Additions to the hydroids (Cnidaria, Hydrozoa) of marine fouling communities on the mainland of Ecuador and in the Galapagos Islands

Hydroids were examined from surveys of marine fouling communities undertaken during 2018 in Ecuador. Specimens were collected on settlement panels in harbours at Salinas and La Libertad on the mainland, and at Isla San Cristóbal in the Galapagos Islands. Of 27 species in the samples, 18 were present in collections from the mainland and 14 from San Cristóbal. Most frequent in samples from the mainland were Bougainvillia cf. muscus (20 samples), Obelia microtheca (20), Clytia delicatula (19) and Pennaria disticha (10). In collections from San Cristóbal, most frequent were Obelia alternata (27), Bougainvillia cf. muscus (16), Ectopleura crocea (13) and Cirrholovenia tetranema (11). Based on genetic evidence, Ectopleura media Fraser, 1948 is assigned to the synonymy of E. crocea (L. Agassiz, 1862). In addition, a COI reference sequence is deposited for the first time for Tridentata turbinata. Male gonophores of Eudendrium breve, previously unknown, were discovered and illustrated. The cnidome of the species comprises small and large microbasic euryteles. Five of the species have not been reported before from the Tropical Eastern Pacific. Of these, three (Amphinema cf. rugosum, Egmundella humilis, and Campanulinida, undetermined) were found only in the Galapagos, one (Clytia delicatula) occurred at both mainland sites and the Galapagos, and one (Opercularella sp.) was collected only from a station on the mainland. Six other species [Ectopleura integra, Coryne repens, Clytia irregularis, C. seriata, Obelia alternata (resurrected here from the synonymy of O. dichotoma), and O. microtheca] are known only from the Tropical Eastern Pacific. Three of them, E. integra, C. irregularis, and C. seriata, are new to the Ecuadorian mainland. Species numbers were similar (range of 6 to 11 taxa) across all stations. One-third (nine species) were found only in Galapagos samples, whereas nearly half (13 species) were found only at mainland sites. More than half (15 species) were restricted to a single station. Previous studies, together with this work, bring the total of introduced and cryptogenic hydroid species in the Galapagos Islands to 12 (previously eight) and nine (previously five) taxa, respectively. We recognize four introduced and eight cryptogenic hydroid species from the coast of mainland Ecuador.