecutive days, and plasma IGF-I concentrations in the two groups were compared. The concentrations of IGF-I rose after the treatments in both groups. The concentrations were significantly higher from 3 to 8 days after the treatment than before the treatment in ovariectomized goats (P<0.05), and from 1 to 3 days after the treatment than before in hysterectomized goats (P<0.05). Thus higher concentrations of plasma IGF-I tended to last longer in ovariectomized than hysterectomized goats. The area under the IGF-I response curve for the 8-day period after the first injection of E2 tended to be greater in ovariectomized than in hysterectomized goats. The results show that E2 increases plasma IGF-I concentrations in goats, and suggest that E2-stimulated IGF-I in plasma may originate mainly from the uterus.     

Topography of ganglion cells in the retina of the duck (Anas platyrhynchos var. domesticus)

The purpose of this study was to define ganglion cell density, size and topography in the retina of the mallard duck. After killing adult mallard ducks (Anas platyrhynchos var. domesticus), their eyes were removed using pentobarbital (30 mg/kg). The retinas were isolated, whole mount specimens were prepared by staining with 0.1% cresyl violet and then fixing the tissues for study. The retinal ganglion cells were counted, mapped and measured. The mean total number of ganglion cells was estimated at approximately 1.7 × 10⁶ and the retinal area centralis had the highest ganglion cell density with 15 820 cells/mm². The number of ganglion cell bodies was highest in the temporal area, followed by the nasal, dorsal and ventral areas. Ganglion cell size ranged from 56 to 406 μm². A population of small ganglion cells persisted into the central area just above the optic disc and the largest soma area was in the ventral zone of the retina. This localization of ganglion cells suggests that the quality of vision is not equal in all the areas of the duck retina and the central part may have the highest vision quality as a function of the retinal ganglion cells.