Reproductive ecology of Fungiacyathus marenzelleri from 4100 m depth in the northeast Pacific Ocean

Fungiacyathus marenzelleri (Vaughan, 1906) is a deep-water solitary coral, cosmopolitan in distribution that is found at depths of 300-6,328 m. This study examined gametogenesis, inter-annual variability and reproductive periodicity of F. marenzelleri collected from Station M (34 degrees 50'N, 123 degrees 00'W) in the northeast Pacific at a depth of 4,100 m. Samples were collected (May, June, October 1996; August 1998; February, June 2001; and June 2002) and histologically processed with spermatogenic stage, oocyte size and fecundity measured. Four stages of spermatogenesis were identified and all males contained multiple stages of sperm development in each seasonal sample. Three stages of oocyte development were identified; previtellogenic (< 28-150 mu m), vitellogenic (150-300 mu m) and late vitellogenic (300-400 mu m). Comparison of mean oocyte diameters among sampling dates showed there were no inter-annual variations or seasonal differences. Overall, fecundity was 1,290 (+/- 407) oocytes polyp(-1), and with no significant differences between sample months. Fecundity was not polyp-size dependent. This study shows a similar quasi-continuous mode of reproduction to this species examined from the Northeast Atlantic Ocean, but the fecundity is reduced by 50%. The reproductive output may fluctuate in relation to the input of organic material at this site, as shown by non-significant trends in the oocyte size-frequency and fecundity data. A quasi-continuous output of gametes would promote successful fertilisation and wide dispersal of the lecithotrophic larvae.