Mar Biol (2009) 156:1659–1671 DOI 10.1007/s00227-009-1201-6 123 ORIGINAL PAPER Gametogenic and reproductive cycles of the sea anemone, Entacmaea quadricolor Anna Scott · Peter Lynton Harrison Received: 15 September 2008 / Accepted: 13 April 2009 / Published online: 30 April 2009  Springer-Verlag 2009 Abstract Host sea anemones are ecologically important as they provide habitat for obligate symbiotic anemoneWsh in many areas of the Indo-PaciWc. Despite their importance, no information is available on their gametogenic cycles. This study aimed to address this lack of knowledge by determining the gametogenic cycles of Entacmaea quadri- color. Gonad samples were taken from January 2003 to February 2005 at North Solitary Island, Solitary Islands Marine Park, Australia using a specially developed non- lethal Weld biopsy sampling technique. Sampling was done 17 times during the study period, with 15–20 individuals being sampled on each occasion. Samples were examined prior to Wxation, and then histologically sectioned to deter- mine the reproductive activity of each individual. Female anemones were signiWcantly more abundant than males, and had asynchronous oocyte development both within and among individuals. Male anemones showed a single annual cycle of spermary growth, development and spawning. Data from the 26-month study indicated that spawning occurred in the austral summer and autumn between Janu- ary and April, which coincided with the observed spawning periods that have previously been documented for this spe- cies in outdoor Xow-through seawater tanks at the study location. The biopsy sampling technique used during this study provides an opportunity to gain a more thorough understanding of the gametogenic cycles and sexual pattern of host sea anemones throughout their distribution. Introduction Gametogenesis has been described for a number of species of sea anemone, with most studies being done on species that are found in intertidal and shallow subtidal habitats (Chia and Rostron 1970; Dunn 1975; Jennison 1979; Carter and Funnell 1980; Sebens 1981; Bucklin 1982; Shaw 1989; Fukui 1995; Lin et al. 2001). Only a few studies have examined the reproductive cycles of deeper water species (Wedi and Dunn 1983; Chia et al. 1989; Van-Praët 1990; Van-Praët et al. 1990). All workers, with the exception of Carter and Funnell (1980), have collected, dissected and sectioned whole animals to determine the reproductive cycles of sea anemones. In contrast, Carter and Funnell (1980) used a repeated biopsy sampling technique in the laboratory, which greatly reduced the number of individu- als taken from the Weld. Biopsy sampling has also been used to determine the reproductive activity of other marine invertebrates such as giant clams (Braley 1984), and poly- chaetes (Olive 1995). While previous studies have provided information on gamete structure, development and seasonal changes during sea anemone oogenesis and spermatogenesis, no studies have been published on the gametogenic cycles of sea anemones that host obligate symbiotic anemoneWsh. These host sea anemones are ecologically important in many parts of the Indo-PaciWc as they provide essential habitat for 28 Communicated by M. Byrne. A. Scott National Marine Science Centre, PO Box J321, CoVs Harbour Jetty, NSW 2450, Australia A. Scott (&) · P. L. Harrison Coral Reef Research Centre, School of Environmental Science and Management, Southern Cross University, PO Box 157, Lismore, NSW 2480, Australia e-mail: ascott@nmsc.edu.au P. L. Harrison e-mail: peter.harrison@scu.edu.au