Exploring mitogenome evolution in Branchiopoda (Crustacea) lineages reveals gene order rearrangements in Cladocera

Abstract

The class Branchiopoda, whose origin dates back to Cambrian, includes ~ 1200 species which mainly occupy freshwater habitats. The phylogeny and systematics of the class have been debated for long time, until recent phylogenomic analyses allowed to better clarify the relationships among major clades. Based on these data, the clade Anostraca (fairy and brine shrimps) is sister to all other branchiopods, and the Notostraca (tadpole shrimps) results as sister group to Diplostraca, which includes Laevicaudata + Spinicaudata (clam shrimps) and Cladoceromorpha (water fleas + Cyclestherida). In the present analysis, thanks to an increased taxon sampling, a complex picture emerges. Most of the analyzed mitogenomes show the Pancrustacea gene order while in several other taxa they are found rearranged. These rearrangements, though, occur unevenly among taxa, most of them being found in Cladocera, and their taxonomic distribution does not agree with the phylogeny. Our data also seems to suggest the possibility of potentially homoplastic, alternative gene order within Daphniidae.

The median eyes of trilobites

“…This may have happened several times independently, or in one ancestor in common. The Cambrian "trilobitomorph" C. eucalla possessed four median eyes also, as did the leanchoiliids, and also phylogenetically old groups such as the crustacean phyllopods 115,116 and some www.nature.com/scientificreports/ Collembola living today. Only pancrustaceans, (crustaceans and hexapods), are equipped with three median eyes.…”

The complete mitogenome of Podonevadne trigona (Sars, 1897) (Cladocera: Onychopoda: Podonidae) sheds light on the age of podonid differentiation

“…If we compare the gene order of P. trigona and the Pancrustacea gene order (Fig. 4), a hypothetical ancestral state [Castellucci et al, 2022] of Pancrustacea, Cladocera, and "Olygopoda" (Anomopoda + Onychopoda), it is clear that changes in Podonevadne affect only tRNA genes, moreover, the affected genes were located in a compact area between CR and trnY. Firstly, trnM, trnC (and, hypothetically, trnW) were transposed relatively to nad2.…”

“…Remarkably, all involved genes preserved their strand orientation. The affected regions appear as rearrangement hotspots in the mitogenomes of the Branchiopoda [Castellucci et al, 2022].…”

Chromosome-Level Assembly of Artemia franciscana Sheds Light on Sex Chromosome Differentiation

“…Artemia brine shrimp are crustaceans belonging to the Anostracan order in the Branchiopoda class, which includes around 1,200 species ( Castellucci et al 2022 ). They live in saline/hypersaline inland water bodies, with a very wide geographical distribution ( Eimanifar et al 2015 ).…”