| The field of epigenetics, defined as the study of the information system which lies on top of DNA, has been rapidly growing over the past decade. Recent findings have shed light on the mechanisms and functions of mammalian epigenetic information systems, including histone modifications, small RNAs, and DNA methylation. The functions and mechanisms of non-mammalian epigenetic information systems have also been investigated, although overall much less is known about invertebrate than mammalian epigenetics. An ultimate role for DNA methylation in invertebrates is yet to be agreed upon, as several invertebrate species seem to be lacking DNA methylation entirely. If DNA methylation is ubiquitously present in all invertebrate phyla, it would provide evidence that the ultimate role of DNA methylation in invertebrates is necessary to invertebrate genome function and not a vestigial phenomenon. The poecilogonous polychaete Streblospio benedicti has dual developmental modes, with individual worms developing either as planktotrophs or lecithotrophs. The mechanism controlling the developmental "choice" between planktotrophy and lecithotrophy is yet unknown, although it has been found that developmental morphs do not have different mitochondrial genetic sequences. In light of recent advances in understanding epigenetics in mammalian systems, it seems plausible that the developmental morphotype "choice" may be governed by an epigenetic system. In mammalian systems, it has been demonstrated that the environment can directly change epigenetic signatures, however such a phenomenon has not been documented in an invertebrate system. Endogenous epigenetic signatures of the polychaete S. benedicti sort by geographic clade, indicating that the environment may directly impact the epigenome of this marine polychaete. This study investigates the distribution of an epigenetic information system, DNA methylation, across the invertebrate phyla, as well as investigating further the DNA methylation system in the poecilogonous polychaete, Streblospio benedicti. |
