Whole-transcriptome RNA sequencing revealed the roles of chitin-related genes in the eyestalk abnormality of a novel mud crab hybrid (Scylla serrata ♀ × S. paramamosain ♂).

Chitin is a kind of insoluble structural polysaccharide and plays different roles in different species. In crustaceans, it forms the structural components in the exoskeleton. In our previous studies, novel mud crab hybrids have been produced from the interspecific hybridization of Scylla serrata ♀ × S. paramamosain ♂. Some of the hybrid crabs have been found to be morphologically (eyestalk) abnormal, but the genetic mechanism remains unknown. To address this question, we performed whole-transcriptome RNA sequencing on the control group (normal hybrids), abnormal hybrids, and S. paramamosain to uncover the genetic basis underlying this morphological abnormality. A total of 695 mRNAs, 10 miRNAs, 44 circRNAs, and 1957 lncRNAs were differentially expressed between normal and abnormal hybrids. Several differentially expressed genes (DEGs) associated with chitin and cuticle metabolism were identified, including chitin synthase, chitinase, chitin deacetylase, ß-N-acetylglucosaminidase, ß-1,4-endoglucanase, N-alpha-acetyltransferase, cuticle proprotein, early cuticle protein, and arthrodial cuticle protein. Functional analysis showed that DE miRNAs, DE circRNAs, DE lncRNAs, and lncRNA/circRNA-miRNA-mRNA network were enriched in pathways related to the amino acid, carbohydrate, and glycogen metabolism. Considering the importance of the chitin and cuticle in exoskeleton formation, it can be concluded that the changes in the chitin and cuticle biosynthesis might have caused the eyestalk abnormality in hybrid crabs. These findings can lay the solid foundation for a better understanding of the important roles of chitin and cuticle related genes and the development of hybridization techniques in crustaceans.

Evidence of Sex Differentiation Based on Morphological Traits During the Early Development Stage of Mud Crab Scylla paramamosain.

In order to uncover the sexual difference in morphology and how early they appear during the development stage of mud crab Scylla paramamosain, we measured, observed, and biostatistically analyzed morphological traits related to sex. For unveiling the morphological differences between sexes, morphological traits involving abdomen width (AW), carapace length (CL), and carapace width (CW) were first measured during the crablet development stage of S. paramamosain in the present study. The correlation analyses and path analyses exhibited that sexual dimorphism in the third abdomen width (AW3) and fourth abdomen width (AW4) could be used for sex identification from stage C VI (stage VI of crablet). Based on the stepwise discriminant analysis and standardized traits, a sex discriminant equation was constructed, which is capable for sex identification in crablets from stage C VI. Observations for secondary sexual traits and abdomen morphology (shape and pleopods) using a dissecting microscope or scanning electron microscope indicated that sexes are easily identified at stage C VIII according to the abdomen shape; meanwhile, at stage C II based on pleopod difference, and at stage C I by the presence or absence of gonopores. The findings in this study contribute greatly to the accuracy of sex identification of S. paramamosain during the early development stage, which promotes the understanding of the morphological differentiation mechanism of sex.

Spatial identification and determinants of trade-offs among multiple land use functions in Jiangsu Province, China.

Understanding the relationships among multiple land use functions (LUFs) is crucial for land-based spatial planning that can guide targeted land use policy-making in complex socio-ecological systems. However, few studies concerned the interactions among various LUFs integrating the issues of economy, environment, and society at a fine scale. In this study, we quantified 12 LUFs using a geospatial model and statistical analysis at the grid scale in Jiangsu Province. Then, we identified the relationships among three primary LUFs-agricultural production function (APF), urban-rural living function (ULF), and ecological maintenance function (EMF)-and further explored the determinants of LUF trade-offs aimed to provide a reference for policy-makers to make decisions in future land use planning and management. The results revealed that the high trade-off areas for APF and ULF are mainly distributed in central and northern Jiangsu, and the trade-offs for both APF-EMF and ULF-EMF were higher in the area covered with water and forest. The determinants of LUF trade-offs mainly refers to land use/land cover, potential evapotranspiration, and vegetation coverage ratio. Moreover, landscape configuration metrics and distance to the nearest county and nearest road also have remarkable impacts on the trade-offs of APF-EMF and ULF-EMF. Finally, we proposed that the concepts of LUF trade-offs should be incorporated into the processes of delineating boundaries for urban growth, farmland, and natural areas. We also propose that land consolidation projects should be implemented in an orderly manner to alleviate LUF trade-offs.

Complete mitochondrial genome of Brochis multiradiatus.

We reported the complete mitochondrial genome yielded by next-generation sequencing of Brochis multiradiatus in this study. The total length of the mitochondrial genome is 16,916 bp, with the base composition of 32.49% A, 25.47% T, 27.12% C, and 14.91% G. It contains 2 ribosomal RNA genes, 13 protein-coding genes, 22 transfer RNA genes, and a major non-coding control region (D-loop region). The arrangement of these genes is the same as that found in the Corydoras. The complete mitochondrial genomes of B. multiradiatus and other 12 species from Siluriformes were used for phylogenetic analysis using neighbor-joining method. The topology demonstrated that all species belong to four genera and are divided into two groups (Siluridae and Callichthyidae), the B. multiradiatus was clustered with genus Corydoras. Brochis multiradiatus' molecular classification is consistent with the external morphological feature results, so the information of the mitogenome could be used for future identification of Brochis.

Complete mitochondrail genome of Corydoras agassizii.

We reported the complete mitochondrial genome yielded using next-generation sequencing of Corydoras agassizii in this study. The total length of the mitochondrial genome is 16,562 bp, with the base composition of 32.6% A, 25.9% T, 26.8% C, and 14.7% G, in several. It contains two rRNA genes, 22 tRNA genes, 13 protein-coding genes, and a 945 bp non-coding control region (D-loop region). The sequence of these genes is consistent with that found in the Siluriformes. The complete mitogenomes of C. agassizii and other 17 species of fish were constructed by phylogenetic analysis using Neighbour-Joining method. The topological structure indicated that species participating in the analysis belong to three groups (Siluridae, Loricariidae, and Callichthyidae) of nine genera, and the C. agassizii was clustered with other species from genus Corydoras. The external morphological characteristics of C. agassizii are consistent with the results of molecular classification, so the mitogenome can be used to identify Corydoras species in the future.