Natural Variation of Model Mutant Phenotypes in Ciona intestinalis

Abstract

BackgroundThe study of ascidians (Chordata, Tunicata) has made a considerable contribution to our understanding of the origin and evolution of basal chordates. To provide further information to support forward genetics in Ciona intestinalis, we used a combination of natural variation and neutral population genetics as an approach for the systematic identification of new mutations. In addition to the significance of developmental variation for phenotype-driven studies, this approach can encompass important implications in evolutionary and population biology.Methodology/Principal FindingsHere, we report a preliminary survey for naturally occurring mutations in three geographically interconnected populations of C. intestinalis. The influence of historical, geographical and environmental factors on the distribution of abnormal phenotypes was assessed by means of 12 microsatellites. We identified 37 possible mutant loci with stereotyped defects in embryonic development that segregate in a way typical of recessive alleles. Local populations were found to differ in genetic organization and frequency distribution of phenotypic classes.Conclusions/SignificanceNatural genetic polymorphism of C. intestinalis constitutes a valuable source of phenotypes for studying embryonic development in ascidians. Correlating genetic structure and the occurrence of abnormal phenotypes is a crucial focus for understanding the selective forces that shape natural finite populations, and may provide insights of great importance into the evolutionary mechanisms that generate animal diversity.

Qualitative variation in colour morphotypes of Ianthella basta (Porifera: Verongida)

“…The phylogenies inferred in this study clearly indicate that the taxonomic integrity and the genealogical relationships of the I. basta morpho-species complex require further assessment. Genetically cryptic lineages often occur in marine invertebrates assumed to be biologically distinct morpho-species and these are often associated with specific geographic patterns of distribution, morphological variation or ecophysiological and reproductive differences (Caputi et al, 2007;Sordino et al, 2008;Poore & Andreakis, 2011). Inconsistent identification of species may have severe implications in biodiversity assessments of (Bickford et al, 2007).…”

“…When selecting a model for studies of ecology, biodiscovery or symbiosis, it is essential to define the taxonomic status of the organism and to uncover any hidden intra-species variation, especially in the case of geographically distinct populations of so-called cosmopolitan species (Caputi et al, 2007;Sordino et al, 2008;Poore & Andreakis, 2011). The taxonomic identification of many marine invertebrates to the species level remains the task of specialists (Ackers & Moss, 1987;Bell & Barnes, 2001).…”

Fine‐ and regional‐scale genetic structure of the exotic ascidian Styela clava (Tunicata) in southwest England, 50 years after its introduction

“…Using five microsatellites, gene diversity values (0.52 < H E < 0.63, with a mean of 0.58 ± 0.04 computed over the eight localities) were lower than values reported for the widespread solitary tunicate Ciona intestinalis sp. A (the mean H E computed over three populations using 12 microsatellites was 0.73, Sordino et al . 2008) but five times higher than values reported for Corella eumyota , a solitary ascidian recently introduced in the English Channel (in which the mean H E computed over two native and one introduced population using 12 microsatellites was 0.13, Dupont et al .…”

Ciona intestinalis and Oxycomanthus japonicus, Representatives of Marine Invertebrates

“…Wild populations of Ciona intestinalis frequently contain spontaneous mutants, and these are useful sources for mutant screening [53]. Recently, a mutant named tail regression failed (trf), that shows defects during metamorphosis, was isolated [28].…”