Mitochondrial genomes of four slug moths (Lepidoptera, Limacodidae): Genome description and phylogenetic implications

The family Limacodidae belongs to the superfamily Zygaenoidea, which includes 1672 species commonly referred to as slug moths. Limacodidae larvae are major pests for many economically important plant species and can cause human dermatitis. At present, the structure of the mitochondrial genome (mitogenome), phylogenetic position, and adaptive evolution of slug moths are poorly understood. Herein, the mitogenomes of Parasa lepida, Phlossa conjuncta, Thosea sinensis, and Setora sinensis were sequenced and compared with other available mitogenome sequences to better characterize the mitogenomic diversity and evolution of this moth family. The mitogenomes of P. lepida, P. conjuncta, T. sinensis, and S. sinensis were confirmed to be circular in structure with lengths of 15,575 bp, 15,553 bp, 15,535 bp, and 15,529 bp, respectively. The Limacodidae mitogenomes exhibited similar nucleotide composition, codon usage, RNA structure, and control region patterns, indicating the conservation of the mitogenome in the family Limacodidae. A sliding window, Ka/Ks, and genetic distance analyses revealed that the atp8 and nad6 genes exhibited the highest levels of variability and the most rapid evolutionary rates among the 13 protein-coding genes (PCGs) encoded in these Limacodidae mitogenomes, suggesting that they may offer value as candidate DNA markers. The phylogenetic analysis recovered the overall relationship as Tortricoidea + (Sesiidae + (Zygaenoidea + (Cossoidea/+Choreutoidea + (others)))). Within Zygaenoidea, Limacodidae was recovered as monophyletic, and the phylogenetic relationships were recovered as (Phaudidae + Zyganidae) + Limacodidae in all six phylogenetic trees. The analysis indicated that P. lepida, P. conjuncta, T. sinensis, and S. sinensis are members of the Limacodidae.

Complete mitochondrial genome of Parasa sinica: New insights into the phylogeny of Limacodidae

In this study, the whole mitochondrial genome (mitogenome) of Parasa sinica was sequenced. It contains 15,306 base pairs (bp), 13 protein-coding genes (PCGs), two ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), and one non-coding regulatory area (CR), all of which are shared by other lepidopterans. It follows the same gene order as ordinary lepidopterans. Further, out of these 37 genes, 23 are present on the heavy strand whereas the remaining 14 are located on the light strand. The A + T composition of the mitogenome is relatively high. Although P. sinica has a negative AT-skew and GC-skew, the GC-skew value is significantly lower than the AT-skew value. All PCGs, with the exception of CO1, carry the same start codon (ATN). All tRNAs exhibit the usual cloverleaf secondary structure. We identified the conserved motif "ATAGA + poly-T″ found in other lepidopteran insects at the beginning of the CR. We collected the concatenated PCGs sequences in the mitochondrial genome of 15 species of Zygaenoidea, with the sequences of Geometridae as outgroups, including P. sinica, and constructed phylogenetic trees using Bayesian inference (BI) and maximum likelihood (ML) methods. The monolineage of each superfamily is usually well supported. Based on phylogenetic analysis, P. sinica is a member of family Limacodidae, strongly supporting the monophyly of the Zygaenoidea groups.

?Two new species of the subgenus Reticularisus (Lepidoptera, Limacodidae, Rhamnosa) from China, with a checklist of the genus Rhamnosa Fixsen, 1887

Two new species of the subgenus Reticularisus Wu, Wu & Han, 2022 of the genus Rhamnosa Fixsen, 1887, Rhamnosa (Reticularisus) chenjunisp. nov. and Rh. (R.) mangshanensissp. nov., are described from the provinces of Hunan and Guangdong, China. The adults and genital structures of the new species and similar examined species are illustrated. A checklist of the genus is provided.

The complete mitochondrial genome of Amesia sanguiflua (Lepidoptera, Zygaenidae)

Amesia sanguiflua (Lepidoptera, Zygaenidae) is found in northern India, Myanmar, Indochina, Malay Peninsula, Sumatra, Java, and China. In the present study, we sequenced the complete mitochondrial genome of A. sanguiflua. The mitochondrial genome was 15,203 bp in length, containing a typical set of 37 genes (13 protein-coding genes, 2 rRNA genes, 22 tRNA genes) and a 346bp non-coding A+T-rich region. Phylogenetic analysis using mitochondrial genomes of 40 species showed that A. sanguiflua formed a well-supported monophyletic group with other Zygaenidae species.

Evolution and losses of spines in slug caterpillars (Lepidoptera: Limacodidae)

Larvae of the cosmopolitan family Limacodidae, commonly known as "slug" caterpillars, are well known because of the widespread occurrence of spines with urticating properties, a morpho-chemical adaptive trait that has been demonstrated to protect the larvae from natural enemies. However, while most species are armed with rows of spines ("nettle" caterpillars), slug caterpillars are morphologically diverse with some species lacking spines and thus are nonstinging. It has been demonstrated that the evolution of spines in slug caterpillars may have a single origin and that this trait is possibly derived from nonstinging slug caterpillars, but these conclusions were based on limited sampling of mainly New World taxa; thus, the evolution of spines and other traits within the family remains unresolved. Here, we analyze morphological variation in slug caterpillars within an evolutionary framework to determine character evolution of spines with samples from Asia, Australia, North America, and South America. The phylogeny of the Limacodidae was reconstructed based on a multigene dataset comprising five molecular markers (5.6 Kbp: COI, 28S, 18S, EF-1α, and wingless) representing 45 species from 40 genera and eight outgroups. Based on this phylogeny, we infer that limacodids evolved from a common ancestor in which the larval type possessed spines, and then slug caterpillars without spines evolved independently multiple times in different continents. While larvae with spines are well adapted to avoiding generalist predators, our results imply that larvae without spines may be suited to different ecological niches. Systematic relationships of our dataset indicate six major lineages, several of which have not previously been identified.

The complete mitochondrial genome of Pidorus atratus (Lepidoptera: Zygaenoidea: Zygaenidae)

The complete mitochondrial genome (mitogenome) of Pidorus atratus (Lepidoptera: Zygaenoidea: Zygaenidae) is described in this study. The circular molecule is 15,383 bp in length and contains 37 typical mitochondrial genes and one non-coding AT-rich region. All protein-coding genes (PCGs) start with ATN, except for cox1 gene with CGA; 10 of the 13 PCGs harbour the typical stop codon TAA, whereas cox1, cox2, and nad4 end with a single T. Two ribosomal RNA genes (rRNAs) are 1366 bp and 544 bp in length, respectively. The AT-rich region is 658 bp in size and harbours several features characteristic of the lepidopterans, including the motif ATAGA followed by a 20 bp poly-T stretch and a microsatellite-like (TA)9 element. The complete mitogenome data would be useful for further understanding the taxonomy and phylogeny of Zygaenoidea.