Molecular identification, growth, and reproduction of Colaconema daviesii (Rhodophyta; Colaconematales) endophyte of the edible red seaweed Chondracanthus chamissoi

In this study we report for the first time the appearance of an endophytic filamentous red alga, living associated with the edible red seaweed Chondracanthus chamissoi . Molecular identification, growth, and reproduction of this endophyte are described under different conditions: photoperiod (8:16, 12:12, and 16:08 L:D), temperature (10 and 15 °C), and photon flux density (40 and 20 μmol photons m −2 s −1 ). Filaments of this endophyte were isolated and cultured, and the growth was recorded according to the number of branches and its reproduction, by quantifying the emergence of monosporangia. By sequencing the COI gene and through phylogeny reconstruction using maximum likelihood, we determined that this endophyte corresponded to Colaconema daviesii. The highest growth was recorded under the treatment 16:08 (L:D), 10 °C, and 20 μmol photons m −2 s −1 , reaching up to 100 branches after 18 days. On the other hand, over 80% of filaments with monosporangia were observed at 12:12 (L:D), 10 °C, and 20 μmol photons m −2 s −1 . This is the first record of C. daviesii on the South-eastern Pacific as an endophyte on thalli of C. chamissoi . The results of the in vitro cultures showed that once C. daviesii is isolated, the filaments are able to grow and reproduce independently of C. chamissoi . This suggests that there may not be a strict relationship between both algae and reveals the possibility of finding C. daviesii living without a host or associated with other species.