Hydrozoa | Marine Invertebrates of Western Africa

For the past month Marta Gil, a PhD student from the University of Vigo, has been with us for her second stay at the University Museum of Bergen. Marta has continued with the study of West African hydroid fauna from the MIWA-project, which was begun when she first visited here together with her supervisor, Professor Francesco Ramil Blanco (Fran) in July 2015.

: Marta

: Fran

: A. latecarinata

: S. caboverdiensis

: P. setacea

Marta has worked with samples collected during several Dr. Fridtjof Nansen surveys. Most of the samples were collected with an epibentic sledge, a sampling device more efficient for small colonies of hydroids. This study provide complementary data to those obtained during the study of hydroid fauna collected with the bottom trawl by the Norwegian and Spanish African surveys, and has allowed her to obtain some little know or even undescribed species.

Their findings are also interesting in terms of biogeography: Moroccon and Mauritanian hydroids show a strong affinity with Atlantic-Mediterranean fauna, whereas those from Guinea Bissau and Guinea Conakry waters show more similarities with tropical fauna. This means that for hydroids, the boundary between the temperate Lusitanian and the warm tropical fauna is located somewhere along the Senegalese or Guinea Bissauan coast. We hope that the complete analysis of data will enhance our knowledge on the marine fauna of this fascinating region.

The first weeks of July have been dedicated to the collections of Hydrozoa. Although the species that is presently known as Sarsia tubulosa has been almost a totem animal to marine biologists in Bergen since Michael Sars’ pioneering studies of cnidarians and other invertebrates on the Bergen coast, this taxonomically complex group has received relatively limited attention from local students.
We are very pleased therefore that Professor Francesco Ramil Blanco and his PhD-student Marta Gil from the University of Vigo are taking the time to examine some of our material of benthic hydrozoans. Benthic hydrozoans are sitting on various forms of substrate like sand, stones or dead shells. But many are also epibionts, which means that they are attached to other organisms such as algae, crustaceans or even other hydrozoans.

Front end of a Hyas crab carrying Hydrozoa and other organisms.

The alternation of generations between polyp and medusa stages, one of M.Sars’ discoveries, is just one of the reasons why these small cnidarians, the more inclusive group that the hydrozoans belong to, have been taxonomically challenging. There are many examples of such different life history stages having been described over time as different species. But there are also other reasons as to why hydrozoans should be studied more thoroughly. Access to new material, better microscopes and molecular techniques are giving researchers new possibilities to assess the diversity of these strange animals.