Evidence of a local spawning site of marine eels along northeastern Japan, based on the distribution of small leptocephali

Evidence of recent spawning by several species of marine eels of the families Congridae, Ophichthidae, and Nettastomatidae was found over the continental shelf along the coast of northeastern Japan in October 2003. Sixty‐three leptocephali of at least three taxa that ranged from 3.8 to 12.3 mm total length were collected in a relatively small area, just to the south of Cape Shioya, primarily over the 100‐and 200‐m‐depth contours. The leptocephali of Gnathophis nystromi nystromi were the most abundant, followed by those of G. nystromi ginanago. This spawning area is located in an area that appeared to include water originating from the Tsugaru Warm Current and is further south than the typical latitude of the cold water of the Oyashio First Intrusion. These findings suggest that some species of marine eels may not migrate past the slope to spawn, and that the oceanographic features of the region may provide favorable conditions for the growth and retention of leptocephali in the area to the south of Cape Shioya.     

Dual appearance of xanthophores,and ontogenetic changes in other pigment cells during early development of Japanese flounder <Emphasis Type="Italic">Paralichthys olivaceus</Emphasis>

Flatfishes display a left–right asymmetry that is unique in the animal kingdom. In order to clarify the mechanisms of the asymmetrical development of pigment cells, changes in pigment cell densities were examined in Japanese flounder Paralichthys olivaceus. During development from symmetrical larvae to asymmetrical juveniles, pigment cell densities were monitored on the skin on both the left side (ocular side in juvenile; eventually has two eyes) and the right side (blind side in juvenile; eventually has no eyes). A symmetrical and constant decrease was observed in leucophores and larval type melanophores. A mostly symmetrical (slightly delayed on the blind side) and constant increase in iridophores from metamorphosis was observed. Adult-type melanophores appeared and then increased only after metamorphosis on the ocular side. However, the pattern of xanthophores was complicated: they first existed symmetrically and decreased symmetrically until metamorphosis, and they later increased only on the ocular side. The dual appearance of the xanthophores, as well as the differences between their depths and sizes on the ocular and blind sides, may suggest the presence of two types of xanthophores—just as melanophores are well known to exhibit two types. The ontogenetic study of pigment cells described here is likely to help to elucidate the process of abnormal pigmentation in flatfishes.     

Effect of the lateral growth rate on wood properties in fast-growing hardwood species

We investigated the feasibility of using several fast-growing tropical or subtropical hardwood species for timber production by measuring key wood qualities in relationship to the high rates of lateral growth. The trees tested were sampled from even-aged plantations of Acacia mangium, A. auriculiformis, hybrid Acacia (A. mangium × A. auriculiformis), Eucalyptus grandis, E. globulus, and Paraserianthes falcataria (Solomon and Java origin) that had already reached commercial harvesting age. The released strain of the surface growth stress (RS), xylem density (XD), microfibril angle (MFA), and fiber length (FL) were measured at the outermost part of the xylem at breast height in each tree. Results were then compared to the lateral growth rate (radius/age) at breast height, which provides a relative indicator of the amount of tree growth per year. Our findings indicated that RS was constant, regardless of lateral growth rate in each species. Similar results were observed for XD, MFA, and FL, with a few exceptions, suggesting that high growth rates do not intrinsically affect the wood properties of fast-growing tropical or subtropical species that have reached harvesting age. However, special attention must be paid to patterns of xylem maturation when developing plantations of such species.     

Effects of the lateral growth rate on wood quality parameters of Eucalyptus grandis from different latitudes in Brazil and Argentina

Climate change resulting from increased atmospheric carbon dioxide (CO₂) and shortages of fossil fuels such as petroleum are major problems worldwide. Under these conditions, demand for woody biomass resources is increasing. We investigated the feasibility of using fast-growing Eucalyptus grandis for material production. Samples of E. grandis were collected from four plantations in different latitude divisions, including tropical and subtropical Brazil and subtropical Argentina. Various xylem qualities were measured and related to the lateral growth rate. Lateral growth rate did not significantly affect the longitudinal released strain of the surface growth stresses or the xylem density at any of the sampling sites. Higher lateral growth rate, higher values of xylem density, and lower absolute values of the released strain were observed in plantations closer to the equator. Higher growth rates in tropical climate promote longer fiber length. In subtropical plantations, smaller diameter trees will produce tension wood with smaller microfibril angles. Planting E. grandis closer to the equator thus produces higher quality wood than in plantations at lower latitudes.     

Number and density of retinal photoreceptor cells with emphasis on oil droplet distribution in the Mallard Duck (Anas platyrhynchos var. domesticus)

This study was intended to determine the number and regional distribution of photoreceptor cells and different colored oil droplets in the retina of the Mallard Duck (Anas platyrhynchos var. domesticus). To estimate the number and density of photoreceptor cells, adult ducks were killed and both eyes were enucleated under deep anesthesia to prepare Nissl‐stained retinal whole‐mount samples. Different colored oil droplets were counted from color microphotographs of the freshly prepared retina. The mean number of retinal photoreceptors was approximately 6 308 828 ± 521 927, with a peak density of 33 573/mm² in the central retina. The density was similar in the nasal, temporal, ventral and dorsal areas of the retina. Five types of oil droplets were identified on the basis of color: red, orange, greenish‐yellow, yellow and clear. The mean density of oil droplets was highest in the central retina (17 639/mm²) and gradually declined towards the nasal, temporal, ventral and dorsal areas. The size of oil droplets gradually increased with retinal eccentricity and varied even within an area. The greenish‐yellow oil droplets were most abundant across the retina. Taken together, these results demonstrate the differential retinal distribution of photoreceptor cells and oil droplets in duck retina. We conclude that the area of high photoreceptor cell density, which is matched by high neuron densities of the ganglion cell layer, corresponds to the site of acute vision in duck retina.     

Magnetic resonance imaging of neuronal ceroid lipofuscinosis in a border collie

A castrated male border collie 23 months of age weighing 19.4 kg was referred to the Animal Medical Center of Nihon University with complaints of visual disturbance and behavioral abnormality, hyperacusis and morbid fear. The MRI examination revealed the slight dilated cerebral sulci and cerebellar fissures and left ventricular enlargement. This is the first report of MRI findings of canine neuronal ceroid lipofuscinosis.     

Molecular typing of Salmonella enterica serovar Enteritidis isolates from food-producing animals in Japan by multilocus variable-number tandem repeat analysis: evidence of clonal dissemination and replacement

Background

Salmonella enterica serovar Enteritidis is a zoonotic pathogen. Human infections are associated with contaminated eggs and egg products. In Japan, since 1989, the incidence of food-borne disease caused by S. Enteritidis has increased and a pandemic has occurred; however, little is known about changes that occurred before and after this pandemic event in the dominant lineage of isolates from food-producing animals. This study aimed to determine the S. Enteritidis lineages in Japan over the last few decades by using multilocus variable-number tandem repeat analysis (MLVA).

Findings

MLVA was used to analyse 79 S. Enteritidis isolates collected from chickens (n = 63), cattle (n = 12), pigs (n = 2), and goats (n = 2) during 1975–2009. The S. Enteritidis isolates showed 14 different MLVA allele combinations, which were classified into two major clusters (A and C) and a minor cluster (B). All the 62 isolates in cluster A were isolated after 1988, whereas 13 of the 17 isolates belonging to cluster B and C were isolated before 1989.

Conclusions

The MLVA results showed that cluster C was predominant before 1989, and isolates in cluster A disseminated since 1989 and replaced the previous dominant clone, suggesting that isolates of cluster A originated from imported S. Enteritidis infection.