Grouped, stacked rods and tapeta lucida in the retina of Japanese anchovy Engraulis japonicus

ABSTRACT: Morphology of the photoreceptor cells and tapetum of the Japanese anchovy Engraulis japonicus was studied by histologically and by chemical analysis. The Japanese anchovy has a duplex retina. The cones form parallel rows consisting of alternately placed long cones and bifid cones. Both types of cones are intimately associated and form triple units that are regularly spaced along the row of cones. The rods are grouped and stacked. This fish has a retinal tapetum lucidum composed of guanine and hypoxanthine. Three structures of the tapetum lucidum were recognized: platelet, diamond and rod types. Photomechanical changes include movements of the photoreceptor cells and the retinal tapetum. The retina of the Japanese anchovy is thought to be highly sensitive and well adapted to a dim light environment.     

Sequence and unique phylogeny of G genes of bovine respiratory syncytial viruses circulating in Japan

Bovine respiratory syncytial virus (BRSV) is an etiologic agent of bovine respiratory disease. The rapid evolutionary rate of BRSV contributes to genetic and antigenic heterogeneity of field strains and causes occasional vaccine failure. We conducted molecular epidemiologic characterization of BRSV circulating in Japan to obtain genetic information for vaccine-based disease control. Phylogenetic analysis of G and F gene sequences revealed that all of the isolated Japanese BRSV strains clustered in the same genetic subgroup, which was distinct from the 9 known groups. We assigned the Japanese group to subgenotype X. The Japanese isolates formed 2 temporal clusters: isolates from 2003 to 2005 clustered in lineage A; isolates from 2017 to 2019 formed lineage B. The alignment of the deduced amino acid sequences of the G gene revealed that the central hydrophobic region responsible for viral antigenicity is conserved in all of the isolates; unique amino acid mutations were found mainly in mucin-like regions. Our results suggest that BRSV has evolved uniquely in Japan to form the new subgenotype X; the antigenic homogeneity of the viruses within this group is inferred.     

Effect of relationships among clinical mastitis incidence,reproductive performance,and culling rate on the lifetime of dairy cows at Hiroshima University Farm

Farm managers' decision to cull dairy cows is based on the cows' milk production, history of disorder(s), and reproductive performance, each of which affects dairy cows' lifetime (herd life and productive lifespan). We investigated the relationships among the incidence of clinical mastitis (CM), the reproductive performance, and the culling rate. We also assessed the effects of these relationships on the lifetimes of dairy cows, using the records made before and after the introduction of an automatic milking system (AMS) at Hiroshima University Farm. Milk yield, CM incidence density, and culling rate of dairy cows increased after the AMS introduction. The CM incidence was associated with an elongation of the calving interval in cows with the same parity. CM in the 1st parity might have caused the reductions of the cows' lifetime and their parity at culling. A higher age at first calving (AFC) was associated with an increase in culling rate but did not lead to a significant decrease in lifetime. Investigations of the factors mediating CM in the 1st parity or AFC with CM incidence or culling rate in the later stages might contribute to the control of lifetime of dairy cows.     

Changes in expression and localization of GPRC5B and RARalpha in the placenta and yolk sac during middle to late gestation in mice

The mRNA expression of GPRC5B, an orphan G protein-coupled receptor, is induced by retinoic acid (RA). Because RA plays critical roles in embryonic development, reproductive functions, metabolism and homeostasis, GPRC5B is also considered crucial in these physiological events. We investigated the changes in expression of GPRC5B and RA receptor (RAR) alpha mRNAs and immunohistochemical localization of their proteins in the murine placenta and yolk sac at 13.5, 15.5 and 17.5 days post coitus. Stable levels of GPRC5B and RARalpha mRNAs were detected in the placenta and yolk sac. In the placenta, GPRC5B was present in maternal and fetal vascular endothelial cells, stromal cells, fibroblast-like cells and glycogen cells. A strong reaction to RARalpha was detected in maternal and fetal vascular endothelial cells and stromal cells. The levels of GPRC5B and RARalpha proteins in maternal and fetal vascular endothelial cells decreased with gestation. In the yolk sac, GPRC5B and RARalpha proteins were detected in vascular endothelial cells, but their levels did not change during the gestation period. These findings indicate that GPRC5B is involved in RA-dependent morphogenesis/angiogenesis and regulation of extracellular matrix synthesis in the murine placenta and yolk sac.     

Influence of light intensity on feeding, growth, and early survival of leopard coral grouper (Plectropomus leopardus) larvae under mass-scale rearing conditions

This study investigated the effect of different light intensities on feeding, growth and survival of early stage leopard coral grouper Plectropomus leopardus larvae. Four different light intensities (0, 500, 1000 and 3000 lx) were used and larvae were kept under constant light conditions from 0 day after hatching (DAH) to 5 DAH. The larvae were fed a small S-type of Thai strain rotifers at a density of 20 individuals/mL from 2 DAH. The number of rotifers in larval digestive organ and total length of larvae were examined at 3 h intervals between 04:00 and 22:00 h on 3 DAH, and thereafter at 6 h intervals until the end of the experiment (5 DAH). Four experimental trials of the larval rearing were repeated using by 60 kL mass-scale rearing tanks. The results indicate that coral grouper larvae are visual feeders and their food intake increases with increasing light intensity. Food intake of larvae reared at 3000 lx was significantly higher than those reared at 0–1000 lx on 3 DAH despite being the first-feeding day (P < 0.01). On 4 DAH, total length of larvae reared at 3000 lx was significantly larger than those reared at the lower light intensities (0, 500 and 1000 lx), and thereafter light intensity significantly influenced larval feeding and growth until the end of the experiment. Survival on 5 DAH did not show a significant difference between light intensities, but survival rate at 3000 lx and 1000 lx had a tendency to be higher than those reared at the lower light intensities (0 and 500 lx). In contrast, larvae reared at 0 lx exhibited stagnant and/or negative growth. These results indicate that light intensity is significantly the factor affecting larval feeding, growth, and survival in coral grouper larvae under the rearing conditions.     

Regional variability in landscape effects on forest bird communities

Landscape Ecology - Functional responses to landscape heterogeneity are context-dependent, hampering the transferability of landscape-scale conservation initiatives. Japan provides a unique...     

Behavior of four broad-leaved tree species used to revegetate eroded granite hill slopes

Information on primary growth behavior after planting is required for mixed-plantation revegetation using broad-leaved species. To estimate primary growth, especially from the perspective of crown coverage and changing growth rates, we examined the growth and survival of four broad-leaved species that are frequently used in erosion-control plantations in Japan. The species studied were Myrica rubra Sieb. et Zucc., Alnus pendula Matsum., Quercus glauca Thunb., and Q. serrata Thunb. The survival, height, and basal diameter of planted trees were measured over a 4-year period, and crown area was calculated over a 3-year period. We found a negative relationship between relative growth rate (RGR) and survival rate, suggesting that fast growth may be fatal when resources are severely limited. The relative height growth rate (RHGR) of A. pendula was especially high during the early period of the study (1997–1999) and then drastically declined, whereas the opposite tendency was observed in Q. glauca. The results of stem allometry analyses conformed to the specific relationships between height growth and diameter growth of the four species; increases in stem thickness based on height increments were smaller in the pioneer species A. pendula. Between-species differences in coverage per planted tree (mean crown area multiplied by survival rate) were small as a result of the negative relationship between coverage area and survival rate.