Quantification of the non-indigenous ophiuroid Ophiothela mirabilis Verrill, 1867 associated with marine sponges with different morphologies

Sponges are normally considered as living hotels and they have been the most common basebionts (45.5%) for the non-indigenous species Ophiothela mirabilis Verrill, 1867 in the Brazilian coast. This ophiuroid is native to the Pacific Ocean but is spreading out in the Tropical Western Atlantic since 2000. Regarding this invasion, quantitative data is necessary to understand O. mirabilis threat. The aim of this study was to quantify the abundance of O. mirabilis on marine sponges along the Brazilian coast, and to evaluate the relationship of the non-indigenous species with sponge phenotypes, to test the hypothesis that this non-indigenous species prefers erect, irregular and yellowish sponges to facilitate attachment and camouflage. Epibiosis of O. mirabilis on sponges were photographed in 27 sites from Maranhão to Rio de Janeiro States, Brazil, and the abundance of sponges and ophiuroids on each sponge individual was counted. Only Bahia and Rio de Janeiro States presented an association, which was positively correlated (R2 = 0.85, F = 36.16, p < 0.001) between sponges and ophiuroid mean abundances. No morphological trait was statistically chosen by O. mirabilis, but the null probabilistic model indicates Mycale (Zygomycale) angulosa (Duchassaing & Michelotti, 1864) may be a preferred sponge basebiont. This first large-scale quantitative study indicates O. mirabilis may become a dangerous invader due to weak host preferences and efficient asexual reproduction strategy. This work can be used as a baseline template for monitoring and eradication programs, especially in Brazilian bays of high diversity and with human impact.