Observations on the rate of growth, sexual maturity and breeding of four sedentary organisms from the Madras harbour

The destruction caused to the underwater harbour installations and ships' bottom by the accumulation of sedentary organisms drew the attention of workers in temperate and subtropical regions to a study of the biology and ecology of such animals as a preliminary step in tackling' the antifouling problem. It has been observed under tropical conditions that fouling is more pronounced due to prolonged period of breeding activity, settlement in larger numbers and constant organic growth (Edmondson, 1944 ; Pyefinch, 1947 ; Daniel, 1954). A fact-finding survey to determine the members of the fouling community, their abundance in relation to different environmental conditions, seasonal or ecological succession, if any, their rate of growth and breeding activities will contribute much towards an understanding of the fouling problem. In an earlier paper the author (Antony Raja, 1959) has dealt with the distribution and succession of sedentary organisms of the Madras harbour with a discussion on the influence of environmental factors. Except for a preliminary survey of marine borers of the Cochin harbour (Erlanson, 1936), observations on the growth of a few sedentary organisms of the Madras harbour (Paul, 1942) and brief records from the Vizakhapatnam harbour (Ganapati et al., 1958), information regarding the growth rate of marine sedentary organisms of sheltered waters is not available. Hence an attempt is made here to estimate the rate of growth, size at sexual maturity and breeding of four sedentary organisms, namely, Modiolus striatulus. Bowerbankia sp., Cynthia sp., and Dasychone cingulata as a continuation of Paul's work, which has not dealt with the above forms