Life in the fast lane: Revisiting the fast growth—High survival paradigm during the early life stages of fishes

Early life survival is critical to successful replenishment of fish populations, and hypotheses developed under the Growth-Survival Paradigm (GSP) have guided investigations of controlling processes. The GSP postulates that recruitment depends on growth and mortality rates during early life stages, as well as their duration, after which the mortality declines substantially. The GSP predicts a shift in the frequency distribution of growth histories with age towards faster growth rates relative to the initial population because slow-growing individuals are subject to high mortality (via starvation and predation). However, mortality data compiled from 387 cases published in 153 studies (1971–2022) showed that the GSP was only supported in 56% of cases. Selection against slow growth occurred in two-thirds of field studies, leaving a non-negligible fraction of cases showing either an absence of or inverse growth-selective survival, suggesting the growth-survival relationship is more complex than currently considered within the GSP framework. Stochastic simulations allowed us to assess the influence of key intrinsic and extrinsic factors on the characteristics of surviving larvae and identify knowledge gaps on the drivers of variability in growth-selective survival. We suggest caution when interpreting patterns of growth selection because changes in variance and autocorrelation of individual growth rates among cohorts can invalidate fundamental GSP assumptions. We argue that breakthroughs in recruitment research require a comprehensive, population-specific characterization of the role of predation and intrinsic factors in driving variability in the distribution and autocorrelation of larval growth rates, and of the life stage corresponding to the endpoint of pre-recruited life.     

Whole-body heat transfer coefficient and body temperature change of juvenile Pacific bluefin tuna <Emphasis Type="Italic">Thunnus orientalis</Emphasis> according to growth

Bluefin tuna maintain a higher body temperature than ambient sea water. Body heat is derived mainly from metabolic heat to elevate and maintain regional body temperature that is higher than the ambient, while heat loss is caused by heat transfer throughout the whole body surface and gills. Retention of high body temperature is thought to differ at each growth stage, so that a larger body mass maintains a higher body temperature. We evaluated the whole-body heat transfer coefficient, thermal difference between each tissue and water temperature, and metabolic heat in tissues during swimming of juvenile bluefin tuna as a function of fork length (FL) using a small thermometer and a treadmill-type flow tank. A system for maintaining high body temperature was well developed in fish with FL greater than 20.0 cm. Whole-body heat transfer coefficient was fitted to a −0.695 power of mass. Juvenile bluefin tuna showed a transition speed of 3.0 FL/s at which they switched from aerobic to anaerobic motion.     

Characterisation of the carboxylesterase enzyme cauxin in the seminal fluid of the cat

The carboxylesterase cauxin is a major urinary protein in cats that is also found in seminal fluid (SF). This study investigated cauxin in feline SF including biochemical features, concentration, distribution and gene expression in epididymal tissue, and its reaction with acylglycerol substrates.Monomeric, dimeric, and/or multimeric forms of cauxin carrying N-glycosylations were detected on Western blots of feline SF but most were monomeric. Cauxin concentrations were markedly lower in SF (0.042 ± 0.020 mg/mL) than in urine (∼0.5 mg/mL) and cauxin gene expression was 60-fold lower in the epididymis than in the kidney. Immunohistochemical examination localised cauxin within the stereocilia and cytoplasm of epithelial cells lining the caput and corpus epididymis. Cauxin-positive spermatozoa were detected in the lumen of the cauda epididymis but not in the cytoplasm of the epithelial cell lining. Using an in vitro assay, cauxin hydrolysed saturated 1-mono- but not di- and tri-acylglycerols. The results suggest that cauxin secreted from the caput and corpus epididymis acts as an esterase on lipid within feline SF.     

Analysis of Ferulic and p‐Coumaric Acids in Japanese Rice for Sake Brewing

Ferulic and p‐coumaric acids were analyzed in 50 rice (Oryza sativa L.) samples from 32 cultivars harvested in Japan. In brown rice, ferulic and p‐coumaric acid levels ranged from 309 to 607 mg/kg and from 49 to 100 mg/kg, respectively. In 70% polished rice, ferulic and p‐coumaric acid levels ranged from 27 to 103 mg/kg and from 0.4 to 3.5 mg/kg, respectively. Ratios of average phenolic acid levels in the 70% polished rice to the brown rice were 13.9% for ferulic acid and 1.9% for p‐coumaric acid. The ferulic acid level was highly correlated between brown and 70% polished rice (R = 0.815; P < 0.01), but there was no clear correlation for p‐coumaric acid. Phenolic acid levels in the 70% polished rice did not show any clear correlations between the analytical index measurements for sake brewing suitability (weight of 1,000 grains, water absorption, digestibility, crude protein, and potassium content). Phenolic acid levels in the 70% polished rice directly affected levels in the rice koji enzyme digest. The results indicated that phenolic acid levels in sake were affected by the levels in ingredient rice grains, which may then influence the sensory quality of sake.     

Prototheca zopfii genotypes isolated from cow barns and bovine mastitis in Japan

This study is the first investigation on Japanese isolates of Prototheca zopfii from bovine mastitis and the cow-barn surroundings by molecular characterization to clarify routes of infection for bovine protothecal mastitis. We performed isolation of Prototheca from cow-barn surroundings (drinking water, sewage and feces) and milk samples from cases of bovine mastitis. Genotypes of the 32 isolates of P. zopfii from cow-barn surroundings and 67 isolates from mastitis were analyzed by genotype-specific PCR assays and restriction fragment length polymorphism (RFLP) assays. All mastitis isolates were identified as P. zopfii genotype 2. Conversely, 29 isolates from cow-barn surroundings were identified as P. zopfii genotypes 1 and 3 isolates as genotype 2, respectively. Given these results, both genotypes of P. zopfii could exist in cow-barn surroundings, but no sites were identified as frequent sources of P. zopfii genotype 2. P. zopfii isolates should thus be further explored with regard to genotype to clarify the reservoir of etiological agents in bovine Prototheca mastitis.     

Protective Effect of Chitin Urocanate Nanofibers against Ultraviolet Radiation

Urocanic acid is a major ultraviolet (UV)-absorbing chromophore. Chitins are highly crystalline structures that are found predominantly in crustacean shells. Alpha-chitin consists of microfibers that contain nanofibrils embedded in a protein matrix. Acid hydrolysis is a common method used to prepare chitin nanofibrils (NFs). We typically obtain NFs by hydrolyzing chitin with acetic acid. However, in the present study, we used urocanic acid to prepare urocanic acid chitin NFs (UNFs) and examined its protective effect against UVB radiation. Hos: HR-1 mice coated with UNFs were UVB irradiated (302 nm, 150 mJ/cm²), and these mice showed markedly lower UVB radiation-induced cutaneous erythema than the control. Additionally, sunburn cells were rarely detected in the epidermis of UNFs-coated mice after UVB irradiation. Although the difference was not as significant as UNFs, the number of sunburn cells in mice treated with acetic acid chitin nanofibrils (ANFs) tended to be lower than in control mice. These results demonstrate that ANFs have a protective effect against UVB and suggest that the anti-inflammatory and antioxidant effects of NFs influence the protective effect of ANFs against UVB radiation. The combination of NFs with other substances that possess UV-protective effects, such as urocanic acid, may provide an enhanced protective effect against UVB radiation.     

Effect of two whole-crop rice (Oryza sativa L.) cultivars on methane emission and Cu and Zn uptake in a paddy field fertilized with biogas slurry

A field experiment was carried out to evaluate the effect of two whole-crop rice (Oryza sativa L.) cultivars, TULT and Takanari, on methane (CH₄) emission in a paddy field fertilized with biogas slurry (BS) at rates of 0 (NF), 100 (BS100) and 300 (BS300) kg nitrogen (N) ha^?1, in comparison with chemical fertilizer CF100 (100 kg N ha^?1). Takanari produced significantly higher biomass (P < 0.001) than TULT and showed significantly (P < 0.01) lower CH₄ emission than TULT. BS applications caused higher CH₄ emission (52 ± 27 and 80 ± 19 g m^?2 in BS100 and BS300, respectively) than did CF100 (42 ± 18 g m^?2) and NF (28 ± 10 g m^?2) in TULT. In contrast, there was no significant difference in CH₄ emission in Takanari among the treatments (26 ± 2, 26 ± 2, 32 ± 4, 29 ± 8 g m^?2 in NF, CF100, BS100 and BS300, respectively). Methane oxidizing bacteria (MOB) showed significantly (P < 0.05) higher populations in Takanari than in TULT at harvest, which might be due to the higher root biomass (10.3 ± 2.2 g hill^?1) in Takanari than in TULT (8.9 ± 1.8 g hill^?1). MOB was significantly correlated with tiller number (R² = 0.176*) and plant biomass (R² = 0.242*). BS application showed higher copper (Cu) uptake in Takanari while it was not high in TULT. In contrast, it showed no difference in zinc (Zn) uptake in both varieties. Uptake of Cu was not different between the two varieties, while uptake of Zn in the grain was higher in TULT than in Takanari. The present study suggests that CH₄ emission deriving from BS application in paddy field can be mitigated by selecting an appropriate cultivar, like Takanari. However, care should be taken for heavy metal uptake in selecting cultivars.     

Spontaneous Glomerular and Tubulointerstitial Lesions in Common Marmosets (Callithrix jacchus)

Spontaneous progressive nephropathy dominated by glomerular lesions in common marmosets has been reported. However, the histopathologic characteristics, including the relationship between glomerular and tubulointerstitial lesions, have not been described in detail. In the present study, the authors examined the histopathologic characteristics of the background renal lesions in common marmosets (3 males and 9 females, 3 to 8 years old). The severity of glomerular lesions was graded into 3 classes: grade I, no alteration; grade II, hilar/focal increase of mesangial matrix; grade III, global/diffuse increase of mesangial matrix. Tubulointerstitial lesions (tubular regeneration and hyperplasia and interstitial inflammation and fibrosis) were scored according to the area of each lesion. The renal lesions were characterized by enlargement of glomeruli, expanded mesangial area with increase of periodic acid-Schiff reaction-positive matrix, tubular regeneration and hyperplasia, and interstitial inflammation and fibrosis. Glomerular lesions progressed with increasing mesangial matrix and aging. Additionally, the tubulointerstitial lesions became exacerbated with progressing glomerular lesions. Tubular hyperplasia was divided into 4 types according to the structure of the cell layer (simple or stratified-like), the area of increased lining cells (partial or entire), cytoplasmic staining (eosinophilic or basophilic), brush border and thickness of basement membrane, and the activity of cell proliferation. In conclusion, the background renal lesions in common marmosets were characterized by glomerular lesions with increase of mesangial matrix, which progressed with aging, and secondary tubulointerstitial lesions, including tubular hyperplasia. Those lesions were thus diagnosed as progressive glomerulonephropathy in common marmosets.     

Influence of weaning age on the villous height and disaccharidase activities in the porcine small intestine

Body weight gain after weaning is correlated with villous height and disaccharidase activity. This evidence suggests that the maintenance of the small intestinal structure and function after weaning is important for the growth of piglets. We demonstrated that the influence of weaning age was obtained by disaccharidase activities and villous height in eight sections of the porcine small intestine. Therefore, we designed three weaning ages (weaned at the ages of 14, 21 or 28 days) and the piglets were slaughtered after 7 or 14 days post‐weaning. The remaining suckling piglets were slaughtered at the age of 1, 7, 14, 21 and 28 days. Four piglets were slaughtered at each event; therefore, 44 piglets were used in this study. Villous height and disaccharidase activities were measured in each section of the small intestine. Early weaning such as that at 14 days had severe influence on villous and disaccharidase activities. In particular, weaning of 14‐day‐olds did not result in maltase activity at least 2 weeks post‐weaning. Accordingly, the weaning age of crossbred piglets is recommended to be at least 21 days or more on the basis of villous height and disaccharidase activity analyses.