Effect of stocking density and addition of proteins on larval survival in Japanese flounder, Paralichthys olivaceus

The effects of larval density, rearing media, and protein additions on fish larval survival were tested by rearing larvae in small containers. Yolk-sac larvae of Japanese flounder, Paralichthys olivaceus, were transferred 1 day after hatching to plastic dishes and cell-culture microplates by Pasture pipette at densities ranging from 0.3 to 30 individuals/ml and incubated at 16 °C without food. Dead larvae were removed and counted every 12 h. Three peaks of larval mortality were observed: the first peak appeared just after the transfer, the second corresponded to the completion of yolk absorption, and the third occurred 10–12 days after the transfer. Since about 50% of larvae survived until the third peak, it was clear that mortality at the second peak (completion of yolk absorption; equivalent to the first feeding) was not due to starvation. At the first mortality peak, better survival was unexpectedly recorded at higher larval densities (30 individuals/ml), suggesting that some material beneficial for survival is derived from the larvae. This idea was further supported by the improved survival in media previously used to rear larvae at high densities. The addition of bovine serum albumin (BSA) at 10 μg/ml effectively reduced mortality in microplates and in 30-l tanks. To reduce the larval mortality just after handling, addition of egg white at a dilution rate of 1/30,000 (vol/vol) or less is recommended as a practical alternative to BSA. Since the addition of polyethylene glycol 6000 (1 μg/ml) also effectively reduced mortality, reduction in mortality could not be attributed to a specific mechanism. The precise determination of the magnitude and timing of larval mortality was attained through the use of small containers, and a method to prevent mortality due to handling was identified in this study. These types of tests may allow the logical evaluation and establishment of better rearing procedures for seed production in aquaculture.     

Complete sequence analysis of two cryptic plasmids from Bifidobacterium kashiwanohense JCM 15439 (type strain) isolated from healthy infant feces

Bifidobacterial plasmids reported so far are derived from a limited number of strains and plasmids of bifidobacterial type strains isolated from humans are unknown. We found that Bifidobacterium kashiwanohense JCM 15439 (type strain) isolated from a healthy infant contained two cryptic plasmids, designated pBBKW‐1 and pBBKW‐2. We determined and analyzed the complete sequences of both plasmids. pBBKW‐1 (7716 bp) was predicted to replicate by a rolling‐circle mechanism and encode six protein‐coding genes, two of which are putative replication proteins. pBBKW‐1 seems to be a cointegrate plasmid containing two copies of the plasmid pMG1 from Bifidobacterium longum. pBBKW‐2 (2920 bp) was predicted to encode six protein‐coding genes and be a theta‐type replicating plasmid, which has been reported to be more stable than a rolling circle‐type replicating plasmid frequently found in bifidobacteria. Our finding will provide new insights into safe recombinant plasmid constructions for humans.     

Effects of modern drainage systems on the spatial distribution of loach in rice ecosystems

• 1. Although rice fields support many aquatic species, recent agricultural intensification in Asia has led to loss of biodiversity, such as freshwater fish, in exchange for increased agricultural productivity. In Japan, modern drainage systems have been introduced in recent decades.
• 2. This study investigated the effects of several aspects of modern drainage systems on the spatial distribution of dojo loach Misgurnus anguillicaudatus, a dominant fish species in Japanese rice fields.
• 3. Multimodel inference approaches and hierarchical partitioning were used to estimate the direction and degree of the effect of each system on the spatial distribution of dojo loach.
• 4. Three variables related to modern drainage systems (gaps between fields and ditches, the type of drainage ditch, and the presence of underground drainage pipes), flooding dates, and spatial autocovariates showed significant influence on the abundance of loach. In particular, gaps had the largest impact among all the variables on loach in the later part of the survey (June).
• 5. Based on the results, the effectiveness of several conservation methods implemented for paddy‐dwelling fish in Japan was discussed. The knowledge will be a guide to the appropriate conservation of freshwater fish in Asia and other countries.

Copyright © 2011 John Wiley & Sons, Ltd.     

Repeated reaching of the harmful algal bloom of Karenia spp. around the Pacific shoreline of Kushiro,eastern Hokkaido,Japan, during autumn 2021

Unprecedented large-scale algal blooms were observed during autumn 2021 around the Katsurakoi fishing port, Kushiro, eastern Hokkaido, Japan. Monitoring of shoreline water showed that chlorophyll a (Chl a) concentrations and the cell density of Karenia spp., dominated by Karenia selliformis, repeatedly increased synchronously between September and November 2021. These increases were associated with a southerly wind-driven current, which transported offshore water on the shelf towards the shoreline at the sea surface. The blooms were prolonged as a result of algal accumulation in the semi-closed fishing port. The maximum Chl a concentration and cell density exceeded 50 µg Chl a/L and 10⁴ cells/mL, respectively. During the autumn bloom of Karenia spp., the nitrate?+?nitrite and phosphate concentrations in the water were lower than those in 2019 and 2020, and the silicate concentration was comparable. The ammonium concentration during the bloom was notably higher than before the bloom period, reaching 15 µM. Mass mortality of several fish species and echinoderms that were cultured using rearing water intake from the same shoreline occurred synchronously with the increase in Karenia spp.

     

Two-week Toxicity of Multi-walled Carbon Nanotubes by Whole-body Inhalation Exposure in Rats

To evaluate pulmonary toxicity of multi-walled carbon nanotubes (MWCNTs), F344 rats of both sexes were exposed by inhalation to 0.2, 1 or 5 mg/m³ MWCNT aerosol for 6 h/day, 5 days/week for 2 weeks using a whole-body exposure system. At the end of the 2-week exposure period, one-half of the rats were necropsied, and at the end of an additional 4-week postexposure period, the remaining rats were necropsied. MWCNTs were deposited in the lungs of all MWCNT-exposed groups and mostly remained in the lungs throughout the 4-week postexposure period. Granulomatous changes in the lung were found in the rats exposed to 5 mg/m³ MWCNTs, and these changes were slightly aggravated at the end of the 4-week postexposure period. In the bronchoalveolar lavage fluid (BALF), the numbers of neutrophils, percentages of bi- and multinucleated alveolar macrophages, levels of ALP activity and concentrations of total protein and albumin were elevated in the rats exposed to 1 and 5 mg/m³ MWCNTs. At the end of the 4-week postexposure period, the values of the BALF parameters tended to remain elevated. In addition, goblet cell hyperplasias in the nasal cavity and nasopharynx were observed in the rats exposed to 1 and 5 mg/m³ MWCNTs, but these lesions had largely regressed by the end of the postexposure period. Based on the histopathological and inflammatory changes, the no-observed-adverse-effect level (NOAEL) for inhalation of MWCNTs for 2 weeks was 0.2 mg/m³.     

Characterization of methicillin-resistant Staphylococcus aureus isolated from retail raw chicken meat in Japan

Two isolates of mecA-positive methicillin-resistant Staphylococcus aureus (MRSA) from retail raw chicken meat were characterized by phenotypic and genotypic methods. One isolate showed the human biovar, coagulase type III, phage group I * III, the lack of production of enterotoxins and TSST-1, and resistance to PCG/ABPC/EM/GM/KM. The other isolate showed the human biovar, coagulase type III, phage group III, production of enterotoxin C and TSST-1, and resistance to PCG/ABPC/CEZ. The biotyping results indicate that the two isolates showed characteristics of human S. aureus. They also harbored SCCmec type IV, which has prevalently been found in community-acquired MRSA isolates. This paper is the first publication regarding MRSA isolates from raw chicken meat in Japan.     

Unilateral intrauterine insemination with cryopreserved caudal epididymal sperm recovered from refrigerated canine epididymides

Canine epididymides were excised and immediately stored at 4 degrees C for 48 hr, and the qualities of caudal epididymal sperm after recovery and cryopreservation were evaluated. To confirm the fertility of the cryopreserved caudal epididymal sperm, artificial intrauterine insemination was performed. The sperm motility (61.0%) immediately after recovery from caudal epididymis stored at 4 degrees C for 48 hr was significantly lower than those of sperm stored for 0 and 24 hr (88.6 and 80.7%, respectively), but there was no significant difference after freeze-thawing (0-, 24-, and 48-hr storage groups: 27.9, 24.3, and 28.3%, respectively). The incidence of abnormal sperm immediately after recovery was significantly higher in the 24-hr and 48-hr storage groups (19.3 and 27.7%, respectively) than in the 0-hr storage group (5.6%), and a significant difference was also observed after freeze-thawing. The incidence of immature sperm with cytoplasmic droplets was significantly higher in the 48-hr storage group (18.4%) than in the 0-hr storage group (4.7%), but there was no difference after freeze-thawing. By unilateral intrauterine insemination (2x10(8) sperm), 4 of 5 bitches (80%) conceived. The above findings demonstrated that sperm motility was good even enough the incidence of abnormal sperm was high in canine epididymal sperm that were recovered from the epididymis stored at 4 degrees C for 48 hr and cryopreseved, and that artificial intrauterine insemination resulted in a high conception rate.     

草莓属二倍体种东北草莓(Fragariamandschurica Staudt)研究

从中国吉林、黑龙江、内蒙古收集到5份形态相近的二倍体野生草莓,经多年植物分类学性状观察鉴定为东北草莓(FragariamandschuricaStaudt),该中文名为首次赋予,此前国内尚无该种的记载。“Manchuria”意为满州,是对中国东北的旧称。该种植株绒毛多少及其着生方式、花器官、种子等诸多性状明显不同于森林草莓(F.vescaL.)。RAPD(RandomAmplifiedPolymorphicDNA)鉴定技术也对这一结果给予有力支持,而且表明二倍体东北草莓与四倍体东方草莓(F.orientalisLozinsk)、六倍体麝香草莓(F.moschataDuch.)的亲缘关系最近,东北草莓可能是它们的原始种。     

Testicular compensatory hypertrophy related to hemicastration in prepubertal dogs

Several studies have reported that the plasma testosterone (T) level and semen volume are compensated after hemicastration (HEC) in adult dogs, but that the sperm count is not. Nevertheless, the effects of HEC in prepubertal dogs have not been reported. In this study, HEC was performed at 16 weeks of age in 8 male beagles, and the function of the residual testis was investigated until 48 weeks of age. The testis volume was consistently higher in the HEC group than the control (CON) group. After 40 weeks of age, compensatory hypertrophy was observed, with a mean testis volume of 125% of that in the CON group (p<0.05). Furthermore, the semen volume and plasma testosterone (T) level were similar to those in the CON group, suggesting functional compensation, but the sperm count was not compensated. These results showed that the testis volume, semen volume, and plasma T level were compensated after HEC in prepubertal dogs, but the spermatogenic function was not.