Hiroshi Yamakawa

Microhabitat and behavior of settled pueruli and juveniles of the Japanese spiny lobster Panulirus japonicus at Kominato, Japan

Field surveys were conducted to understand the benthic ecology of the settled puerulus and juvenile stages, up to 23-mm carapace length, of the Japanese spiny lobster Panulirusjaponicus. Both the settled puerulus and juvenile stages were found individually in small holes near algae on the side or underside of rocks or boulders in nearshore shallow waters. The study suggested that settled pueruli and juveniles have a diurnal homing ability; they hid in their holes during daytime and emerged at night, then returned to the same holes early next morning. The first juvenile stage generally continued to occupy the same holes that it used during the puerulus stage, for some period after molting. As juveniles became larger, they moved to larger holes.

Habitat Selection, Growth Rate and Density of Juvenile Panulirus Japonicus (Von Siebold, 1824) (Decapoda, Palinuridae) At Banda, Chiba Prefecture, Japan

[Preliminary observations via SCUBA found juvenile Panulirus japonicus using small holes as a daytime refuge in the rock surface of shallow reefs (2-3 m below Chart Datum) adjacent to the Banda Marine Laboratory of Tokyo University of Fisheries. Monthly samples of juvenile P. japonicus and regular observations along a vertical rock face (area 53.2 m2) were carried out between April 1991 and December 1992, in order to detail the growth rate, density on the reef face, morphology of holes occupied and period of retention of juveniles in individual holes. Peak settlement of pueruli occurred in September with pueruli and first stage juveniles using holes of a mean diameter of approximately 12±4 mm. Initially pholad holes, predominantly of the species Lithophaga curta, were used by juveniles at Banda, however with growth the availability of suitably sized pholad holes diminished and holes of various morphologies were used. At the observation site, pueruli and first stage specimens were followed over several consecutive molts. Mean intermolt period increased with juveniles size and molting from the first through to the sixth molt stage required approximately 2.5 months (78.5±2.2 days). The maximum number of individuals on the rock face occurred immediately after peak settlement in autumn (0.21 and 0.32 inds.m-2, September 1991 and 1992 respectively) with this density declining prior to winter. Densities on the rock face from November (0.094 inds.m-2) remained relatively constant over winter period and from May/June declined further as juveniles changed from using holes to cave/crevice style habitats situated off the rock face. Growth rate of juvenile P. japonicus was fast, from peak settlement ofpueruli [carapace length (C.L.) ~ 7.5 mm] in September, a mean size of C.L. 35-40 mm was attained after one year. Recruitment to the fishery (minimum landing size C.L. 42 mm) is estimated to occur over the second winter after settlement as a puerulus., Preliminary observations via SCUBA found juvenile Panulirus japonicus using small holes as a daytime refuge in the rock surface of shallow reefs (2-3 m below Chart Datum) adjacent to the Banda Marine Laboratory of Tokyo University of Fisheries. Monthly samples of juvenile P. japonicus and regular observations along a vertical rock face (area 53.2 m2) were carried out between April 1991 and December 1992, in order to detail the growth rate, density on the reef face, morphology of holes occupied and period of retention of juveniles in individual holes. Peak settlement of pueruli occurred in September with pueruli and first stage juveniles using holes of a mean diameter of approximately 12±4 mm. Initially pholad holes, predominantly of the species Lithophaga curta, were used by juveniles at Banda, however with growth the availability of suitably sized pholad holes diminished and holes of various morphologies were used. At the observation site, pueruli and first stage specimens were followed over several consecutive molts. Mean intermolt period increased with juveniles size and molting from the first through to the sixth molt stage required approximately 2.5 months (78.5±2.2 days). The maximum number of individuals on the rock face occurred immediately after peak settlement in autumn (0.21 and 0.32 inds.m-2, September 1991 and 1992 respectively) with this density declining prior to winter. Densities on the rock face from November (0.094 inds.m-2) remained relatively constant over winter period and from May/June declined further as juveniles changed from using holes to cave/crevice style habitats situated off the rock face. Growth rate of juvenile P. japonicus was fast, from peak settlement ofpueruli [carapace length (C.L.) ~ 7.5 mm] in September, a mean size of C.L. 35-40 mm was attained after one year. Recruitment to the fishery (minimum landing size C.L. 42 mm) is estimated to occur over the second winter after settlement as a puerulus.]

Comparison of Hole and Seaweed Habitats of Post-Settled Pueruli and Early Benthic Juvenile Lobsters, Panulirus-Japonicus (Von Siebold, 1824)

The habitats used by pueruli and early bcnthic juvenile Panulirus japonicus were examined at 5 locations along the coast of southern Japan. At Kawazu in the Izu area, from reefs covered by agar algae (Rhodophyta: Gelidiaceae) and Ecklonia cava (Phaeophyta), of a total of 67 juveniles sampled, 64 were sampled from small holes in the rock face and 3 specimens were taken from within the agar algae. At the remaining 4 locations, no agar algal beds occurred and the macroalgae cover was dominated by Laminariaceae and/or Sargassum spp. At these sites, the 81 pueruli and 268 juveniles sampled were observed only within holes on the reef surface and not in association with the macroalgae. Diurnal use of both small holes and the dense foliage of agar algae, allows almost complete concealment of the main part of the body of the juvenile which may not be provided by other macroalgae. Agar algae, however, occur intermittently along the coast of Japan, with extensive beds being found only in the Izu area. It is concluded that holes within the reef face, rather than seaweed, are the main diurnal microhabitat of post-settled pueruli and early benthic juvenile P. japonicus.

Evaluation of wearable gyroscope and accelerometer sensor (PocketIMU2) during walking and sit-to-stand motions

Recently healthcare of the elderly people has become a serious issue in medical and rehabilitation areas. In order to know their functional mobility and provide sufficient medical treatment, it is important to measure their body state precisely and objectively. Therefore we developed a wearable and wireless sensor of gyroscope and accelerometer (PocketIMU2) as an easy and precise measurement of human motions. In the sensor, we employed a small and high accurate LiNbO3 crystal to achieve joint angle computation with simple integration of angular velocity. In the current paper, we evaluate the accuracy of the sensor in two important basic motion, such as a walking and sit-to-stand motions. Computed joint angles of ankle, knee, and hip are compared to the reference data measured from a optical motion capture system in term of coefficients of correlation and root mean square error. As a result, coefficient of correlation showed very high value for all joint angles, and root mean square error was adequately small. This strongly supports the usage of our developed gyroscope and accelerometer sensor for monitoring human body movement for medical usage.

Lead behavior in abalone shell

Abstract In order to gain information about the behavior of heavy metals in biological assimilation processes in a marine food chain and to investigate the possibility that lead pollution in a marine environment can be estimated by measurement of a small number of key materials from such a food chain, muscle and shell were analyzed from abalone (Haliotis) from a shallow water locality in a Japanese coastal region. Lead concentrations in muscle were about 26 ppb for abalone of approximately 3 years old and decreased systematically with increasing age of animals sampled, to about 3.3 ppb for a specimen approximately 8 years old. Lead concentrations in shell material gradually decreased also, from 150 ppb to 82 ppb in the oldest specimen. The decrease of concentration in tissues with increasing age indicates that a mechanism for exclusion of lead during tissue growth becomes more efficient with age. Along the food chain in which abalone is the final stage, lead was enriched at the first stage, from seawater to algae, by a factor of 100. Lead was diminished at all subsequent stages of the chain. Tissue of artificially cultured abalone had four times higher lead values compared to abalone grown in natural conditions, and this appears to reflect the fact that lead concentration was three times higher in seawater in the cultured environment.

A UPS study of liquid and solid bismuth using synchrotron radiation

The photoelectron spectra of Bi in both liquid and solid phases were measured at excitation energies between 18 and 60 eV using synchrotron radiation. It was found that the profiles of the energy distribution curves are quite similar to those obtained in the XPS region and there is little difference in the spectral profile between liquid and solid phases. On melting the density of states at the Fermi level increases more than twice as much as in the solid phase. In both liquid and solid phases, the photoelectron spectra change their profiles associated with the 5d core electron excitation, which is attributed to the O4.5VV Auger electrons.

Analysis of muscle synergy contribution on human standing-up motion using a neuro-musculoskeletal model

It is important to understand the mechanism of human standing-up motion to improve the declined physical ability of the elderly people. This study employs the concept of muscle synergies (modular structure of coordinative muscle activation) to understand how humans coordinate their muscles to achieve the standing-up motion. Neuro-musculoskeletal model was developed to represent human body to generate standing-up motion. Using the developed model, forward dynamic simulation was used to analyze how humans utilized the muscle synergies to realize the motion. Results showed that the developed model could generate the standing-up motion with four muscle synergies rather than controlling individual muscles. Moreover, further analysis showed that three different strategies of the standing-up motion could be generated only by changing the start time of the particular muscle synergy.

Generation of human standing-up motion with muscle synergies using forward dynamic simulation

The standing-up motion is one of the most important activities of daily livings. In order to understand the strategy to achieve the standing-up motion, muscle synergy analysis is applied to the measured data during human standing-up motion. In addition, musculoskeletal model which consists of three body segments and nine muscles in lower limb is developed to ensure that the standing-up motion can be generated by muscle synergies. As a result, three muscle synergies have been extracted from the human standing-up motion, and each synergy strongly corresponded to characteristic kinematic events: momentum flexion, momentum transfer, and posture stabilization. Results of forward dynamic simulation show that the standing-up motion can be achieved by controlling time-varying weighting coefficient of three muscle synergies instead of controlling individual nine muscles.

Muscle Synergy Analysis of Human Standing-up Motion Using Forward Dynamic Simulation with Four Body Segment Model

Human motor behavior can be generated by distributed system. In this study, human standing-up motion is focused as an important daily activity. Especially, 13 muscle activation of lower body and trunk measured during human standing-up motion is decomposed into small numbers of modules of synchronized muscle activation called muscle synergy. Moreover human musculoskeletal model is developed with four rigid body segments based on dynamics and anatomical characteristics of human body. Forward dynamic simulation with the developed model showed that four muscle synergies had their own contribution toward body function: bending forward, moving the center of mass forward, extending whole body, and decelerating the center of mass. Results also indicated that combinations of four modules of synchronized muscle activation could generate human standing-up motion rather than controlling individual muscles.

Goal-Directed Movement Enhances Body Representation Updating

Body representation refers to perception, memory, and cognition related to the body and is updated continuously by sensory input. The present study examined the influence of goals on body representation updating with two experiments of the rubber hand paradigm. In the experiments, participants moved their hidden left hands forward and backward either in response to instruction to touch a virtual object or without any specific goal, while a virtual left hand was presented 250 mm above the real hand and moved in synchrony with the real hand. Participants then provided information concerning the perceived heights of their real left hands and rated their sense of agency and ownership of the virtual hand. Results of Experiment 1 showed that when participants moved their hands with the goal of touching a virtual object and received feedback indicating goal attainment, the perceived positions of their real hands shifted more toward that of the virtual hand relative to that in the condition without a goal, indicating that their body representations underwent greater modification. Furthermore, results of Experiment 2 showed that the effect of goal-directed movement occurred in the active condition, in which participants moved their own hands, but did not occur in the passive condition, in which participants’ hands were moved by the experimenter. Therefore, we concluded that the sense of agency probably contributed to the updating of body representation involving goal-directed movement.