Inventory of the free–living marine nematode species from el Bibane Lagoon (Tunisia)

Inventory of the free–living marine nematode species from el Bibane Lagoon (Tunisia). A detailed inventory of the free–living nematodes of Tunisia has been made for the northern part of Tunisia, but the southern part of the country is unexplored. El Bibane is the second largest lagoon in Tunisia. It is thus of high importance for future conservation actions, but little is known about its biodiversity. In this study, we identified 71 nematode species, belonging to 68 genera and 22 families. Richness was lowest in the central area of the lagoon where the highest percentages of mud and organic matter were found. The number of species detected in this study is high compared to other transitional environments in the Mediterranean basin, but lower than those reported for North Europe. Most of the species are typical of transitional environments or sediments rich in the fine fraction and detritus. The richest families were Cyatholaimidae and Chromadoridae, but the most frequently found species were Xyalidae, Linhomoeidae and Cyatholaimidae. Six of the species collected are new to science, seven are new records for Tunisian waters, and four are new for the Mediterranean basin. This study adds also important information to the biogeography of the phylum because some of the species detected here were previously known only for other geographical regions. Species that currently appear endemic to the Mediterranean Sea include Chromadorina metulata, Synonchiella edax, Paralongicyatholaimus mastigodes, Trichotheristus setifer and Metalinhomoeus numidicus.