Heterogeneous and compensatory growth in Melithaea flabellifera (Octocorallia: Melithaeidae) in Japan

Melithaea flabellifera (Kükenthal, 1909) (Octocorallia, Gorgonacea), an endemic and predominant gorgonian in Japanese shallow waters, grows mostly in one plane and ramifies in a dichotomous way. The growth rates of all branches and of the colony were measured from photographs of tagged gorgonian corals for approximately 1 year from June 1995 to May 1996 on the western Pacific coast of Japan (34° 39′ N, 138° 56′ E). The most rapid growth occurred when the water temperature was less than 20 °C. Mean growth ranged from 2.9 to 11.4 mm year⁻¹. Linear growth of individual branches ranged between −30.4 and 24.8 mm year ^-1−1. Both seasonal and non-seasonal variations in growth rate were observed in each colony. When branches were lost, the adjacent branches grew faster, filling the open space in the fan. Heterogeneity in growth rate within a colony was partly caused by this compensatory growth. This indicates that the regular branching pattern of gorgonians is due to irregular and heterogeneous growth. The compensatory growth suggests that M. flabellifera is constrained by some potential optimal size or form.