Sperm of the Solitary Coral Ctenactis echinata Exhibit Longer Telomeres than that of Somatic Tissues Michiko C. Ojimi 1, *, Yossi Loya 2 , and Michio Hidaka 1 1 Department of Chemistry, Biology and Marine Science, Faculty of Science, Univ. of the Ryukyus, Nishihara, Okinawa 903-0213, Japan 2 Department of Zoology, Tel Aviv Univ., Tel Aviv 69978, Israel (Accepted October 31, 2012) Michiko C. Ojimi, Yossi Loya, and Michio Hidaka (2012) Sperm of the solitary coral Ctenactis echinata exhibit longer telomeres than that of somatic tissues. Zoological Studies 51(8): 1475-1480. Because many corals reproduce asexually through regeneration from fragments, establishing a simple relationship between the age and size of a coral is problematic. Here, we attempted to test the coral telomere length as an indicator of age and senescence, because telomere shortening occurs during cell division. We examined the association between the size (weight) of a coral and the average length of its telomeres as determined by single telomere length analysis (STELA) products. We chose as our study species the solitary coral Ctenactis echinata, which is unlikely to reproduce via fragmentation and has never been observed to reproduce asexually via budding. We ampliied DNA fragments containing part of a telomere with part of the subtelomeric region using a dual- suppression PCR, and determined DNA sequences of subtelomeric regions in order to design chromosome- speciic primers for the STELA. The average length of STELA products was calculated from densitometric data, and it was plotted against the weight of the coral. Although sperm exhibited a longer telomere length than that of somatic tissues, there was no signiicant relationship between the average length of the STELA products and the weight of individuals. These results suggest that telomere shortening occurs during early development in this solitary coral. Moreover, our indings are expected to provide a genetic basis for coral aging. Future research on the range of telomere changes occurring in this coral would further our understanding of how age and size are related. http://zoolstud.sinica.edu.tw/Journals/51.8/1475.pdf Key words: Ageing, Coral, Lifespan, Senescence. *To whom correspondence and reprint requests should be addressed. Tel: 81-98-8958547. Fax: 81-98-8958576. E-mail:m.c.ojimi@gmail.com Scleractinian corals display asexual repro- duction in various ways, such as fragmentation (Highsmith 1982, Smith and Hughes 1999), transverse fission (Wells 1966), polyp bailout (Sammarco 1982), polyp expulsion (Karmarsky- Winter et al. 1997), and asexual planulae (Stoddart 1983), in addition to sexual reproduction. Corals also display a high capacity to regenerate from small pieces of tissue (Krupp et al. 1992, Vizel et al. 2011). Currently, it is not possible to determine whether both asexually produced corals and those regenerated from fragments are of the same age as their source colonies. Furthermore, the occasionally occurring fission and fusion of coral colonies make it difficult to estimate the age of corals from their size (Hughes and Jackson 1980, Hughes and Connell 1987, Babcock 1991). Coral age (in years) can be estimated from growth bands, but this method is applicable only to corals with a massive growth form. It is hard to estimate the age of branching corals due to difficulties in obtaining a complete growth band, and to possible fragmentation. It is thus important to establish a method with which to estimate coral age based on soft tissues. Such a method would contribute much to our understanding of coral population biology, demographics, and various life history traits such as age at reproductive Zoological Studies 51(8): 1475-1480 (2012) 1475