What Forms, Maintains, and Changes the Boldness of Swimming Crabs (Portunus trituberculatus)?

Boldness of personality is an important theme in animal behavior and has significant ecological and evolutionary consequences. Studies on boldness in crustaceans typically focus on their behavior, while relatively few studies have focused on the formation and maintenance of and change in boldness, such as energy metabolism and neurotransmission. In this study, we measured the boldness of swimming crabs (Portunus trituberculatus) and analyzed the relationship between boldness and oxygen consumption rate, energy concentration, and the relative expression of energy-metabolism-related and 5-HT genes in mRNA. The results showed that boldness remained stable across repeated tests but changed under dangerous conditions. Swimming crabs could be divided into bold and shy individuals. Bold individuals consumed oxygen at a significantly higher rate than shy individuals. Lactate and glucose concentrations in hemolymph were significantly lower in bold individuals than in shy individuals, and mRNA relative expression of Na+/K+-ATPase and 5-HT genes was significantly higher in bold than in shy individuals. Preliminary results indicate that energy metabolism and neurotransmitters may underlie the formation and maintenance of personality characteristics of swimming crabs. Swimming crabs also exhibit behavioral flexibility in order to cope with risks. This may be an adaptation to their complex environments

Differences in Agonistic Behavior and Energy Metabolism between Male and Female Swimming Crab <i>Portunus trituberculatus</i> Based on the Analysis of Boldness

Individual differences in metabolism and agonistic behavior have been a key research area in evolution and ecology recently. In this study, we investigated the boldness of swimming crabs Portunus trituberculatus and explored the agonistic behavior between female and male crabs, specifically examining competitions between bold females vs. bold males (BF–BM), bold females vs. shy males (BF–SM), shy females vs. shy males (SF–SM), and shy females vs. bold males (SF_BM) and its relationship with energy metabolism. The main results revealed the following: There was no significant difference in boldness between females and males, while there were more bold individuals than shy in both females and males. Bold individuals initiated significantly more fights than shy individuals, and male initiators won significantly more fights than female initiators. The duration and intensity of fight between bold individuals was significantly higher than fights between shy individuals. For males, the concentration of glucose in the hemolymph was significantly higher in shy crabs than bold crabs, while there was no significant difference between shy and bold individuals in females. After fighting, the concentration of glycogen in claws was lower than that before fighting, and the concentrations of glucose and lactate in hemolymph were significantly higher after fighting than before. We found that the fighting willingness and ability were higher in male crabs than females and higher in bold crabs than shy. Fighting ability varied between sexes and was influenced by boldness and energy state

Shelter Color Selection of Juvenile Swimming Crabs (<i>Portunus trituberculatus</i>)

Color preference testing for animals is a prerequisite for optimizing facilities and ensuring animal welfare in aquaculture. Swimming crabs (Portunus trituberculatus) are aggressive, and shelters are often installed in ponds to reduce the high mortality rate caused by their agonistic behavior. To test the preference of juvenile crabs for the color of shelters, this study observes the preferences of crabs for shelters of different colors (white, yellow, blue, and black). The counts and duration of crabs occupying different colored shelters were quantified. The probability of fighting and the probability of abandoning the shelter were also calculated. The results revealed that: (i) when all colors were presented simultaneously, the z-scores of the blue shelters were far higher than others during the day; (ii) when only one color was present, crabs occupied the blue shelter significantly more often and for longer periods of time than others during the day, with invasive crabs exacerbating this preference; and (iii) the probability of fighting between crabs was relatively low in the presence of the blue shelter, and the probability of abandoning the shelter was significantly lower than that of others. Based on these results, blue shelters are recommended for use in swimming crab ponds

Each Personality Performs Its Own Function: Boldness and Exploration Lead to Differences in the Territoriality of Swimming Crabs (<i>Portunus trituberculatus</i>)

The boldness and exploration of animals are closely related to their territoriality, with relevant studies having important applications in wildlife conservation. The present study establishes a behavior observation system measuring the boldness and exploration of swimming crabs (Portunus trituberculatus) to clarify the relationship between boldness, exploration, and territoriality, as well as to provide a behavioral basis for the construction of marine ranching. The behavioral tests of crabs in a safe environment (predator absence), a dangerous environment (predator presence), and habitat selection (complex and simple habitat) are analyzed. A territorial behavior score is calculated as an evaluation index of territoriality. The correlation between the swimming crabs’ boldness, exploration, and territoriality is analyzed. The results show that there is no boldness-exploratory behavioral syndrome. In predator absence or presence environments, boldness is dominant in territorial behavior and positively correlates with territoriality. Exploration plays a vital role in habitat selection tests but has no significant correlation with territoriality. The experimental results preliminarily show that boldness and exploration jointly develop the difference in the space utilization ability of crabs with different personalities, improving the adaptability of swimming crabs in different conditions. The results of this study supplement the behavior rules of the dominant species of typical fishery resources in marine ranches, providing a basis for achieving animal behavior management function in marine ranches

A Dynamic Energy Budget Model for Kuruma Shrimp Penaeus japonicus: Parameterization and Application in Integrated Marine Pond Aquaculture

Individual growth models can form the basis of population dynamics assessment and ecosystem model construction. In order to provide a basic module for an ecosystem model of an integrated marine aquaculture pond, an individual growth model was constructed for kuruma shrimp (Penaeus japonicus) based on dynamic energy budget (DEB) theory. The model was first parameterized based on a covariation method using the Add-my-Pet (AmP) procedure. The parametric estimation model underestimated the ultimate abdominal length for female shrimp, and the predicted values of other zero-variate parameters were generally consistent with observed values. The relative errors of the predicted and observed values of the univariate data set within three geographical regions showed acceptable goodness of fit. Parameter estimation achieved an overall goodness of fit with a mean relative error of 0.048 and a symmetric mean squared error of 0.066. A DEB model was constructed using the estimated parameters, and the goodness-of-fit indicators (R square, mean bias and absolute and relative root mean square error) showed that the model was able to reproduce the growth of kuruma shrimp in terms of total length and wet weight with high accuracy. The results provide data to support the subsequent development of integrated aquaculture management at the ecosystem level

Analysis of Water Chemistry Characteristics and Main Ion Controlling Factors of Lakes in the Nagqu Area of the Qinghai–Tibet Plateau in Summer

The Nagqu area is in the northern part of the Qinghai–Tibet Plateau, and its average altitude is above 4000 m. Due to the area’s high altitude, there is relatively little information about its lakes. Therefore, to supplement the basic information of lakes in the area, this study collected surface water samples from 12 lakes, including Gangtang Co, Pusaier Co, Guojialin Co, Dagze Co, Yangnapeng Co, Bankog Co, Dangqung Co, Chaxiabu Co, Angdar Co, Bengze Co, Guogen Co, and Yibug Caka from July to August 2020. Furthermore, the factors controlling the lake water chemistry characteristics and the main ion sources were explored using the Piper, Gibbs, and ion ratio methods. The results were as follows: (1) The lakes had high levels of salt, alkalinity, and mineralization, and all the lakes except Bengze Co were salt lakes. The 12 lakes met the Class V water standard. (2) Dangqung Co, Bankog Co, Guojialin Co, Daze Co, and Yangnapeng Co were in the initial stage of lake succession, while the others were in the later stages of lake succession. (3) Evaporation–crystallization was the most important factor controlling the water chemistry of the 12 lakes, and most of the ions in the lakes come from the dissolution of evaporite