The complete mitochondrial genome of the writing spider Argiope amoena (Araneae: Araneidae)

Comparative Mitogenomics of Jumping Spiders with First Complete Mitochondrial Genomes of Euophryini (Araneae: Salticidae)

Salticidae is the most species-rich family of spiders with diverse morphology, ecology and behavior. However, the characteristics of the mitogenomes within this group are poorly understood with relatively few well-characterized complete mitochondrial genomes. In this study, we provide completely annotated mitogenomes for Corythalia opima and Parabathippus shelfordi, which represent the first complete mitogenomes of the tribe Euophryini of Salticidae. The features and characteristics of the mitochondrial genomes are elucidated for Salticidae by thoroughly comparing the known well-characterized mitogenomes. The gene rearrangement between trnL2 and trnN was found in two jumping spider species, Corythalia opima and Heliophanus lineiventris Simon, 1868. Additionally, the rearrangement of nad1 to between trnE and trnF found in Asemonea sichuanensis Song & Chai, 1992 is the first protein-coding gene rearrangement in Salticidae, which may have an important phylogenetic implication for the family. Tandem repeats of various copy numbers and lengths were discovered in three jumping spider species. The codon usage analyses showed that the evolution of codon usage bias in salticid mitogenomes was affected by both selection and mutational pressure, but selection may have played a more important role. The phylogenetic analyses provided insight into the taxonomy of Colopsus longipalpis (Żabka, 1985). The data presented in this study will improve our understanding of the evolution of mitochondrial genomes within Salticidae.

The gene arrangement and phylogeny using mitochondrial genomes in spiders (Arachnida: Araneae)

The complete mitochondrial genome (mitogenome) of Cheiracanthium triviale was sequenced for the first time. The 14,595 bp C. triviale mitogenome contained 37 genes (13 protein coding genes, 2 ribosomal RNAs, 22 transfer RNAs) and one control region. The mitogenome of Dysdera silvatica which was available at NCBI GenBank was annotated. The mitogenome of C. triviale was compared with 43 previously sequenced spider species to observe the gene arrangements, control region and phylogeny. TreeREx analysis identified 19 mitochondrial gene rearrangements (11 transposition, 6 inversion, 2 inverse transposition) in spiders as compared with the putative ancestral gene order and lead to form new gene boundaries: trnQ-trnA, trnA-trnM for Loxosceles similis; nad3-trnS1, trnE-trnL2, trnL2-trnA, trnN-trnF for Agelena silvatica; trnN-trnE, trnE-trnA, trnR-trnF, nad4L-trnW, trnW-trnP for Carrhotus xanthogramma; trnQ-trnW, trnW-trnG, trnG-trnM for Tetragnatha nitens. Our study revealed that the gene rearrangement in spiders with putative ancestor is accelerated in Araneomorphae as compared to Mygalomorphae. Phylogenetic analysis of spiders using mitochondrial sequence data supports the monophyly of two infraorders, and sister relationship of Cheiracanthiidae with Selenopidae and Salticidae. The systematic position of the Cheiracanthium species always a controversial issue as this taxa was placed in different families by different authors.

Complete mitochodrial genome of the crab spider Ebrechtella tricuspidata (Araneae: Thomisidae): A novel tRNA rearrangement and phylogenetic implications for Araneae

Mitochondrial genomes are widely used for phylogenetic and phylogeographic analyses among arthropods, but there is a lack of sufficient mitochondrial genome sequence data for spiders. Herein, we sequenced and characterized the complete mitochondrial genome of a crab spider Ebrechtella tricuspidata (Araneae: Thomisidae). The circular mitochondrial genome is 14,352 bp long, including a standard set of 37 genes and an A + T-rich region. Nucleotide composition is highly biased toward A + T nucleotides (77.3%). A novel gene order rearrangement is detected by a tRNA (trnL1) translocation. Tandem repeats are not identified in the A + T-rich region. Most of the tRNAs are greatly reduced in size and cannot be folded into typical cloverleaf-shaped secondary structures. The phylogenetic analysis confirms that the mitochondrial genome sequences are useful in resolving higher-level relationship of Araneae. Overall, our data present in this study will elevate our knowledge on the architecture and evolution of spider mitochondrial genome.

Characterization of the complete mitogenomes of two Neoscona spiders (Araneae: Araneidae) and its phylogenetic implications

The complete mitogenomes of two orb-weaving spiders Neoscona doenitzi and Neoscona nautica were determined and a comparative mitogenomic analysis was performed to depict evolutionary trends of spider mitogenomes. The circular mitogenomes are 14,161bp with A+T content of 74.6% in N. doenitzi and 14,049bp with A+T content of 78.8% in N. nautica, respectively. Both mitogenomes contain a standard set of 37 genes typically presented in metazoans. Gene content and orientation are identical to all previously sequenced spider mitogenomes, while gene order is rearranged by tRNAs translocation when compared with the putative ancestral gene arrangement pattern presented by Limulus polyphemus. A comparative mitogenomic analysis reveals that the nucleotide composition bias is obviously divergent between spiders in suborder Opisthothelae and Mesothelae. The loss of D-arm in the trnS(UCN) among all of Opisthothelae spiders highly suggested that this common feature is a synapomorphy for entire suborder Opisthothelae. Moreover, the trnS(AGN) in araneoids preferred to use TCT as an anticodon rather than the typical anticodon GCT. Phylogenetic analysis based on the 13 protein-coding gene sequences consistently yields trees that nest the two Neoscona spiders within Araneidae and recover superfamily Araneoidea as a monophyletic group. The molecular information acquired from the results of this study should be very useful for future research on mitogenomic evolution and genetic diversities in spiders.