Hydroid diversity of Eilat Bay with the description of a new Zanclea species

Eilat Bay is located at the southernmost tip of Israel in the Gulf of Aqaba (Red Sea). The list of hydroids currently known from there includes 51 species, and when extending it to the entire Red Sea, it includes 157 species belonging to 41 families. Nevertheless, the information regarding hydroids in the Gulf of Aqaba, and in particular in Eilat Bay, is not exhaustive. The aim of this work is to improve knowledge of hydroid biodiversity in this area. The specimens collected during the HyDRa project (Hydroid Diversity of the Northern Red Sea) revealed the presence of 27 species, 13 Anthoathecata and 14 Leptothecata, belonging to 17 families and 20 genera. Two families, Cladonematidae and Corynidae, and five genera, Cladonema, Slabberia, Campanularia, Nemalecium and Lafoeina, are new findings for the Red Sea. Furthermore, Nemalecium lighti, Zanclea gallii and the new species Zanclea eilatensis sp. nov. have never before been recorded in the Red Sea. Zanclea eilatensis sp. nov. lives in association with a bryozoan, has a monomorphic colony lacking a perisarc and only has stenoteles in the polyps. The medusa stage has two prominent perradial exumbrellar nematocyst pouches and two tentacles with about 50 cnidophores having long flagella and containing macrobasic euryteles. In the present work, 54% of the species were associated with other organisms, such as hydroids, corals and bryozoans. New ecological data about the Zanclea–scleractinian coral association are documented. The present investigation provides new information about diversity in the Red Sea, and in particular in Eilat Bay. In addition, our data also have significance for Mediterranean and Red Sea biodiversity conservation due to the recent expansion of the Suez Canal and the consequent possible increase in the introduction of nonindigenous species in both directions.