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Redbelly tilapia (Coptodon zillii) is a member of a group of fishes in the Cichlidae family endemic to the northern half of Africa and the Middle East. In the literature, the name C. zillii is mostly associated with a negative impact on the ecosystem and biodiversity in the areas to which it was introduced. In its native range, it is not a much-appreciated fish species from both fisheries and aquaculture perspectives because of its small size and difficulty to catch when compared to Nile tilapia, Oreochromis niloticus. Although C. zillii has several desirable aquaculture traits such as feeding at lower trophic levels, high fecundity, saltwater and cold tolerance, the attempts to capitalize on this potential are lacking. Moreover, comprehensive studies that characterize its ecological niche in its native range and adaptive mechanisms of invasiveness in introduced areas are also limited. Notwithstanding, it is a species of invasion concern that requires continuous monitoring and implementation of mitigation actions in non-native regions. Compilation of information regarding the environmental requirements, feeding, and reproductive biology of C. zillii may serve as a starting ingredient for further research and management of its invasiveness, which is highly required in the face of freshwater ecosystem modifications as a result of climate change. This paper also addresses the current state and potential of C. zillii for utilization in capture fisheries and fish farming.

Researchers in cryogenic magnetic refrigeration have never stopped pursuing magnetic refrigerants with lower ordering temperatures and larger magnetocaloric effects. Rare earth borates have been found to be potential cryogenic magnetocaloric materials due to their low phase transition temperatures and considerable magnetic entropy changes. Here, two rare earth borates RE8.66(BO3)2(B2O5)O8 (RE = Er, Tm) were successfully fabricated, and the crystallographic and magnetic parameters as well as cryogenic magnetocaloric effects were systematically evaluated. The compounds are deemed to crystalize in a monoclinic structure belonging to space group C2/m. They are both second-order phase transition materials without any long-range order above 2 K. These monoclinic rare earth borates, especially for Er8.66(BO3)2(B2O5)O8, show more considerable low-field magnetocaloric effects than rare earth orthoborates. For ΔH = 1 and 2 T, the values of −Δ S M max are 5.1 and 11.2 J/(kg K) for Er8.66(BO3)2(B2O5)O8, 3.0 and 5.3 J/(kg K) for Tm8.66(BO3)2(B2O5)O8, respectively. Therefore, they are regarded as potential candidates for cryogenic magnetic refrigeration. [ABSTRACT FROM AUTHOR]

Skewed sex development is prevalent in fish hybrids. However, the histological observation and molecular mechanisms remain elusive. In this study, we showed that the interspecific hybrids of the two fish species, Oreochromis niloticus and Oreochromis aureus, had a male ratio of 98.02%. Microscopic examination revealed that the gonads of both male and female hybrids were developmentally retarded. Compared with the ovaries, the testes of both O. niloticus and hybrids showed higher DNA methylation level in two selected regions in the promoter of cyp19a, the gonadal aromatase gene that converts androgens into estrogens, cyp19a showed higher level gene expression in the ovary than in the testis in both O. niloticus and hybrid tilapia. Methylation and gene expression level of cyp19a were negative correlation between the testis and ovary. Gene transcription was suppressed by the methylation of the cyp19a promoter in vitro. While there is no obvious difference of the methylation level in testis or ovary between O. niloticus and hybrids. Thus, the DNA methylation of the promoter of cyp19a may be an essential component of the sex maintenance, but not a determinant of high male ratio and developmental retardation of gonads in tilapia hybrids.

Siniperca chuatsi and Siniperca kneri are two economically important freshwater fishes endemic to East Asia. Recently, some Siniperca specimens collected from Lake Poyang and Lake Dongting in the middle reaches of the Yangtze River couldn't be clearly identified as they showed intermediate morphological characteristics between S. chuatsi and S. kneri, and some inter-species hybrids were detected by microsatellite loci. To further verify genetic composition of these intermediate individuals, and determine the prevalence and degree of introgression between the two Siniperca species, a large set of high-quality, independent, diagnostic genetic markers were necessarily required. Based on enrichment and sequencing of target genes in sinipercid fishes, 463 loci (FST = 1) between S. chuatsi and S. kneri were selected and verified for species diagnosis. A total of 349 loci with 458 diagnostic SNPs were identified for discriminating S. chuatsi and S. kneri. From those markers, 224 diagnostic SNPs (only one SNP per locus) were selected to identify and categorize 48 specimens with intermediate morphological characters. The results showed that there were 8 specimens identified as hybrids, 8 specimens as S. chuatsi and 32 specimens as S. kneri. NEWHYBRIDS analysis showed that the hybrid offsprings were composed of the first-generation hybrid (2 individuals), first-generation backcross (1 individual), second-generation backcross (1 individual) and fourth-generation backcross (4 individuals), and the backcrossing could happen to both S. chuatsi and S. kneri. These hybrids could occur naturally, or escaped from farmed fish, due to extensive artificial breeding practice in these regions. However, the origin of the introgressive hybridization can't be easily traced. Therefore, some measures for protecting genetic resource of Siniperca speies in the Yangtze River should be enforced, such as assessing genetic background of the cultured stocks, reducing the escapement from farmed fish, and monitoring the trend of introgressive hybridization between Siniperca species in the future.

An improved Informed-RRT* path planning algorithm based on node optimization is proposed to address the characteristics of the current Informed-RRT* algorithm that is slow, poorly purposeful and unsmooth in path planning. The adaptive t-distribution function is introduced to change the distribution probability of random points in different environments to improve the efficiency of the algorithm. Then an elliptic focal bias strategy is used to extend a single bias point to the whole elliptic focal point to make the random tree grow close to the minimum distance between the starting point and the target point, which increases the purposefulness of the algorithm. Finally, the re-election grandparent node strategy is used to reduce redundancy for the whole path, and the symmetric multipole type curve method is used to smooth for the path turns. The improved Informed-RRT* algorithm has higher search efficiency, more purposefulness, and smoother planned paths by comparing the surface with multiple sets of experiments. [ABSTRACT FROM AUTHOR]

Metabolite changes in Nile tilapia in response to carbonate alkalinity stress were investigated by transferring the fish directly from freshwater into different carbonate alkaline water. Levels of plasma pH/HCO3− concentration, the mRNA and protein expression of two carbonic anhydrases (CAhz and CAIV), and two HCO3− transporters (Na+/HCO3− cotransporter and Cl−/HCO3– exchanger) in the gill, kidney, and intestine were determined using a pH meter, UV spectrophotometer, quantitative real-time PCR, and western blotting within 192 h of exposure. Plasma pH showed an "up-peak-down" variation, whereas HCO3− concentration decreased at first and then increased in all alkaline water groups. The overall mRNA expression was regulated in an alkalinity- and time-dependent manner. Western blot results showed that the Cl−/HCO3− exchanger protein was detected in all tissues examined, whereas the two carbonic anhydrases and Na+/HCO3− cotransporter proteins were only expressed in the gill and kidney. Therefore, the studied carbonic anhydrases and HCO3− transporters are involved in the HCO3− metabolism and transport to maintain acid–base balance in Nile tilapia under carbonate alkalinity stress. [ABSTRACT FROM AUTHOR]