Background:

Hydrozoan populations have an important role on the dynamic of the coastal ecosystems. However, the studies on hydromedusae in coastal lagoons from the Yucatán State are scarce.

Goals:

This study focuses on describe the first taxonomic list of hydromedusae in a coastal lagoon of the State of Yucatan.

Methods:

Samples were obtained through circular surface trawls using a zooplankton net in the coastal lagoon of Bocas de Dzilam. Six sampling stations were established inside the lagoon and eight outside, in adjacent zones to the mouth of the lagoon. The collected hydromedusae were fixed in a 4% formalin solution and identified with specialized literature.

Results:

Nine hydromedusae were identified, grouped into three orders and eight families, from which Hydractinia carica constitutes a new record for the Gulf of Mexico; the descriptions and images of the specimens are presented in the paper.

Conclusions:

These results set a basis to start understanding the composition of hydromedusae in the coastal lagoon of Dzilam and continue researching about this complex group in the coasts of Yucatán. However, further research efforts are required in coastal environments of the peninsula, in order to better understand its species composition and richness.