Hiroyuki Tado's research while affiliated with Yamaguchi Prefectural University and other places

Forestry workers endure highly physical workloads. Japanese forestry workers experience additional up-and-down movements due to geographical features. Fatigue is a common cause of injury. This pilot study aimed to determine an appropriate method for estimating energy expenditure while moving across inclined ground to simulate a Japanese forest. Six participants wore a portable indirect calorimeter (V˙O2), heart rate (HR) monitor (17 g), accelerometer (20 g; vector magnitude; VM), and a global navigation satellite system (GNSS) device. They walked shouldering 20 kg of weight on flat, 15°- and 30°-slopes. The time course of HR was similar to that of V˙O2, but that of VM and the vertical movement varied from that of V˙O2. GNSS cannot correctly detect vertical movements. The HR index (HRI), indicating the ratio of activity HR to resting HR, was significantly correlated with the metabolic equivalent of the task (MET) calculated from V˙O2 (r = 0.932, p < 0.0001), which fit the previously proposed formula for METs (METs = HRI × 6 − 5). However, VM was not correlated with VM (r = 0.354, p = 0.150). We can use HRI to measure the workload of Japanese forestry workers with a small burden in the field.

Overwintering is important for the survival of northern mammals, and northern ungulates deposit body fat. Researchers have interpreted fat deposition as an adaptation to food shortages during winter. However, it is likely that reproductive activities also affect fat deposition. We compared kidney fat indices (KFIs) of sika deer (Cervus nippon) between the northern and southern populations in Japan. In the northern population, the KFIs of adult males and females peaked during summer and autumn, respectively. In adult males, the KFIs abruptly declined during the rut (October), while in yearling males and fawns, they were low in summer. In the southern population, KFIs of adult males were high in summer but decreased in October. KFIs of adult females were low and increased in December–January. KFIs of fawns were low. These results suggest that most classes of the southern population did not deposit much fat during the summer except for adult males. The result that southern adult males displayed as much fat deposition as the northern males suggests that body fat was deposited not only for overwintering but also for reproductive activity of adult males.

Functionality of cheek teeth is essential for ruminants to masticate plant materials thoroughly and promote microbial degradation in their rumens. Thus, an excessive rate of tooth wear is expected to lead to premature loss of tooth functionality, and hence to reduced longevity. So far, however, the relationships between food habits, molar wear and longevity have not been investigated. We first compared molar wear rates among nine sika deer Cervus nippon populations with different food habits. We then investigated correlations between molar wear rate and two ecological factors, percentage of graminoids in diet and annual precipitation, relating to intrinsic and extrinsic abrasiveness of the ingested food, respectively. Secondly, we estimated ‘retained molar durability’ (molar height at a given age divided by wear rate) at successive ages for each population, and tested for correlation between molar durability and life expectancy among populations. The M1 and M3 wear rates differed among the populations and showed a positive correlation with graminoid consumption and a negative correlation with precipitation, suggesting that both ecological factors influence molar wear rates in the Japanese sika deer. M3 durability had a stronger correlation with life expectancy than M1 durability, especially at the older age stages. This implies that the influence of M3 durability on life expectancy becomes stronger at the time when the M1 is severely worn and loses its functionality, and is therefore more important for life span elongation than the M1. These results are concordant with the fact that the M3 is the most hypsodont molar in many ungulates. In the Japanese sika deer, microevolutionary acquisition of hypsodonty appears to be the case in a northern population (the Kinkazan Island), whose molar wear rates are extremely rapid due to their food habits.

Samples of the sika deer (Cervus nippon) were collected from Kyushu and Shikoku Islands of Japan and surrounding areas, and their nucleotide sequences were analyzed. Sequences of the whole control region of the mitochondrial DNA were determined and phylogenetic trees were constructed using the neighbor-joining method and the maximum likelihood method. We also investigated gene genealogies for the sequences using the statistical parsimony network approach. Phylogenetic trees showed that only the Yakushima/Tanegashima populations were genetically distant from other populations. The statistical parsimony network, however, indicated a close relationship of the Miyazaki populations to some of the Shikoku populations. It was suggested that Shikoku Island played an important role in the divergence from the southern Japan lineage of C. nippon.

Nucleotide sequences of sika deer (Cervus nippon) collected from the eastern part of Shikoku Island were investigated & compared with those from other areas. Nucleotide sequence of the whole D-loop region of the mitochondrial DNA was determined by direct sequencing technique for each sample. The phylogenetic tree constructed by the sequences indicates that sika deer from Shikoku Island are divided into two distinct lineages: the northern Japan group and the southern Japan group. Proportion of the northern Japan lineage was higher in the northeastern part of the sampling area. There was no border between the distribution of the two lineages, rather it seemed that their distribution intermingled. Besides, there were locations where both lineages were found within a small area. These results indicate that two lineages might be hybridized in some areas of eastern Shikoku.

Bombyx mori chitinase (Bm-CHI), with a molecular mass of 75 kDa, was investigated on the possibility that it can serve as a biocontrol agent against the adult Japanese pine sawyer (JPS), Monochamus alternatus (Coleoptera: Cerambycidae). Oral ingestion of purified chitinase at concentrations of 3 microM (11.25 microg/50 microl) and 0.3 micoM (1.125 microg/50 microl) caused high mortality in JPS, a significant decrease in bark consumption, and, only in high concentration, a slight reduction of body weight. Fluorescence assays indicated that peritrophic membrane (PM) chitin is degraded by the action of orally ingested Bm-CHI at 3 microM concentration only. Scanning electron micrographs clearly indicated that the beetles that ingested Bm-CHI of the same high concentration had their PM perforated and disrupted, but ultrastructural studies showed that the ingested chitinase did not affect the midgut epithelium. These findings open up the possibility of using insect chitinase as a biopesticidal enzyme. It should have agronomic potential for insect control.

To investigate genetic diversity among populations of the sika deer, Cervus nippon, nucleotide sequences (705–824 bases) of the mitochondrial D-loop regions were determined in animals from 13 localities in the Japanese islands. Phylogenetic trees constructed by the sequences indicated that the Japanese sika deer is separated into two distinct lineages: the northern Japan group (the Hokkaido island and most of the Honshu mainland) and the southern Japan group (a part of the southern Honshu mainland, the Kyushu island, and small islands around the Kyushu island). All sika deer examined in this study shared four to seven units of repetitive sequences (37 to 40 bases each) within the D-loop sequences. The number of tandem repeats was different among the populations, and it was specific to each population. Six or seven repeats occurred in populations of the northern Japan group, while four or five repeats occurred in populations of the southern Japan group. Each repeat unit included several nucleotide substitutions, compared with others, and 26 types were identified from 31 animals. Sequences of the first, second, and third units in arrays were clearly different between the northern and the southern groups. Based on these D-loop data, colonization and separation of the sika deer populations in the Japanese islands were estimated to have occurred less than 0.5 million years before present. Our results provide an invaluable insight into better understanding the evolutionary history, phylogeny, taxonomy, and population genetics of the sika deer.

A partial sequence of the mitochondrial cytochrome-b gene was determined for seven subspecies of sika deer (Cervus nippon) in the Japanese Islands. Nine mitochondrial DNA genotypes were distinguishable among deer sampled. Sequence analysis revealed two major phylogenetic groups comprised of northern (Hokkaido-Honshu) and southern (Kyushu) local populations. Estimated nucleotide divergence between genotypes found in southern populations was ≤1.1%, which indicated that genetic differentiation within this group occurred recently. Phylogenetic data suggest that the biogeographical boundary between northern and southern populations of sika deer lies somewhere in the Honshu mainland and not in channels that separate each Japanese Island as has been suggested. C. n. keramae, an endangered subspecies in the Kerama Islands, was found to be genotypically close to other subspecies from southern populations. C. n. keramae may have descended from deer originally introduced from Kyushu Island.