Patterns of Sexuality, Asexual Reproduction and Recruitment in Some Subtidal Marine Demospongiae

The patterns of sexuality and asexual reproduction in 10 species of subtidal Demospongiae were investigated by following reproductive activity in particular individuals and in the populations of each species over a 2-year period. Potential reproductive output was measured and related to recruitment rates recorded from natural and artificial surfaces. 2. The ceractinomorph sponges were found to be all hermaphrodites producing viviparous larvae while most of the tetractinomorph sponges were found to be gonochoric over the period of study and apparently oviparous. In the tetractinomorph sponge populations there was usually a majority of females and in two species no males were found. Three of the tetractinomorph species also produced buds. 3. Viviparous larvae are thought to be adaptations to habitats with high levels of disturbance. 4. Recruitment in both groups of sponges was low and unpredictable except in Polymastia sp. (yellow) which produced buds all year round and had predictable recruitment of low numbers of individuals. Recruitment occurred predominantly on natural surfaces.