# The Families of Non-LTR Transposable Elements within Neritimorpha and Other Gastropoda

## TL;DR

This study identifies and characterizes non-LTR transposable elements in neritimorph snails and other gastropods, revealing insights into their diversity and evolutionary relationships.

## Contribution

The study provides the first detailed characterization of non-LTR transposable element families in neritimorph snails and highlights their phylogenetic patterns.

## Key findings

- Multiple families of non-LTR TEs from I, Jockey, L1, R2, and RTE superfamilies were identified in neritimorph snails.
- Phylogenetic analysis of ORF2 regions showed interspersion of neritimorph taxa within TE families.
- ORF1 sequences revealed monophyletic groups for individual species, with close relationships between Neritidae species.

## Abstract

Repeated sequences, especially transposable elements (TEs), are known to be abundant in some members of the important invertebrate class Gastropoda. TEs that do not have long terminal repeated sequences (non-LTR TEs) are frequently the most abundant type but have not been well characterised in any gastropod. Despite this, sequences in draft gastropod genomes are often described as non-LTR TEs, but without identification to family type. This study was conducted to characterise non-LTR TEs in neritimorph snails, using genomic skimming surveys of three species and the recently published draft genome of Theodoxus fluviatilis. Multiple families of non-LTR TEs from the I, Jockey, L1, R2 and RTE superfamilies were found, although there were notably few representatives of the first of these, which is nevertheless abundant in other Gastropoda. Phylogenetic analyses of amino acid sequences of the reverse transcriptase domain from the elements ORF2 regions found considerable interspersion of representatives of the four neritimorph taxa within non-LTR families and sub-families. In contrast, phylogenetic analyses of sequences from the elements’ ORF1 region resolved the representatives from individual species as monophyletic. However, using either region, members of the two species of the Neritidae were closely related, suggesting their potential for investigation of phyletic evolution at the family level.