Body size is a critical trait influencing reproductive success through mate competition, female choice, and parental care ability. In fish species with alternative reproductive tactics, large males typically adopt dominant tactics, while smaller males employ parasitic tactics, such as sneaking tactics. However, the reproductive advantage of larger males can be compromised by intense sperm competition with small males. We investigated the effects of body size on the reproductive success of nest-holding males in the dusky frillgoby Bathygobius fuscus, a species where small males frequently engage in sneaking tactics. Field investigations using artificial nests revealed that larger nest-holding males had significantly higher mating success (number of eggs acquired) and parental care success (egg survival rate). In contrast, DNA paternity analysis showed that fertilization success (paternity rate) was not correlated with male body size. This is because of the presence of males with extremely low paternity rate, including two cases of zero paternity, suggesting high sneaking pressure and replacement of nest-holding males (i.e., alloparental care). Consequently, the cumulative reproductive success of nest-holding males showed no significant relationship with body size. These results showed that the size-advantages of nest-holding males in attracting females and tending eggs are offset by the sperm competition with sneaker males. The lack of a clear size advantage in reproductive success may explain the plastic nature of reproductive tactics in this species, where large males may occasionally adopt sneaking tactics or abandon nests.
The petroleum and petrochemical industries operate in highly aggressive environments where corrosion can severely compromise the integrity of critical equipment. This work investigates how key high-velocity oxygen fuel (HVOF) spraying factors influence the coating integrity and corrosion performance of tungsten carbide layers deposited on AISI 4130 steel. The powder feed rate (ranging from 60 to 80 g/min) and spray pressure (ranging from 6.5 to 7.4 bar) were systematically varied for samples C1-C5, while an uncoated specimen served as the control. Microstructural characterization using scanning electron microscopy confirmed variations in coating density and thickness across the samples. Mechanical performance was evaluated through Vickers hardness measurements, indicating a significant increase (from 225 HV for the uncoated steel to 2060 HV and 2020 HV for samples C3 and C5, respectively). Corrosion performance was examined using Tafel polarization testing and EIS (electrochemical impedance spectroscopy). The HVOF-processed coatings significantly enhanced corrosion resistance compared with the bare substrate, with sample C3 demonstrating the lowest corrosion current density and a more noble corrosion potential. Nyquist analysis further indicated that C3 possessed the highest charge-transfer resistance due to its uniform WC distribution and reduced porosity. Overall, the optimal performance was achieved using a spray pressure of 7.2 bar and a powder feed rate of 72 g/min, identifying sample C3 as the most effective configuration for corrosion protection.
Anti-predator behaviours are generally considered as those that prevent death from predation. However, even if prey animals survive, they might suffer sub-lethal injuries. Although it is predicted that prey would minimise injury by protecting vital body parts, such defensive strategies have not been widely recognised in previous studies. While cephalopods frequently lose arms, males rarely lose their hectocotylus, an essential arm for reproduction. This is considered to be a result of the male's protection of the hectocotylus, but it has not been verified. This study investigated arm loss in Octopus parvus in the wild and tested whether males protect their hectocotylus (right third arm, R3) by avoiding its use during tasks with unpredictable truncation risk. Arm loss was observed in 78% of wild-caught individuals, and males lost R3 arm significantly less often than females. In Experiment 1, males did not use their hectocotylus at all to physically explore a novel object (fishing sinker), while females used R3 arm just as frequent as her other arms. In Experiment 2, the number of individuals explored prey in a hole using R3 arm did not differed significantly between sexes, but males explored the hole with arms other than R3 arm longer than females before inserting R3 arm. These results suggest that O. parvus males avoid risk more for the hectocotylus than for the other arms, i.e., hectocotylus arm protection. Males did not always protect their hectocotylus, and they sometimes inserted their hectocotylus after exploring the hole with other arms in Experiment 2. Males might suffer behavioural disadvantages by persistently guarding their hectocotylus.
BACKGROUND Using muscle flaps for reinforcing weakened tissue is an established technique that is widely used in the treatment of anastomotic leakage and intractable fistulas after esophagectomy. However, it has certain limitations including invasiveness and compromised cosmetic outcomes. Several studies have reported the efficacy of myoblast cell sheet transplantation in the prevention of digestive fistulas by reinforcing the gastrointestinal wall. However, its structural integrity and temporal changes after transplantation remain unclear. AIM To clarify the behavior of myoblast cell sheets and histological progression of wall reconstruction and alternative muscle flaps. METHODS Myoblast cell sheets were cultured for 7-10 days. In rats 67% of the abdominal esophageal muscle layers were removed. Myoblast cell sheets were transplanted to the resected site in the transplantation group while the control group received no transplantation. Body weight gain and histological evaluation were performed at weeks 1, 2, and 4 after surgery. RESULTS The fabricated myoblast cell sheets formed multilayered cell structures 50-mu m thick with desmin-positive cells and Ki67-positive cells (Ki67 rate: 39.6% +/- 6.8%). All esophageal wall resections and immediately subsequent myoblast cell sheet transplants were successful. Peritonitis was not observed in either group. At 4 weeks postoperatively, the transplant group showed a significantly higher rate of weight gain than the control group (67.8% +/- 17.3% vs 44.7% +/- 9.6%, P < 0.05). The transplantation group showed proliferating desmin-positive myoblasts 1 week postoperative and significantly thicker esophageal wall (1174.0 +/- 177.0 mu m vs 267.6 +/- 257.6 mu m, P < 0.05). The esophageal muscle layer thickness was not significantly different between the groups at 2 weeks and 4 weeks postoperative. CONCLUSION The short-term histological efficacy of allogeneic myoblast cell sheet transplantation for esophageal wall reinforcement was confirmed in an established rat model.
Introduction: Frailty in older adults is a multidimensional condition that affects healthy life expectancy. Engagement in meaningful activities (MA) is thought to support healthy aging, but the specific relationship between satisfaction with MA and frailty remains underexplored. This study investigated the longitudinal association between satisfaction with MA and frailty (physical, social, and cognitive domains) in community-dwelling older adults.Method: A total of 231 community-dwelling older adults who completed a 2-year follow-up were analyzed. Frailty in each domain was assessed at baseline and at 1- and 2-years. Participants' MA and satisfaction were obtained through face-to-face interviews. Mixed-effects logistic regression models were used to examine the longitudinal associations between satisfaction with MA and frailty status trajectories.Results: At follow-up, changes in physical frailty status were observed in most participants. Robust status was commonly maintained in the social and cognitive frailty domain. Participants' MA primarily involved leisure, sports, and domestic activities. Mixed-effects logistic regression analysis showed that satisfaction with MA was significantly associated with physical frailty, even after adjusting for potential covariates (odds ratio 0.68; 95% confidence interval 0.45, 0.99, p = 0.045). However, this association was not significant for social or cognitive frailty.Conclusion: Satisfaction with MA was longitudinally associated with physical frailty, but not with social or cognitive frailty.
