Habitat use and movement patterns of small (age‐0) juvenile Pacific bluefin tuna (Thunnus orientalis) relative to the Kuroshio

The habitat use of Pacific bluefin tuna (Thunnus orientalis; PBF) in nursery waters off the southern coast of Japan was investigated using archival tags over a 3 year study period (2012–2015), and the data were used to examine the free‐ranging habitat preferences of PBF and the relationship between their horizontal movements and the path of the Kuroshio off the Pacific coast of Japan. The path of the Kuroshio fluctuated seasonally, leading to changes in water temperature that strongly influenced the habitat use of small PBF (2–3 months after hatching). Most PBF were present in coastal waters inshore of the path of the current, and their habitat use changed in response to the distance of the current from the coast. The Kuroshio typically flowed along the coast from summer to autumn, and PBF remained in the coastal waters off Kochi Prefecture during this period. In contrast, PBF quickly moved eastward in winter when the current moved away from the coast. Throughout the winter and spring, the area of habitat use extended widely from the eastern end of the southern coast of Japan (the Boso Peninsula) to the offshore Kuroshio‐Oyashio transition region. These findings suggest that the seasonal habitat use and movement behavior of juvenile PBF are influenced by the distance of the Kuroshio axis from the coast, and the ultimate drivers are likely variations in oceanographic conditions and prey availability along the southern coast of Japan.     

Characterization of the morphological and physiological traits of rice cultivars with adaptation to unflooded condition during early vegetative growth

This study aimed to characterize the physiological and morphological traits that are associated with adaptation to unflooded soil conditions in rice. Four indica rice cultivars (Puluik Arang, Badari Dhan, Shwe Nang Gyi, and Ratul), which were previously identified as highly or less adaptable to unflooded soil conditions, were grown under flooded and unflooded (soil water potential; －0.10 MPa) soil conditions. Water uptake was measured every day for three weeks, and then the leaf water potential, the stomatal conductance, the dry matter weight, shoot and root morphological traits were measured. Puluik Arang and Badari Dhan exhibited greater leaf area expansion and higher maintenance of root development under the unflooded condition than that by other cultivars. The leaf water potential and stomatal conductance of fully expanded highest leaf in Puluik Arang and Badari Dhan were not affected by unflooded soil regime. Leaf area and root morphological traits were significantly correlated with water uptake regardless of soil moisture regimes. These results suggested that Puluik Arang and Badari Dhan exhibited great water uptake capacity through physiological and morphological adaptation of shoot and root traits to unflooded condition, resulting in great biomass productivity under the condition.     

Effects of time and duration of rearing with bottom sand on the occurrence and expansion of staining-type hypermelanosis in the Japanese flounder Paralichthys olivaceus

We previously reported that the progression of staining-type hypermelanosis spontaneously ceased at a specific time and area in Japanese flounder Paralichthys olivaceus. To examine whether time is a limiting factor in the spontaneous cessation of staining, we experimentally controlled the initiation and duration of staining by manipulating the bottom substrate condition in the fish tanks. At 151 days post hatching (DPH; 11 weeks), spontaneous cessation of staining was observed in fish reared in tanks without a sandy substrate. However, staining resumed (or was initiated) in tanks where sand was removed from 11 weeks, indicating a strong but temporary effect of bottom sand and the absence of time limitation in the staining progression by 151 DPH. Extended duration of the inhibitory period of hypermelanosis expansion (9 weeks or more) aided in only a 20 % reduction of the final staining area because of the increased rate of staining expansion. The bottom sandy substrate decreased the visibility of the staining area in individuals, but this was observed only before the completion of the staining expansion. These findings are discussed in relation to possible presence of area limitation of future staining, as well as the fundamental nature of staining.     

Concordance between Results of Medium-term Liver Carcinogenesis Bioassays and Long-term Findings for Carcinogenic 2-Nitropropane and Non-carcinogenic1-Nitropropane in F344 Rats

This study was conducted to determine the concordance of results for a pair of structural isomers, 2-nitropropane (2-NP) and 1-nitropropane (1-NP), using the rat medium-term liver carcinogenesis bioassay (Ito test) and previously published long-term carcinogenicity tests. Male F344 rats were given a single intraperitoneal injection of DEN (200 mg/kg b.w.) to initiate hepatocarcinogenesis. After 2 weeks, they received per os 0, 0.8, 4 or 20 mg/kg/day of 2-NP or 1-NP six times a week and were subjected to two-thirds partial hepatectomy at week 3. Non-initiated groups receiving 0 or 20 mg/kg/day were also included. The animals were sacrificed for quantitative analysis of GST-P-positive foci at week 8. With the highest dose of 2-NP, significantly increased numbers and areas of GST-P-positive foci were demonstrated as compared with the respective control but were not noted with 1-NP. In the non-DEN-initiated groups, many small GST-P-positive foci of less than 0.2 mm in diameter were also induced in the rats treated with 2-NP at 20 mg/kg/day but were lacking with 1-NP. These results strongly support that 2-NP is a complete hepatocarcinogen with a potent initiation activity, whereas 1-NP is not.     

Specific and non-specific adsorption of inorganic ions I. Evaluation of specific adsorbability by means of minimum concentration for specific adsorption

The Minimum Concentration for Specific Adsorption (MCSA) was defined as a reversal of the charge concentration of the ion at the infinite dilution of sol (adsorbent), or practically at such concentration of sol that equilibrium of the ion Is but negligibly affected by adsorption of the ion.

The MCSAs of 15 species of cations were measured with respect to SiO₂ at pH 4,6,5, and 10; the MCSAs of 10 species of anions were measured with respect to Fe(OH)₃ at pH 4, and 6.5; and the MCSAs of 10 species of anions were measured with respect to Al-coated-SiO₂ at pH 6.5. Relative specificities of the inorganic ions based on the MCSAs at pH 6.5 were as follows:

The MCSAs of cations with respect to SiO₂ and of anions to Fe(OH)₃ and Al-coated-SiO₂ at pH 6.5 had close relationships to ionic potentials and general solubility of the elements in water. Based on these results, the authors concluded that the MCSA could be used u an index of specificity (i.e. covalent bond-forming tendency) of an Jon at adsorption reactions.

The values corresponding to the apparent stability constants of surface complexes formed by adsorption reaction with SiO₂ and cations at pH 4 were calculated from the values of the MCSAs.     

Squamous cell carcinoma in a digit of the hind limb with systemic metastasis in a 17-year-old female koala

We encountered a case of cutaneous squamous cell carcinoma (SCC) in a 17-year-old female koala at a zoo. A fragile, papillary, elevated mass was found on the third digit of the right hind limb. SCC was identified histopathologically: squamous cell-like polygonal tumor cells showed a nest-like growth pattern with epidermal down growth, central keratinization and necrotic foci, and invaded dermal connective tissues. Metastatic lesions were observed in various organs, including the lung and axillary lymph node: in the lung, multiple metastatic foci similar to the primary lesion, and in the axillary lymph node, individual polygonal tumor cells infiltrated the sinusoids. Immunohistochemistry revealed that the tumor cells were positive for proliferating cell nuclear antigen, which exhibited 32–33% of labeling indices in the tumor cells. To our knowledge, this is the first report of a case of SCC in a digit of a koala.     

Frequencies and evolution of organophosphate insensitive acetylcholinesterase alleles in laboratory and field populations of the house fly, Musca domestica L.

Resistance to organophosphate (OP) and/or carbamate insecticides can be due to mutations in the acetylcholinesterase gene (Ace). Genotypes of house fly, Musca domestica L., Ace were determined in twelve laboratory maintained strains (originally from North America, Europe and Asia) and two field collected populations from New York and Florida. There were 15 Ace alleles found and 11 of the alleles coded for a susceptible form of the enzyme (i.e., V260, A316, G342 and F407). Three of the four resistance alleles were previously described, while one is new. Phylogenetic analysis of the alleles suggests multiple origins of the F407Y mutation and multiple origins of the G342A mutation that confer OP resistance. Genotyping of field collected house flies from New York and Florida populations revealed the presence of only one resistance allele, Acev10 (containing the non-synonymous mutations for A342 and Y407). All other alleles detected from the field-collected flies coded for a susceptible AChE. Thus, we were able to categorize individual flies as having homozygous susceptible (Ace^S/Ace^S), homozygous insensitive (Ace^I/Ace^I or Acev10/Acev10) or heterozygous AChE. The frequencies of Ace^S and Ace^I were not different between the NY2002 and FL2002 populations. Both populations were out of Castle-Hardy-Weinberg equilibrium, having an excess of Ace^S/Ace^I individuals and very few Ace^S/Ace^S individuals. Comparison of Ace, Vssc and CYP6D1 genotypes indicates individual house flies commonly have resistance alleles at multiple loci. Comparison of genotype data with bioassays, as well as the use of genotype data in resistance studies is discussed.