Environmental enrichment is a method to increase environmental heterogeneity, which may reduce stress and improve animal welfare. Previous studies have shown that environmental enrichment can increase the growth rate, decrease aggressive and anxiety-like behaviors, improve learning ability and agility, and reduce cortisol levels in animals. These effects usually differ between species. Unfortunately, habitat enrichment on laboratory fish is poorly studied and seldom adopted in care guidance. Rare minnows (Gobiocypris rarus) have been cultured as a native laboratory fish in China in barren banks without environmental enrichment since 1990; they have been widely used in studies on ecotoxicology, environmental science, and other topics. The purpose of this study was to investigate the effect of environment enrichment on the growth, physiological status, and anxiety-like behavior of laboratory rare minnows. We observed and analyzed SGR, cortisol levels, DA, DOPAC, 5-HT and 5-HIAA, and anxiety-like behavior indexes after one month of treatment in barren (control) and enrichment tanks. We found that there were no significant differences in SGR, anxiety-like behavior, DA, DOPAC, or 5-HIAA levels between the two treatments. However, higher cortisol and 5-HT levels were observed in the enrichment tanks. This study suggests that rare minnows might be influenced by their living environment, and future related studies should consider their environmental enrichment.

Mountain channels have received relatively little study compared to lowland rivers due to their complicated fluvial geomorphology and inconvenient traffic. Classification schemes and habitat assessments in mountain channels should be strengthened to provide a scientific basis for river ecological restoration. Therefore, we tried to simplify the habitat assessment of mountain channels using a suitable habitat classification scheme based on high-resolution satellite imagery. We used China’s Chishui River basin because it is a typical mountain river system. Five parameters (stream order, elevation, slope, sinuosity and river network density) and 120 sites were used for habitat classification. In addition, we recorded 20 metrics in four categories (water environmental status, river morphology, riparian zone and human disturbance). Our results identified a total of 40 representative sampling sections belonging to six habitat types that were useful for habitat assessment across the Chishui River basin. The basin was given a mean comprehensive habitat quality index (CHQI) score of 130.66 ± 24.14 and classified under the status “good.” However, the headwaters, Tongmin River, Tongzi River and Xishui River were disturbed by various human activities. We conclude that the process of developing and simplifying our habitat assessment systems can be regarded as a reference for biomonitoring in other mountain river systems.

Fishes often adjust their behaviour patterns and physiological responses to cope with changing environments, and different life experiences affect them differently. Fishes might adapt to short-term stress, whereas long-term unpredictable stress may lead to various adverse effects. Although some studies have constructed unpredictable stress models of fish, the effect of unpredictable chronic stress (UCS) in the laboratory is poorly understood in fishes. In the current study, we exposed adult rare minnow to an unpredictable chronic stress protocol over 7 and 14 days and measured their response in terms of growth performance, cortisol, neurotransmitter levels (DA, 5-HT, and related metabolites), and behaviour patterns to comprehensively assess the effects of UCS on laboratory rare minnow. We discovered that specific growth rates were significantly decreased, and cortisol levels were lowered in both 7-days and 14-days stress groups. In the behaviour test, the activity level of the 14-days stress group increased, but there was no significant difference in the number of crossings to the center areas, time spent in the center areas, or the speed. In addition, the levels of DA and 5-HT did not change in the stress groups, but the DOPAC and 5-HIAA levels in the 14 days stress group were significantly higher than those in the control group. These results suggested that UCS influences rare minnow growth performance, behaviour patterns, and cortisol levels, and similar stress should be minimised in the laboratory.

Bellamya limnophila is a mollusk of significant medical and economic value in China. Understanding the complete mitochondrial genome of this species will better establish a foundation for systematic classification research on Viviparidae. Therefore, we sequenced the complete mitochondrial genome of B. limnophila, conducted a comprehensive analysis of its structural characteristics, and constructed a phylogenetic tree using maximum likelihood and Bayesian methods. The results showed that the genome sequence is 16,991 bp in length, including 13 protein-coding genes (PCGs), 20 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and 1 non-coding region (D-loop). In summary, the Ka/Ks ratios of all PCGs were <1, indicating that purifying selection dominated the evolutionary process of these snails. The entire genome structure exhibited conservative features, such as the majority of start codons being the standard ATG codon and the majority of tRNA genes having the standard cloverleaf secondary structure. B. limnophila and B. quadrata showed collinearity in terms of sequence homology. Phylogenetic analysis indicates that the clade formed by the genera Margarya, Cipangopaludina, and Bellamya is the sister group of the genus Viviparus; Bellamya limnophila is more closely related to B. quadrata than to other species. This study contributes to the mitochondrial genome database of the family Viviparidae and provides valuable insights into the phylogenetic relationships of related snails.