Annual monitoring of growth of red sea bream by multi-stereo-image measurement

Fisheries Science - In aquaculture, periodic measurement of fish body size is required to suitably assess growth progress. The aim of this study is to monitor the growth of free-swimming red sea...     

The effects of distance from coral reefs on seagrass nursery use by 5 emperor fishes at the southern Ryukyu Islands,Japan

Whilst the importance of seagrass beds as nurseries for coral reef fishes has been clearly recognized, the vast majority of early studies on fish nursery habitats emphasized the close proximity of the latter to coral reefs. To determine the potential nursery role of isolated seagrass beds, we investigated the degree to which juvenile emperor fishes (Lethrinidae) utilized seagrass beds in the presence/absence of adjacent coral habitats at Ishigaki Island (southern Japan), such fishes being known to use seagrass beds as nurseries. Seagrass beds in close proximity to coral habitats (distance between the two habitats of 50–200 m) had greater densities of lethrinid juveniles than those without adjacent coral habitats (2.5–4 km) for 3 different sites investigated, although a significant difference was obtained only for 1 site. Juveniles of Lethrinus atkinsoni, L. obsoletus, L. harak, and L. nebulosus were observed in seagrass beds with and without adjacent coral habitats, whereas L. ornatus occurred only in the former. Overall, most lethrinid juveniles utilize seagrass beds irrespective of the presence of adjacent adult coral habitat, suggesting that both types of seagrass beds would contribute to lethrinid adult populations. Therefore, management efforts for lethrinid populations should be applied not only to contiguous coral-seagrass habitat systems but also to isolated habitats.     

Effects of light quality on conidiophore formation of the melon powdery mildew pathogen <Emphasis Type="Italic">Podosphaera xanthii</Emphasis>

The lengths of conidiophores in fungal colonies of the melon powdery mildew pathogen Podosphaera xanthii Pollacci KMP-6 N cultured under greenhouse (natural) conditions differed markedly from those cultured in a growth chamber. We hypothesized that light wavelength was responsible for the differences in conidiophore length. In this study, we examined the effects of light-emitting diode (LED) irradiation (purple, blue, green, orange, and red light) and white light on colony development and conidiophore formation in KMP-6 N using a stereomicroscope and a high-fidelity digital microscope. Colonies on leaves were flat under greenhouse conditions and under red LED light irradiation but were stacked under growth chamber conditions and under purple, blue, green, and orange LED light irradiation. In addition, KMP-6 N formed catenated conidia comprising six conidia per conidiophore under greenhouse conditions and red light but more than seven conidia per conidiophore under growth chamber conditions and purple, blue, green, and orange light. Furthermore, almost none of the conidia on top of the conidiophores grown under blue light were fully constricted. Therefore, these fungi could not scatter their conidia and spread infection. This is the first report of the effects of LED lights on conidiophore formation in the melon powdery mildew fungus P. xanthii. The results provide insight into the mechanisms underlying the responses of conidiophores to light of specific wavelengths and conidial scatter from conidiophores of melon powdery mildew fungi.     

Assessment of environmental nitrogen pollution load potential from sewage treatment water in the Tedori River Alluvial Fan Area, Japan

An evaluation of the nitrogen pollution load potential (NPLP) arising from several sewage treatment systems in the Tedori River Alluvial Fan Area was evaluated by determining the removal percentage of nitrogen as a result of sewage treatment and amounts of nitrogen lost from the different treatment systems. These data were applied to the entire area resulting in an estimated total NPLP of 734 t year⁻¹ (10³ kg year⁻¹), of which 548 t year⁻¹ discharges into the Japan Sea and so does not contribute to the pollution of the environment considered here. The residual 186 t year⁻¹ of the NPLP has a high probability of causing groundwater or downstream pollution, with 58% of the NPLP being contributed from septic tanks not connected to public sewage systems. Rural sewage system accounted for about 18% of the NPLP. Material directly flowing into the middle stream of the Tedori River together with sewage water from small companies and untreated sewage water from local family dwellings made up about 3–12% of the NPLP. To improve water quality due to sewage effluent, it is essential to increase the number of connections to public sewage systems from septic tanks.     

Survival of ovarian somatic cells during sex change in the protogynous wrasse, Halichoeres trimaculatus

The three-spot wrasse (Halichoeres trimaculatus), which inhabits the coral reefs of Okinawa, changes sex from female to male. Sex change in this species is controlled by a social system. Oocytes disappear completely from the ovary, and male germ cells and somatic cells comprising testicular tissue arise a new during the sex change process. However, little is known of the fate and origin of the gonadal tissue-forming cells during sex change. In particular, the fate of ovarian somatic cells has not been determined, although the ovarian tissue regresses histologically. To approach this question, we analyzed apoptosis and cell proliferation in the sex-changing gonads. Unexpectedly, we found that few apoptotic somatic cells were present during sex change, suggesting that ovarian somatic cells might survive during the regression of the ovarian tissue. On the other hand, cell proliferation was detected in many granulosa cells surrounding the degenerating oocytes, a few epithelial cells covering ovigerous lamella and a few somatic cells associated with gonial germ cells at an early stage of sex change. Then, we found that proliferative ovarian somatic cells remained in the gonads late in the sex change process. Based on these results, we concluded that some functional somatic cells of the ovary are reused as testicular somatic cells during the gonadal sex change in the three-spot wrasse.     

Trypanocidal Action of (?)-Elatol Involves an Oxidative Stress Triggered by Mitochondria Dysfunction

Natural compounds have shown good potential for the discovery of new chemotherapeutics for the treatment of Chagas’ disease. Recently, our group reported the effective trypanocidal activity of (−)-elatol, extracted from the red macroalgae Laurencia dendroidea present in the Brazilian coast against Trypanosoma cruzi. However, the mechanism of action of this compound has remained unclear. There are only hypotheses concerning its action on mitochondrial function. Here, we further investigated the mechanisms of action of (−)-elatol on trypomastigotes of T. cruzi. For this, we evaluated some biochemical alterations in trypomastigotes treated with (−)-elatol. Our results show that (−)-elatol induced depolarization of the mitochondrial membrane, an increase in the formation of mitochondrial superoxide anion and loss of cell membrane and DNA integrity. Additionally, (−)-elatol induced formation of autophagic vacuoles and a decrease in cell volume. All together, these results suggest that the trypanocidal action of (−)-elatol involves multiple events and mitochondria might be the initial target organelle. Our hypothesis is that the mitochondrial dysfunction leads to an increase of ROS production through the electron transport chain, which affects cell membrane and DNA integrity leading to different types of parasite death.     

Small-radius turning performance of an articulated vehicle by direct yaw moment control

This paper reports the turning performance of an articulated vehicle in which applying direct yaw-moment control is applied to reduce the turning radius. In the proposed method, a braking force is applied to the inner tires when the articulation angle reaches its maximum in turning, which generates a yaw-moment around the vehicle's centre of gravity. The yaw-moment allows the vehicle to turn in a small radius. To evaluate the performance in tight turns, experiments were conducted using a wheel loader on paved ground. The vehicle's turning radius, yaw rate and side-slip angle were determined from the data measured using two global positioning systems and a fibre-optic gyro sensor. In addition, results of a simulation were compared with experimental results from a test vehicle. The turning radius at a braking pressure of 4 MPa was at least 0.41 m smaller than that of 0 MPa. Experimental and simulated results proved that generating a yaw-moment by applying one-sided braking forces during turning decreases the turning radius.     

The quality after culture in vitro or in vivo of porcine oocytes matured and fertilized in vitro and their ability to develop to term

The quality of porcine blastocysts produced in vitro is poor in comparison with those that develop in vivo. We examined the quality of in vitro‐matured and fertilized (IVM/IVF) oocytes, their abilities to develop to blastocysts under in vivo and in vitro conditions, and the potential of the embryos to develop to term after transfer. IVM/IVF oocytes were either transferred and the embryos recovered on Days 5 and 6 (100% and 87.5%, respectively) (‘ET‐vivo’ embryos), or cultured in vitro for 5 or 6 days (‘IVC’ embryos). The proportion of blastocysts differed significantly between the two groups on Day 5 (20.6% and 8.0%, respectively), but not on Day 6 (23.8% and 21.2%, respectively). The mean number of cells in ET‐vivo blastocysts on Days 5 or 6 was significantly higher (72.8 and 78.7, respectively) than that in IVC blastocysts (22.1 and 39.7, respectively). When IVM/IVF oocytes and IVC blastocysts on Day 6 were transferred, all (three and three, respectively) developed to piglets (16 and 16, respectively), without any difference in the rates of development to term (2.1% and 2.6%, respectively). These data suggest that, although blastocyst production differs between the two culture conditions, IVM/IVF oocytes possess the same ability to develop to term.