Abstract:
The aim of this study was to identify the pattern of egg release in the brown seaweed Hormosira banksii (Turner) Decaisne (hereafter Hormosira) from north-eastern New Zealand and its relationship with a number of environmental factors (lunar cycle, light / dark cycle, and height on shore). Hormosira females released eggs (based on number of eggs released per receptacle) with no apparent lunar cycle preference, and ceased releasing gametes at the end of the day; this may be due to their being entrained to the natural light / dark cycle. Maximum egg output occurred from receptacles 3 to 6 (numbered from the apex), and there was a gradient of age along the thallus, i.e. only young receptacles were reproductively active. Hormosira released larger eggs more rapidly at its upper limit in the intertidal compared with individuals lower down on the shore. However, though egg release was greater when expressed per receptacle it was not when expressed per conceptacle or per g dry weight. The implications of these findings and avenues for future investigation are discussed.
