In the tropics, the marine sponge Dysidea janiae lives in obligatory symbiosis with the red macroalga Jania adhaerens. However, how this symbiosis is achieved, and how it influences the reproduction of the sponge is still unknown. We analysed the influence of environmental variables on the gametogenesis and embryogenesis of the sponge. We also investigated the histology of the reproductive propagules of the sponge over 3 years, aiming to understand how this symbiosis is established. Dysidea janiae is viviparous and gonochoristic, with a continuous but small reproductive effort. The reproductive dynamics of gametes and embryos were explained by different sets of environmental variables. Although the temperature was not directly related to the reproduction of the sponge in general, there was an increase in the density of spermatic cysts during the year when the El Niño occurred. The day length was related to the embryo dynamics, which were interpreted as an indirect effect of the increase in photosynthetic rates of the symbiont on the energetic budget of the sponge. As no algal propagules were found associated with the eggs or larvae of the sponge, the acquisition of the algae by the sponge is probably a ‘trial-and-error’ relationship after larval release. We propose that the symbiosis increases the fitness of the adult sponge, forcing the larvae to seek new macroalgae to settle on and start a new symbiosis all over again.

在热带地区，海洋海绵Dysidea janiae与红色巨藻Jania adhaerens处于强制性共生关系。然而，如何实现这种共生以及如何影响海绵的繁殖仍是未知的。我们分析了环境变量对海绵的配子发生和胚胎发生的影响。我们还调查了3年多的海绵繁殖繁殖体的组织学，旨在了解这种共生是如何建立的。dydya janiae是胎生和生殖腺，持续不断但繁殖力很小。配子和胚胎的生殖动力学通过不同的环境变量集来解释。尽管温度通常与海绵的繁殖没有直接关系，但在发生厄尔尼诺现象的那一年中，精囊肿的密度有所增加。日长与胚胎动力学有关，这被解释为共生生物光合作用速率增加对海绵能量预算的间接影响。由于未发现与海绵的卵或幼虫相关的藻类繁殖体，因此在释放幼虫后，海绵对藻类的吸收可能是“试错”的关系。我们建议共生可以增加成人海绵的适应性，