Abstract
Polyclad flatworms are an early branching clade within the rhabditophoran Platyhelminthes. They provide an interesting system with which to explore the evolution of development within Platyhelminthes and amongst Spiralia (Lophotrochozoa). Unlike most other flatworms, polyclads undergo spiral cleavage (similar to that seen in some other spiralian taxa), they are the only free-living flatworms where development via a larval stage occurs, and they are the only flatworms in which embryos can be reared outside of their protective egg case, enabling embryonic manipulations. Past work has focused on comparing early cleavage patterns and larval anatomy between polyclads and other spiralians. We have selected Maritigrella crozieri, the tiger flatworm, as a suitable polyclad species for developmental studies, because it is abundant and large in size compared to other species. These characteristics have facilitated the generation of a transcriptome from embryonic and larval material and are enabling us to develop methods for gene expression analysis and immunofluorescence techniques. Here we give an overview of M. crozieri and its development, we highlight the advantages and current limitations of this animal as a potential evo-devo model and discuss current lines of research.
Highlights
Polyclad flatworms are an early branching clade within the rhabditophoran Platyhelminthes
More than one developmental type has been described in a genus, sometimes even in the same species. This may be partly attributed to the difficulty of correct species determination in many acotyleans, which is reflected in frequent taxonomic rearrangements, such as in the cases of Hoploplana inquilina, Stylochus ellipticus and Stylochoplana maculata
Whilst our attempts to identify in the transcriptome of M. crozieri homologs of brachyury and xlox have been unsuccessful so far, we found homologs of gsx and cdx (Additional file 5: Figure S1, and Additional file 6)
Summary
M. crozieri’s large size at maturity facilitates the extraction of hundreds of naked embryos from the adult and makes the collection of individuals from the field easier. An embryonic and larval transcriptome has been sequenced and assembled and is currently being analysed and complemented by full-genome sequencing. These resources are facilitating obtaining genes of interest for in situ probe synthesis, among others. Additional file 1: Sperm transfer of adult Maritigrella crozieri. Additional file 3: Phototactic behaviour of 2-day-old Maritigrella crozieri larvae in an embryo dish illuminated on the left side. Additional file 4: Trajectories of 2-day-old Maritigrella crozieri larvae swimming towards a light source situated on the left side. The sequences of the contigs corresponding to the Maritigrella cdx and gsx genes can be found in Additional file 1. Additional file 6: Sequence of the contigs from Maritigrella crozieri’s transcriptome corresponding to the cdx and gsx genes.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have