New evidence to demystify the supposed holoplanktonic life cycle in Ceriantharia (Cnidaria)

From the late 1890s to the mid-1900s, descriptions of Ceriantharia species based solely on analyses of the larval forms were a common practice. Such approaches resulted in taxonomic inconsistencies and an extensive number of species with unreviewed descriptions. The present study discusses the taxonomic position of individuals from the northern Amazon coast, Brazil, using morphological, molecular, and biogeographic data. DNA samples of three larvae were collected, the COI marker was amplified, and the sequences were analyzed and checked on the NCBI databases. The morphology of each larva collected was analyzed and compared with available data. Morphological, molecular, and biogeographical evidence led to identification of the larvae from Maiandeua Island (Para) as Isarachnanthus nocturnus (den Hartog, 1977), which has a wide distribution along the Brazilian coast (from southern to northern Brazil) and the Caribbean Sea. The records also support the occurrence of the taxa in areas with estuarine influence. The larvae from Para are morphologically similar to Ovactis brasiliensis van Beneden, 1897. However, due to inconsistent description performed by van Beneden (1897), we suggest that O. brasiliensis be considered a species inquirenda.