第 297 回 三崎談話会

下記の通り、第297回 三崎談話会を開催いたします。今回は、特異な繁殖様式を示す環形動物であるシリス類について、世界に先駆けた研究を行っている M. Teresa Aguado博士、Guillermo Ponz Segrellesさん(スペイン)をお招きしてご講演頂きます。ご興味のあるかたは是非ご参加下さい。談話会・懇親会の申込は、三浦(または宇田川(世話人まで。



講演者:M. Teresa Aguado (1, 2)

    Guillermo Ponz Segrelles (2)

     1) Georg-August-Universität Göttingen, Germany

     2) Universidad Autónoma de Madrid, Spain

懇親会: 18時30分〜 場所未定 

M. Teresa Aguado (Georg-August-Universität Göttingen, Germany; Universidad Autónoma de Madrid, Spain)
「Branching annelids and the tree syllid worm」

 The occasional occurrence of annelids with two tails have been recorded both in nature, and, more frequently, in worms in which regeneration has been studied experimentally since the XIX century. These aberrant forms have been considered the result of punctual “mistakes” or induced experiments during the regeneration process; and there are no reports of these animals living further for reproductive activity. However, within Syllinae, two species have been described with a morphology that makes them unique among all so far ~20,000 described annelids: Syllis ramosa McIntosh, 1879 (from Philippines) and Ramisyllis multicaudata Glasby, Schroeder and Aguado, 2012, the so-called Tree syllid worm (from Australia). These animals are the only two branching annelids and they live in strict symbiosis within sponges. They have one “head” but multiple branches; each of them goes into a canal of their host, growing within the sponge by producing new branches and enlarging the existing ones. This body pattern and biology has astonished biologists and the general public since they were first described. The recent studies with R. multicaudata are currently stimulating many lines of research both within and outside of the fields of systematics and development. Other records without proper identification of possible branching syllids have been provided from the Red Sea, New Zealand and Japan. Fortunately, we have recently identified a possible population in Japan. Our recent results in external and internal anatomy, reproduction, symbiotic and feeding behavior as well as phylogenetic relationships and genomic data from R. multicaudata will be summarized herein and future perspectives for the study of branching annelids from Japan will be presented.

Guillermo Ponz Segrelles (Universidad Autónoma de Madrid, Spain)
「Male-specific changes characterize differential gene expression analysis of reproducing Syllis prolifera and Nudisyllis pulligera (Syllidae, Annelida)」

 Of the staggeringly diverse reproductive strategies of annelids, perhaps none is more interesting than that of syllids (Annelida, Syllidae). During their reproduction, syllids not only undergo epitoky-related morphological changes as those observed in other annelids (e.g. nereidids), but, in some cases, also create independent reproductive unites called stolons. This, creates a uniquely complex life cycle which has been studied by many authors. Several studies during the 80’s and 90’s concluded that the process of stolonization was related to environmental factors such as water temperature and moon cylces, and that there is a male-as-default hormonal regulatory system. However, the physiological and genetic mechanisms behind this process are still largely unknown and only recently there have been new efforts to try to understand this process in more detail. In order to find mechanisms potentially involved in reproductive processes in syllids, we selected female, male, and non-reproducing individuals of Syllis prolifera (Stolonizing) and Nudisyllis pulligera (non-stolonizing) and used them for comparative transcriptomic analyses. For that, we assembled transcriptomes de novo, annotated them, and calculated and compared expression values for each of the assembled transcripts. This comparison allowed us to find that gene expression is altered to a greater extent in males than in females when compared to the non-reproducing individuals, pointing to a sex determination system in which negative regulation of gene expression might be playing an important role. Finally, we also used this data to find sex-specific changes in Gene Ontology categories not previously known to play a role in syllid reproduction.